BAD-mediated apoptotic pathway is associated with human cancer development

The malignant transformation of normal cells is caused in part by aberrant gene expression disrupting the regulation of cell proliferation, apoptosis, senescence and DNA repair. Evidence suggests that the Bcl-2 antagonist of cell death (BAD)-mediated apoptotic pathway influences cancer chemoresistance. In the present study, we explored the role of the BAD-mediated apoptotic pathway in the development and progression of cancer. Using principal component analysis to derive a numeric score representing pathway expression, we evaluated clinico-genomic datasets (n=427) from corresponding normal, pre-invasive and invasive cancers of different types, such as ovarian, endometrial, breast and colon cancers in order to determine the associations between the BAD-mediated apoptotic pathway and cancer development. Immunofluorescence was used to compare the expression levels of phosphorylated BAD [pBAD (serine-112, -136 and -155)] in immortalized normal and invasive ovarian, colon and breast cancer cells. The expression of the BAD-mediated apoptotic pathway phosphatase, PP2C, was evaluated by RT-qPCR in the normal and ovarian cancer tissue samples. The growth-promoting effects of pBAD protein levels in the immortalized normal and cancer cells were assessed using siRNA depletion experiments with MTS assays. The expression of the BAD-mediated apoptotic pathway was associated with the development and/or progression of ovarian (n=106, p<0.001), breast (n=185, p<0.0008; n=61, p=0.04), colon (n=22, p<0.001) and endometrial (n=33, p<0.001) cancers, as well as with ovarian endometriosis (n=20, p<0.001). Higher pBAD protein levels were observed in the cancer cells compared to the immortalized normal cells, whereas PP2C gene expression was lower in the cancer compared to the ovarian tumor tissue samples (n=76, p<0.001). The increased pBAD protein levels after the depletion of PP2C conferred a growth advantage to the immortalized normal and cancer cells. The BAD-mediated apoptotic pathway is thus associated with the development of human cancers likely influenced by the protein levels of pBAD.

A novel c-Met inhibitor, MK8033, synergizes with carboplatin plus paclitaxel to inhibit ovarian cancer cell growth

Elevated serum levels of hepatocyte growth factor (HGF) and high tumor expression of c-Met are both indicators of poor overall survival from ovarian cancer (OVCA). In the present study, we evaluated the role of the HGF signaling pathway in OVCA cell line chemoresistance and OVCA patient overall survival as well as the influence of HGF/c-Met signaling inhibition on the sensitivity of OVCA cells to combinational carboplatin plus paclitaxel therapy. The prevalence of the HGF receptor, c-Met, was determined by immunohistochemistry in primary OVCA samples (n=79) and OVCA cell lines (n=41). The influence of the c-Met-specific inhibitor MK8033 on OVCA cell sensitivity to combinations of carboplatin plus paclitaxel was examined in a subset of OVCA cells (n=8) by CellTiter-Blue cell viability assays. Correlation tests were used to identify genes associated with response to MK8033 and carboplatin plus paclitaxel. Identified genes were evaluated for influence on overall survival from OVCA using principal component analysis (PCA) modeling in an independent clinical OVCA dataset (n=218). Immunohistochemistry analysis indicated that 83% of OVCA cells and 92% of primary OVCA expressed the HGF receptor, c-Met. MK8033 exhibited significant anti-proliferative effects against a panel of human OVCA cell lines. Combination index values determined by the Chou-Talalay isobologram equation indicated synergistic activity in combinations of MK8033 and carboplatin plus paclitaxel. Pearson's correlation identified a 47-gene signature to be associated with MK8033-carboplatin plus paclitaxel response. PCA modeling indicated an association of this 47-gene response signature with overall survival from OVCA (P=0.013). These data indicate that HGF/c-Met pathway signaling may influence OVCA chemosensitivity and overall patient survival. Furthermore, HGF/c-Met inhibition by MK8033 represents a promising new therapeutic avenue to increase OVCA sensitivity to carboplatin plus paclitaxel.

In vitro analysis of ovarian cancer response to cisplatin, carboplatin, and paclitaxel identifies common pathways that are also associated with overall patient survival

Background:

Carboplatin and cisplatin, alone or in combination with paclitaxel, have similar efficacies against ovarian cancer (OVCA) yet exhibit different toxicity profiles. We characterised the common and unique cellular pathways that underlie OVCA response to these drugs and analyse whether they have a role in OVCA survival.

Methods:

Ovarian cancer cell lines (n=36) were treated with carboplatin, cisplatin, paclitaxel, or carboplatin–paclitaxel (CPTX). For each cell line, IC₅₀ levels were quantified and pre-treatment gene expression analyses were performed. Genes demonstrating expression/IC₅₀ correlations (measured by Pearson; P<0.01) were subjected to biological pathway analysis. An independent OVCA clinico-genomic data set (n=142) was evaluated for clinical features associated with represented pathways.

Results:

Cell line sensitivity to carboplatin, cisplatin, paclitaxel, and CPTX was associated with the expression of 77, 68, 64, and 25 biological pathways (P<0.01), respectively. We found three common pathways when drug combinations were compared. Expression of one pathway (‘Transcription/CREB pathway’) was associated with OVCA overall survival.

Conclusion:

The identification of the Transcription/CREB pathway (associated with OVCA cell line platinum sensitivity and overall survival) could improve patient stratification for treatment with current therapies and the rational selection of future OVCA therapy agents targeted to these pathways.

The O-glycan pathway is associated with in vitro sensitivity to gemcitabine and overall survival from ovarian cancer

Ovarian cancer (OVCA) is the most lethal gynecological malignancy. The high mortality rate associated with this disease is due in large part to the development of resistance to chemotherapy; however, the biological basis of this remains unclear. Gemcitabine is frequently used for the treatment of patients with platinum-resistant OVCA. We report molecular signaling pathways associated with OVCA response to gemcitabine. Forty-one OVCA cell lines were subjected to gene expression analysis; in parallel, IC50 values for gemcitabine were quantified using CellTiter-Blue viability assays. Pearson's correlation coefficients were calculated for gene expression and gemcitabine IC50 values. The genes associated with gemcitabine sensitivity were subjected to pathway analysis. For the identified pathways, principal component analysis was used to derive pathway signatures and corresponding scores, which represent overall measures of pathway expression. Expression levels of the identified pathways were then evaluated in a series of clinico-genomic datasets from 142 patients with stage III/IV serous OVCA. We found that in vitro gemcitabine sensitivity was associated with expression of 131 genes (p<0.001). These genes include significant representation of three molecular signaling pathways (p<0.02): O-glycan biosynthesis, Role of Nek in cell cycle regulation and Antiviral actions of Interferons. In an external clinico-genomic OVCA dataset (n=142), expression of the O-glycan pathway was associated with overall survival, independent of surgical cytoreductive status, grade and age (p<0.001). Expression levels of Role of Nek in cell cycle regulation and Antiviral actions of Interferons were not associated with survival (p=0.31 and p=0.54, respectively). Collectively, expression of the O-glycan biosynthesis pathway, which modifies protein function via post-translational carbohydrate binding, is independently associated with overall survival from OVCA. Our findings shed light on the molecular basis of OVCA responsiveness to gemcitabine and also identify a signaling pathway that may influence patient survival.

BCL2 antagonist of cell death kinases, phosphatases, and ovarian cancer sensitivity to cisplatin

Objective

The BCL2 family proteins are critical mediators of cellular apoptosis and, as such, have been implicated as determinants of cancer cell chemo-sensitivity. Recently, it has been demonstrated that the phosphorylation status of the BCL2 antagonist of cell death (BAD) protein may influence ovarian cancer (OVCA) cell sensitivity to cisplatin. Here, we sought to evaluate how kinase and phosphatase components of the BAD apoptosis pathway influence OVCA chemo-sensitivity.

Methods

Protein levels of cyclin-dependent kinase 1 (CDK1) and protein phosphatase 2C (PP2C) were measured by immunofluorescence in a series of 64 primary advanced-stage serous OVCA patient samples. In parallel, levels of cAMP-dependent protein kinase (PKA), AKT, and PP2C were quantified by Western blot analysis in paired mother/daughter platinum-sensitive/resistant OVCA cell lines (A2008/C13, A2780S/A2780CP, Chi/ChiR). BAD pathway kinase CDK1 was depleted using siRNA transfection, and the influence on BAD phosphorylation and cisplatin-induced apoptosis was evaluated.

Results

OVCA patient samples that demonstrated complete responses to primary platinum-based therapy demonstrated 4-fold higher CDK1 (p<0.0001) and 2-fold lower PP2C (p=0.14) protein levels than samples that demonstrated incomplete responses. Protein levels of PP2C were lower in the platinum-resistant versus that shown in the platinum-sensitive OVCA cell line sub-clones. Levels of PKA were higher in all platinum-resistant than in platinum-sensitive OVCA cell line sub-clones. Selective siRNA depletion of CDK1 increased sensitivity to cisplatin-induced apoptosis (p<0.002).

Conclusion

BAD pathway kinases and phosphatases, including CDK1 and PP2C, are associated with OVCA sensitivity to platinum and may represent therapeutic opportunities to enhance cytotoxic efficacy.

The BCL2 antagonist of cell death pathway influences endometrial cancer cell sensitivity to cisplatin

OBJECTIVE

To identify pathways that influence endometrial cancer (EC) cell sensitivity to cisplatin and to characterize the BCL2 antagonist of cell death (BAD) pathway as a therapeutic target to increase cisplatin sensitivity.

METHODS

Eight EC cell lines (Ishikawa, MFE296, RL 95-2, AN3CA, KLE, MFE280, MFE319, HEC-1-A) were subjected to Affymetrix Human U133A GeneChip expression analysis of approximately 22,000 probe sets. In parallel, endometrial cell line sensitivity to cisplatin was quantified by MTS assay, and IC(50) values were calculated. Pearson's correlation test was used to identify genes associated with response to cisplatin. Genes associated with cisplatin responsiveness were subjected to pathway analysis. The BAD pathway was identified and subjected to targeted modulation, and the effect on cisplatin sensitivity was evaluated.

RESULTS

Pearson's correlation analysis identified 1443 genes associated with cisplatin resistance (P<0.05), which included representation of the BAD-apoptosis pathway. Small interfering RNA (siRNA) knockdown of BAD pathway protein phosphatase PP2C expression was associated with increased phosphorylated BAD (serine-155) levels and a parallel increase in cisplatin resistance in Ishikawa (P=0.004) and HEC-1-A (P=0.02) cell lines. In contrast, siRNA knockdown of protein kinase A expression increased cisplatin sensitivity in the Ishikawa (P=0.02) cell line.

CONCLUSION

The BAD pathway influences EC cell sensitivity to cisplatin, likely via modulation of the phosphorylation status of the BAD protein. The BAD pathway represents an appealing therapeutic target to increase EC cell sensitivity to cisplatin.

BAD phosphorylation determines ovarian cancer chemosensitivity and patient survival

PURPOSE

Despite initial sensitivity to chemotherapy, ovarian cancers (OVCA) often develop drug resistance, which limits patient survival. Using specimens and/or genomic data from 289 patients and a panel of cancer cell lines, we explored genome-wide expression changes that underlie the evolution of OVCA chemoresistance and characterized the BCL2 antagonist of cell death (BAD) apoptosis pathway as a determinant of chemosensitivity and patient survival.

EXPERIMENTAL DESIGN

Serial OVCA cell cisplatin treatments were performed in parallel with measurements of genome-wide expression changes. Pathway analysis was carried out on genes associated with increasing cisplatin resistance (EC(50)). BAD-pathway expression and BAD protein phosphorylation were evaluated in patient samples and cell lines as determinants of chemosensitivity and/or clinical outcome and as therapeutic targets.

RESULTS

Induced in vitro OVCA cisplatin resistance was associated with BAD-pathway expression (P < 0.001). In OVCA cell lines and primary specimens, BAD protein phosphorylation was associated with platinum resistance (n = 147, P < 0.0001) and also with overall patient survival (n = 134, P = 0.0007). Targeted modulation of BAD-phosphorylation levels influenced cisplatin sensitivity. A 47-gene BAD-pathway score was associated with in vitro phosphorylated BAD levels and with survival in 142 patients with advanced-stage (III/IV) serous OVCA. Integration of BAD-phosphorylation or BAD-pathway score with OVCA surgical cytoreductive status was significantly associated with overall survival by log-rank test (P = 0.004 and P < 0.0001, respectively).

CONCLUSION

The BAD apoptosis pathway influences OVCA chemosensitivity and overall survival, likely via modulation of BAD phosphorylation. The pathway has clinical relevance as a biomarker of therapeutic response, patient survival, and as a promising therapeutic target.

Abstract 1645: The phosphorylation status of BAD pathway influence to chemo-sensitivity

Objective: Patients with advanced or recurrent endometrial cancer have a poor prognosis in part due to lack of efficacy of currently available chemotherapies and incomplete understanding of the biology that underlies chemo-response. In the current study we used genomic expression data to identify molecular signaling pathways associated with endometrial cancer cell resistance to cisplatin, doxorubicin chemotherapy and further characterized the role of the BAD apoptosis pathway as a therapeutic target and determinant of chemo-response.

Methods: Eight endometrial cell lines were subject to genome-wide expression analysis using Affymetrix HG-U133Plus GeneChips and in parallel, ranked by relative sensitivity to cisplatin and doxorubicin using MTS cell proliferation assays. Gene array data from sensitive versus resistant cell lines was compared by student's t-test and Pearson's correlation to identify those genes associated with drug resistance and further evaluated by GeneGo Metacore software for representation of molecular signaling pathways. Furthermore, the role of the BAD pathway in chemo-resistance was evaluated by selective inhibition of BAD pathway members, PKA, PP2C, AKT1, AKT2 and AKT3 by siRNA or pharmacologic agents in the presence and absence of cisplatin. Cell death and growth arrest in the presence of cisplatin were evaluated by Western blot for PARP cleavage as well as nuclear condensation and fragmentation and MTS assays.

Results: Student's t-test and Pearson's correlation identified the expression of 325 and 1136 genes to be associated with cisplatin (p&lt;0.01) and doxorubicin (p&lt;0.01) resistance, respectively. Pathway analysis of genes associated with both cisplatin and doxorubicin resistance indicated significant representation of the BAD apoptosis pathway (p&lt;0.002). Selective depletion of the phosphatase, PP2C by siRNA resulted in increased phosphorylation of BAD, serine 118 and increased resistance to cisplatin induced cell growth arrest and cell death. In contrast, depletion of the kinase, PKA resulted in decreased phosphorylation of BAD, serine 118 and increased cell death in the presence of cisplatin. In addition, depletion of AKT1 using siRNA as wells as treatment of cells with the AKT inhibitor, triciribine, increased cisplatin-induced growth arrest and cell death, whereas depletion of AKT2 or AKT3 did not affect cisplatin sensitivity.

Conclusions: The phosphorylation status BAD may influence endometrial cancer cell sensitivity to chemotherapy and represents a compelling target for future therapeutic development.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1645.

Abstract C1: HDAC inhibitors trigger the autophagic switch from prosurvival to prodeath in tamoxifen-treated breast cancer cells

Background: Hormone therapy remains the treatment of choice for patients with estrogen receptor-positive breast cancer. The majority of patients with an initial response to tamoxifen or aromatase inhibitors will develop resistance, and many patients present with tumors that are a priori resistant. One of the known survival strategies of breast cancer cells treated with hormone therapy is the induction of autophagy. Autophagy is a process by which cellular components are catabolized in autophagic lysosomes, enabling the clearance of damaged organelles and the recycling of nutrients during periods of starvation. Autophagy has been reported in response to treatment with both aromatase inhibitors and tamoxifen, in part by upregulating expression of the essential autophagy protein beclin-1. Inhibition of autophagy in breast cancer cells, increases the cytotoxicity of tamoxifen, suggesting that autophagy in these cells is oncogenic and potentially a contributor to resistance. We have shown that HDAC inhibitors potentiate the cytotoxicity of tamoxifen in breast cancer cells. These results raise the possibility that HDAC inhibitors achieve synergy by inhibiting autophagy.

Methods: We sought to determine how HDAC inhibition impacts tamoxifen-induced autophagy in breast cancer cell line models.

Results: Using several HDAC inhibitors, we show a synergistic increase in apoptosis and cell death with tamoxifen. The addition of an HDAC inhibitor to tamoxifen increased autophagy, in both a time and dose dependent manner. Increased autophagy required functional estrogen-mediated signaling, as depletion of ER by siRNA or treatment with fulvestrant did not result in increased autophagy as measured by LC3 levels. The inhibition of autophagy in tamoxifen-treated cells by 3-methyladenine circumvented autophagy and induced apoptosis supporting prior reports that autophagy acts as a survival mechanism in these cells. When combined with tamoxifen, HDAC inhibitors increased the expression of LC3 and Beclin1, suggesting enhanced induction of autophagy. Furthermore, LC3 and cleaved PARP were sequentially expressed in a dose and time dependent manner, with LC3 increasing first followed by PARP cleavage. In these cells, annexin-V staining further supports apoptotic rather than autophagic cell death. Together, this suggests cells transition from autophagic cell preservation to apoptotic cell death.

Conclusion: An autophagic survival response in breast cancer cells has been described after nutrient starvation, tamoxifen treatment as well as following exposure to DNA damaging agents. Our data further suggests that with the synergistic induction of beclin-1 by HDAC inhibition and tamoxifen, the excess of autophagic lysosomes can no longer sustain self-preservation and triggers elimination of cells by apoptotic cell death in a fatal switch. Thus, combining tamoxifen with an HDAC inhibitor may represent a new therapeutic approach to overcome hormone therapy resistance.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C1.

HDAC2 regulates chromatin plasticity and enhances DNA vulnerability

Histone deacetylases (HDAC) may have a prominent role in the development of cancer and the response to anticancer therapy. However, the therapeutic relevance and tissue specificity of individual HDAC enzymes remain largely unknown. HDAC inhibitors may function as sensitizing agents to chemotherapies that target DNA through their effects on chromatin structure and plasticity. Here, we report a new role for HDAC2 as a regulator of chromatin compaction status and the mediator of HDAC inhibitor-induced sensitization to chemotherapy. The selective depletion of HDAC2 by small interfering RNA led to reduced expression of heterochromatin maintenance proteins and morphologic changes indicative of chromatin decondensation. Furthermore, depletion of HDAC2 but not HDAC1 or HDAC6 was sufficient to sensitize breast cancer cells to topoisomerase inhibitor-induced apoptosis. The levels of HDAC2 expression appear to correlate with the degree of HDAC inhibitor-induced histone acetylation in a surrogate tissue in patients. These data suggest that HDAC2 may be a relevant pharmacologic and biological target for combination therapy involving drugs that target DNA.

Clinical and biological effects of valproic acid as a histone deacetylase inhibitor on tumor and surrogate tissues: phase I/II trial of valproic acid and epirubicin/FEC

PURPOSE

The aim was to study the biological and molecular effects of the histone deacetylase (HDAC) inhibitor, valproic acid, in patients with solid tumor malignancies.

EXPERIMENTAL DESIGN

A phase I dose escalation of valproic acid given on days 1 to 3 followed by epirubicin (day 3) was followed by a dose expansion of valproic acid combined with 5-fluorouracil, epirubicin, and cyclophosphamide (FEC100). Pharmacodynamic and pharmacokinetic studies entailed valproic acid and epirubicin plasma levels and their interaction, the effects of valproic acid on histone acetylation in peripheral blood mononuclear cells (PBMC) and tumor cells at baseline and day 3, and baseline expression of HDAC2 and HDAC6 as therapeutic targets.

RESULTS

Forty-four patients were enrolled in the phase I part, with a disease-specific cohort expansion of 15 breast cancer patients (median age, 55 years; range, 28-66 years) receiving 120 mg/kg/day valproic acid followed by FEC100. Partial responses were seen in 9 of 41 (22%) patients during the phase I part. Objective responses were seen in 9 of 14 (64%) evaluable patients at the dose expansion with a median number of 6 administered cycles. Predominant toxicities were valproic acid-associated somnolence and epirubicin-induced myelosuppression. Valproic acid plasma levels were associated with short-term, reversible depletion of WBC and neutrophils within 48 hours. Histone acetylation in tumor samples and in PBMCs correlated with valproic acid levels and was further linked to baseline HDAC2 but not to HDAC6 expression.

CONCLUSION

Valproic acid is a clinically relevant HDAC inhibitor, and PBMCs may serve as a surrogate for tumor histone acetylation in solid tumor malignancies. HDAC2 should be further considered as a relevant therapeutic target.

Potentiation of a topoisomerase I inhibitor, karenitecin, by the histone deacetylase inhibitor valproic acid in melanoma: translational and phase I/II clinical trial

PURPOSE

The novel topoisomerase I inhibitor karenitecin (KTN) shows activity against melanoma. We examined whether histone deacetylase inhibition could potentiate the DNA strand cleavage, cytotoxicity as well as the clinical toxicity, and efficacy of KTN in melanoma.

EXPERIMENTAL DESIGN

Apoptosis, COMET, and xenograft experiments were carried out as described previously. A phase I/II trial of valproic acid (VPA) and KTN was conducted in patients with stage IV melanoma, with any number of prior therapies, Eastern Cooperative Oncology Group performance status 0-2, and adequate organ function.

RESULTS

VPA pretreatment potentiated KTN-induced apoptosis in multiple melanoma cell lines and in mouse A375 xenografts. VPA increased KTN-induced DNA strand breaks. In the phase I/II trial, 39 patients were entered, with 37 evaluable for toxicity and 33 evaluable for response. Somnolence was the dose-limiting toxicity. The maximum tolerated dose for VPA was 75 mg/kg/d; at maximum tolerated dose, serum VPA was approximately 200 microg/mL (1.28 mmol/L). At the dose expansion cohort, 47% (7 of 15) of patients had stable disease; median overall survival and time to progression were 32.8 and 10.2 weeks, respectively. Histone hyperacetylation was observed in peripheral blood mononuclear cells at maximum tolerated dose.

CONCLUSION

VPA potentiates KTN-induced DNA strand breaks and cytotoxicity. VPA can be combined at 75 mg/kg/d for 5 days with full-dose KTN without overlapping toxicities. In metastatic poor prognosis melanoma, this combination is associated with disease stabilization in 47% of patients. Further testing of this combination appears warranted.

Phase I/II trial combining the HDAC inhibitor, valproic acid (VPA) and FEC100 (5-fluorouracil, epirubicin and cyclophosphamide) in locally advanced/metastatic breast cancer

1065

Background: Cell culture and xenograft studies suggest a synergistic interaction between histone deacetylase inhibitors (HDACi) and topoisomerase (topo) inhibitors, as well as other DNA targeting agents. Methods: In this phase I/II study, we determined the effects of escalating doses of VPA on the clinical efficacy and tolerability of epirubicin. The phase I part was open to patients will all solid tumors. A limited phase II part at the maximum tolerated dose (MTD) of VPA enrolled 10 breast cancer patients and incorporated the breast cancer regimen FEC100 (5-fluorouracil, epirubicin, cyclophosphamide (600/100/600 mg/m2)). VPA was given on days 1–3 prior to epirubicin/FEC100 in 3-week cycles. HDAC expression, histone acetylation and topo II expression were evaluated in pre-and post-VPA peripheral blood mononuclear cells and tumor samples. Results: Fifty-four (44 in phase I and 10 in phase II) patients [median age 55 (39–78)] received VPA (mg/kg/day): 15, 30, 45, 60, 75, 90, 100, 120, 140 and 160. Tumor types included: breast (10+10), melanoma (11), lung (6), sarcoma (2), GYN (2), GI (5) and others (8). Dose-limiting toxicities included somnolence, confusion and febrile neutropenia. No exacerbation of FEC100/epirubicin-related toxicities was observed. Objective responses in the phase I part 9/41 (22%) were seen across different tumor types despite a median number of 3 (0–6) prior regimens with stable disease/minor response in 16/41 (39%). In the breast-specific phase II part, partial responses to date were seen in 4/8 (50%) and stable disease in 2/8 (25%), progression in 1/8 (12.5%), 1/8 (12.5%) patients withdrew consent. All breast cancer patients with a response/stable disease received the maximal number of seven cycles. VPA plasma concentrations correlated with VPA dose. There was a positive correlation between histone acetylation and VPA dose as well as plasma levels in PBMC and further correlated with those in tumors. Conclusion: A sequence-specific combination of VPA and FEC100 in breast cancer is highly active without exacerbation of chemotherapy-induced toxicities. A neoadjuvant phase II trial using VPA (120 mg/kg) -> FEC100 in patients with early stage breast cancer is ongoing.

[Table: see text]

Phase I trial of a sequence-specific combination of the HDAC inhibitor, vorinostat (SAHA) followed by doxorubicin in advanced solid tumor malignancies

3502

Background: Preclinical cell culture and xenograft studies suggest that pre-exposure of cancer cells to a histone deacetylase inhibitor (HDACi) may potentiate topoisomerase (topo) inhibitors. The HDACi-induced histone acetylation and chromatin modulation facilitates DNA access and target recruitment for topo II inhibitors. Methods: This Phase I trial explores the safety, tolerability and maximum tolerated dose (MTD) of a weekly schedule of escalating vorinostat doses (twice daily days 1–3) followed by doxorubicin (20 mg/m2) on day 3 (3 out of 4 weeks). Histone acetylation and topo II expression are evaluated in pre-and post-vorinostat peripheral blood mononuclear cells and in tumor cells of the 30 patients treated at the MTD. Results: To date, 15 patients [median age 54 (38–73)] have been treated in 4 vorinostat cohorts: 200, 300, 400, 500 mg bid. Tumor types included: breast (3), melanoma (3), pancreatic (2) and one each of SCLC, sarcoma, endometrial, colon, prostate, renal cell and bladder cancer. Dose-limiting toxicities included a grade 3 thrombocytopenia (1/6) at the 400 mg bid dose. Non-dose limiting Grade 3 and 4 toxicities include neutropenia, thrombocytopenia, fatigue, pulmonary embolus, and anemia (1 pt each). Currently, vorinostat doses of 500 mg bid are being evaluated. One confirmed partial response in a breast cancer patient, as well as minor responses in a melanoma and a prostate cancer patient were seen in 10 evaluable patients. Patients received a median number of 2 (1–9+) treatment cycles. Doxorubicin is stopped after 6 cycles and patients continue on vorinostat alone. H3 and H4 histone acetylation and topo II expression will be correlated with vorinostat dose, plasma concentration and response. Conclusion: A sequence-specific combination of vorinostat and doxorubicin is active without exacerbation of doxorubicin toxicity. The tolerated vorinostat dose exceeds the proposed single agent dose for vorinostat derived from patients with hematological malignancies. Histone hyperacetylation occurs in peripheral blood mononuclear cells at all levels. The anti-tumor activity in breast cancer and melanoma will be further explored.

No significant financial relationships to disclose.

Phase I trial of histone deacetylase inhibition by valproic acid followed by the topoisomerase II inhibitor epirubicin in advanced solid tumors: a clinical and translational study

PURPOSE

To determine the safety, toxicity, and maximum-tolerated dose of a sequence-specific combination of the histone deacetylase inhibitor (HDACi), valproic acid (VPA), and epirubicin in solid tumor malignancies and to define the clinical feasibility of VPA as an HDACi.

PATIENTS AND METHODS

Patients were treated with increasing doses of VPA (days 1 through 3) followed by epirubicin (day 3) in 3-week cycles. The study evaluated pharmacokinetic and pharmacodynamic end points, toxicities, and tumor response.

RESULTS

Forty-eight patients were enrolled, and 44 received at least one cycle of therapy. Patients (median age, 54 years; range, 39 to 78 years) received the following doses of VPA: 15, 30, 45, 60, 75, 90, 100, 120, 140, and 160 mg/kg/d. Dose-limiting toxicities were somnolence (n = 1), confusion (n = 3), and febrile neutropenia (n = 1). No exacerbation of epirubicin-related toxicities was observed. Partial responses were seen across different tumor types in nine patients (22%), and stable disease/minor responses were seen in 16 patients (39%), despite a median number of three prior regimens (range, zero to 10 prior regimens). Patients received a median number of four treatment cycles (range, one to 10 cycles), and treatment was stopped after reaching maximal epirubicin doses rather than progression in 13 (32%) of 41 patients patients. Total and free VPA plasma concentrations increased linearly with dose and correlated with histone acetylation in peripheral-blood mononuclear cells.

CONCLUSION

The maximum-tolerated dose and recommended phase II dose was VPA 140 mg/kg/d for 48 hours followed by epirubicin 100 mg/m2. Sustained plasma concentrations of VPA exceeding those required for in vitro synergy were achieved with acceptable toxicity. Noteworthy antitumor activity was observed in heavily pretreated patients and historically anthracycline-resistant tumors.

Phase I trial of a sequence-specific combination of the HDAC inhibitor, valproic acid (VPA), and the topoisomerase II inhibitor, epirubicin, in advanced solid tumors: Clinical results and correlative studies

3068

Background: Multiple lines of evidence indicate that histone deacetylase inhibitors (HDACi) potentiate topoisomerase (topo) inhibitors. The HDACi-induced histone acetylation and chromatin modulation facilitates DNA access and target recruitment for topo II inhibitors. Methods: This Phase I trial explored a sequence-specific combination of VPA and epirubicin in solid tumors. A VPA loading dose and 6 oral doses (q12h) were given prior to epirubicin in 3-week cycles. Histone acetylation and topo II expression were evaluated in pre-and post-VPA peripheral blood mononuclear cells and tumor samples. Results: To date, 42 patients [median age 53 (39–78)] have been treated in 12 cohorts: IV VPA loading (mg/kg)/epirubicin (mg/m2): 15/75, 30/75, 45/75, 60/75, 75/75 and 75/100, oral loading: 75/100, 90/100, 100/100, 120/100, 140/100 and 160/100. Tumor types included: breast (10), melanoma (11), lung (6), sarcoma (2), GYN (2), GI (5) and others (6). Dose-limiting toxicities included somnolence (1) and neutropenia (1). No exacerbation of epirubicin-related toxicities was observed. Objective responses were seen across different tumor types in anthracycline-resistant and -refractory tumors, despite a median number of 3 (0–6) prior regimens: Partial response; 7/37 (19%), stable disease/minor response: 16/37 (43%). Patients received a median number of 4 (1–10) treatment cycles. Study treatment was stopped despite a clinical benefit or response in 4/33 patients after reaching maximal epirubicin doses (≤750 mg/m2). VPA peak and trough plasma concentrations increased linearly up to 120 mg/m2. MTD is being defined at 160/100 mg/kg/d VPA. H3 and H4 histone acetylation and topo II expression have been correlated with VPA dose, plasma concentration and response. Conclusion: A sequence-specific combination of VPA and epirubicin is active without exacerbation of epirubicin toxicity. VPA plasma peak and trough levels exceeding concentrations needed for biological effects and in vitro synergy are easily achievable with minimal toxicity. The noteworthy anti-tumor activity seen in this heavily pretreated Phase I population warrants further exploration.

[Table: see text]

In vivo synergy between topoisomerase II and histone deacetylase inhibitors: predictive correlates

Histone deacetylase inhibitors (HDACi) are a promising class of anticancer agents, yet the specific biological effects resulting in cell death are still poorly understood and clinically relevant markers of response are not adequately defined. The anticonvulsant valproic acid has recently emerged as an HDACi, and in vitro studies suggested that valproic acid may potentiate cytotoxic agents. We evaluated the pharmacologic and biological effects of valproic acid on histone acetylation, chromatin structure, and DNA damage induced by topoisomerase II inhibitors in mice bearing breast cancer tumors and developed an ex vivo methodology for response prediction using comet assays. The exposure of mice to valproic acid before exposure to epirubicin led to tumor regression when valproic acid was given for 48 hours at concentrations sufficient for histone hyperacetylation, down-regulation of heterochromatin maintenance proteins, and chromatin decondensation. Tumor response was accurately predicted by ex vivo comet moments. Valproic acid did not exacerbate epirubicin-related toxicity. Antitumor effects were not observed with valproic acid alone despite biologically active valproic acid concentrations. These findings suggest that exposure of tumor-bearing mice to valproic acid potentiated the antitumor effects of topoisomerase II inhibitors without enhancing toxicity. The HDACi-induced histone acetylation and modulation of heterochromatin correlated with potentiation of epirubicin-mediated DNA damage. However, these effects did not result in antitumor activity when using a HDACi alone and hence should not be considered a surrogate marker. Ex vivo comet assays may be useful as a predictive tool when tumor cells are limited and serial biopsies are difficult to obtain.

Synergistic interaction between histone deacetylase and topoisomerase II inhibitors is mediated through topoisomerase IIbeta

BACKGROUND

DNA topoisomerase II inhibitors and poisons are among the most efficacious drugs for the treatment of cancer. Sensitivity of cancer cells to the cytotoxic effects of topoisomerase II targeting agents is thought to depend on the expression of the topoisomerase IIalpha isoform, and drug resistance is often associated with loss or mutation of topoisomerase IIalpha. Histone deacetylase inhibitors (HDACi) are a novel class of compounds that potentiate the antitumor effects of topoisomerase II-targeting agents.

METHODS

The interaction between HDACi and topoisomerase II-targeting agents in cancer cells was evaluated as a function of topoisomerase IIalpha and topoisomerase IIbeta expression. Topoisomerase II isoforms were selectively depleted using small interfering RNA and antisense. Drug-induced formation of cleavable complexes involving topoisomerase IIalpha and topoisomerase IIbeta was evaluated by trapped-in-agarose DNA immunostaining and band depletion assays in the presence and absence of HDACi.

RESULTS

Preexposure to HDACi increased the cytotoxicity of topoisomerase II poisons. This was associated with a down-regulation of topoisomerase IIalpha expression but had no effects on topoisomerase IIbeta. In the setting of HDACi-induced chromatin decondensation and topoisomerase IIalpha depletion, topoisomerase II poison cytotoxicity was mediated through topoisomerase IIbeta cleavable complex formation. The HDACi-induced sensitization was also observed in cells with target-specific resistance to topoisomerase II poisons.

CONCLUSIONS

The recruitment of topoisomerase IIbeta as a target may overcome primary or emergent drug resistance to topoisomerase II-targeting agents and hence may broaden the applicability of this important class of anticancer agents.

Valproic acid alters chromatin structure by regulation of chromatin modulation proteins

Histone acetylation and deacetylation are crucial in the regulation of gene expression. Dynamic changes in gene expression may affect chromatin structure and, consequently, the interaction of chromatin with regulatory factors. In this study, the effects of the antiseizure drug valproic acid (VPA) on the expression of genes that regulate the structure of chromatin and the access of macromolecules to the DNA were investigated. Exposure of breast cancer cells to VPA resulted in rapid dose-dependent hyperacetylation of the histones H3 and H4. VPA further induced a depletion of several members of the structural maintenance of chromatin (SMC) proteins, SMC-associated proteins, DNA methyltransferase, and heterochromatin proteins. Down-regulation of these proteins was associated with chromatin decondensation. The observed alterations of chromatin structure correlated with enhanced sensitivity of DNA to nucleases and increased interaction of DNA with intercalating agents. VPA-induced chromatin decondensation led to a sequence-specific potentiation of DNA-damaging agents in cell culture and xenograft models. Modulation of heterochromatin maintenance proteins was not a direct, but a downstream, effect of histone acetylation. The effects on the chromatin structure were reversible upon drug withdrawal, but obligatory for the potentiation of DNA-damaging agents. In addition to their antitumor activity as single agents, the chromatin decondensation induced by histone deacetylase inhibitors may enhance the efficacy of cytotoxic agents that act by targeting DNA. The proposed mechanism of action suggests an effect of drug sequencing on the antitumor activity of these drugs.

Cyclin-dependent kinase activating kinase/Cdk7 co-localizes with PKC-iota in human glioma cells

Cyclin-dependent kinase activating kinase (CAK) is a trimeric complex composed of cdk7, cyclin H and MAT1. CAK/cdk7 functions as a master cell cycle regulator by phosphorylating cyclin-dependent kinases for cell cycle progression. We have previously reported that protein kinase C-iota (PKC-iota) associates with CAK/cdk7. In this investigation, immunofluorescence confocal microscopy was used to provide further evidence for the co-localization of PKC-iota with CAK/cdk7. PKC-iota was labeled with Alexa Fluor 488 (green fluorescent dye) and CAK/cdk7 was labeled with Alexa Fluor 555 (red fluorescent dye). The fusion of the red and green fluorescent colors produced a yellow color, which was used to quantify co-localization of PKC-iota and CAK/cdk7. Confocal microscopy revealed the co-localization of PKC-iota with CAK/cdk7 in both the cytoplasm and nucleus of U-373 MG cells.

Sequence-specific potentiation of topoisomerase II inhibitors by the histone deacetylase inhibitor suberoylanilide hydroxamic acid

Acetylation of histones leads to conformational changes of DNA. We have previously shown that the histone deacetylase (HDAC) inhibitor, suberoylanilide hydroxamic acid (SAHA), induced cell cycle arrest, differentiation, and apoptosis. In addition to their antitumor effects as single agents, HDAC inhibitors may cause conformational changes in the chromatin, rendering the DNA more vulnerable to DNA damaging agents. We examined the effects of SAHA on cell death induced by topo II inhibitors in breast cancer cell lines. Topo II inhibitors stabilize the topo II-DNA complex, resulting in DNA damage. Treatment of cells with SAHA promoted chromatin decondensation associated with increased nuclear concentration and DNA binding of the topo II inhibitor and subsequent potentiation of DNA damage. While SAHA-induced histone hyperacetylation occurred as early as 4 h, chromatin decondensation was most profound at 48 h. SAHA-induced potentiation of topo II inhibitors was sequence-specific. Pre-exposure of cells to SAHA for 48 h was synergistic, whereas shorter pre-exposure periods abrogated synergy and exposure of cells to SAHA after the topo II inhibitor resulted in antagonistic effects. Synergy was not observed in cells with depleted topo II levels. These effects were not limited to specific types of topo II inhibitors. We propose that SAHA significantly potentiates the DNA damage induced by topo II inhibitors; however, synergy is dependent on the sequence of drug administration and the expression of the target. These findings may impact the clinical development of combining HDAC inhibitors with DNA damaging agents.

Human glioma PKC-iota and PKC-betaII phosphorylate cyclin-dependent kinase activating kinase during the cell cycle

Cell cycle phase transition is regulated in part by the trimeric enzyme, cyclin-dependent kinase activating kinase (CAK) which phosphorylates and activates cyclin-dependent kinases (cdks). Protein kinase C (PKC) inhibitors prevent cell cycle phase transition, suggesting a fundamental role for PKCs in cell cycle regulation. We report that in glioma cells, CAK (cdk7) is constitutively associated with PKC-iota. In vitro phosphorylation, co-immunoprecipitation, and analysis of phosphorylated proteins by autoradiography indicate that CAK (cdk7) is a substrate for PKC-iota and PKC-betaII hyperphosphorylation. These results establish a role for PKC-iota and PKC-betaII in the activation of CAK during the glioma cell cycle.