Radiosensitization of epidermal growth factor receptor/HER2-positive pancreatic cancer is mediated by inhibition of Akt independent of ras mutational status

The Cellular Origins of Cancer-Associated Fibroblasts and Their Opposing Contributions to Pancreatic Cancer Growth

Pancreatic tumors are known to harbor an abundant and highly desmoplastic stroma. Among the various cell types that reside within tumor stroma, cancer-associated fibroblasts (CAFs) have gained a lot of attention in the cancer field due to their contributions to carcinogenesis and tumor architecture. These cells are not a homogeneous population, but have been shown to have different origins, phenotypes, and contributions. In pancreatic tumors, CAFs generally emerge through the activation and/or recruitment of various cell types, most notably resident fibroblasts, pancreatic stellate cells (PSCs), and tumor-infiltrating mesenchymal stem cells (MSCs). In recent years, single cell transcriptomic studies allowed the identification of distinct CAF populations in pancreatic tumors. Nonetheless, the exact sources and functions of those different CAF phenotypes remain to be fully understood. Considering the importance of stromal cells in pancreatic cancer, many novel approaches have aimed at targeting the stroma but current stroma-targeting therapies have yielded subpar results, which may be attributed to heterogeneity in the fibroblast population. Thus, fully understanding the roles of different subsets of CAFs within the stroma, and the cellular dynamics at play that contribute to heterogeneity in CAF subsets may be essential for the design of novel therapies and improving clinical outcomes. Fortunately, recent advances in technologies such as microfluidics and bio-printing have made it possible to establish more advanced ex vivo models that will likely prove useful. In this review, we will present the different roles of stromal cells in pancreatic cancer, focusing on CAF origin as a source of heterogeneity, and the role this may play in therapy failure. We will discuss preclinical models that could be of benefit to the field and that may contribute to further clinical development.

Therapy-Naïve and Radioresistant 3-Dimensional Pancreatic Cancer Cell Cultures Are Effectively Radiosensitized by β1 Integrin Targeting

PURPOSE

Pancreatic ductal adenocarcinoma (PDAC) is a cancer with unmet needs. The role of highly conformal radiation therapy is still under debate for PDAC. Owing to its desmoplastic nature, integrin-mediated interactions between PDAC cells and extracellular matrix (ECM) profoundly contribute to PDAC therapy resistance. In this study, we investigated the radiochemosensitizing potential of β1 integrin targeting in therapy-naïve and radioresistant PDAC cell cultures grown in 3-dimensional (3D) ECM.

METHODS AND MATERIALS

In a panel of 3D, ECM-based PDAC cell cultures, β1 integrin was inhibited by antibodies or siRNA-mediated knockdown. Together with x-ray irradiation and specific chemotherapies, we determined 3D colony formation capacity in therapy-naïve and radioresistant PDAC cultures. We used kinome profiling, Western blotting, and immunofluorescence stainings to characterize these cell lines. Various siRNA screens were conducted to identify novel therapeutic targets.

RESULTS

We found a significant radiosensitizing potential of β1 integrin inhibition both in therapy-naïve and radioresistant PDAC cell cultures. Kinome profiling upon β1 integrin targeting identified a generally declined tyrosine and serine/threonine kinase activity, which presented less prominent in radioresistant than in therapy-naïve PDAC cells. siRNA screens employing the top 34 deregulated kinases in combination with β1 integrin inhibition revealed less efficacy and less radiosensitization in radioresistant relative to therapy-naïve PDAC cell cultures. Triple inhibition of β1 integrin, protein kinase D1, and rearranged during transfection turned out to be most effective in reducing 3D colony formation of radioresistant PDAC cells.

CONCLUSIONS

Our study clearly shows that β1 integrins are robust targets for overcoming radioresistance in PDAC. This seems to apply equally to therapy-sensitive and radioresistant cells. Concerning tumor heterogeneity, this dual therapy-sensitizing potential might be exploitable for a significant improvement of patient survival.

Drug Repurposing, an Attractive Strategy in Pancreatic Cancer Treatment: Preclinical and Clinical Updates

Pancreatic cancer (PC) is one of the deadliest malignancies worldwide, since patients rarely display symptoms until an advanced and unresectable stage of the disease. Current chemotherapy options are unsatisfactory and there is an urgent need for more effective and less toxic drugs to improve the dismal PC therapy. Repurposing of non-oncology drugs in PC treatment represents a very promising therapeutic option and different compounds are currently being considered as candidates for repurposing in the treatment of this tumor. In this review, we provide an update on some of the most promising FDA-approved, non-oncology, repurposed drug candidates that show prominent clinical and preclinical data in pancreatic cancer. We also focus on proposed mechanisms of action and known molecular targets that they modulate in PC. Furthermore, we provide an explorative bioinformatic analysis, which suggests that some of the PC repurposed drug candidates have additional, unexplored, oncology-relevant targets. Finally, we discuss recent developments regarding the immunomodulatory role displayed by some of these drugs, which may expand their potential application in synergy with approved anticancer immunomodulatory agents that are mostly ineffective as single agents in PC.

The Anti-Cancer Properties of the HIV Protease Inhibitor Nelfinavir

Simple Summary

To this day, cancer remains a medical challenge despite the development of cutting-edge diagnostic methods and therapeutics. Thus, there is a continual demand for improved therapeutic options for managing cancer patients. However, novel drug development requires decade-long time commitment and financial investments. Repurposing approved and market-available drugs for cancer therapy is a way to reduce cost and the timeframe for developing new therapies. Nelfinavir is an anti-infective agent that has extensively been used to treat acquired immunodeficiency syndrome (AIDS) in adult and pediatric patients. In addition to its anti-infective properties, nelfinavir has demonstrated potent off-target anti-cancer effects, suggesting that it could be a suitable candidate for drug repurposing for cancer. In this review, we systematically compiled the therapeutic benefits of nelfinavir against cancer as a single drug or in combination with chemoradiotherapy, and outlined the possible underlying mechanistic pathways contributing to the anti-cancer effects.

Abstract

Traditional cancer treatments may lose efficacy following the emergence of novel mutations or the development of chemoradiotherapy resistance. Late diagnosis, high-cost of treatment, and the requirement of highly efficient infrastructure to dispense cancer therapies hinder the availability of adequate treatment in low-income and resource-limited settings. Repositioning approved drugs as cancer therapeutics may reduce the cost and timeline for novel drug development and expedite the availability of newer, efficacious options for patients in need. Nelfinavir is a human immunodeficiency virus (HIV) protease inhibitor that has been approved and is extensively used as an anti-infective agent to treat acquired immunodeficiency syndrome (AIDS). Yet nelfinavir has also shown anti-cancer effects in in vitro and in vivo studies. The anti-cancer mechanism of nelfinavir includes modulation of different cellular conditions, such as unfolded protein response, cell cycle, apoptosis, autophagy, the proteasome pathway, oxidative stress, the tumor microenvironment, and multidrug efflux pumps. Multiple clinical trials indicated tolerable and reversible toxicities during nelfinavir treatment in cancer patients, either as a monotherapy or in combination with chemo- or radiotherapy. Since orally available nelfinavir has been a safe drug of choice for both adult and pediatric HIV-infected patients for over two decades, exploiting its anti-cancer off-target effects will enable fast-tracking this newer option into the existing repertoire of cancer chemotherapeutics.

Comparative Proton and Photon Irradiation Combined with Pharmacological Inhibitors in 3D Pancreatic Cancer Cultures

Simple Summary

Due to higher precision and consequent sparing of normal tissue, pancreatic cancer patients might profit from proton beam radiotherapy, a treatment modality increasingly used. Since molecular data upon proton irradiation in comparison to standard photon radiotherapy are limited in pancreatic cancer, the aims of our study were to unravel differences in the effectiveness of photon versus proton irradiation and to exploit radiation type-specific molecular changes for radiosensitizing 3D PDAC cell cultures. Although protons showed a slightly higher effectiveness and a stronger induction of molecular alterations than photons, our results revealed a radiation-type independent sensitization of molecular-targeted agents selected according to the discovered molecular, radiation-induced alterations.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is a highly therapy-resistant tumor entity of unmet needs. Over the last decades, radiotherapy has been considered as an additional treatment modality to surgery and chemotherapy. Owing to radiosensitive abdominal organs, high-precision proton beam radiotherapy has been regarded as superior to photon radiotherapy. To further elucidate the potential of combination therapies, we employed a more physiological 3D, matrix-based cell culture model to assess tumoroid formation capacity after photon and proton irradiation. Additionally, we investigated proton- and photon-irradiation-induced phosphoproteomic changes for identifying clinically exploitable targets. Here, we show that proton irradiation elicits a higher efficacy to reduce 3D PDAC tumoroid formation and a greater extent of phosphoproteome alterations compared with photon irradiation. The targeting of proteins identified in the phosphoproteome that were uniquely altered by protons or photons failed to cause radiation-type-specific radiosensitization. Targeting DNA repair proteins associated with non-homologous endjoining, however, revealed a strong radiosensitizing potential independent of the radiation type. In conclusion, our findings suggest proton irradiation to be potentially more effective in PDAC than photons without additional efficacy when combined with DNA repair inhibitors.

Natural tyrosine kinase inhibitors acting on the epidermal growth factor receptor: Their relevance for cancer therapy

Epidermal growth factor receptor (EGFR), also known as ErbB-1/HER-1, plays a key role in the regulation of the cell proliferation, migration, differentiation, and survival. Since the constitutive activation or overexpression of EGFR is nearly found in various cancers, the applications focused on EGFR are the most widely used in the clinical level, including the therapeutic drugs of targeting EGFR, monoclonal antibodies (mAbs) and tyrosine kinase inhibitors (TKIs).Over the past decades, the compounds from natural sources have been a productive source of novel drugs, especially in both discovery and development of anti-tumor drugs by targeting the EGFR pathways as the TKIs. This work presents a review of the compounds from natural sources as potential EGFR-TKIs involved in the regulation of cancer. Moreover, high-throughput drug screening of EGFR-TKIs from the natural compounds has also been summarized.

Improving the Efficacy of Tumor Radiosensitization Through Combined Molecular Targeting

Chemoradiation, either alone or in combination with surgery or induction chemotherapy, is the current standard of care for most locally advanced solid tumors. Though chemoradiation is usually performed at the maximum tolerated doses of both chemotherapy and radiation, current cure rates are not satisfactory for many tumor entities, since tumor heterogeneity and plasticity result in chemo- and radioresistance. Advances in the understanding of tumor biology, a rapidly growing number of molecular targeting agents and novel technologies enabling the in-depth characterization of individual tumors, have fuelled the hope of entering an era of precision oncology, where each tumor will be treated according to its individual characteristics and weaknesses. At present though, molecular targeting approaches in combination with radiotherapy or chemoradiation have not yet proven to be beneficial over standard chemoradiation treatment in the clinical setting. A promising approach to improve efficacy is the combined usage of two targeting agents in order to inhibit backup pathways or achieve a more complete pathway inhibition. Here we review preclinical attempts to utilize such dual targeting strategies for future tumor radiosensitization.

Vorinostat upregulates MICA via the PI3K/Akt pathway to enhance the ability of natural killer cells to kill tumor cells

Vorinostat has good therapeutic efficacy against primary cutaneous T-cell lymphoma in the refractory stage. However, the molecular mechanism by which it inhibits solid tumors has not been clarified. To investigate the tumor inhibitory mechanism of vorinostat in cervical cancer, this study used Cell Counting Kit-8, flow cytometry, cell invasion and migration assays and the wound healing assay to evaluate the effects of vorinostat on cervical cancer cell proliferation, apoptosis, cell cycle, migration, and invasion. Real-time quantitative PCR and immunoblotting were used to detect gene and protein expression, respectively, of major histocompatibility class I-related chain A, phosphoinositide 3-kinase, phosphorylated PI3K p55 (Tyr199), and p-Akt (Ser473). The lactate dehydrogenase cytotoxicity assay was used to evaluate the ability of natural killer-92 cells to lyse cervical cancer cells. A xenograft nude mouse model was established to analyze the anti-tumor effect of vorinostat in vivo. Our results showed that vorinostat inhibited the proliferation, migration, and invasion of cervical cancer cells. Vorinostat also induced apoptosis and cell-cycle arrest in the S phase, inhibited PI3K (p110α), p-PI3K p55 (Tyr199), and p-Akt (Ser473) protein expression and upregulated MICA expression in vitro and in vivo, and promoted NK-92 cell-mediated cervical cancer cell lysis. The ability of vorinostat to upregulate MICA expression in cervical cancer cells was related to PI3K/Akt signaling. In brief, vorinostat upregulated MICA through the PI3K/Akt pathway and enhanced the sensitivity of cervical cancer cells to the NK cell-mediated cytolytic reaction. The results of this study demonstrate that vorinostat has anti-solid tumor effects on cervical cancer.

Study protocol: a multi-centre randomised study of induction chemotherapy followed by capecitabine ± nelfinavir with high- or standard-dose radiotherapy for locally advanced pancreatic cancer (SCALOP-2)

BACKGROUND

Induction chemotherapy followed by chemoradiation is a treatment option for patients with locally advanced pancreatic cancer (LAPC). However, overall survival is comparable to chemotherapy alone and local progression occurs in nearly half of all patients, suggesting chemoradiation strategies should be optimised. SCALOP-2 is a randomised phase II trial testing the role of radiotherapy dose escalation and/or the addition of the radiosensitiser nelfinavir, following induction chemotherapy of gemcitabine and nab-paclitaxel (GEMABX). A safety run-in phase (stage 1) established the nelfinavir dose to administer with chemoradiation in the randomised phase (stage 2).

METHODS

Patients with locally advanced, inoperable, non-metastatic pancreatic adenocarcinoma receive three cycles of induction GEMABX chemotherapy prior to radiological assessment. Those with stable/responding disease are eligible for further trial treatment. In Stage 1, participants received one further cycle of GEMABX followed by capecitabine-chemoradiation with escalating doses of nelfinavir in a rolling-six design. Stage 2 aims to register 262 and randomise 170 patients with responding/stable disease to one of five arms: capecitabine with high- (arms C + D) or standard-dose (arms A + B) radiotherapy with (arms A + C) or without (arms B + D) nelfinavir, or three more cycles of GEMABX (arm E). Participants allocated to the chemoradiation arms receive another cycle of GEMABX before chemoradiation begins. Co-primary outcomes are 12-month overall survival (radiotherapy dose-escalation question) and progression-free survival (nelfinavir question). Secondary outcomes include toxicity, quality of life, disease response rate, resection rate, treatment compliance, and CA19-9 response. SCALOP-2 incorporates a detailed radiotherapy quality assurance programme.

DISCUSSION

SCALOP-2 aims to optimise chemoradiation in LAPC and incorporates a modern induction regimen.

TRIAL REGISTRATION

Eudract No: 2013-004968-56; ClinicalTrials.gov : NCT02024009.

Biodistribution, pharmacokinetics and radioimmunotherapy of 188Re-cetuximab in NCI-H292 human lung tumor-bearing nude mice

Background Cetuximab is a fully humanized IgG1 subclass monoclonal that binds specifically to the human epidermal growth factor receptor (EGFR). Although EGFR is expressed in normal cells, the overexpression of EGFR is detected in many human cancers, such as colon, rectum and lung tumors. In this study, cetuximab with a combination of radiotherapy nuclear ¹⁸⁸Re achieved better therapeutic effect on lung cancer. Methods¹⁸⁸Re-cetuximab administered by the i.v. route in human NCI-H292 lung tumor-bearing mice was investigated. NanoSPECT/CT images were taken to evaluate the distribution and tumor targeting of ¹⁸⁸Re-cetuximab in mice. The anti-tumor effect of ¹⁸⁸Re-cetuximab was assessed by the tumor growth inhibition, survival ratio. Results For nanoSPECT/CT imaging, a significant uptake in tumor was observed at 24 and 48 h following the injection of ¹⁸⁸Re-cetuximab. The anti-tumor effect of ¹⁸⁸Re-cetuximab was assessed by tumor growth inhibition and the survival ratio. The tumor-bearing mice treated with ¹⁸⁸Re-cetuximab showed a better mean tumor growth inhibition rate (MGI = 0.049) and longer median survival time and lifespan (62.50 d; 70.07%) than those treated with ¹⁸⁸Re-perrhenate and cetuximab only by single injection. A synergistic effect of tumor growth inhibition was observed with the combination index exceeding one for ¹⁸⁸Re-cetuximab (CI = 6.135 and 9.276). Conclusion The tumor targeting and localization of 188Re-cetuximab were confirmed in this study. Synergistic therapeutic efficacy was demonstrated for the radioimmunotherapy of ¹⁸⁸Re-cetuximab. The results of this study reveal the potential advantage and benefit obtained from ¹⁸⁸Re-cetuximab for diagnosis and therapy of oncology applications in the future.

Altering the response to radiation: radiosensitizers and targeted therapies in pancreatic ductal adenocarcinoma: preclinical and emerging clinical evidence

Radiation therapy continues to have an evolving role in pancreatic ductal adenocarcinoma. While metastatic failure likely contributes to the majority of patient mortality, achieving local control through surgery and/or radiation appears to be important as certain studies suggest that mortality is contributed by local failure. Many studies support that pancreatic cancer is a relatively radiation resistant tumor type. In addition, the ability to further improve radiation through dose escalation strategies in the non-metastatic setting is hampered by closeness of normal organs, including small bowel and stomach, to the tumor. Thus subverting molecular pathways that promote radiation resistance will be critical to further success of radiation in this disease. There is a wealth of preclinical data supporting the targeting of various molecular pathways in combination with radiation therapy, including DNA repair, cell cycle checkpoint proteins, receptor tyrosine kinases, oncoproteins, stem cells, and immunomodulation. A number of clinical trials have been completed or are on-going with novel molecular inhibitors. In this review, we summarize existing preclinical and clinical molecular strategies for improving the efficacy of radiation in pancreatic cancer, and highlight recent and ongoing clinical trials combining radiation and various targeted therapies.

Enhanced Radiosensitivity in Solid Tumors using a Tumor-selective Alkyl Phospholipid Ether Analog

Antitumor alkyl phospholipid (APL) analogs comprise a group of structurally related molecules with remarkable tumor selectivity. Some of these compounds have shown radiosensitizing capabilities. CLR127 is a novel, clinical-grade antitumor APL ether analog, a subtype of synthetic APL broadly targeting cancer cells with limited uptake in normal tissues. The purpose of this study was to investigate the effect of CLR127 to modulate radiation response across several adult and pediatric cancer types in vitro as well as in murine xenograft models of human prostate adenocarcinoma, neuroblastoma, Ewing sarcoma, and rhabdomyosarcoma. In vitro, CLR127 demonstrated selective uptake in cancer cells compared to normal cells. In cancer cells, CLR127 treatment prior to radiation significantly decreased clonogenic survival in vitro, and led to increased radiation-induced double-stranded DNA (dsDNA) breakage compared with radiation alone, which was not observed in normal controls. In animal models, CLR127 effectively increased the antitumor response to fractionated radiotherapy and led to delayed tumor regrowth at potentially clinically achievable doses. In conclusion, our study highlights the ability of CLR127 to increase radiation response in several cancer types. Given almost universal uptake of CLR127 in malignant cells, future research should test whether the observed effects can be extended to other tumor types. Our data provide a strong rationale for clinical testing of CLR127 as a tumor-targeted radiosensitizing agent. Mol Cancer Ther; 17(11); 2320-8. ©2018 AACR.

miR-21 expression and clinical outcome in locally advanced pancreatic cancer: exploratory analysis of the pancreatic cancer Erbitux, radiotherapy and UFT (PERU) trial

Background

Locally advanced pancreatic cancer (LAPC) is associated with high mortality, and biomarker-driven treatment approach is currently lacking. This study evaluated safety and efficacy of a combination approach of chemotherapy followed by chemo-radiotherapy (CRT) +/− cetuximab, and the prognostic role of miR-21 in patients with LAPC treated with a multimodality approach.

Patients and Methods

This was a randomised phase II trial in which patients with inoperable LAPC were offered gemcitabine and capecitabine (GEM-CAP) for 16 weeks. Patients with stable disease or response after GEM-CAP were randomised to capecitabine or UFT plus radiotherapy (RT) (A), or capecitabine or UFT plus cetuximab plus RT (B). The primary outcome of the study was overall survival (OS). Clinical outcome was compared according to baseline circulating miR-21 levels.

Results

17 patients were enrolled and treated with GEM-CAP, with 13 patients achieving disease control and being randomised to arms A (n:7) and B (n:6). After a median follow-up of 61.2 months, median progression free survival (PFS) was 10.4 months and 12.7 months, median OS was 15.8 months and 22.0 months in arms A and B respectively (p > 0.05). Patients with high baseline plasma miR-21 had worse PFS (3.5 vs. 12.7 months; p:0.032) and OS (5.1 vs 15.3 months; p:0.5) compared to patients with low miR-21. Circulating miR-21 levels reflected miR-21 expression within the tissues.

Conclusions

Addition of Cetuximab to CRT following induction chemotherapy did not improve survival. High miR-21 baseline plasma expression was associated with poor clinical outcome in LAPC patients treated with induction chemotherapy followed by chemo-radiotherapy.

Afatinib, an Irreversible EGFR Family Inhibitor, Shows Activity Toward Pancreatic Cancer Cells, Alone and in Combination with Radiotherapy, Independent of KRAS Status

BACKGROUND

Pancreatic adenocarcinoma is characterized by a high frequency of KRAS mutations and frequent deregulation of the epidermal growth factor receptor (EGFR) and other EGFR family members such as HER2/ErbB2. The EGFR inhibitor erlotinib is approved for treatment of pancreatic cancer, but has shown modest activity in most patients.

OBJECTIVE

Here we investigated the activity of afatinib, a second-generation irreversible pan-EGFR family kinase inhibitor, alone or in combination with ionizing radiation, toward pancreatic cancer cells.

METHODS

The influence of afatinib on cell proliferation, cell cycle distribution, clonogenic survival, nuclear fragmentation, ploidy, and centrosome amplification following irradiation was determined. Expression and phosphorylation of HER receptors, Akt, DNA-PKcs, and ERK1/2 was characterized by Western blot analysis.

RESULTS

Afatinib was growth-inhibitory for all three cell lines but cytotoxic only toward BxPC3 (KRAS (wt)) and Capan-2 (KRAS (mut)) cells, both of which express high levels of EGFR, HER2, and HER3 receptors. Afatinib increased the radiosensitivity of BxPC3 and Capan-2 cells, prevented the radio-induced phosphorylation of Akt, and induced mitotic catastrophe following irradiation. In comparison, Panc-1 cells (KRAS (mut)) expressing low levels of EGFR family receptors were resistant to afatinib-induced radiosensitization.

LIMITATIONS

These results must be confirmed in vivo.

CONCLUSIONS

Afatinib showed cytotoxic and radiosensitizing effects toward a subset of pancreatic cancer cells which was closely correlated with expression of EGFR, HER2, and HER3 receptors, but not with KRAS status.

Biological determinants of radioresistance and their remediation in pancreatic cancer

Despite recent advances in radiotherapy, a majority of patients diagnosed with pancreatic cancer (PC) do not achieve objective responses due to the existence of intrinsic and acquired radioresistance. Identification of molecular mechanisms that compromise the efficacy of radiation therapy and targeting these pathways is paramount for improving radiation response in PC patients. In this review, we have summarized molecular mechanisms associated with the radio-resistant phenotype of PC. Briefly, we discuss the reversible and irreversible biological consequences of radiotherapy, such as DNA damage and DNA repair, mechanisms of cancer cell survival and radiation-induced apoptosis following radiotherapy. We further describe various small molecule inhibitors and molecular targeting agents currently being tested in preclinical and clinical studies as potential radiosensitizers for PC. Notably, we draw attention towards the confounding effects of cancer stem cells, immune system, and the tumor microenvironment in the context of PC radioresistance and radiosensitization. Finally, we discuss the need for examining selective radioprotectors in light of the emerging evidence on radiation toxicity to non-target tissue associated with PC radiotherapy.

Radiosensitization of Adenoid Cystic Carcinoma with MDM2 Inhibition

Purpose: Adenoid cystic carcinoma (ACC) is a rare cancer arising from the major or minor salivary gland tissues of the head and neck. There are currently no approved systemic agents or known radiosensitizers for ACC. Unlike the more common head and neck squamous cell carcinomas that frequently harbor TP53 mutations, ACCs contain TP53 mutations at a rate of <5%, rendering them an attractive target for MDM2 inhibition.Experimental Design: We report the successful establishment and detailed characterization of a TP53-WT ACC patient-derived xenograft (PDX), which retained the histologic features of the original patient tumor. We evaluated this model for response to the MDM2 inhibitor AMG 232 as monotherapy and in combination with radiotherapy.Results: AMG 232 monotherapy induced modest tumor growth inhibition, and radiation monotherapy induced a transient tumor growth delay in a dose-dependent fashion. Strikingly, combination treatment of AMG 232 with radiotherapy (including low-dose radiotherapy of 2 Gy/fraction) induced dramatic tumor response and high local tumor control rates 3 months following treatment. Posttreatment analysis revealed that although both AMG 232 and radiotherapy alone induced TP53 tumor-suppressive activities, combination therapy amplified this response with potent induction of apoptosis after combination treatment.Conclusions: These data identify that MDM2 inhibition can provide potent radiosensitization in TP53-WT ACC. In light of the absence of effective systemic agents for ACC, the powerful response profile observed here suggests that clinical trial evaluation of this drug/radiotherapy combination may be warranted to improve local control in this challenging malignancy. Clin Cancer Res; 23(20); 6044-53. ©2017 AACR.

RPA3 is a potential marker of prognosis and radioresistance for nasopharyngeal carcinoma

Radioresistance-induced residual and recurrent tumours are the main cause of treatment failure in nasopharyngeal carcinoma (NPC). Thus, the mechanisms of NPC radioresistance and predictive markers of NPC prognosis and radioresistance need to be investigated and identified. In this study, we identified RPA3 as a candidate radioresistance marker using RNA-seq of NPC samples. In vitro studies further confirmed that RPA3 affected the radiosensitivity of NPC cells. Specifically, the overexpression of RPA3 enhanced radioresistance and the capacity for DNA repair of NPC cells, whereas inhibiting RPA3 expression sensitized NPC cells to irradiation and decreased the DNA repair capacity. Furthermore, the overexpression of RPA3 enhanced RAD51 foci formation in NPC cells after irradiation. Immunohistochemical assays in 104 NPC specimens and 21 normal epithelium specimens indicated that RPA3 was significantly up-regulated in NPC tissues, and a log-rank test suggested that in patients with NPC, high RPA3 expression was associated with shorter overall survival (OS) and a higher recurrence rate compared with low expression (5-year OS rates: 67.2% versus 86.2%; 5-year recurrence rates: 14.8% versus 2.3%). Moreover, TCGA data also indicated that high RPA3 expression correlated with poor OS and a high recurrence rate in patients with head and neck squamous cell carcinoma (HNSC) after radiotherapy. Taken together, the results of our study demonstrated that RPA3 regulated the radiosensitivity and DNA repair capacity of NPC cells. Thus, RPA3 may serve as a new predictive biomarker for NPC prognosis and radioresistance to help guide the diagnosis and individualized treatment of patients with NPC.

HIV-protease inhibitors for the treatment of cancer: Repositioning HIV protease inhibitors while developing more potent NO-hybridized derivatives?

The possible use of HIV protease inhibitors (HIV-PI) as new therapeutic option for the treatment of cancer primarily originated from their success in treating HIV-related Kaposi's sarcoma (KS). While these findings were initially attributed to immune reconstitution and better control of oncogenic viral infections, the number of reports on solid tumors, KS, lymphoma, fibrosarcoma, multiple myeloma and prostate cancer suggest other mechanisms for the anti-neoplastic activity of PIs. However, a major drawback for the possible adoption of HIV-PIs in the therapy of cancer relies on their relatively weak anticancer potency and important side effects. This has propelled several groups to generate derivatives of HIV-PIs for anticancer use, through modifications such as attachment of different moieties, ligands and transporters, including saquinavir-loaded folic acid conjugated nanoparticles and nitric oxide (NO) derivatives of HIV-PIs. In this article, we discuss the current preclinical and clinical evidences for the potential use of HIV-PIs, and of novel derivatives, such as saquinavir-NO in the treatment of cancer.

The HIV protease and PI3K/Akt inhibitor nelfinavir does not improve the curative effect of fractionated irradiation in PC-3 prostate cancer in vitro and in vivo

Background

Radiotherapy has a high curative potential in localized prostate cancer, however, there are still patients with locally advanced tumours who face a considerable risk of recurrence. Radiosensitization using molecular targeted drugs could help to optimize treatment for this high-risk group. The PI3K/Akt pathway is overexpressed in many prostate cancers and is correlated to radioresistance. Nelfinavir, an HIV protease inhibitor (HPI), was found to block this pathway and to radiosensitize cancer cells of different origin. This is the first study examining the effect of nelfinavir in combination with irradiation on prostate cancer cell survival in vitro as well as on growth time and local tumour control in vivo.

Methods

The in vitro effect of nelfinavir on radioresponse of PC-3 was tested by colony formation assay with 10 μM nelfinavir. In vivo, the effect of nelfinavir alone and in combination with irradiation was tested in nude mice carrying PC-3 xenografts. For evaluating tumour growth time, mice were treated with 80 mg nelfinavir/kg body weight, daily at 5 days per week over 6 weeks. Simultaneous irradiation with 30 fractions and total doses between 30 and 120 Gy was applied to calculate local tumour control for day 180 after treatment.

Results

Nelfinavir inhibited Akt phosphorylation at Ser473 and showed a minor but significant effect on clonogenic cell survival in vitro with slightly higher cell survival rates after combined treatment. The treatment of PC-3 xenografts with nelfinavir alone led to no significant increase of tumour growth time and no improvement of local tumour control.

Conclusions

Despite promising growth delay effects of nelfinavir in other tumour models and first clinical applications of this drug as anti-cancer agent, PC-3 prostate cancer cells express no or only minor sensitivity to nelfinavir treatment alone and no radiosensitizing effect in vitro or in vivo.

Microenvironment in determining chemo-resistance in pancreatic cancer: Neighborhood matters

Every year, nearly 300,000 people are diagnosed with pancreatic cancer worldwide, and an equivalent number succumb to this disease. One of the major challenges of pancreatic cancer that contributes to its poor survival rates is the development of resistance to the standard chemotherapy. Heterogeneity of the tumor, the dense fibroblastic stroma, and the aggressive biology of the tumor all contribute to the chemoresistant phenotype. In addition, the acellular components of the tumor microenvironment like hypoxia, stress pathways in the stromal cells, and the cytokines that are secreted by the immune cells, have a definitive role in orchestrating the chemoresistant property of the tumor. In this review, we systematically focus on the role played by the different microenvironmental components in determining chemoresistance of pancreatic tumors.

Radiation Promptly Alters Cancer Live Cell Metabolic Fluxes: An In Vitro Demonstration

Quantitative data is presented that shows significant changes in cellular metabolism in a head and neck cancer cell line 30 min after irradiation. A head and neck cancer cell line (UM-SCC-22B) and a comparable normal cell line, normal oral keratinocyte (NOK) were each separately exposed to 10 Gy and treated with a control drug for disrupting metabolism (potassium cyanide; KCN). The metabolic changes were measured live by fluorescence lifetime imaging of the intrinsically fluorescent intermediate metabolite nicotinamide adenosine dinucleotide (NADH) fluorescence; this method is sensitive to the ratio of bound to free NADH. The results indicated a prompt shift in metabolic signature in the cancer cell line, but not in the normal cell line. Control KCN treatment demonstrated expected metabolic fluxes due to mitochondrial disruption. The detected radiation shift in the cancer cells was blunted in the presence of both a radical scavenger and a HIF-1α inhibitor. The HIF-1α abundance as detected by immunohistochemical staining also increased substantially for these cancer cells, but not for the normal cells. This type of live-cell metabolic monitoring could be helpful for future real-time studies and in designing adaptive radiotherapy approaches.

Xenograft assessment of predictive biomarkers for standard head and neck cancer therapies

Head and neck squamous cell carcinoma (HNSCC) remains a challenging cancer to treat with overall 5-year survival on the order of 50–60%. Therefore, predictive biomarkers for this disease would be valuable to provide more effective and individualized therapeutic approaches for these patients. While prognostic biomarkers such as p16 expression correlate with outcome; to date, no predictive biomarkers have been clinically validated for HNSCC. We generated xenografts in immunocompromised mice from six established HNSCC cell lines and evaluated response to cisplatin, cetuximab, and radiation. Tissue microarrays were constructed from pre- and posttreatment tumor samples derived from each xenograft experiment. Quantitative immunohistochemistry was performed using a semiautomated imaging and analysis platform to determine the relative expression of five potential predictive biomarkers: epidermal growth factor receptor (EGFR), phospho-EGFR, phospho-Akt, phospho-ERK, and excision repair cross-complementation group 1 (ERCC1). Biomarker levels were compared between xenografts that were sensitive versus resistant to a specific therapy utilizing a two-sample t-test with equal standard deviations. Indeed the xenografts displayed heterogeneous responses to each treatment, and we linked a number of baseline biomarker levels to response. This included low ERCC1 being associated with cisplatin sensitivity, low phospho-Akt correlated with cetuximab sensitivity, and high total EGFR was related to radiation resistance. Overall, we developed a systematic approach to identifying predictive biomarkers and demonstrated several connections between biomarker levels and treatment response. Despite these promising initial results, this work requires additional preclinical validation, likely involving the use of patient-derived xenografts, prior to moving into the clinical realm for confirmation among patients with HNSCC.

Synergistic Blockade of EGFR and HER2 by New-Generation EGFR Tyrosine Kinase Inhibitor Enhances Radiation Effect in Bladder Cancer Cells

Blockade of EGFR has been proved useful in enhancing the effect of radiotherapy, but the advantages of new-generation EGFR tyrosine kinase inhibitors (TKI) in radiosensitization are not well known. We used two human bladder cancer cells with wild-type EGFR to study the synergism between irradiation and afatinib (an EGFR/HER2 dual kinase inhibitor) or erlotinib (an EGFR kinase inhibitor). Here, we showed that afatinib has better radiosensitizing effect than erlotinib in increasing cancer cell killing, the percentage of apoptotic cells, and DNA damage. Afatinib is also superior to erlotinib in combining radiation to decrease tumor size, inhibit glucose metabolism, and enhance apoptotic proteins in vivo. Finally, erlotinib suppressed cell growth and induced more DNA damage in bladder cancer cells transfected with HER2 shRNA, but not in control vector-treated cells. In conclusion, concomitant blockade of radiation-activated EGFR and HER2 signaling by a new-generation EGFR TKI better inhibits the growth of bladder cancer cells both in vitro and in vivo. The absence of radiosensitization by EGFR inhibition alone and the greater radiosensitizing effect of EGFR inhibitor in HER2 knocked down cells suggest the synergism between HER2 and EGFR in determining radiosensitivity. The regained radiosensitizing activity of erlotinib implies that with proper HER2 inhibition, EGFR tyrosine kinase is still a potential target to enhance radiotherapy effect in these seemingly unresponsive bladder cancer cells.

Nelfinavir and other protease inhibitors in cancer: mechanisms involved in anticancer activity

OBJECTIVE

To review the mechanisms of anti-cancer activity of nelfinavir and other protease inhibitors (PIs) based on evidences reported in the published literature.

METHODS

We extensively reviewed the literature concerning nelfinavir (NFV) as an off target anti-cancer drug and other PIs. A classification of PIs based on anti-cancer mode of action was proposed. Controversies regarding nelfinavir mode of action were also addressed.

CONCLUSIONS

The two main mechanisms involved in anti-cancer activity are endoplasmic reticulum stress-unfolded protein response pathway and Akt inhibition. However there are many other effects, partially dependent and independent of those mentioned, that may be useful in cancer treatment, including MMP-9 and MMP-2 inhibition, down-regulation of CDK-2, VEGF, bFGF, NF-kB, STAT-3, HIF-1 alfa, IGF, EGFR, survivin, BCRP, androgen receptor, proteasome, fatty acid synthase (FAS), decrease in cellular ATP concentration and upregulation of TRAIL receptor DR5, Bax, increased radiosensitivity, and autophagy. The end result of all these effects is slower growth, decreased angiogenesis, decreased invasion and increased apoptosis, which means reduced proliferation and increased cancer cells death. PIs may be classified according to their anticancer activity at clinically achievable doses, in AKT inhibitors, ER stressors and Akt inhibitors/ER stressors. Beyond the phase I trials that have been recently completed, adequately powered and well-designed clinical trials are needed in the various cancer type settings, and specific trials where NFV is tested in association with other known anti-cancer pharmaceuticals should be sought, in order to find an appropriate place for NFV in cancer treatment. The analysis of controversies on the molecular mechanisms of NFV hints to the possibility that NFV works in a different way in tumor cells and in hepatocytes and adipocytes.

Human papillomavirus type 16 E7 oncoprotein causes a delay in repair of DNA damage

BACKGROUND AND PURPOSE

Patients with human papillomavirus related (HPV+) head and neck cancers (HNCs) demonstrate improved clinical outcomes compared to traditional HPV negative (HPV-) HNC patients. We have recently shown that HPV+ HNC cells are more sensitive to radiation than HPV- HNC cells. However, roles of HPV oncogenes in regulating the response of DNA damage repair remain unknown.

MATERIAL AND METHODS

Using immortalized normal oral epithelial cell lines, HPV+ HNC derived cell lines, and HPV16 E7-transgenic mice we assessed the repair of DNA damage using γ-H2AX foci, single and split dose clonogenic survival assays, and immunoblot. The ability of E7 to modulate expression of proteins associated with DNA repair pathways was assessed by immunoblot.

RESULTS

HPV16 E7 increased retention of γ-H2AX nuclear foci and significantly decreased sublethal DNA damage repair. While phospho-ATM, phospho-ATR, Ku70, and Ku80 expressions were not altered by E7, Rad51 was induced by E7. Correspondingly, HPV+ HNC cell lines showed retention of Rad51 after γ-radiation.

CONCLUSIONS

Our findings provide further understanding as to how HPV16 E7 manipulates cellular DNA damage responses that may underlie its oncogenic potential and influence the altered sensitivity to radiation seen in HPV+ HNC as compared to HPV- HNC.

Unbiased analysis of pancreatic cancer radiation resistance reveals cholesterol biosynthesis as a novel target for radiosensitisation

BACKGROUND

Despite its promise as a highly useful therapy for pancreatic cancer (PC), the addition of external beam radiation therapy to PC treatment has shown varying success in clinical trials. Understanding PC radioresistance and discovery of methods to sensitise PC to radiation will increase patient survival and improve quality of life. In this study, we identified PC radioresistance-associated pathways using global, unbiased techniques.

METHODS

Radioresistant cells were generated by sequential irradiation and recovery, and global genome cDNA microarray analysis was performed to identify differentially expressed genes in radiosensitive and radioresistant cells. Ingenuity pathway analysis was performed to discover cellular pathways and functions associated with differential radioresponse and identify potential small-molecule inhibitors for radiosensitisation. The expression of FDPS, one of the most differentially expressed genes, was determined in human PC tissues by IHC and the impact of its pharmacological inhibition with zoledronic acid (ZOL, Zometa) on radiosensitivity was determined by colony-forming assays. The radiosensitising effect of Zol in vivo was determined using allograft transplantation mouse model.

RESULTS

Microarray analysis indicated that 11 genes (FDPS, ACAT2, AG2, CLDN7, DHCR7, ELFN2, FASN, SC4MOL, SIX6, SLC12A2, and SQLE) were consistently associated with radioresistance in the cell lines, a majority of which are involved in cholesterol biosynthesis. We demonstrated that knockdown of farnesyl diphosphate synthase (FDPS), a branchpoint enzyme of the cholesterol synthesis pathway, radiosensitised PC cells. FDPS was significantly overexpressed in human PC tumour tissues compared with healthy pancreas samples. Also, pharmacologic inhibition of FDPS by ZOL radiosensitised PC cell lines, with a radiation enhancement ratio between 1.26 and 1.5. Further, ZOL treatment resulted in radiosensitisation of PC tumours in an allograft mouse model.

CONCLUSIONS

Unbiased pathway analysis of radioresistance allowed for the discovery of novel pathways associated with resistance to ionising radiation in PC. Specifically, our analysis indicates the importance of the cholesterol synthesis pathway in PC radioresistance. Further, a novel radiosensitiser, ZOL, showed promising results and warrants further study into the universality of these findings in PC, as well as the true potential of this drug as a clinical radiosensitiser.

Valproic acid sensitizes pancreatic cancer cells to natural killer cell-mediated lysis by upregulating MICA and MICB via the PI3K/Akt signaling pathway

Background

Valproic acid (VPA), a histone deacetylase (HDAC) inhibitor, is reported to exert anti-tumor effects by upregulating the expression of the natural killer group 2D (NKG2D) ligands on tumor cells; however, the mechanisms vary in different tumor types, and the effect and mechanism of action of VPA in pancreatic cancer cells are unknown.

Methods

The present study evaluated the effect of VPA to susceptibility of pancreatic cancer cells to the NK cell-mediated lysis in vitro and in vivo. Then we investigated the mechanism which the effect of VPA depend on.

Results

The lactate dehydrogenase assay (LDH) and xenograft experiment demonstrated that VPA significantly sensitized pancreatic cancer cells to NK cell-mediated lysis in vitro and in vivo. Quantitative real time- polymerase chain reaction (qRT-PCR) and flow cytometry demonstrated that VPA upregulated the mRNA and cell surface expression of the NKG2D ligands major histocompatibility complex class I-related chain A and B (MICA and MICB) in pancreatic cancer cells. Effects of VPA both in vitro and in vivo were significantly attenuated by the PI3K/Akt pathway inhibitor LY294002 or a siRNA targeting PI3K catalytic subunit alpha isoform (PI3KCA).

Conclusion

VPA enhances the susceptibility of pancreatic cancer cells to NK cell-mediated cytotoxicity both in vitro and in vivo by upregulating the expression of MICA and MICB via a PI3K/Akt signaling pathway-dependent mechanism.

Sequence-specific alterations of epitope production by HIV protease inhibitors

Ag processing by intracellular proteases and peptidases and epitope presentation are critical for recognition of pathogen-infected cells by CD8+ T lymphocytes. First-generation HIV protease inhibitors (PIs) alter proteasome activity, but the effect of first- or second-generation PIs on other cellular peptidases, the underlying mechanism, and impact on Ag processing and epitope presentation to CTL are still unknown. In this article, we demonstrate that several HIV PIs altered not only proteasome but also aminopeptidase activities in PBMCs. Using an in vitro degradation assay involving PBMC cytosolic extracts, we showed that PIs altered the degradation patterns of oligopeptides and peptide production in a sequence-specific manner, enhancing the cleavage of certain residues and reducing others. PIs affected the sensitivity of peptides to intracellular degradation, and altered the kinetics and amount of HIV epitopes produced intracellularly. Accordingly, the endogenous degradation of incoming virions in the presence of PIs led to variations in CTL-mediated killing of HIV-infected cells. By altering host protease activities and the degradation patterns of proteins in a sequence-specific manner, HIV PIs may diversify peptides available for MHC class I presentation to CTL, alter the patterns of CTL responses, and provide a complementary approach to current therapies for the CTL-mediated clearance of abnormal cells in infection, cancer, or other immune disease.

Phase II Trial of Cetuximab and Conformal Radiotherapy Only in Locally Advanced Pancreatic Cancer with Concurrent Tissue Sampling Feasibility Study

BACKGROUND

Preclinical data have indicated the anti-epidermal growth factor receptor (EGFR) agent cetuximab (Erbitux) as a radiosensitizer in pancreatic cancer, but this has not been specifically addressed in a clinical study. We report the results of an original study initiated in 2007, where cetuximab was tested with radiotherapy (RT) alone in locally advanced pancreatic cancer in a phase II trial (PACER).

METHODS

Patients (n = 21) received cetuximab loading dose (400 mg/m(2)) and weekly dose (250 mg/m(2)) during RT (50.4 Gy in 28 fractions). Toxicity and disease response end point data were prospectively assessed. A feasibility study of on-trial patient blood and skin sampling was incorporated.

RESULTS

Treatment was well tolerated, and toxicity was low; most patients (71%) experienced acute toxicities of grade 2 or less. Six months posttreatment, stable local disease was achieved in 90% of evaluable patients, but only 33% were free from metastatic progression. Median overall survival was 7.5 months, and actuarial survival was 33% at 1 year and 11% at 3 years, reflecting swift metastatic progression in some patients but good long-term control of localized disease in others. High-grade acneiform rash (P = .0027), posttreatment stable disease (P = .0059), and pretreatment cancer antigen 19.9 (CA19.9) level (P = .0042) associated with extended survival. Patient skin and blood samples yielded sufficient RNA and good quality protein, respectively.

CONCLUSIONS

The results indicate that cetuximab inhibits EGFR-mediated radioresistance to achieve excellent local control with minimal toxicity but does not sufficiently control metastatic progression in all patients. Translational studies of patient tissue samples may yield molecular information that may enable individual treatment response prediction.

Enhanced radiation sensitivity in HPV-positive head and neck cancer

Patients with human papillomavirus (HPV+)-associated head and neck cancer (HNC) show significantly improved survival outcome compared with those with HPV-negative (HPV-) tumors. Published data examining this difference offers conflicting results to date. We systematically investigated the radiation sensitivity of all available validated HPV+ HNC cell lines and a series of HPV- HNC cell lines using in vitro and in vivo techniques. HPV+ HNCs exhibited greater intrinsic radiation sensitivity (average SF2 HPV-: 0.59 vs. HPV+: 0.22; P < 0.0001), corresponding with a prolonged G2-M cell-cycle arrest and increased apoptosis following radiation exposure (percent change 0% vs. 85%; P = 0.002). A genome-wide microarray was used to compare gene expression 24 hours following radiation between HPV+ and HPV- cell lines. Multiple genes in TP53 pathway were upregulated in HPV+ cells (Z score 4.90), including a 4.6-fold increase in TP53 (P < 0.0001). Using immortalized human tonsillar epithelial (HTE) cells, increased radiation sensitivity was seen in cell expressing HPV-16 E6 despite the effect of E6 to degrade p53. This suggested that low levels of normally functioning p53 in HPV+ HNC cells could be activated by radiation, leading to cell death. Consistent with this, more complete knockdown of TP53 by siRNA resulted in radiation resistance. These results provide clear evidence, and a supporting mechanism, for increased radiation sensitivity in HPV+ HNC relative to HPV- HNC. This issue is under active investigation in a series of clinical trials attempting to de-escalate radiation (and chemotherapy) in selected patients with HPV+ HNC in light of their favorable overall survival outcome.

Upregulation of epidermal growth factor receptor 4 in oral leukoplakia

In the present study, we investigate the expression profile of the epidermal growth factor receptor family, which comprises EGFR/ErbB1, HER2/ErbB2, HER3/ErbB3 and HER4/ErbB4 in oral leukoplakia (LP). The expression of four epidermal growth factor receptor (EGFR) family genes and their ligands were measured in LP tissues from 14 patients and compared with levels in 10 patients with oral lichen planus (OLP) and normal oral mucosa (NOM) from 14 healthy donors by real-time polymerase chain reaction (PCR) and immunohistochemistry. Synchronous mRNA coexpression of ErbB1, ErbB2, ErbB3 and ErbB4 was detected in LP lesions. Out of the receptors, only ErbB4 mRNA and protein was more highly expressed in LP compared with NOM tissues. These were strongly expressed by epithelial keratinocytes in LP lesions, as shown by immunohistochemistry. Regarding the ligands, the mRNA of Neuregulin2 and 4 were more highly expressed in OLP compared with NOM tissues. Therefore, enhanced ErbB4 on the keratinocytes and synchronous modulation of EGFR family genes may contribute to the pathogenesis and carcinogenesis of LP.

Dual targeting of EGFR and HER3 with MEHD7945A overcomes acquired resistance to EGFR inhibitors and radiation

EGF receptor (EGFR) inhibition is efficacious in cancer therapy, but initially sensitive tumors often develop resistance. In this study, we investigated the potential to overcome acquired resistance to EGFR inhibitors with MEHD7945A, a monoclonal antibody that dually targets EGFR and HER3 (ErbB3). In cancer cells resistant to cetuximab and erlotinib, we found that MEHD7945A, but not single target EGFR inhibitors, could inhibit tumor growth and cell-cycle progression in parallel with EGFR/HER3 signaling pathway modulation. MEHD7945A was more effective than a combination of cetuximab and anti-HER3 antibody at inhibiting both EGFR/HER3 signaling and tumor growth. In human tumor xenograft models, we confirmed the greater antitumor potency of MEHD7945A than cetuximab or erlotinib. MEHD7945A retained potent activity in tumors refractory to EGFR inhibitor alone. Furthermore, MEHD7945A also limited cross-resistance to radiation in EGFR inhibitor-resistant cells by modulating cell-cycle progression and repair processes that control apoptotic cell death. Taken together, our findings confirm an important role of compensatory HER3 signaling in the development of acquired resistance to EGFR inhibitors and offer preclinical proof-of-concept that MEHD7945A can effectively overcome EGFR inhibitor resistance.

The role of chemoradiation for patients with resectable or potentially resectable pancreatic cancer

Conflicting data and substantial controversy exist regarding optimal adjuvant treatment for those patients with resectable or potentially resectable adenocarcinoma of the pancreas. Despite improvements in short-term surgical outcomes, the use of newer chemotherapeutic agents, development of targeted agents and more precise delivery of radiation, the 5-year survival rates for early-stage patients remains less than 25%. This article critically reviews the existing data for various adjuvant treatment approaches for patients with surgically resectable pancreatic cancer. Our review confirms that despite several randomized clinical trials, the optimal adjuvant treatment approach for these patients remains unclear.

In pancreatic carcinoma, dual EGFR/HER2 targeting with cetuximab/trastuzumab is more effective than treatment with trastuzumab/erlotinib or lapatinib alone: implication of receptors' down-regulation and dimers' disruption

We previously demonstrated the synergistic therapeutic effect of the cetuximab (anti-epidermal growth factor receptor [EGFR] monoclonal antibody, mAb)-trastuzumab (anti-HER2 mAb) combination (2mAbs therapy) in HER2(low) human pancreatic carcinoma xenografts. Here, we compared the 2mAbs therapy, the erlotinib (EGFR tyrosine kinase inhibitor [TKI])-trastuzumab combination and lapatinib alone (dual HER2/EGFR TKI) and explored their possible mechanisms of action. The effects on tumor growth and animal survival of the three therapies were assessed in nude mice xenografted with the human pancreatic carcinoma cell lines Capan-1 and BxPC-3. After therapy, EGFR and HER2 expression and AKT phosphorylation in tumor cells were analyzed by Western blot analysis. EGFR/HER2 heterodimerization was quantified in BxPC-3 cells by time-resolved FRET. In K-ras-mutated Capan-1 xenografts, the 2mAbs therapy gave significantly higher inhibition of tumor growth than the erlotinib/trastuzumab combination, whereas in BxPC-3 (wild-type K-ras) xenografts, the erlotinib/trastuzumab combination showed similar growth inhibition but fewer tumor-free mice. Lapatinib showed no antitumor effect in both types of xenografts. The efficacy of the 2mAbs therapy was partly Fc-independent because F(ab')(2) fragments of the two mAbs significantly inhibited BxPC-3 growth, although with a time-limited therapeutic effect. The 2mAbs therapy was associated with a reduction of EGFR and HER2 expression and AKT phosphorylation. BxPC-3 cells preincubated with the two mAbs showed 50% less EGFR/HER2 heterodimers than controls. In pancreatic carcinoma xenografts, the 2mAbs therapy is more effective than treatments involving dual EGFR/HER2 TKIs. The mechanism of action may involve decreased AKT phosphorylation and/or disruption of EGFR/HER2 heterodimerization.

Nelfinavir induces radiation sensitization in pituitary adenoma cells

Pituitary adenomas with local invasion and high secretory activity remain a therapeutic challenge. The HIV protease inhibitor nelfinavir is a radiosensitizer in multiple tumor models. We tested nelfinavir as a radiosensitizer in pituitary adenoma cells in vitro and in vivo. We examined the effect of nelfinavir with radiation on in vitro cell viability, clonogenic survival, apoptosis, prolactin secretion, cell cycle distribution, and the PI3K-AKT-mTOR pathway. We evaluated tumor growth delay and confirmed nelfinavir's effect on the PI3K-AKT-mTOR pathway in a hind-flank model. Nelfinavir sensitized pituitary adenoma cells to ionizing radiation as shown by viability assays and clonogenic assay with an enhancement ratio of 1.2 (p < 0.05). There is increased apoptotic cell death, as determined by annexin-V expression and cleaved caspase-3 levels. Nelfinavir does not affect prolactin secretion or cell cycle distribution. In vivo, untreated tumors reached 4-fold volume in 12 days, 17 days with nelfinavir treatment, 27 days with radiation 6 Gy, and 41 days with nelfinavir plus radiation (one-way ANOVA p < 0.001). Decreased phospho-S6 on Western blotting in vitro and immunohistochemistry in vivo demonstrated nelfinavir inhibition of the PI3K-AKT-mTOR pathway. Our data suggests a promising combination therapy with nelfinavir plus radiation in pituitary adenomas, which should be investigated in clinical studies.

Identification and evaluation of a potent novel ATR inhibitor, NU6027, in breast and ovarian cancer cell lines

Background:

The ataxia telangiectasia mutated and Rad3-related kinase (ATR) has a key role in the signalling of stalled replication forks and DNA damage to cell cycle checkpoints and DNA repair. It has long been recognised as an important target for cancer therapy but inhibitors have proved elusive. As NU6027, originally developed as a CDK2 inhibitor, potentiated cisplatin in a CDK2-independent manner we postulated that it may inhibit ATR.

Methods:

Cellular ATR kinase activity was determined by CHK1 phosphorylation in human fibroblasts with inducible dominant-negative ATR-kinase dead expression and human breast cancer MCF7 cells. Cell cycle effects and chemo- and radiopotentiation by NU6027 were determined in MCF7 cells and the role of mismatch repair and p53 was determined in isogenically matched ovarian cancer A2780 cells.

Results:

NU6027 is a potent inhibitor of cellular ATR activity (IC₅₀=6.7 μM) and enhanced hydroxyurea and cisplatin cytotoxicity in an ATR-dependent manner. NU6027 attenuated G2/M arrest following DNA damage, inhibited RAD51 focus formation and increased the cytotoxicity of the major classes of DNA-damaging anticancer cytotoxic therapy but not the antimitotic, paclitaxel. In A2780 cells sensitisation to cisplatin was greatest in cells with functional p53 and mismatch repair (MMR) and sensitisation to temozolomide was greatest in p53 mutant cells with functional MMR. Importantly, NU6027 was synthetically lethal when DNA single-strand break repair is impaired either through poly(ADP-ribose) polymerase (PARP) inhibition or defects in XRCC1.

Conclusion:

NU6027 inhibits ATR, impairing G2/M arrest and homologous recombination thus increasing sensitivity to DNA-damaging agents and PARP inhibitors. It provides proof of concept data for clinical development of ATR inhibitors.

[New perspectives for radiosensitization in pancreatic carcinoma: a review of mechanisms involved in pancreatic tumorigenesis]

Pancreatic carcinoma is the fifth leading cause of cancer-related mortality. The 5-year overall survival is less than 5 %. This very poor prognosis can be explained both by late diagnosis and by treatment resistance, including resistance to radiation therapy. A better understanding of the pancreatic tumorigenesis and knowledge of the most frequent mutations in pancreatic adenocarcinoma (KRAS, p16, TP53, Smad4) open new perspectives for the development of more effective treatments. This review presents the major genetic and molecular alterations in pancreatic cancer that could be targeted to improve radiosensitization.

Activation of PDGFr-β Signaling Pathway after Imatinib and Radioimmunotherapy Treatment in Experimental Pancreatic Cancer

Pancreatic cancer does not respond to a single-agent imatinib therapy. Consequently, multimodality treatments are contemplated. Published data indicate that in colorectal cancer, imatinib and radioimmunotherapy synergize to delay tumor growth. In pancreatic cancer, the tumor response is additive. This disparity of outcomes merited further studies because interactions between these modalities depend on the imatinib-induced reduction of the tumor interstitial fluid pressure. The examination of human and murine PDGFr-β/PDGF-B pathways in SW1990 pancreatic cancer xenografts revealed that the human branch is practically dormant in untreated tumors but the insult on the stromal component produces massive responses of human cancer cells. Inhibition of the stromal PDGFr-β with imatinib activates human PDGFr-β/PDGF-B signaling loop, silent in untreated xenografts, via an apparent paracrine rescue pathway. Responses are treatment-and time-dependent. Soon after treatment, levels of human PDGFr-β, compared to untreated tumors, are 3.4×, 12.4×, and 5.7× higher in imatinib-, radioimmunotherapy + imatinib-, and radioimmunotherapy-treated tumors, respectively. A continuous 14-day irradiation of imatinib-treated xenografts reduces levels of PDGFr-β and phosphorylated PDGFr-β by 5.3× and 4×, compared to earlier times. Human PDGF-B is upregulated suggesting that the survival signaling via the autocrine pathway is also triggered after stromal injury. These findings indicate that therapies targeting pancreatic cancer stromal components may have unintended mitogenic effects and that these effects can be reversed when imatinib is used in conjunction with radioimmunotherapy.

Acute toxicity of second generation HIV protease-inhibitors in combination with radiotherapy: a retrospective case series

BACKGROUND

There is little data on the safety of combining radiation therapy and human immunodeficiency virus (HIV) protease inhibitors to treat cancers in HIV-positive patients. We describe acute toxicities observed in a series of HIV-positive patients receiving modern radiation treatments, and compare patients receiving HIV protease inhibitors (PI) with patients not receiving HIV PIs.

METHODS

By reviewing the clinical records beginning January 1, 2009 from the radiation oncology department, we identified 29 HIV-positive patients who received radiation therapy to 34 body sites. Baseline information, treatment regimen, and toxicities were documented by review of medical records: patient age, histology and source of the primary tumor, HIV medication regimen, pre-radiation CD4 count, systemic chemotherapy, radiation therapy dose and fractionation, irradiated body region, toxicities, and duration of follow-up. Patients were grouped according to whether they received concurrent HIV PIs and compared using Pearson's chi-square test.

RESULTS

At baseline, the patients in the two groups were similar with the exception of HIV medication regimens, CD4 count and presence of AIDS-defining malignancy. Patients taking concurrent PIs were more likely to be taking other HIV medications (p = 0.001) and have CD4 count >500 (p = 0.006). Patients taking PIs were borderline less likely to have an AIDS-defining malignancy (p = 0.06). After radiation treatment, 100 acute toxicities were observed and were equally common in both groups (64 [median 3 per patient, IQR 1-7] with PIs; 36 [median 3 per patient, IQR 2-3] without PIs). The observed toxicities were also equally severe in the two groups (Grades I, II, III respectively: 30, 30, 4 with PIs; 23, 13, 0 without PIs: p = 0.38). There were two cases that were stopped early, one in each group; these were not attributable to toxicity.

CONCLUSIONS

In this study of recent radiotherapy in HIV-positive patients taking second generation PIs, no difference in toxicities was observed in patients taking PIs compared to patients not taking PIs during radiation therapy. This suggests that it is safe to use unmodified doses of PIs and radiation therapy in HIV cancer patients, and that it is feasible to use PIs as a radiosensitizer in cancer therapy, as has been suggested by pre-clinical results.

Inhibition of MCL-1 in breast cancer cells promotes cell death in vitro and in vivo

The present studies have examined approaches to suppress MCL-1 function in breast cancer cells, as a means to promote tumor cell death. Treatment of breast cancer cells with CDK inhibitors (flavopiridol; roscovitine) enhanced the lethality of the ERBB1 inhibitor lapatinib in a synergistic fashion. CDK inhibitors interacted with lapatinib to reduce MCL-1 expression and over-expression of MCL-1 or knock down of BAX and BAK suppressed drug combination lethality. Lapatinib-mediated inhibition of ERK1/2 and to a lesser extent AKT facilitated CDK inhibitor -induced suppression of MCL-1 levels. Treatment of cells with the BH3 domain / MCL-1 inhibitor obatoclax enhanced the lethality of lapatinib in a synergistic fashion. Knock out of MCL-1 and BCL-XL enhanced lapatinib toxicity to a similar extent as obatoclax and suppressed the ability of obatoclax to promote lapatinib lethality. Pre-treatment of cells with lapatinib or with obatoclax enhanced basal levels of BAX and BAK activity and further enhanced drug combination toxicity. In vivo tumor growth data in xenograft and syngeneic model systems confirmed our in vitro findings. Treatment of cells with CDK inhibitors enhanced the lethality of obatoclax in a synergistic fashion. Over-expression of MCL-1 or knock down of BAX and BAK suppressed the toxic interaction between CDK inhibitors and obatoclax. Obatoclax and lapatinib treatment or obatoclax and CDK inhibitor treatment or lapatinib and CDK inhibitor treatment radiosensitized breast cancer cells. Lapatinib and obatoclax interacted to suppress mammary tumor growth in vivo. Collectively our data demonstrate that manipulation of MCL-1 protein expression by CDK inhibition or inhibition of sequestering function MCL-1 by Obatoclax renders breast cancer cells more susceptible to BAX/BAK-dependent mitochondrial dysfunction and tumor cell death.

A combination of the metabolic enzyme inhibitor APO866 and the immune adjuvant L-1-methyl tryptophan induces additive antitumor activity

Many types of malignant cells have a higher nicotinamide adenine dinucleotide (NAD) turnover rate than normal cells, as well as the ability to escape immune responses. Indoleamine 2,3-dioxygenase (IDO) is reported to be a negative immune regulator. Overexpression of IDO in dendritic cells is observed in tumor-draining lymph nodes. IDO-expressing dendritic cells suppress T-cell activation and promote immune tolerance. The nicotinamide phosphoribosyl transferase (NAMPT) inhibitor APO866 (also called FK866 or WK175) selectively inhibits tumor growth through intracellular NAD depletion. The IDO-specific inhibitor L-1-methyl-tryptophan (L-1MT) activates immune responses and reduces tumor volume in murine tumor models. We combined L-1MT and APO866 treatments and tested their antitumor effects in the murine gastric and bladder tumor models. In immune-competent mice, a combination of APO866 and L-1MT had a better therapeutic effect than did either L-1MT or APO866 alone. The intracellular level of NAD was suppressed by APO866 but not L-1MT. However, an additive inhibitory effect on tumor growth was not observed in tumor-bearing immune-deficient mice. The new strategy of combining a metabolic inhibitor and an immune adjuvant induced a potent therapeutic effect.