It's a Trap! Aldolase-Prescribed C4 Deoxyradiofluorination Affords Intracellular Trapping and the Tracing of Fructose Metabolism by PET

Fructose metabolism has been implicated in various diseases, including metabolic disorders, neurodegenerative disorders, cardiac disorders, and cancer. However, the limited availability of a quantitative imaging radiotracer has hindered its exploration in pathology and diagnostic imaging. Methods: We adopted a molecular design strategy based on the catalytic mechanism of aldolase, a key enzyme in fructolysis. We successfully synthesized a radiodeoxyfluorinated fructose analog, [18F]4-fluoro-4-deoxyfructose ([18F]4-FDF), in high molar activity. Results: Through heavy isotope tracing by mass spectrometry, we demonstrated that C4-deoxyfluorination of fructose led to effective trapping as fluorodeoxysorbitol and fluorodeoxyfructose-1-phosphate in vitro, unlike C1- and C6-fluorinated analogs that resulted in fluorolactate accumulation. This observation was consistent in vivo, where [18F]6-fluoro-6-deoxyfructose displayed substantial bone uptake due to metabolic processing whereas [18F]4-FDF did not. Importantly, [18F]4-FDF exhibited low uptake in healthy brain and heart tissues, known for their high glycolytic activity and background levels of [18F]FDG uptake. [18F]4-FDF PET/CT allowed for sensitive mapping of neuro- and cardioinflammatory responses to systemic lipopolysaccharide administration. Conclusion: Our study highlights the significance of aldolase-guided C4 radiodeoxyfluorination of fructose in enabling effective radiotracer trapping, overcoming limitations of C1 and C6 radioanalogs toward a clinically viable tool for imaging fructolysis in highly glycolytic tissues.

Focal Adhesion Kinase Inhibitors Prevent Osteoblast Mineralization in Part Due to Suppression of Akt-mediated stabilization of Osterix

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Pharmacological blockade of FAK results in reduced ALP expression and mineralization by differentiated osteoblasts.

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Although FAK inhibition resulted in increased levels of BMP2, Wnt3a and Mdm2, and decreased p53, alteration of these pathways was unable to restore mineralization in the presence of FAK tyrosine kinase inhibitors.

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FAK tyrosine kinase inhibitors resulted in decreased levels of phospho-S473 Akt which led to increased levels of active GSK3β which in turn inhibited Runx2 activity that could contribute to the observed reduced ALP levels.

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FAK tyrosine kinase inhibitors blocked Akt-mediated stabilization of osterix leading to decreased overall levels of osterix and impaired mineralization in MC3T3-E1 cells differentiated into osteoblasts.

Focal Adhesion Kinase (FAK) is an important regulator of tumor cell proliferation, survival and metastasis. As such it has become a therapeutic target of interest in cancer. Previous studies suggested that use of FAK tyrosine kinase inhibitors (TKIs) blocks osteolysis in in vivo models of bone metastasis. However, from these studies it was not clear whether FAK TKIs blocked bone degradation by osteoclasts or also promoted bone formation by osteoblasts. In this study we evaluated whether use of the FAK TKI PF-562,271 affected the differentiation of pre-osteoblasts, or activity of mature differentiated osteoblasts. MC3T3-E1 pre-osteoblastic cells were treated with various doses of PF-562,271 following 3 or 10 days of differentiation which led to the inhibition of alkaline phosphatase (ALP) expression and reduced viable cell numbers in a dose-dependent manner. MC3T3-E1 cells which had been differentiated for 21 days prior to treatment with PF-562,271 showed a dose dependent decrease in mineralization as assessed by Alizarin Red staining, with concomitant decreased expression of ALP which is known to facilitate the bone mineralization activity of osteoblasts, however mRNA levels of the transcription factors RUNX2 and osterix which are important for osteoblast maturation and mineralization appeared unaffected at this time point. We speculated that this may be due to altered function of RUNX2 protein due to inhibitory phosphorylation by GSK3β. We found treatment with PF-562,271 resulted in increased GSK3β activity as measured by reduced levels of phospho-Ser9-GSK3β which would result in phosphorylation and inhibition of RUNX2. Treatment of 21 day differentiated MC3T3-E1 cells with PF-562,271 in combination with GSK3β inhibitors partially restored mineralization however this was not statistically significant. As we observed that FAK TKI also resulted in suppression of Akt, which is known to alter osterix protein stability downstream of RUNX2, we examined protein levels by western blot and found a dose-dependent decrease in osterix in FAK TKI treated differentiated MC3T3-E1 cells which is likely responsible for the reduced mineralization observed. Taken together our results suggest that use of FAK TKIs as therapeutics in the bone metastatic setting may block new bone formation as an off-target effect and thereby exacerbate the defective bone regulation that is characteristic of the bone metastatic environment.

VIVA1: a more invasive subclone of MDA-MB-134VI invasive lobular carcinoma cells with increased metastatic potential in xenograft models

BACKGROUND

Invasive lobular carcinoma (ILC) is the second most common type of breast cancer. As few tools exist to study ILC metastasis, we isolated ILC cells with increased invasive properties to establish a spontaneously metastasising xenograft model.

METHODS

MDA-MB-134VI ILC cells were placed in transwells for 7 days. Migrated cells were isolated and expanded to create the VIVA1 cell line. VIVA1 cells were compared to parental MDA-MB-134VI cells in vitro for ILC marker expression and relative proliferative and invasive ability. An intraductally injected orthotopic xenograft model was used to assess primary and metastatic tumour growth in vivo.

RESULTS

Similar to MDA-MB-134VI, VIVA1 cells retained expression of oestrogen receptor (ER) and lacked expression of E-cadherin, however showed increased invasion in vitro. Following intraductal injection, VIVA1 and MDA-MB-134VI cells had similar primary tumour growth and survival kinetics. However, macrometastases were apparent in 7/10 VIVA1-injected animals. Cells from a primary orthotopic tumour (VIVA-LIG43) were isolated and showed similar proliferative rates but were also more invasive than parental cells. Upon re-injection intraductally, VIVA-LIG43 cells had more rapid tumour growth with similar metastatic incidence and location.

CONCLUSIONS

We generated a new orthotopic spontaneously metastasising xenograft model for ER+ ILC amenable for the study of ILC metastasis.

Mapping vitamin B6 metabolism by hydrazoCEST magnetic resonance imaging

A new CEST-MRI contrast agent, 2-HYNIC, capable of sensing aromatic aldehydes is reported. Pyridoxal 5'-phosphate, a key Vitamin B₆ metabolite necessary for >140 biotransformations was mapped by CEST-MRI in vitro and in vivo in lung cancer. 2-HYNIC provided access to this key biomarker associated with a variety of human diseases.

Targeting Intercellular Communication in the Bone Microenvironment to Prevent Disseminated Tumor Cell Escape from Dormancy and Bone Metastatic Tumor Growth

Metastasis to the bone is a common feature of many cancers including those of the breast, prostate, lung, thyroid and kidney. Once tumors metastasize to the bone, they are essentially incurable. Bone metastasis is a complex process involving not only intravasation of tumor cells from the primary tumor into circulation, but extravasation from circulation into the bone where they meet an environment that is generally suppressive of their growth. The bone microenvironment can inhibit the growth of disseminated tumor cells (DTC) by inducing dormancy of the DTC directly and later on following formation of a micrometastatic tumour mass by inhibiting metastatic processes including angiogenesis, bone remodeling and immunosuppressive cell functions. In this review we will highlight some of the mechanisms mediating DTC dormancy and the complex relationships which occur between tumor cells and bone resident cells in the bone metastatic microenvironment. These inter-cellular interactions may be important targets to consider for development of novel effective therapies for the prevention or treatment of bone metastases.

Abstract B35: Palbociclib treatment activates FAK and use of palbociclib in combination with the FAK inhibitor PF-562,271 enhances antitumor activity in ER-positive breast cancer cells

Cell survival and proliferation is tightly regulated by a number of interacting coordinated signaling proteins including the cyclin-dependent kinases (CDK). Palbociclib, a CDK4/6 inhibitor, has recently been shown to be very effective in the treatment of estrogen receptor (ER) positive breast cancer; however, many patients develop an acquired resistance through as yet incompletely characterized mechanisms. One recently proposed mechanism is compensation by CDK2 (Herrera-Abreu et al., Can Res 2016;76:2301). Focal adhesion kinase (FAK) is a tyrosine kinase that plays a central role in signaling pathway crosstalk and cell survival and invasion. FAK has been previously shown to activate CDK2 in hepatocytes (Flinder et al., J Cell Phys 2013;228:1304), and given its important role in mediating cell survival, we were interested in determining whether FAK-mediated upregulation of CDK2 occurs in palbociclib-treated breast cancer cells, thereby limiting its efficacy. ER-positive MCF7, MDA-MB-134VI, and T47D breast cancer cell lines were thus treated with increasing doses of palbociclib. We observed dose-dependent increases in phospho-FAK Y397, a marker of the active kinase, following palbociclib treatment. We thus used PF-562,271, a selective FAK tyrosine kinase inhibitor, in combination with palbociclib and, not surprisingly, observed an enhanced ability to inhibit cell viability as compared to use of either drug alone. This was concomitant with observed increases in the CDK4/6 inhibitor p27, and with decreases in phospho-RB, which are indicative of reduced CDK2 activity, following treatment with PF-562,271. Our results highlight an unexpected side effect of palbociclib treatment, namely FAK activation, which could potentially contribute to resistance due to activation of CDK2 and inhibition of p27. The mechanism by which palbociclib activates FAK is currently under investigation.

Citation Format: Grant Howe, Victoria Allen, Christina L. Addison. Palbociclib treatment activates FAK and use of palbociclib in combination with the FAK inhibitor PF-562,271 enhances antitumor activity in ER-positive breast cancer cells [abstract]. In: Proceedings of the AACR Special Conference: Advances in Breast Cancer Research; 2017 Oct 7-10; Hollywood, CA. Philadelphia (PA): AACR; Mol Cancer Res 2018;16(8_Suppl):Abstract nr B35.

Effects on bone resorption markers of continuing pamidronate or switching to zoledronic acid in patients with high risk bone metastases from breast cancer

Background

Switching patients who remain at high risk of skeletal related events (SREs) despite pamidronate to the more potent bisphosphonate zoledronate, may be an effective treatment strategy. As part of a previously reported clinic study in this setting, we evaluated whether biomarkers for bone resorption, such as Bone-Specific Alkaline Phosphatase (BSAP), bone sialoprotein (BSP), and N-terminal telopeptide (NTX) correlated with subsequent SRE risk.

Methods

Breast cancer patients who remained at high risk of SREs despite at least 3 months of q.3–4 weekly pamidronate were randomized to either continue on pamidronate or to switch to zoledronate (4 mg) once every 4 weeks for 12-weeks. High risk bone metastases were defined by either: occurrence of a prior SRE, bone pain, radiologic progression of bone metastases and/or serum C-terminal telopeptide (CTx) levels > 400 ng/L despite pamidronate use. Serum samples were collected at baseline and weeks 1, 4, 8 and 12 (CTx and BSAP) and baseline and week 12 (NTx and BSP), and all putative biomarkers were measured by ELISA. Follow up was extended to 2 years post trial entry for risk of subsequent SREs. The Kaplan-Meier method was used to estimate time-to-event outcomes. Generalized estimating equations (GEE) were used to evaluate if laboratory values over time or the change in laboratory values from baseline were associated with having a SRE within the time frame of this study.

Results

From March 2012 to May 2014, 76 patients were screened, with 73 eligible for enrolment. All 73 patients were available for biochemical analysis, with 35 patients receiving pamidronate and 38 patients receiving zoledronate. The GEE analysis found that no laboratory value was associated with having a subsequent SRE. Interaction between visit and laboratory values was also investigated, but no interaction effect was statistically significant. Only increased number of lines of prior hormonal treatment was associated with subsequent SRE risk.

Conclusion

Our analysis failed to find any association between serum BSAP, BSP, CTx or NTx levels and subsequent SRE risk in this cohort of patients. This lack of correlation between serum biomarkers and clinical outcomes could be due to influences of prior bisphosphonate treatment or presence of extra-osseous metastases in a significant proportion of enrolled patients. As such, caution should be used in biomarker interpretation and use to direct decision making regarding SRE risk for high risk patients in this setting.

MicroRNA-30b controls endothelial cell capillary morphogenesis through regulation of transforming growth factor beta 2

The importance of microRNA (miRNA) to vascular biology is becoming increasingly evident; however, the function of a significant number of miRNA remains to be determined. In particular, the effect of growth factor regulation of miRNAs on endothelial cell morphogenesis is incomplete. Thus, we aimed to identify miRNAs regulated by pro-angiogenic vascular endothelial growth factor (VEGF) and determine the effects of VEGF-regulated miRNAs and their targets on processes important for angiogenesis. Human umbilical vein endothelial cells (HUVECs) were thus stimulated with VEGF and miRNA levels assessed using microarrays. We found that VEGF altered expression of many miRNA, and for this study focused on one of the most significantly down-regulated miRNA in HUVECs following VEGF treatment, miR-30b. Using specific miRNA mimics, we found that overexpression of miR-30b inhibited capillary morphogenesis in vitro, while depletion of endogenous miR-30b resulted in increased capillary morphogenesis indicating the potential significance of down-regulation of miR-30b as a pro-angiogenic response to VEGF stimulation. MiR-30b overexpression in HUVEC regulated transforming growth factor beta 2 (TGFβ2) production, which led to increased phosphorylation of Smad2, indicating activation of an autocrine TGFβ signaling pathway. Up-regulation of TGFβ2 by miR-30b overexpression was found to be dependent on ATF2 activation, a transcription factor known to regulate TGFβ2 expression, as miR-30b overexpressing cells exhibited increased levels of phosphorylated ATF2 and depletion of ATF2 inhibited miR-30b-induced TGFβ2 expression. However, miR-30b effects on ATF2 were indirect and found to be via targeting of the known ATF2 repressor protein JDP2 whose mRNA levels were indirectly correlated with miR-30b levels. Increased secretion of TGFβ2 from HUVEC was shown to mediate the inhibitory effects of miR-30b on capillary morphogenesis as treatment with a neutralizing antibody to TGFβ2 restored capillary morphogenesis to normal levels in miR-30b overexpressing cells. These results support that the regulation of miR-30b by VEGF in HUVEC is important for capillary morphogenesis, as increased miR-30b expression inhibits capillary morphogenesis through enhanced expression of TGFβ2.

Estrogen, progesterone, and HER2/neu receptor discordance between primary and metastatic breast tumours-a review

Discordance in estrogen (ER), progesterone (PR), and HER2/neu status between primary breast tumours and metastatic disease is well recognized. In this review, we highlight how receptor discordance between primary tumours and paired metastasis can help elucidate the mechanism of metastasis but can also effect patient management and the design of future trials. Discordance rates and ranges were available from 47 studies (3384 matched primary and metastatic pairs) reporting ER, PR, and HER2/neu expression for both primary and metastatic sites. Median discordance rates for ER, PR, and HER2/neu were 14 % (range 0-67 %, IQR 9-25 %), 21 % (range 0-62 %, IQR 15-41 %), and 10 % (range 0-44 %, IQR 4-17 %), respectively. Loss of receptor expression was more common (9.17 %) than gain (4.51 %). Discordance rates varied amongst site of metastasis with ER discordance being highest in bone metastases suggesting that discordance is a true biological phenomenon. Discordance rates vary for both the biomarker and the metastatic site. Loss of expression is more common than gain. This can affect patient management as it can lead to a reduction in both the efficacy and availability of potential therapeutic agents. Future studies are recommended to explore both the mechanisms of discordance as well as its impact on patient outcome and management.

A phase II trial of dovitinib in previously-treated advanced pleural mesothelioma: The Ontario Clinical Oncology Group

OBJECTIVES

Following failure of a platinum-antifolate combination regimen, there is no standard therapy for advanced malignant pleural mesothelioma (MPM). The fibroblast growth factor receptor (FGFR) signaling pathways may be a relevant target in MPM. Dovitinib inhibits multiple tyrosine receptor kinases, predominantly the vascular endothelial growth factor receptors (VEGFR), but also FGFRs, and could be active in MPM.

METHODS

This open-label multicentre phase II trial [NCT01769547] enrolled fit, consenting adult patients with advanced MPM who had previously received platinum-antifolate combination chemotherapy and up to one additional line of systemic therapy. Dovitinib was administered orally at 500mg/day for 5days on, 2days off, in 28-day cycles. Response was assessed every 2 cycles using RECIST 1.1 criteria modified for MPM. Correlative studies included FGFR-1 amplification on archival tumour and serum samples for circulating angiogenesis factors. The primary end-point was the proportion of patients progression-free at 3 months (PF3) using a two-stage design.

RESULTS

12 patients (10 males, median age 67) were enrolled. The median number of cycles administered was 2.5 (range 1-8). One unconfirmed partial response was observed. PF3 was 50% (95% confidence interval 28.4% to 88.0%); although the criterion for proceeding to stage II accrual was met, the trial was halted due to a combination of minimal activity with several early progression events and poor tolerability in this patient population. One of 12 tumour specimens had low amplification of FGFR-1.

CONCLUSIONS

Dovitinib has minimal activity in previously-treated MPM. The role of the FGFR pathway in MPM remains unclear.

Cardamonin reduces chemotherapy-enriched breast cancer stem-like cells in vitro and in vivo

The failure of cytotoxic chemotherapy in breast cancers has been closely associated with the presence of drug resistant cancer stem cells (CSCs). Thus, screening for small molecules that selectively inhibit growth of CSCs may offer great promise for cancer control, particularly in combination with chemotherapy. In this report, we provide the first demonstration that cardamonin, a small molecule, selectively inhibits breast CSCs that have been enriched by chemotherapeutic drugs. In addition, cardamonin also sufficiently prevents the enrichment of CSCs when simultaneously used with chemotherapeutic drugs. Specifically, cardamonin effectively abolishes chemotherapeutic drug-induced up-regulation of IL-6, IL-8 and MCP-1 and activation of NF-κB/IKBα and Stat3. Furthermore, in a xenograft mouse model, co-administration of cardamonin and the chemotherapeutic drug doxorubicin significantly retards tumor growth and simultaneously decreases CSC pools in vivo. Since cardamonin has been found in some herbs, this work suggests a potential new approach for the effective treatment of breast CSCs by administration of cardamonin either concurrent with or after chemotherapeutic drugs.

A phase 2 trial exploring the clinical and correlative effects of combining doxycycline with bone-targeted therapy in patients with metastatic breast cancer

Background

Bone-targeting agents (BTAs), such as bisphosphonates and denosumab, have demonstrated no discernable effects on tumour response or disease free/overall survival in patients with bone metastases from breast cancer. Doxycycline is both osteotropic and has anti-cancer effects. When combined with zoledronate in animal models, doxycycline showed significantly increased inhibition of tumour burden and increased bone formation. We evaluated the effects of adding doxycycline to ongoing anti-cancer therapy in patients with metastatic breast cancer.

Methods

Breast cancer patients with bone metastases and ≥3 months of BTA use, entered this single-arm study. Patients received doxycycline 100 mg orally, twice a day for 12 weeks. The co-primary endpoints were; effect on validated pain scores (FACT-Bone pain and Brief Pain Inventory) and bone resorption markers (serum C-telopeptide, [sCTx]). All endpoints (pain scores, sCTx, bone-specific alkaline phosphatase, skeletal-related events, toxicity) were evaluated at baseline, 4, 8 and 12 weeks. Bone marrow was sampled at baseline and week 12 for exploratory biomarker analysis.

Results

Out of 37 enroled patients, 27 (73%) completed 12 weeks of therapy. No significant changes were seen in pain scores or bone turnover markers. Failure to complete treatment: drug toxicity (70%) and disease progression (30%). Sixteen (43%) patients had GI adverse events.

Conclusions

Doxycycline 100 mg twice daily for 12 weeks had no significant effects on either bone pain or bone turnover markers. Its toxicity profile in this patient population would make further evaluation challenging.

Focal Adhesion Kinase Inhibitors in Combination with Erlotinib Demonstrate Enhanced Anti-Tumor Activity in Non-Small Cell Lung Cancer

Blockade of epidermal growth factor receptor (EGFR) activity has been a primary therapeutic target for non-small cell lung cancers (NSCLC). As patients with wild-type EGFR have demonstrated only modest benefit from EGFR tyrosine kinase inhibitors (TKIs), there is a need for additional therapeutic approaches in patients with wild-type EGFR. As a key component of downstream integrin signalling and known receptor cross-talk with EGFR, we hypothesized that targeting focal adhesion kinase (FAK) activity, which has also been shown to correlate with aggressive stage in NSCLC, would lead to enhanced activity of EGFR TKIs. As such, EGFR TKI-resistant NSCLC cells (A549, H1299, H1975) were treated with the EGFR TKI erlotinib and FAK inhibitors (PF-573,228 or PF-562,271) both as single agents and in combination. We determined cell viability, apoptosis and 3-dimensional growth in vitro and assessed tumor growth in vivo. Treatment of EGFR TKI-resistant NSCLC cells with FAK inhibitor alone effectively inhibited cell viability in all cell lines tested; however, its use in combination with the EGFR TKI erlotinib was more effective at reducing cell viability than either treatment alone when tested in both 2- and 3-dimensional assays in vitro, with enhanced benefit seen in A549 cells. This increased efficacy may be due in part to the observed inhibition of Akt phosphorylation when the drugs were used in combination, where again A549 cells demonstrated the most inhibition following treatment with the drug combination. Combining erlotinib with FAK inhibitor was also potent in vivo as evidenced by reduced tumor growth in the A549 mouse xenograft model. We further ascertained that the enhanced sensitivity was irrespective of the LKB1 mutational status. In summary, we demonstrate the effectiveness of combining erlotinib and FAK inhibitors for use in known EGFR wild-type, EGFR TKI resistant cells, with the potential that a subset of cell types, which includes A549, could be particularly sensitive to this combination treatment. As such, further evaluation of this combination therapy is warranted and could prove to be an effective therapeutic approach for patients with inherent EGFR TKI-resistant NSCLC.

Abstract P4-09-08: miR-135a is associated with a metastatic phenotype in invasive lobular carcinoma

Invasive lobular carcinoma (ILC) is the second most common type of breast cancer. Classic type ILC is generally regarded as indolent in nature with its favourable biologic characteristics such as low grade, ER positivity and luminal A subtype. Despite this, patients with ILC can develop significant distant recurrence or metastases. Thus the ability to identify those patients at highest risk of recurrence or metastasis, and identification of novel therapies for ILC are urgently required. To this end, we recently profiled the miRNA expression in primary surgical ILC specimens from patients who went on to have metastatic disease compared to those who remained tumor free long term. As miRNA are stable in formalin fixed paraffin embedded tissues1, we speculated they could be robust biomarkers. RNA was isolated from laser capture microdissected ILC tumor epithelium, and subjected to miRNome analysis using a PCR-based amplification method. Many differentially expressed miRNAs were identified, and we initially focused further validation on those which had been previously linked to metastasis. One of these, miR-135a, was elevated in tumors from ILC patients who developed metastases compared to those that did not. We utilized two representative ILC cell lines which differ in their invasive ability, MDA-MB-134VI (non-invasive) and MDA-MB-330 (invasive), to test whether miR-135a regulated ILC invasion. We found that levels of miR-135a correlated with the invasive potential of ILC cell lines and was elevated in the invasive MDA-MB-330 cells compared to less invasive MDA-MB-134VI cells. We also found that decreasing miR-135a expression using specific hairpin inhibitors in MDA-MB-330 cells resulted in decreased cell invasion. As miR-135a has been shown to regulate invasion via targeting metastasis suppressor 1 (MTSS1) mRNA for degradation2, we examined whether MTSS1 levels were inversely associated with miR-135a levels in ILC cells. As predicted, in MDA-MB-330 cells where miR-135a levels were significantly higher, levels of MTSS1 were the lowest while MTSS1 levels were higher in parallel with decreased levels of miR-135a in the non-invasive MDA-MB-134VI cells. Overexpressing miR-135a using miRNA mimics in normal mammary epithelial cells (HMEC) where miR-135a is normally low, reduced levels of MTSS1 supporting suggestions it is a direct target of miR-135a. We also confirmed reduced mRNA levels of MTSS1 in surgical specimens from ILC patients who developed metastases compared to those that did not. Taken together, our results suggest that high levels of miR-135a, and low levels of MTSS1 may be useful prognostic information to assess risk of metastasis in ILC.

References

1. Bovell L, Shanmugam C, Katkoori VR, et al: miRNAs are stable in colorectal cancer archival tissue blocks. Front Biosci (Elite Ed) 4:1937-40, 2012

2. Zhou W, Li X, Liu F, et al: MiR-135a promotes growth and invasion of colorectal cancer via metastasis suppressor 1 in vitro. Acta Biochim Biophys Sin (Shanghai) 44:838-46, 2012.

Citation Format: Howe GA, Zhao H, Daneshmand M, Clemons M, Robertson SJ, Arnaout A, Addison CL. miR-135a is associated with a metastatic phenotype in invasive lobular carcinoma. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-09-08.

Abstract P2-05-26: Focal adhesion kinase is required for efficient tumor-induced osteoclastogenesis via control of macrophage colony stimulating factor expression

Breast cancer most commonly metastasizes to bone where metastases cause the potentiation of the vicious cycle. During this process, breast cancer bone metastases inhibit osteoblasts from forming new bone, while also activating osteoclasts to degrade bone. This in turn causes release of bone-matrix bound growth factors which propagate tumor growth. The overall net bone destruction can lead to significant adverse clinical consequences for patients including fractures or substantial pain. While agents such as bisphosphonates or the monoclonal antibody to RANKL denosumab, both of which inhibit the osteolytic activity of osteoclasts, are currently used in breast cancer bone metastatic patients to alleviate these adverse clinical outcomes, they have not been associated with increased patient survival. Given the lack of successful treatments for bone metastases providing survival advantages, we sought to evaluate the role of focal adhesion kinase (FAK), a novel therapeutic target, in breast cancer mediated osteolysis. FAK is a non-receptor tyrosine kinase that regulates many pathways that contribute to enhanced tumor progression and metastasis. FAK is also expressed in all the cell types involved in the vicious cycle. We thus hypothesized that FAK plays an important role in breast tumor-induced osteolysis and that its inhibition would lead to restoration of bone homeostasis, in addition to inhibition of tumor progression. Using in vitro siRNA-targeted depletion of FAK in breast cancer tumor cell lines, we found that production of numerous soluble growth factors, many of which are known contributors to osteoclastogenesis, was inhibited. We confirmed that FAK regulates the expression of the osteoclastogenic factor macrophage colony stimulating factor in breast cancer cell lines. Further, using conditioned media from FAK expressing versus depleted breast cancer tumor cells in osteoclastogenesis assays, we show that FAK-depletion results in impaired osteoclastogenesis. These data suggest that in addition to its proven direct anti-tumor effects, inhibition of FAK may also result in therapeutic blockade of bone degradation.

Citation Format: Landon K, Howe GA, Zhao H, Addison CL. Focal adhesion kinase is required for efficient tumor-induced osteoclastogenesis via control of macrophage colony stimulating factor expression. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-05-26.

VEGF-Mediated Induction of PRD1-BF1/Blimp1 Expression Sensitizes Tumor Vasculature to Oncolytic Virus Infection

Oncolytic viruses designed to attack malignant cells can in addition infect and destroy tumor vascular endothelial cells. We show here that this expanded tropism of oncolytic vaccinia virus to the endothelial compartment is a consequence of VEGF-mediated suppression of the intrinsic antiviral response. VEGF/VEGFR2 signaling through Erk1/2 and Stat3 leads to upregulation, nuclear localization, and activation of the transcription repressor PRD1-BF1/Blimp1. PRD1-BF1 does not contribute to the mitogenic effects of VEGF, but directly represses genes involved in type I interferon (IFN)-mediated antiviral signaling. In vivo suppression of VEGF signaling diminishes PRD1-BF1/Blimp1 expression in tumor vasculature and inhibits intravenously administered oncolytic vaccinia delivery to and consequent spread within the tumor.

Correlation of baseline biomarkers with clinical outcomes and response to fulvestrant with vandetanib or placebo in patients with bone predominant metastatic breast cancer: An OCOG ZAMBONEY sub-study

Background

Bone metastases are common in women with breast cancer and often result in skeletal related events (SREs). As the angiogenic factor vascular endothelial growth factor (VEGF) regulates osteoclast activity and is associated with more extensive bone metastases and SRE risk in metastatic breast cancer, we hypothesized that blockade of VEGF signaling could be a therapeutic strategy for inhibiting bone metastases progression and possibly prolonging overall (OS) or progression-free survival (PFS). The Zamboney trial was a randomized placebo-controlled study designed to assess whether patients with bone predominant metastatic breast cancer benefited from addition of the VEGF receptor (VEGFR) targeting agent, vandetanib, to endocrine therapy with fulvestrant. As a companion study, evaluation of biomarkers and their potential association with response to vandetanib or SRE risk was performed.

Methods

Baseline overnight fasted serum from enrolled patients was analyzed for levels of various putative biomarkers including; VEGF-A, soluble (s)VEGFR2, sVEGFR3, transforming growth factor (TGF)-β1 and activinA by ELISA. Spearman correlation coefficients and Wilcoxon rank sum tests were used to investigate potential relationships between biomarker values and baseline clinical parameters. Prognostic and predictive ability of each marker was investigated using Cox proportional hazards regression with adjustments for treatment and baseline strata of serum CTx (<400 versus ≥400 ng/L).

Results

Of 129 enrolled patients, serum was available for analysis in 101; 51 in vandetanib and 50 in placebo arm. Mean age amongst consenting patients was 59.8 years. Clinical characteristics were not significantly different between patients with or without serum biomarker data and serum markers were similar for patients by treatment arm. Baseline sVEGFR2 was prognostic for OS (HR=0.77, 95% CI=0.61–0.96, p=0.020), and although a modest association was observed, it was not significant for PFS (HR=0.90, 95% CI=0.80–1.01, p=0.085) nor time to first SRE (HR=0.82, 95% CI=0.66–1.02, p=0.079). When interaction terms were evaluated, sVEGFR2 was not found to be predictive of response to vandetanib, although a modest association remained with respect to PFS (interaction p=0.085). No other marker showed any significant prognostic or predictive ability with any measured outcome.

Conclusions

In this clinical trial, sVEGFR2 appeared prognostic for OS, hence validation of sVEGFR2 should be conducted. Moreover, the role of sVEGFR2 in breast cancer bone metastasis progression should be elucidated.

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Baseline VEGF, sVEGFR3, TGF-β or activinA were not associated with clinical outcomes in patients treated with fulvestrant in conjunction with vandetanib or placebo.

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Baseline sVEGFR2 was modestly associated with clinical outcomes including PFS, OS and time to first skeletal event.

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Increased baseline sVEGFR2 was associated with improved clinical outcomes in this study sample.

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These findings support the need for future studies of the role of sVEGFR2 in bone metastasis progression.

Essential role for the SLK protein kinase in embryogenesis and placental tissue development

BACKGROUND

Over the past decade, the Ste20-like kinase SLK, has been implicated in several signaling processes. SLK repression has been shown to impair cell cycle kinetics and inhibit FAK-mediated cell migration. Here, using a gene trapped allele, we have generated mice expressing a truncated form of the SLK kinase.

RESULTS

Our results show that an SLK-LacZ fusion protein is expressed in embryonic stem cells and in embryos throughout development. We find that the SLK-LacZ fusion protein is less efficient at phosphorylating substrates resulting in reduced cell proliferation within the embryos and angiogenic defects in the placentae of the homozygous mutant animals at embryonic day (E) 12.5. This results in marked developmental defects and apoptotic lesions in the embryos by E14.5.

CONCLUSIONS

Homozygotes expressing the SLK-LacZ fusion protein present with an embryonic lethal phenotype occurring between E12.5 and E14.5. Overall, we demonstrate a requirement for SLK kinase activity in the developing embryo and placenta.

Abstract 1121: Extracellular matrix-integrin B1 signaling is a major mediator of epithelial-to-mesenchymal transition and contributes to prostate cancer invasion and metastasis

Within North America, prostate cancer is the most commonly diagnosed cancer in men with devastating implications deriving from metastasis, particularly those established in the bone. We have elucidated mechanisms by which prostate cancer undergoes metastasis with particular focus on the relationship between extracellular-matrix binding proteins, Integrin B1 (ITGB1) and epithelial-to-mesenchymal transition (EMT). Previous results in the laboratory suggested that prostate tumor cells depleted of ITGB1 were unable to form colonies in soft agarose and were impaired in their invasive abilities in vitro. In order to determine the possible mechanisms by which ITGB1 controlled these phenotypes, we performed numerous genetic techniques including siRNA targeted depletion of ITGB1 and subsequent profiling of pathway specific message RNA by RTqPCR to monitor the effects ITGB1 depletion on factors known to control EMT which is also associated with cell invasion. We found that prostate tumor cells depleted of ITGB1 had altered expression of numerous genes associated with EMT or cell invasion, many of which have been validated by RT-qPCR and western blot. In particular, a protease inhibitor SERPINE1 also known as Plasminogen Activator Inhibitor 1 (PAI-1) which is associated with EMT has been established as a target of ITGB1 regulation, in part via the ability of ITGB1 to regulate upstream factors associated with SERPINE1 expression such as TGFB2. Of particular interest to prostate cancer bone metastasis, we further found that collagen I interacting with ITGB1 significantly upregulated this pathway, and given the known role of EMT in mediating resistance to anti-cancer agents, this finding could help elucidate novel targets for the development of new drugs to treat prostate cancer bone metastasis.

Citation Format: Steven R. Bugiel, Elisabeth McKittrick, Huijun Zhao, Grant A. Howe, Christina L. Addison. Extracellular matrix-integrin B1 signaling is a major mediator of epithelial-to-mesenchymal transition and contributes to prostate cancer invasion and metastasis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1121. doi:10.1158/1538-7445.AM2014-1121

Abstract 753: Enhanced anti-tumor activity of erlotinib in combination with FAK tyrosine kinase inhibitors in non-small cell lung cancer

The epidermal growth factor receptor (EGFR) is over-expressed in approximately 90% of non-small cell lung cancer (NSCLC) and as such, blockade of EGFR activity has been a primary therapeutic target for NSCLC. As patients with wild-type EGFR have demonstrated only modest benefit from EGFR tyrosine kinase inhibitors (TKIs) there is a need for additional therapeutic approaches in patients with wild-type EGFR. The extracellular matrix (ECM) has been shown to play an important role in tumor growth and response to therapy, and focal adhesion kinase (FAK) expression, a key component of signaling downstream of ECM binding to cell surface integrins, has been shown to correlate with aggressive stage in NSCLC. As the FAK-Src signaling axis can activate EGFR signaling independently of EGFR ligand-binding and kinase activity, the use of FAK tyrosine kinase inhibitors in combination with EGFR TKIs was assessed as a means of enhancing response to treatment in NSCLC. Treatment of EGFR TKI-resistant NSCLC cells (A549 and H1299 with wild-type EGFR, and H1975 with T790M acquired resistance mutation in EGFR) with FAK tyrosine kinase inhibitor PF-573,228 alone decreased cell viability. Treatment of these cell lines with a combination of PF-573,228 and the EGFR TKI erlotinib was more effective at reducing cell viability and cell migration than either treatment alone. Additionally, the growth of EGFR TKI-resistant NSCLC cells in 3-dimensional culture was significantly impaired with a combination of FAK inhibitor and erlotinib compared to either treatment alone. Interestingly, although erlotinib alone could inhibit the phosphorylation of Akt to an extent in NSCLC cell lines, the combination of erlotinib and FAK inhibitor was able to almost completely inhibit Akt phosphorylation. As persistent Akt activity is associated with lack of response to EGFR TKIs, the enhanced reduction in cell viability seen with the addition of a FAK inhibitor to treatment with erlotinib appears to be, at least in part, due to enhanced inhibition of Akt activity in these cells. The efficacy of the combination treatment was confirmed in vivo using a xenograft model with subcutaneously implanted A549 cells in nude mice. Significant inhibition of tumor growth was observed for A549-derived tumors when erlotinib was used in combination with FAK inhibitor, with some animals not yet developing palpable tumors by the end-point of the experiment. Thus, the combination of FAK inhibition with EGFR TKIs such as erlotinib results in decreased growth of NSCLC cells both in vitro and in vivo and could prove to be an effective therapeutic approach for patients with EGFR TKI-resistant NSCLC.

Citation Format: Grant A. Howe, Bin Xiao, Huijun Zhao, Glenwood Goss, Christina L. Addison. Enhanced anti-tumor activity of erlotinib in combination with FAK tyrosine kinase inhibitors in non-small cell lung cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 753. doi:10.1158/1538-7445.AM2014-753

Effects of de-escalated bisphosphonate therapy on bone turnover biomarkers in breast cancer patients with bone metastases

While de-escalation of bisphosphonates from 4 to 12-weekly dosing has been shown to be clinically non-inferior to standard dosing, there is evidence the de-escalation is associated with increased bone turnover biomarkers. Here we evaluated the effect of de-escalated dosing on a panel of biomarkers and determined their association with incidence of skeletal related events (SREs) in breast cancer patients with ‘low risk’ bone metastases. As part of a pilot randomized trial, women with baseline C-telopeptide levels <600 ng/L after >3 months of 3–4 weekly pamidronate were randomized to continue pamidronate every 4 weeks or de-escalation to 12-weekly treatment. Serum was analysed for bone biomarkers (C-telopeptide, N-telopeptide, bone-specific alkaline phosphatase, transforming growth factor-β, procollagen type 1 N-propeptide, activinA and bone sialoprotein) using ELISA. The associations between changes in biomarkers, pain scores and SREs were assessed by univariable logistic regression. Numerical increases in all biomarkers were observed between baseline and 12 weeks but were of higher magnitude in the de-escalated arm. Pain scores in the de-escalated treatment arm showed a greater magnitude of pain reduction from baseline to 12 weeks. Neither baseline levels nor changes in biomarkers from baseline to 12 weeks on treatment were associated with on study SREs. Baseline pain as measured by the FACT-BP was associated with increased risk of SRE. In conclusion, biomarkers of bone activity do not appear to predict for SREs in ‘low risk’ cohorts. However, baseline bone pain appears to be associated with SRE occurrence, a finding which warrants evaluation in larger cohorts.

Incidence, consequences and treatment of bone metastases in breast cancer patients-Experience from a single cancer centre

Background

There is a paucity of literature about the benefits of bone-targeted agents for breast cancer patients with bone metastases treated in the non-trial setting. We explored the incidence, consequences, and treatment of bone metastases at a single cancer centre.

Methods

Electronic records of metastatic breast cancer patients were reviewed and pertinent information was extracted.

Results

Of 264 metastatic breast cancer patients, 195 (73%) developed bone metastases. Of these patients, 176 were eligible for analysis. Median age at bone metastases diagnosis was 56.9 years (IQR 48–67) and initial presentation of bone metastases included asymptomatic radiological findings (58%), bone pain (40%), or a SRE (12.5%). Most patients (88%) received a bone-targeted agent, starting a median of 1.5 months (IQR 0.8–3.30) after bone metastasis diagnosis. 62% of patients had ≥1 SRE. The median time from bone metastasis diagnosis to first SRE was 1.8 months (IQR 0.20–8.43 months). Median number of SREs per patient was 1.5 (IQR 0–3). Overall, 26.8% of all SREs were clinically asymptomatic. Within the entire cohort, 51% required opioids and 20% were hospitalized due to either an SRE or bone pain.

Conclusions

Despite extensive use of bone-targeted agents, the incidence of SREs remains high. Nearly half of SREs occur prior to starting a bone-targeted agent. Use of opioids and hospitalizations secondary to bone metastases remain common. More effective treatment options are clearly needed.

Bone-Targeted Agents for the Management of Breast Cancer Patients with Bone Metastases

Despite advances in adjuvant therapy for breast cancer, bone remains the most common site of recurrence. The goal of therapy for these patients is palliative and focused on maximizing the duration and quality of their life, while concurrently minimizing any disease or treatment-related complications. Bone metastases predispose patients to reduced survival, pain, impaired quality of life and the development of skeletal-related events. With an increased understanding of the pathophysiology of bone metastasis, effective treatments for their management have evolved and are now in widespread clinical use. This article will discuss the pathogenesis of bone metastases and review the key clinical evidence for the efficacy and safety of currently available systemic bone-targeted therapies in breast cancer patients with an emphasis on bisphosphonates and the receptor activator of nuclear factor kappa B ligand (RANKL) inhibitors. We will also discuss novel strategies and therapies currently in development.

Effects of de-escalated bisphosphonate therapy on the Functional Assessment of Cancer Therapy-Bone Pain, Brief Pain Inventory and bone biomarkers

Background

The Brief Pain Inventory (BPI) and Functional Assessment of Cancer Therapy-Bone Pain (FACT-BP) are commonly used measures of patient reported pain outcomes. We report on the performance of the FACT-BP in comparison to the BPI within a small, randomized trial.

Methods

Patients with biochemically defined low risk bone metastases were randomized to 4 weekly (control arm) or 12 weekly (de-escalating arm) pamidronate for 1 year. FACT-BP, BPI and serum markers of bone turnover were recorded at baseline and weeks 12, 24, 36 and 48. Mixed effects models were used to compare scores over time between arms. Correlation coefficients were calculated to evaluate the association between FACT-BP and BPI scores, as well as with markers of bone turnover.

Results

Nineteen patients were randomized to each study arm. Pain scores determined by the two instruments were moderately to highly correlated with each other. Baseline C-telopeptide (CTx) level was correlated with baseline FACT-BP and BPI scores. Baseline bone-specific alkaline phosphatase showed a non-significant association with pain scores. There were no correlations between the markers of bone turnover and pain scores at week 12.

Conclusions

In the current study the FACT-BP and BPI correlated well with each other, and with baseline CTx. The possibility of linking subjective pain scores with objective biomarkers of response requires more investigation.

miR-105 inhibits prostate tumour growth by suppressing CDK6 levels

A significant role for micro (mi)RNA in the regulation of gene expression in tumours has been recently established. In order to further understand how miRNA expression may contribute to prostate tumour growth and progression, we evaluated expression of miRNA in two invasive prostate tumour lines, PC3 and DU145, and compared it to that in normal prostate epithelial cells. Although a number of miRNAs were differentially expressed, we focused our analysis on miR-105, a novel miRNA not previously linked to prostate cancer. miR-105 levels were significantly decreased in both tumour cell lines in comparison to normal prostate epithelial cells. To determine its potential role in prostate cancer pathogenesis, we overexpressed miR-105 in both PC3 and DU145 cells and determined its effect on various tumourigenic properties. miR-105 overexpression inhibited tumour cell proliferation, tumour growth in anchorage-independent three-dimensional conditions and tumour invasion in vitro, properties of highly aggressive tumour cells. Of potential clinical significance, miR-105 overexpression inhibited tumour growth in vivo in xenograft models using these cell lines. We further identified CDK6 as a putative target of miR-105 which is likely a main contributor to the inhibition of tumour cell growth observed in our assays. Our results suggest that miR-105 inhibits tumour cell proliferation and hence may represent a novel therapeutically relevant cellular target to inhibit tumour growth or a marker of aggressive tumours in prostate cancer patients.

Breast cancer biomarker discordance between primary and sites of metastasis: A systematic review

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Background: Systemic treatment choices for breast cancer patients with recurrent disease are usually based on the ER/PR/Her2 biomarker status of the primary cancer. Biomarker discordance between the primary and metastatic sites is well recognised and could have important therapeutic implications. A systematic review was conducted to assess the extent of biomarker discordance between the primary cancer and metastasis, and whether is influenced by the site of metastasis. Methods: An electronic search of multiple literature databases implemented by an information scientist was conducted to identify studies reporting outcomes of ER/PR/Her2 receptor stability between primary site and recurrent disease. Seven reviewers independently screened the 5034 abstracts and full text articles, which were identified according to pre-defined selection criteria. The same reviewers performed data collection from all included studies. Studies that were identified reported on receptor conversion between primary sites of breast cancer and various sites of metastasis including lymph node, liver, brain, lung, skin, GI sites and bone marrow. Results: Preliminary results from 385 eligible studies consistently demonstrated discordance between the primary and metastatic sites. When discordance occurred, the general trend was for loss of hormone receptor. ER hormone status was more stable (discordance 10.2-32.5%) than PR (discordance 25.5-40.7%). HER2 was found to have lower rates of discordance (2.6-14.5%). In general, higher ER/PR discordance was found in bone (40-68%) and liver (0-54%) when compared to other sites brain (36%), lung (9-18%), skin (6-22%), GI (15-40%). In the prospective studies, biomarker discordance led to change in patient management in up to 20% of the patient population. Conclusions: Our results demonstrate that biomarker discordance between primary and distant metastases does occur in breast cancer, occurs more frequently with PR, and the extent of discordance is influenced by the site of metastasis. Further research is required to have a better explanation about the pathophysiology of the biomarker status change and its clinical implications.

Skeletal-related events (SRE) and bone-targeted agents for metastatic prostate cancer: Are we changing outcomes?

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Background: Bone-targeted agents (BTA) have been extensively studied in patients (pts) with prostate cancer (PC) and bone metastases (BM). Relatively little is known about the impact of BTAs on skeletal morbidity in the non-trial setting. We evaluated the impact BTAs on SRE and survival at a large Canadian cancer centre. Methods: Electronic heath records were reviewed for PC pts referred for further management from January 2008-June 2012. Demographic, clinical, and treatment data including: date of CRPC, occurrence of SRE, and BTA use were collected and analyzed. Results: A total of 141 pt charts were examined and were included in the analysis. Median age was 74 years (IQR 63-82), and 95% were stage IV at time of referral. Consequences of BMs included:101 pts had at least one SRE (72%), 58 (40%) pts had ≥1 SRE and 39% were hospitalised due to an SRE. Median overall survival from diagnosis of BM was 35.4 months (m) (IQR 16.1-65.9). Overall, 74 pts (52%) developed castration resistant PC (CRPC). In the CRPC group, the use of imaging to assess BM was highly variable, ranging from only once (12%) to every 1-2 m (4%), however the mode was every 3-5 m (43%). Sixty one percent (45/74) received a BTA, primarilyzoledronic acid (ZA). Despite having CRPC and BM, 39% never received a BTA, mainly because it was not offered (64%), or due to patient’s refusal (29%). Median time from diagnosis of CRPC to start of BTA was 1 month. Sixty-nine percent of pts had BTA discontinued, mainly due to progression of disease and pts deterioration. Osteonecrosis of the jaw occurred in 4% (2/45). In 39 pts (53%) the first SRE occurred prior to CRPC diagnosis, and 62 pts (84%) had at least 1 SRE after CRPC diagnosis. Forty seven percent (21/45) had a new SRE after starting BTA. Conclusions: BM have significant consequences for pts with PC irrespective of hormone sensitivity. Even for pts with CRPC the use of BTAs is highly variable. This reflects physician’s belief in the efficacy of BTAs, tailored by the expected benefits to each pt according to performance status and extent of disease. Interestingly in the CRPC group 53% have had an SRE prior to CRPC diagnosis. Strategies to optimise the care of pts with BM are clearly warranted.

Exploratory analysis of angiotensin converting enzyme (ACE) and aldosterone (Ald) serum levels as prognostic and predictive biomarkers on the NCIC CTG BR24 trial

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Background: Benefit from angiogenesis inhibitors (AI) has been linked to high blood pressure. One of the main determinants of blood pressure is the renin-angiotensin axis. We undertook an exploratory, retrospective analysis of ACE and Ald serum levels on specimens banked during the conduct of the BR24 study. The aim was to evaluate these markers for their prognostic significance and their predictive value regarding Cediranib (Ced) treatment. Methods: The NCIC CTG BR24 study randomized advanced non-small cell lung cancer patients (pts) to carboplatin and paclitaxel (CP) +/- Ced. ACE and Ald serum levels were retrospectively tested on baseline samples using commercial ELISA kits. A graphic method, differentiating treatment effect by the range of marker, was used to determine cutoff points (JCO 2010, 28: 5247). Exploratory analyses were performed to correlate biomarkers levels with pts characteristics and overall survival (OS). Association between categorical variables was assessed by Chi-square test or Fisher’s exact test; time to event correlation with biomarkers was tested using a Cox regression model. Potential confounding factors including medications were integrated into the statistical model. Results: Biomarker data was available in 226 of 296 randomized pts. The tested pts vs. all the randomized pts were more likely to have a lower performance status (PS, p=0.03), a normal LDH (p=0.05) and to be ever-smokers (p=0.015). The determined cutoffs were ACE: 115ng/ml and Ald: 250 pg/ml. High ACE was associated with a better PS (p=0.03). High ACE levels were prognostic for longer OS (adjusted HR 0.52 [95%C.I. 0.29-0.92], p=0.025). High ACE pts had no OS benefit (HR 1.27 [95% C.I. 0.78–2.08], p=0.34), while low ACE predicted OS benefit from the addition of Ced to CP (HR 0.64 [95%CI 0.42-0.97], p=0.03). Interaction p value=0.03; this remained significant after adjustment in multivariate analyses. Ald levels were neither prognostic nor predictive. Conclusions: This exploratory analysis suggests high ACE serum levels maybe prognostic for better OS, while low ACE may predict benefit from Ced when added to CP.

A systematic review of dosing frequency with bone-targeted agents for patients with bone metastases from breast cancer

Background

Bone-targeted agents are usually administered to breast cancer patients with bone metastases every 3–4 weeks. Less frequent (‘de-escalated’) treatment may provide similar benefits with improved safety and reduced cost.

Methods

To systematically review randomised trials comparing de-escalated treatment with bone-targeted agents (i.e. every 12–16 weeks) to standard treatment (i.e. every 3–4 weeks), a formal systematic review of the literature was performed. Two individuals independently screened citations and full text articles. Random effects meta-analyses of clinically important outcomes were planned provided homogeneous studies were identified.

Results

Five relevant studies (n=1287 patients) were identified. Sample size ranged from 38 to 425. Information on outcomes including occurrence of SREs, bone pain, urinary N-telopeptide concentrations, serum C-telopeptide concentrations, pain medication use and safety outcomes was not consistently available. Two trials were non-inferiority studies, two dose-response evaluations and one was a pilot study. Bone-targeted agents use varied between studies, as did duration of prior therapy. Patient populations were considered heterogeneous in several ways, and thus no meta-analyses were performed. Observations from the included studies suggest there is potential that 3 month de-escalated treatment may provide similar benefits compared to 3–4 weekly treatment and that lower doses of zoledronic acid and denosumab might be equally effective.

Conclusions

Studies comparing standard and de-escalated treatment with bone-targeted agents in breast cancer are rare. The benefits of standard treatment compared to de-escalated therapy on important clinical outcomes remain unclear. Future pragmatic studies must be conducted to determine the merits of this approach.

Oral care and the use of bone-targeted agents in patients with metastatic cancers: A practical guide for dental surgeons and oncologists

BACKGROUND

Bone-targeted agents such as bisphosphonates and the RANKL antibody have revolutionised the care of patients with bone metastases. There has, however been increasing concern about the oral health of these patients and in particular osteonecrosis of the jaw (ONJ), especially with the increasing use of these agents at higher potencies for greater periods of time.

METHODS

A review of the published data in PubMed and meeting abstracts was performed to examine incidence, risk factors, pathogenesis, clinical course and management of osteonecrosis of the jaw with focus on cancer patients treated with bone-targeted agents (BTA) for bone metastases. This manuscript takes the most frequent and pertinent questions raised by oncologists, dentists and oral and maxillofacial surgeons and tries to give a pragmatic overview of the literature.

RESULTS

The incidence of ONJ varies depending on types of bone-targeted agents, duration of treatment and additional risk factors. The causes and pathogenesis of ONJ is not fully elucidated, however bone-targeted therapy induced impaired bone remodelling, microtrauma secondary to jaw activity, and oral bacterial infection seem to be important factors. Since the treatment options for ONJ are limited and not well established, preventive strategies have to be included in patients management.

CONCLUSIONS

Many unanswered questions remain about the optimal oral care of patients receiving bone-targeted agents. Prospective data collection will remedy this and help to provide practical guidelines for the management and treatment of those patients that require dental intervention.

Incidence and consequences of bone metastases in lung cancer patients

Background

Bone metastases (BM) are common in NSCLC patients. Despite some potential positive effects of bone-targeted therapies, their use in NSCLC is infrequent, which may relate to the overall poor prognosis of advanced lung cancer. We reviewed the literature to evaluate the incidence, consequences and use of bone-targeting agents in lung cancer patients with BM in both the trial and non-trial clinical setting.

Methods

Published prospective and retrospective papers investigating lung cancer and BM, in trial and non-trial settings, were identified and are discussed in this review.

Results

BM are common in patients with advanced lung cancer and often present symptomatically with pain and skeletal related events (SREs). Patients with high bone turnover marker levels, multiple BM, and history of pathological fractures have shorter overall survival. In randomized studies bone-targeted therapies reduced the risk of SREs and prolonged the time to first SRE. The use of bone-targeted agents may also be associated with a survival benefit.

Conclusion

BM are a common problem in advanced lung cancer. While the benefits of bone-targeted therapies have been demonstrated, their use is limited in non-trial populations. If better predictive markers of individual risk were available this might increase the appropriate use of bone-targeted agents.

Abstract P2-05-13: Correlation of conventional versus experimental biomarkers of bone turnover and metastasis behaviour with skeletal related events – A biomarker analysis in conjunction with the TRIUMPH study

BACKGROUND: Despite considerable variability in patient (pt) risk of skeletal related events (SREs) from bone metastases (BM), all pts are treated using a one size fits all approach, namely the same dose and dosing schedule (q3-4 wk) of IV bisphosphonate (BP). Identification of novel markers of individual SRE risk are thus required to better tailor treatment. TRIUMPH is an ongoing clinical trial evaluating q12 wk IV BP therapy for 1 year, following &gt;3 months of standard q3-4 wk BP, in women with low risk bone metastases [defined by the bone resorption marker C-telopeptide (CTx) levels &lt;600 ng/L]. This sub-study evaluated the utility of novel biomarkers in better predicting SRE risk in this low-risk cohort.

METHODS: Seventy-one pts enrolled in TRIUMPH. Pt serum at baseline (69), 6 (67) and 12 (59) wks post-entry were analyzed for CTx and bone-specific alkaline phosphatase (BSAP) as per study protocol. Urine N-telopeptide (NTx) levels and serum levels of transforming growth factor-β (TGF-β), activinA, procollagen type I amino-terminal propeptide (P1NP), and bone sialoprotein (BSP) levels were also assessed by ELISA (for n=63, 63 and 57 patients at baseline, wk 6 and wk 12 respectively). Biomarker levels were correlated with pt parameters including; time to development of BM, previous SREs, and SREs post-study entry using linear regression analysis. Changes in levels of biomarkers from baseline to 6 or 12 weeks were used to calculate odds ratios of coming off study as per protocol (due to either CTx&gt;600 ng/ml or SRE) or of SRE alone using logistic regression analysis.

RESULTS: Although baseline CTx and NTx were elevated in pts who went on to develop SREs, this did not reach statistical significance. Baseline activinA trended towards total number of prior SREs (p = 0.07). Baseline TGF-β correlated with duration of BM (p = 0.004). Change in activinA (baseline to week 6) was the only biomarker that trended to predict coming off study early (p = 0.043). Results of other baseline biomarkers and changes in biomarkers from baseline to wk 12 will also be presented.

CONCLUSIONS: This study further questions the role of CTx and NTx for driving treatment decisions around de-intensification of BP therapy (Coleman et al. J Clin Oncol 2012, suppl; abstr 511), and highlights the need for novel markers of SRE risk. Baseline levels of activinA was associated with the incidence of SREs in patients with BM and changes in levels from baseline to 6 weeks correlated with coming off study early. These findings warrant future studies in breast cancer pts assessing activinA as a predictor of SRE risk associated with breast cancer bone metastases.

This study was supported by grants from the Ontario Institute for Cancer Research with funding from the Government of Ontario, and from the Ontario Chapter of the Canadian Breast Cancer Foundation.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-05-13.

Abstract P2-05-12: Effects of de-escalated bisphosphonate therapy on bone turnover or metastasis markers and their correlation with risk of skeletal related events – A biomarker analysis in conjunction with the REFORM study

Background: Despite variability in an individual's risk of skeletal related events (SREs) from bone metastases (BM), all patients are treated using a similar dose and schedule (q3-4 wk) of IV bisphosphonate (BP). The REFORM trial (Amir et al., Am J Clin Oncol, in press) was a pilot randomised study evaluating the efficacy of de-escalated (q12 wk) versus standard (q3-4 wk) pamidronate in maintaining C-telopeptide (CTx) levels in the low risk range (&lt;600ng/L) in patients with BM from breast cancer. Here we report a biomarker substudy, where additional biomarkers of bone turnover and BM behaviour were measured and correlated with SRE risk.

Methods: Eligible patients with BM, who had received ≥ 3 months of q3-4 wk IV BP and no systemic treatment change within 4 wks of study entry were enrolled. Serum & urine obtained at baseline and at 12 wks were assessed for urinary N-telopeptide (uNTx), serum procollagen type I amino-terminal propeptide (P1NP), transforming growth factor (TGF)-β, activinA and bone sialoprotein (BSP) by ELISA. Levels were correlated with number of SREs using linear regression analysis. Changes in biomarkers from baseline to 12 wks were used to calculate odds ratios for coming off study (due to either elevated CTx or SRE) or having an SRE alone using logistic regression analysis.

Results: REFORM randomized 19 patients to each treatment arm, and found that the SRE rate at 1 year in both arms was the same (n = 2). Although the mean level of the standard bone turnover marker CTx decreased slightly from baseline to wk 12 in the q3-4 wk group (240±50ng/L to 206±46ng/L), and slightly increased in the q12 wk treated group (263±65ng/L to 313±71ng/L), these changes were not statistically significant (p = 0.8). Mean activinA levels were slightly increased in both treatment arms from baseline to wk 12 (730±93pg/ml to 875±148pg/ml in q3-4 wk group vs 445±35pg/ml to 582±61pg/ml in q12 wk group) but did not quite reach statistical significance (p = 0.1). Levels of TGF-β from baseline to 12 wks in both groups was similar (22±1.6ng/ml to 22±2.3ng/ml for q3-4 wk vs 23±2.2ng/ml to 24±2.4ng/ml for q12 wk group, p = 0.8). Although the number of SREs was small, mean CTx levels at wk 12 were statistically different between patients who experienced SREs vs those that did not (615±72ng/L, n=4 vs 190±26ng/L, n=19, p &lt; 0.0001). Although it did not reach statistical significance, mean activinA levels at wk 12 were also higher in patients who had SREs than those that did not (1069±358pg/ml, n=3 vs 681±83pg/ml, n=18, p = 0.12). Results of NTx, BSP and P1NP and correlations with more mature clinical data will also be presented.

Conclusions: In patients with BM from breast cancer with low levels of bone resorption markers, CTx predicted and activinA trended to predict SRE risk. However the non-significant trends in increasing CTx in de-escalated BP treatment, together with the observation that activinA levels are similar regardless of dosing regimen, suggest that analysis of conventional and experimental biomarkers of SRE risk requires further examination in other larger patient cohorts comparing de-escalated therapy.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-05-12.

Adjuvant bisphosphonate treatment for breast cancer: Where are we heading and can the pre-clinical literature help us get there?

Bisphosphonates have demonstrated anti-tumour activity in preclinical studies of bone metastatic disease, thus it was natural to transition these agents into the adjuvant cancer therapy setting. Surprisingly, the results of adjuvant breast cancer trials have shown either modest to no benefit or even harm. We sought to explore whether the preclinical results supporting bisphosphonate use provided clues to help explain the current clinical data. Interestingly, the majority of preclinical data suggested that bisphosphonate treatment was more efficacious when administered after the establishment of osseous metastases. This is similar to the findings of one clinical study whereby patients with biopsy evidence of osseous micrometastases derive greater survival benefit from bisphosphonate treatment. Another clinical study found bisphosphonates were associated with increased incidence of visceral metastases, similar to what has been previously published in preclinical models using “preventative” dosing strategies. While the current clinical data suggest bisphosphonates may be more efficacious in post-menopausal or oestrogen depleted patients, or those with hormone receptor positive tumours, to date no appropriately designed preclinical studies have evaluated these effects. Furthermore, putative mechanisms that regulate response to bisphosphonates in other tumour types remain to be evaluated in breast cancer. Despite the initial optimism regarding adjuvant bisphosphonate therapy, the conflicting clinical results from large trials suggest that we should return to the bench to further investigate factors that may influence response to bisphosphonate treatment or identify appropriate characteristics that would indicate the sub-groups of patients most likely to benefit from bisphosphonate treatment.

Serum activinA and TGF-β as biomarkers of breast cancer bone metastasis behavior

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Background: Bisphosphonates (BP) are prescribed to pts with metastatic bone disease every 3-4 weeks regardless of individual risk for skeletal related events (SREs). In an era of personalized medicine this “one size fits all” approach is not appropriate and novel markers of SRE risk are required. TRIUMPH is an ongoing clinical trial evaluating 12 weekly IV BP therapy for 1 year in women with low risk bone metastases from breast cancer (BC) as defined by the bone resorption marker C-telopeptide (CTx,) levels <600 ng/L. This sub-study evaluated the utility of novel biomarkers in better predicting the risk of developing SREs. Methods: Serum obtained from pts at baseline and 6 weeks post-entry were analyzed for tumor growth factor-β (TGF-β) and activinA levels by ELISA (sensitivity ~15-30 pg/ml). Levels were correlated with pt parameters including time to development of bone metastasis, and number of previous SREs using linear regression analysis. Changes in levels of biomarkers from baseline to 6 weeks were used to calculate odds ratios using logistic regression analysis. Results: Baseline activinA correlated with baseline CTx and bone specific alkaline phosphatase (p=0.004 and p<0.0001 respectively). Baseline activinA also correlated with weight (p=0.02), BMI (p=0.007) and trended towards total number of prior SREs (p=0.07). Baseline TGF-β correlated with pt age (p=0.02), weight (0.006), BMI (p=0.0005) and duration of metastatic bone disease (p=0.004), but did not correlate with any other biomarker. Change in activinA (baseline to week 6) was the only biomarker that trended to predict coming off study early (p=0.053) as per protocol (i.e. CTx>600 ng/ml, SREs or pt/physician choice). Conclusions: Baseline levels of activinA trended to predict incidence of SREs in patients with bone metastases, and changes in levels from baseline to 6 weeks trended to predict coming off study early. These findings warrant future studies in BC pts assessing activinA as a predictor of risk associated with breast cancer bone metastases. This study was conducted with the support of the Ontario Institute for Cancer Research through funding provided by the Government of Ontario, and with funding from the Ontario Chapter of the Canadian Breast Cancer Foundation.

Distinct profile of vascular progenitor attachment to extracellular matrix proteins in cancer patients

BACKGROUND

Vascular progenitor cells (VPCs) facilitate angiogenesis and initiate vascular repair by homing in on sites of damage and adhering to extracellular matrix (ECM) proteins. VPCs also contribute to tumor angiogenesis and induce angiogenic switching in sites of metastatic cancer. In this study, the binding of attaching cells in VPC clusters that form in vitro on specific ECM proteins was investigated.

METHODS

VPC cluster assays were performed in vitro on ECM proteins enriched in cancer cells and in remodelling tissue. Profiles of VPC clusters from patients with cancer were compared to healthy controls. The role of VEGF and integrin-specific binding of angiogenic attaching cells was addressed.

RESULTS

VPC clusters from cancer patients were markedly increased on fibronectin relative to other ECM proteins tested, in contrast to VPC clusters from control subjects, which formed preferentially on laminin. Specific integrin-mediated binding of attaching cells in VPC clusters was matrix protein-dependent. Furthermore, cancer patients had elevated plasma VEGF levels compared to healthy controls and VEGF facilitated preferential VPC cluster formation on fibronectin. Incubating cells from healthy controls with VEGF induced a switch from the 'healthy' VPC binding profile to the profile observed in cancer patients with a marked increase in VPC cluster formation on fibronectin.

CONCLUSION

The ECM proteins laminin and fibronectin support VPC cluster formation via specific integrins on attaching cells and can facilitate patterns of VPC cluster formation that are distinct in cancer patients. Larger studies, however, are needed to gain insight on how tumor angiogenesis may differ from normal repair processes.

β1 integrin: an emerging player in the modulation of tumorigenesis and response to therapy

Historically, a hallmark of tumorigenesis was the ability to grow in an anchorage-independent manner. Hence, tumors were thought to proliferate and survive independently of integrin attachment to the substratum. However, recent data suggest that integrins regulate not only tumor cell proliferation, survival and migration, but may also influence their response to anti-cancer agents. Interestingly, these influences are largely masked by growth of tumor cells in the standard, yet artificial, environment of 2D cell culture, but are readily apparent under 3D in vitro culture conditions and in tumor growth in vivo. We, and others, have recently demonstrated that the β1 integrin subunit controls the growth and invasion of prostate tumor cells in 3D culture conditions. Recently, the importance of integrins has also been demonstrated using tissue specific conditional knockout strategies in transgenic mouse tumor models, where they control primary tumor growth and dictate the site of metastatic spread. Furthermore, integrin-extracellular matrix interactions may modulate the response of tumors to standard chemotherapy agents or radiation. Taken together, these results highlight the important role of integrins in regulating tumor growth and metastasis; however, point out that the evaluation of their contribution to these processes requires appropriate contextual modeling.

RhoB controls endothelial cell morphogenesis in part via negative regulation of RhoA

Recent studies have suggested a role for the small GTPase RhoB in the control of processes required for angiogenesis. However, the mechanisms whereby RhoB exerts control over these processes are not well understood. Given the role of vascular endothelial growth factor (VEGF) in pathological angiogenesis, we were interested in examining whether RhoB contributed to VEGF-induced angiogenic processes. To assess this, RhoB was specifically depleted in human umbilical vein endothelial cells (HUVEC), using siRNA-targeted strategies. The effects of RhoB depletion on VEGF-induced angiogenic activities were assessed using a variety of standard in vitro angiogenesis assays to assess endothelial cell viability, migration and capillary morphogenesis. Effects of RhoB depletion on signaling from other Rho family member proteins was also assessed using specific activity assays for RhoA and RhoC. We observed that although RhoB appeared dispensable for HUVEC viability, RhoB was required for endothelial cell migration, sprouting, and capillary morphogenesis. We also observed that siRNA-mediated depletion of RhoB in HUVEC resulted in increased RhoA activation in response to VEGF stimulation. This increased RhoA activation contributed to the cellular morphogenesis defects observed in RhoB-depleted cells, as inhibition of RhoA activity using C3 transferase, or inhibition of the activity of the downstream RhoA effectors Rho-dependent kinases I and II (ROCK I and II) led to a partial restoration of capillary morphogenesis in the absence of RhoB. Thus our data indicate that RhoB plays a significant role in VEGF-induced endothelial cell morphogenesis in part by negatively regulating the activity of RhoA and the RhoA/ROCK pathway.

β1 integrin is required for anchorage-independent growth and invasion of tumor cells in a context dependent manner

Recent studies suggest that extracellular matrix (ECM) components within the tumor microenvironment can influence malignant progression, thus we investigated the influence of the ECM binding receptor β1 integrin, on the hallmark properties of tumorigenesis. Small interfering (si) or short hairpin (sh) RNA approaches were used to deplete β1 integrin in cancer cell lines. β1 integrin-depleted cells were then assessed for their growth and invasive capabilities using 2-dimensional (2D) or 3D culture conditions. Depletion of β1 integrin expression did not impact cell growth in 2D assay systems; however, β1 integrin and its ligand fibronectin were required for growth in 3D. β1 integrin-depleted cells also had reduced invasive capabilities, in part due to increased tissue inhibitor of metalloprotease (TIMP)-2 expression in conjunction with down-regulation of matrix metalloprotease (MMP)-9 levels in β1 integrin-depleted cells. Our results suggest that despite no apparent effect on 2D cell growth, fibronectin-β1 integrin signaling is a critical mediator of the 3D growth and invasive properties of tumor cells. These observations highlight the importance of investigating the role of adhesion molecules in the appropriate context and furthermore identify β1 integrin as a possible therapeutic target to inhibit the aggressive growth and invasion of tumor cells.

Focal adhesion kinase inhibitors are potent anti-angiogenic agents

Focal adhesion kinase (FAK), a cytoplasmic tyrosine kinase and scaffold protein localized to focal adhesions, is uniquely positioned at the convergence point of integrin and receptor tyrosine kinase signal transduction pathways. FAK is overexpressed in many tumor cells, hence various inhibitors targeting its activity have been tested for anti-tumor activity. However, the direct effects of these pharmacologic agents on the endothelial cells of the vasculature have not been examined. Using primary human umbilical vein endothelial cells (HUVEC), we characterized the effects of two FAK inhibitors, PF-573,228 and FAK Inhibitor 14 on essential processes for angiogenesis, such as migration, proliferation, viability and endothelial cell tube formation. We observed that treatment with either FAK Inhibitor 14 or PF-573,228 resulted in reduced HUVEC viability, migration and tube formation in response to vascular endothelial growth factor (VEGF). Furthermore, we found that PF-573,228 had the added ability to induce apoptosis of endothelial cells within 36 h post-drug administration even in the continued presence of VEGF stimulation. FAK inhibitors also resulted in modification of the actin cytoskeleton within HUVEC, with observed increased stress fiber formation in the presence of drug. Given that endothelial cells were sensitive to FAK inhibitors at concentrations well below those reported to inhibit tumor cell migration, we confirmed their ability to inhibit endothelial-derived FAK autophosphorylation and FAK-mediated phosphorylation of recombinant paxillin at these doses. Taken together, our data indicate that small molecule inhibitors of FAK are potent anti-angiogenic agents and suggest their utility in combinatorial therapeutic approaches targeting tumor angiogenesis.

Plasma transforming growth factor alpha and amphiregulin protein levels in NCIC Clinical Trials Group BR.21

PURPOSE

To evaluate the prognostic and predictive significance of plasma levels of the epidermal growth factor receptor (EGFR) ligands, transforming growth factor α (TGF-α) and amphiregulin, in patients with non-small-cell lung cancer (NSCLC) enrolled in NCIC Clinical Trials Group BR.21 comparing erlotinib with placebo.

PATIENTS AND METHODS

TGF-α and amphiregulin were assessed retrospectively by enzyme-linked immunosorbent assay from available prospectively collected baseline plasma samples in 565 of 731 BR.21 patients. Cutoff points were determined for both amphiregulin (low, <10 pg/mL; high, ≥10 pg/mL) and TGF-α (low, ≤12 pg/mL; high, >12 pg/mL) using a graphical method. Cox regression models were used to correlate biomarker data and baseline characteristics with outcomes including overall (OS) and progression-free survival (PFS).

RESULTS

High TGF-α and amphiregulin were associated with poorer performance status (P=.06 and P<.0001, respectively) and no prior platinum therapy (P=.06 and P=.02, respectively). High amphiregulin was also associated with anemia (P=.001), increased lactate dehydrogenase (P=.03), ever-smokers (P=.04), and non-Asian ethnicity (P=.001). Patients on the placebo arm with high amphiregulin had poorer OS than patients with low amphiregulin (hazard ratio [HR]=1.88; 95% CI, 1.34 to 2.64; P=.0002), which remained significant in multivariate analysis. Amphiregulin levels did not predict for benefit from erlotinib (interaction P=.87). Conversely, TGF-α levels did not have prognostic significance, but high TGF-α predicted lack of benefit from erlotinib compared with low TGF-α (TGF-α low, OS HR=0.66; 95% CI, 0.54 to 0.81; P<.0001; high, OS HR=1.32; 95% CI, 0.73 to 2.39; P=.36; interaction P=.04).

CONCLUSION

High baseline amphiregulin is a poor prognostic factor, whereas high baseline TGF-α predicts for lack of benefit from erlotinib in advanced NSCLC.

Lovastatin inhibits VEGFR and AKT activation: synergistic cytotoxicity in combination with VEGFR inhibitors

Background

In a recent study, we demonstrated the ability of lovastatin, a potent inhibitor of mevalonate synthesis, to inhibit the function of the epidermal growth factor receptor (EGFR). Lovastatin attenuated ligand-induced receptor activation and downstream signaling through the PI3K/AKT pathway. Combining lovastatin with gefitinib, a potent EGFR inhibitor, induced synergistic cytotoxicity in a variety of tumor derived cell lines. The vascular endothelial growth factor receptor (VEGFR) and EGFR share similar activation, internalization and downstream signaling characteristics.

Methodology/Principal Findings

The VEGFRs, particularly VEGFR-2 (KDR, Flt-1), play important roles in regulating tumor angiogenesis by promoting endothelial cell proliferation, survival and migration. Certain tumors, such as malignant mesothelioma (MM), also express both the VEGF ligand and VEGFRs that act in an autocrine loop to directly stimulate tumor cell growth and survival. In this study, we have shown that lovastatin inhibits ligand-induced VEGFR-2 activation through inhibition of receptor internalization and also inhibits VEGF activation of AKT in human umbilical vein endothelial cells (HUVEC) and H28 MM cells employing immunofluorescence and Western blotting. Combinations of lovastatin and a VEGFR-2 inhibitor showed more robust AKT inhibition than either agent alone in the H28 MM cell line. Furthermore, combining 5 µM lovastatin treatment, a therapeutically relevant dose, with two different VEGFR-2 inhibitors in HUVEC and the H28 and H2052 mesothelioma derived cell lines demonstrated synergistic cytotoxicity as demonstrated by MTT cell viability and flow cytometric analyses.

Conclusions/Significance

These results highlight a novel mechanism by which lovastatin can regulate VEGFR-2 function and a potential therapeutic approach for MM through combining statins with VEGFR-2 inhibitors.

Precipitation and selective extraction of human serum endogenous peptides with analysis by quadrupole time-of-flight mass spectrometry reveals posttranslational modifications and low-abundance peptides

The endogenous peptides of human serum may have regulatory functions, have been associated with physiological states, and their modifications may reveal some mechanisms of disease. In order to correlate levels of specific peptides with disease alongside internal standards, the polypeptides must first be reliably extracted and identified. Endogenous blood peptides can be effectively enriched by precipitation of the serum with organic solvents followed by selective extraction of peptides using aqueous solutions modified with organic solvents. Polypeptides on filter paper were assayed with Coomasie brilliant blue binding. The polypeptides were resolved by detergent tricine polyacrylamide electrophoresis and visualized by diamine silver staining. Peptides in the extracts were collected by C18 and analyzed by matrix-assisted laser desorption/ionization and liquid chromatography-electrospray ionization-tandem mass spectrometry (MS/MS) quadrupole time-of-flight MS/MS. Peptides were resolved as multiple isotopic peaks in MS mode with mass deviation of 0.1 Da or less and similar accuracy for fragments. The sensitivity of MS and MS/MS analysis was estimated to be in the picomolar range or less. The peptide composition of the extracts was dependent on solvent formulation. Multiple peptides from apolipoproteins, complement proteins, coagulation factors, and many others were identified by X!Tandem with high mass accuracy of peptide ions and fragments from collision-induced dissociation. Many previously unreported posttranslational modifications of peptides including phosphorylations, oxidations, glycosylations, and others were detected with high mass accuracy and may be of clinical importance. About 4,630 redundant peptides were identified with 99% confidence separately, and together some 1,251 distinct proteins were identified with 99% confidence or greater using the Paragon algorithm.

Comparison of a reference region model with direct measurement of an AIF in the analysis of DCE-MRI data

Models have been developed for analyzing dynamic contrast-enhanced (DCE)-MRI data that do not require measurements of the arterial input function (AIF). In this study, experimental results obtained from a reference region (RR) analysis are compared with results of an AIF analysis in the same set of five animals (four imaged twice, yielding nine data sets), returning estimates of the volume transfer constant (Ktrans) and the extravascular extracellular volume fraction (ve). Student's t-test values for comparisons of Ktrans and ve between the two models were 0.14 (P=0.88) and 0.85 (P>0.4), respectively (where the high P-values indicate no significant difference between values derived from the two models). Linear regression analysis indicated there was a correlation between Ktrans extracted by the two methods: r2=0.80, P=0.001 (where the low P-value indicates a significant linear correlation). For ve there was no such correlation (r2=0.02). The mean (absolute) percent difference between the models was 22.0% for Ktrans and 28.1% for ve. However, the RR parameter values were much less precise than the AIF method. The mean SDs for Ktrans and ve for the RR analysis were 0.024 min-1 and 0.06, respectively, vs. 0.002 min-1 and 0.03 for AIF analysis.

Supplementation with l-carnitine does not reduce the efficacy of epirubicin treatment in breast cancer cells

One of the cornerstones of therapy for invasive breast cancer includes the use of anthracyclines. Epirubicin, a stereoisomer of doxorubicin, is one of the commonly used anthracyclines. Anthracyclines while effective therapy for breast cancer, have their own unique toxicities, such as cardiomyopathy. l-Carnitine, a quarternary ammonium compound synthesized from methionine and lysine, is required for oxidative metabolism in mitochondria. Cardiac function is closely linked with oxidative metabolism whereby l-carnitine is an essential cofactor. A hypothesis is being investigated to determine if supplementation with carnitine in breast cancer patients treated with epirubicin will reduce the development of cardiac toxicity. We determined whether addition of l-carnitine altered the tumor cytotoxic effects of epirubicin using a number of in vitro cell viability assays in different breast cancer cell lines including BT549, MDA-MB-435, NCI-ADR-RES, MCF7 and T47D. Additionally we investigated the ability of cells to respond to l-carnitine following analysis of the expression of carnitine metabolic enzymes by RT-PCR. We determined that supplementation with l-carnitine had no effect on the ability of epirubicin to kill a variety of breast cancer cell lines. Additionally, no differences in the induction of apoptosis by epirubicin were observed. Furthermore, all cell lines examined expressed proteins required for carnitine uptake and use. Our data suggest that supplementation with l-carnitine does not impair the ability of epirubicin to kill breast cancer cells. These results suggest that supplementation with l-carnitine in patients undergoing epirubicin treatment could be safely used to reduce associated cardiotoxicities without fear that the efficacy of chemotherapy is jeopardized.

Perk-dependent translational regulation promotes tumor cell adaptation and angiogenesis in response to hypoxic stress

It has been well established that the tumor microenvironment can promote tumor cell adaptation and survival. However, the mechanisms that influence malignant progression have not been clearly elucidated. We have previously demonstrated that cells cultured under hypoxic/anoxic conditions and transformed cells in hypoxic areas of tumors activate a translational control program known as the integrated stress response (ISR). Here, we show that tumors derived from K-Ras-transformed Perk(-/-) mouse embryonic fibroblasts (MEFs) are smaller and exhibit less angiogenesis than tumors with an intact ISR. Furthermore, Perk promotes a tumor microenvironment that favors the formation of functional microvessels. These observations were corroborated by a microarray analysis of polysome-bound RNA in aerobic and hypoxic Perk(+/+) and Perk(-/-) MEFs. This analysis revealed that a subset of proangiogenic transcripts is preferentially translated in a Perk-dependent manner; these transcripts include VCIP, an adhesion molecule that promotes cellular adhesion, integrin binding, and capillary morphogenesis. Taken with the concomitant Perk-dependent translational induction of additional proangiogenic genes identified by our microarray analysis, this study suggests that Perk plays a role in tumor cell adaptation to hypoxic stress by regulating the translation of angiogenic factors necessary for the development of functional microvessels and further supports the contention that the Perk pathway could be an attractive target for novel antitumor modalities.

Modulation of response to tumor therapies by the extracellular matrix

The composition of the extracellular matrix in tumors is vastly different from that found in the normal tissue counterparts. As the extracellular matrix can signal to cells via integrin binding and activation, which is known to modulate cell proliferation, survival and migration, it may influence the response of both tumor and endothelial cells to anticancer therapies. Certain tumor-associated extracellular matrix proteins have been shown to confer resistance to chemotherapeutic drugs, radiation and anti-angiogenic factors. The current literature regarding this phenomenon and the potential therapeutic modalities to overcome extracellular matrix-induced resistance will be discussed.

The inhibitory effects of endostatin on endothelial cells are modulated by extracellular matrix

We investigated the ability of extracellular matrix (ECM) proteins to modulate the response of endothelial cells to both promoters and inhibitors of angiogenesis. Using human dermal microvascular endothelial cells (HDMEC), we found that cells demonstrated different adhesive properties and proliferative responses to the growth factor VEGF depending upon which ECM protein with which they were in contact, with fibronectin having the most impact on VEGF-induced HDMEC proliferation and survival. More importantly, we observed that ECM could modulate the ability of the angiogenic inhibitor endostatin to prevent endothelial cell proliferation, survival and migration. We observed that growth on vitronectin or fibronectin impaired the ability of endostatin to inhibit VEGF-induced HDMEC proliferation to the greatest extent as determined by BrdU incorporation. We found that, following growth on collagen I or collagen IV, endostatin only inhibited VEGF-induced HDMEC proliferation at the highest dose tested (2500 ng/ml). In a similar manner, we observed that growth on ECM proteins modulated the ability of endostatin to induce endothelial cell apoptosis, with growth on collagen I, fibronectin and collagen IV impairing endostatin-induced apoptosis. Interestingly, endostatin inhibited VEGF-induced HDMEC migration following culture on collagen I, collagen IV and laminin, while migration was not inhibited by endostatin following HDMEC culture on other matrices including vitronectin, fibronectin and tenascin-C. These results suggest that different matrix proteins may affect different mechanisms of endostatin inhibition of angiogenesis. Taken together, our results suggest that the ECM may have a profound impact on the ability of angiostatic molecules such as endostatin to inhibit angiogenesis and thus may have impact on the clinical efficacy of such inhibitors.