Phase I Trial of Pembrolizumab and Radiation Therapy after Induction Chemotherapy for Extensive-Stage Small Cell Lung Cancer.

INTRUDUCTION: Radiation and immunotherapy have separately been shown to confer survival advantages to patients with extensive-stage small cell lung cancer (ESCLC), but failure rates remain high and combination therapy has been understudied. In this single-arm phase I trial (NCT02402920), we assessed the safety of combining pembrolizumab with thoracic radiotherapy (TRT) after induction chemotherapy for SCLC. METHODS: Patients with ESCLC who had completed chemotherapy received TRT with pembrolizumab. The maximum tolerated dose of pembrolizumab was assessed by 3+3 dose-escalation; doses began at 100 mg and increased in 50 mg increments to 200 mg. Pembrolizumab was given every 3 weeks for up to 16 cycles; TRT was prescribed as 45 Gy in 15 daily fractions. Toxicity was evaluated with the Common Terminology Criteria for Adverse Events v4.0. The primary endpoint was safety of the combined therapy based on the incidence of dose-limiting toxicity in the 35 days following initiation of treatment. RESULTS: Thirty-eight patients with ESCLC (median age 65 years, range: 37-79 years) were enrolled from September 2015 through September 2017; 33 received per-protocol treatment, and all tolerated pembrolizumab at 100 to 200 mg with no dose-limiting toxicity in the 35-day window. There were no grade 4-5 toxicities; 2 (6%) patients experienced grade 3 events (n = 1 rash, n = 1 asthenia/paresthesia/autoimmune disorder) that were unlikely/doubtfully related to protocol therapy. The median follow-up time was 7.3 months (range: 1-13 months); median progression-free and overall survival times were 6.1 months (95% confidence interval: 4.1-8.1) and 8.4 months (95% confidence interval: 6.7-10.1). CONCLUSIONS: Concurrent pembrolizumab-TRT was tolerated well with few high-grade adverse events in the short-term; progression-free and overall survival rates are difficult to interpret due to heterogeneity in eligibility criteria (e.g., enrolling progressors on induction chemotherapy). Although randomized studies have shown benefits to TRT alone and immunotherapy alone, the safety of the combined regimen supports further investigation as a foundational approach for future prospective studies.

Phase II Trial of Ipilimumab with Stereotactic Radiation Therapy for Metastatic Disease: Outcomes, Toxicities, and Low-Dose Radiation-Related Abscopal Responses.

Ipilimumab is effective for patients with melanoma, but not for those with less immunogenic tumors. We report a phase II trial of ipilimumab with concurrent or sequential stereotactic ablative radiotherapy to metastatic lesions in the liver or lung (NCT02239900). Ipilimumab (every 3 weeks for 4 doses) was given with radiotherapy begun during the first dose (concurrent) or 1 week after the second dose (sequential) and delivered as 50 Gy in 4 fractions or 60 Gy in 10 fractions to metastatic liver or lung lesions. In total, 106 patients received ≥1 cycle of ipilimumab with radiation. Median follow-up was 10.5 months. Median progression-free survival time was 2.9 months (95% confidence interval, 2.45-3.40), and median overall survival time was not reached. Rates of clinical benefit of nonirradiated tumor volume were 26% overall, 28% for sequential versus 20% for concurrent therapy (P = 0.250), and 31% for lung versus 14% for liver metastases (P = 0.061). The sequential lung group had the highest rate of clinical benefit at 42%. There were no differences in treatment-related adverse events between groups. Exploratory analysis of nontargeted lesions revealed that lesions receiving low-dose radiation were more likely to respond than those that received no radiation (31% vs. 5%, P = 0.0091). This phase II trial of ipilimumab with stereotactic radiotherapy describes satisfactory outcomes and low toxicities, lending support to further investigation of combined-modality therapy for metastatic cancers.

Accumulation of RNA-dependent protein kinase (PKR) in the nuclei of lung cancer cells mediates radiation resistance.

We have previously demonstrated that radiation induced cell death in PKR (-/-) deficient mouse embryo fibroblasts (MEFs) but not in PKR (+/+) wild type MEFs. Our study indicated that PKR can also be involved in survival pathways following radiation therapy through activation of the AKT survival pathways in these MEFs is mediated in part through PKR. The role of PKR on radiation sensitivity in cancer cells has not been evaluated. In this study, we demonstrated that radiation treatment causes nuclear translocation of PKR in human lung cancer cells. The transduction of lung cancer cells with a dominant negative adenoviral PKR vector blocks nuclear translocation of PKR and leads to the reversal of radiation resistance. Plasmid transduction of lung cancer cells with nuclear targeted wild type PKR vectors also increased radiation resistance. This effect is selectively abrogated by plasmid transduction of dominant negative PKR vectors which restore radiation sensitivity. These findings suggest a novel role for PKR in lung cancer cells as a mediator of radiation resistance possibly through translocation of the protein product to the nucleus.

Zerumbone increases oxidative stress in a thiol-dependent ROS-independent manner to increase DNA damage and sensitize colorectal cancer cells to radiation.

Locally advanced rectal cancers are treated with neoadjuvant chemoradiation therapy followed by surgery. In a minority (~20%) of patients, no tumor is present at the time of surgery; these patients with a complete pathologic response (pathCR) to neoadjuvant therapy have better treatment outcomes. Unfortunately, the inherent radioresistance of colorectal cancer (CRC) cells dictates that the majority of patients do not achieve a pathCR. Efforts to improve these odds have fueled the search for novel, relatively less-toxic radiosensitizers with distinct molecular mechanism(s) and broad-spectrum anticancer activities. Here, we use zerumbone, a sesquiterpene from the edible ginger (Zingiber zerumbet Smith), to enhance radiosensitivity of CRC cells. Short exposure to zerumbone (7 h) profoundly sensitized CRC cells, independent of their p53 or k-RAS status. Zerumbone enhanced radiation-induced cell cycle arrest (G2/M), increased radiation-induced apoptosis, but induced little apoptosis by itself. Zerumbone significantly enhanced radiation-induced DNA damage, as evident by delayed resolution of post-irradiation nuclear γH2AX foci, whereas zerumbone treatment alone did not induce γH2AX foci formation. Zerumbone pretreatment inhibited radiation-induced nuclear expression of DNA repair proteins ataxia-telangiectasia mutated (ATM) and DNA-PKcs. Interestingly, zerumbone-mediated radiosensitization did not involve reactive oxygen species (ROS), but was mediated through depletion of cellular glutathione (GSH). Ability of only thiol-based antioxidants to abrogate zerumbone-mediated radiosensitization further corroborated this hypothesis. The α,ß-unsaturated carbonyl group in zerumbone was found to be essential for its bioactivity as zerumbone analog α-Humulene that lacks this functional group, could neither radiosensitize CRC cells, nor deplete cellular GSH. Our studies elucidate novel mechanism(s) of zerumbone's ability to enhance CRC radiosensitivity.

Inhibition of EGFR or IGF-1R signaling enhances radiation response in head and neck cancer models but concurrent inhibition has no added benefit.

Interaction between the epidermal growth factor receptor (EGFR) and the insulin-like growth factor receptor (IGF-1R) has been well established in many cancer types. We investigated the effects of cetuximab (EGFR antibody) and IMC-A12 (IGF-1R antibody) on the response of head and neck squamous cell carcinoma (HNSCC) to radiation therapy (RT). The effects of cetuximab and IMC-A12 on cell viability and radiosensitivity were determined by clonogenic cell survival assay. Formation of nuclear γ-H2AX and 53BP1 foci was monitored by immunofluorescence. Alterations in target signaling were analyzed by Western blots. In vivo tumor growth delay assay was performed to determine the efficacy of triple therapy with IMC-A12, cetuximab, and RT. In vitro data showed that cetuximab differentially affected the survival and the radiosensitivity of HNSCC cells. Cetuximab suppressed DNA repair that was evident by the prolonged presence of nuclear γ-H2AX and 53BP1 foci. IMC-A12 did not have any effect on the cell survival. However, it increased the radiosensitivity of one of the cell lines. EGFR inhibition increased IGF-1R expression levels and also the association between EGFR and IGF-1R. Addition of IMC-A12 to cetuximab did not increase the radiosensitivity of these cells. Tumor xenografts exhibited enhanced response to RT in the presence of either cetuximab or IMC-A12. Concurrent treatment regimen failed to further enhance the tumor response to cetuximab and/or RT. Taken together our data suggest that concomitant inhibition of both EGFR and IGF-1R pathways did not yield additional therapeutic benefit in overcoming resistance to RT.

Inhibition of P-TEFb by DRB suppresses SIRT1/CK2α pathway and enhances radiosensitivity of human cancer cells.

BACKGROUND: Positive transcription elongation factor-b (P-TEFb) is a complex containing CDK9 and a cyclin (T1, T2 or K). The effect of inhibition of P-TEFb by 5,6-dichloro-l-ß-D-ribofuranosyl benzimidazole (DRB) on cell radiosensitivity and the underlying mechanisms were investigated. MATERIALS AND METHODS: Six human cancer cell lines were subjected to (3)H-uridine incorporation, cell viability and clonogenic cell survival assays; cell-cycle redistribution and apoptosis assay; western blots and nuclear 53BP1 foci analysis after exposing the cells to DRB with/without γ-radiation. RESULTS: DRB suppressed colony formation and enhanced radiosensitivity of all cell lines. DRB caused a further increase in radiation-induced apoptosis and cell-cycle redistribution depending on p53 status. DRB prolonged the presence of radiation-induced nuclear p53 binding protein-1 (53BP1) foci and suppressed the expression of sirtuin-1 (SIRT1) and casein kinase 2-alpha (CK2α), suggesting an inhibition of DNA repair processes. CONCLUSION: Our findings indicate that DRB has the potential to increase the efficacy of radiotherapy and warrants further investigation using in vivo tumor models.

Poly (ADP-ribose) polymerase inhibitors in cancer treatment.

Recent research on inhibitors of poly (ADP-ribose) polymerase (PARP) has demonstrated their potential for improving cancer therapy. They inhibit protein poly (ADP-ribosyl)ation and thus affect numerous molecular and cellular functions, including DNA repair and cell survival, that are critical for such physiological and patho-physiological states as carcinogenesis, inflammation, and resistance to cancer therapy. In this review, we describe the biological basis underlying the use of these agents in cancer therapy, providing data from preclinical studies that demonstrate the synergistic interaction of PARP inhibitors with radiation and chemotherapeutics. We also summarize initial clinical trials of PARP inhibitors for cancer treatment.

Dasatinib, a multi-kinase inhibitor increased radiation sensitivity by interfering with nuclear localization of epidermal growth factor receptor and by blocking DNA repair pathways.

BACKGROUND AND PURPOSE: Although inhibition of epidermal growth factor receptor (EGFR) signaling during radiation led to improvement of tumor control and survival, novel strategies are needed to further improve the outcome of patients with locally advanced head and neck carcinoma. Because EGFR is known to interact with c-Src kinases, the present study investigated dasatinib (BMS-354825), an inhibitor of c-Src kinases, for its efficacy in enhancing radiosensitivity of human head and neck squamous cell carcinomas (HNSCC) in vitro and examined the underlying mechanisms for this effect. MATERIALS AND METHODS: Six HNSCC lines were exposed to dasatinib, radiation, or both, and assessed for c-Src and EGFR expression, cell survival and colony forming ability. Among these cell lines, HN-5 and FaDu lines were analyzed for induction of apoptosis, cell cycle re-distribution and for nuclear localization of EGFR, γ-H2AX and 53BP1 proteins. Immuno-precipitation and Western blots were performed to analyze the levels and binding of proteins involved in cell survival, apoptosis and DNA repair pathways. Suppression of c-Src by siRNA and subsequent clonogenic assay was performed in HN-5 cells. RESULTS: All six HNSCC lines that were examined expressed high levels of c-Src. Two (HN-5 and MDA-183) expressed higher levels of EGFR than other lines. Dasatinib suppressed cell survival of all cell lines tested independent of c-Src or EGFR levels but enhanced the radiosensitivity of HN-5 and MDA-183. HN-5 and FaDu were analyzed further. Dasatinib suppressed phosphorylation of c-Src in both cell lines, but decreased repair of radiation-induced DNA damage in HN-5 cells only as evidenced by suppression of c-Abl and Nbs-1 activity, inhibition of the association between c-Src and EGFR or Her-2, prolongation of nuclear γ-H2AX and 53BP1 foci and inhibition of EGFR nuclear localization and its association with DNA-PKcs. Finally, partial suppression of c-Src resulted in a small increase in HN-5 cell radiosensitivity. CONCLUSIONS: Our data demonstrate that dasatinib induces apoptosis and blocks DNA repair in EGFR-expressing HNSCC cells and improves radiotherapy outcome. These findings warrant further investigation using in vivo tumor models for potential translation into clinical testing.

The impact of timing of EGFR and IGF-1R inhibition for sensitizing head and neck cancer to radiation.

BACKGROUND: Targeting the epidermal growth factor receptor (EGFR) improved radiotherapy outcome by 10-15% in head and neck tumors (HNSCC). We tested the therapeutic benefits of co-targeting EGFR and insulin-like growth factor-1 receptor (IGF-1R) to further enhance tumor response to radiation. MATERIALS AND METHODS: Mice bearing FaDu tumor xenografts were treated with ganitumab (previously known as AMG479, an anti-IGF-1R antibody), panitumumab (an anti-EGFR antibody), or both in combination with fractionated doses of radiation. Tumor growth delay and tumor cure/recurrence served as end-points. RESULTS: The best tumor growth delay was achieved when ganitumab and panitumumab were given concurrently with radiation. Tumor cure/recurrence studies showed that combining ganitumab, panitumumab and radiation resulted in significantly higher radiocurability rates than use of either of the agents given with radiation. CONCLUSION: These findings provide the rationale for clinical testing of the combination of ganitumab and panitumumab for the treatment of HNSCC.

C-Met inhibitor MK-8003 radiosensitizes c-Met-expressing non-small-cell lung cancer cells with radiation-induced c-Met-expression.

INTRODUCTION: The radiation doses used to treat unresectable lung cancer are often limited by the proximity of normal tissues. Overexpression of c-Met, a receptor tyrosine kinase, occurs in about half of non-small-cell lung cancers (NSCLCs) and has been associated with resistance to radiation therapy and poor patient survival. We hypothesized that inhibiting c-Met would increase the sensitivity of NSCLC cells to radiation, enhancing the therapeutic ratio, which may potentially translate into improved local control. METHODS: We tested the radiosensitivity of two high-c-Met-expressing NSCLC lines, EBC-1 and H1993, and two low-c-Met-expressing lines, A549 and H460, with and without the small-molecule c-Met inhibitor MK-8033. Proliferation and protein expression were measured with clonogenic survival assays and Western blotting, respectively. γ-H2AX levels were evaluated by immunofluorescence staining. RESULTS: MK-8033 radiosensitized the high-c-Met-expressing EBC-1 and H1993 cells but not the low-c-Met-expressing cell lines A549 and H460. However, irradiation of A549 and H460 cells increased the expression of c-Met protein at 30 minutes after the irradiation. Subsequent targeting of this up-regulated c-Met by using MK-8033 followed by a second radiation dose reduced the clonogenic survival of both A549 and H460 cells. MK-8033 reduced the levels of radiation-induced phosphorylated (activated) c-Met in A549 cells. CONCLUSIONS: These results suggest that inhibition of c-Met could be an effective strategy to radiosensitize NSCLC tumors with high basal c-Met expression or tumors that acquired resistance to radiation because of up-regulation of c-Met.

A case of 9p deletion syndrome with Duane retraction syndrome.

The chromosome 9p deletion syndrome is a rare but specific clinical event. The clinical manifestations include dysmorphic facial features (trigonocephaly, midface hypoplasia, upward slanting palpebral fissures, and a long philtrum) and psychomotor retardation. Here we report a child with chromosome 9p deletion with Duane retraction syndrome, which has never been reported in the literature before.

Huachansu, containing cardiac glycosides, enhances radiosensitivity of human lung cancer cells.

AIM: To assess radiosensitzing potential of huachansu (HCS) and delineate the underlying mechanisms. MATERIALS AND METHODS: Lung cancer cell lines were exposed to HCS, radiation or both and subjected to survival assays, Western blots, apoptosis assay and immunocytochemical analysis. RESULTS: HCS suppressed the viability of all three lung lines tested and enhanced radiosensitivity of H460 and A549 (wild-type p53) only with no effect on H1299 (p53 null) cells. HCS prolonged the presence of radiation-induced γH2AX foci and increased radiation-induced apoptosis. Western blots showed that HCS increased cleaved caspase-3 and cleaved poly-(ADP-ribose) polymerase (PARP) levels, as well as reducing BCL-2 and p53 protein levels in H460 cells. CONCLUSION: HCS-enhanced radiosensitivity of human lung cancer lines appeared to be p53-dependent. Inhibition of DNA repair and increase in radiation-induced apoptosis may have served as underlying mechanisms. These data suggest that HCS may have potential to improve the efficacy of radiotherapy.

DNA repair biomarker profiling of head and neck cancer: Ku80 expression predicts locoregional failure and death following radiotherapy.

PURPOSE: Radiotherapy plays an integral role in the treatment of head and neck squamous cell carcinoma (HNSCC). Although proteins involved in DNA repair may predict HNSCC response to radiotherapy, none has been validated in this context. We examined whether differential expression of double-strand DNA break (DSB) repair proteins in HNSCC, the chief mediators of DNA repair following irradiation, predict for treatment outcomes. EXPERIMENTAL DESIGN: Archival HNSCC tumor specimens (n = 89) were assembled onto a tissue microarray and stained with antibodies raised against 38 biomarkers. The biomarker set was enriched for proteins involved in DSB repair, in addition to established mechanistic markers of radioresistance. Staining was correlated with treatment response and survival alongside established clinical and pathologic covariates. Results were validated in an independent intramural cohort (n = 34). RESULTS: Ku80, a key mediator of DSB repair, correlated most closely with clinical outcomes. Ku80 was overexpressed in half of all tumors, and its expression was independent of all other covariates examined. Ku80 overexpression was an independent predictor for both locoregional failure and mortality following radiotherapy (P < 0.01). The predictive power of Ku80 overexpression was confined largely to HPV-negative HNSCC, where it conferred a nine-fold greater risk of death at two years. CONCLUSIONS: Ku80 overexpression is a common feature of HNSCC, and is a candidate DNA repair-related biomarker for radiation treatment failure and death, particularly in patients with high-risk HPV-negative disease. It is a promising, mechanistically rational biomarker to select individual HPV-negative HNSCC patients for strategies to intensify treatment.

Human lymphoma cells develop resistance to radiation in the presence of astrocytes in vitro.

BACKGROUND: Lymphomas growing in the central nervous system exhibit resistance to radiotherapy compared to lymphomas of the lymph nodes. Because astrocytes have been shown to reduce radiation-induced neuronal toxicity, this study hypothesized that astrocytes might protect lymphoma cells from radiation-induced cell killing. MATERIALS AND METHODS: A human lymphoma cell line, H9, and normal human astrocytes were grown in culture, exposed to radiation and assessed for cell viability, radiation sensitivity, glutathione content, induction of apoptosis and cell-cycle distribution. RESULTS: Cell survival assays demonstrated that H9 cells growing in an astrocyte-monolayer and also in an astrocyte-conditioned medium displayed radioresistance compared with H9 cells growing under standard conditions. The radioresistance correlated with accumulation of H9 cells in the G(2) phase of the cell cycle, suppression of radiation-induced apoptosis and coincided with a moderate increase in glutathione. CONCLUSION: The findings of this study suggest that astrocytes may play a role in the radioresistance exhibited by lymphomas of the central nervous system.

AC480, formerly BMS-599626, a pan Her inhibitor, enhances radiosensitivity and radioresponse of head and neck squamous cell carcinoma cells in vitro and in vivo.

PURPOSE: The present study investigated the effect of AC480, a small molecule pan-HER tyrosine kinase inhibitor, on in vitro radiosensitivity and in vivo radioresponse of a human head and neck squamous cell carcinoma cell line. METHODS: HN-5 cells were exposed to γ-radiation with and without AC480 and assayed for proliferation, clonogenic survival, apoptosis, cell cycle distribution, and DNA damage. The cells were analyzed by immunoprecipitation and western blotting for proteins involved in apoptosis, cell cycle regulation, and the EGFR pathway. The effect of AC480 on tumor radioresponse was assessed by tumor growth delay assay using HN5 tumor xenografts generated in nude mice. RESULTS: At the molecular level, in HN-5 cells the agent inhibited the expression of pEGFR, pHER2, cyclins D and E, pRb, pAkt, pMAPK, pCDK1 and 2, CDK 6, and Ku70 proteins. The drug also induced accumulation of cells in the G1 cell cycle phase, inhibited cell growth, enhanced radiosensitivity, and prolonged the presence of γ-H2AX foci up to 24 h after radiation. AC480 did not increase the percentage of cells undergoing radiation-induced apoptosis. The drug given before and during irradiation improved the radioresponse of HN5 tumors in vivo. CONCLUSION: AC480 significantly enhanced the radiosensitivity of HN-5 cells, expressing both EGFR and Her2. The mechanisms involved in the enhancement included cell cycle redistribution and inhibition of DNA repair. Both in vitro and in vivo data from our study suggest that AC480 has potential to increase tumor response to radiotherapy.

A novel Chk inhibitor, XL-844, increases human cancer cell radiosensitivity through promotion of mitotic catastrophe.

Check point kinases (Chk) play a major role in facilitating DNA repair upon radiation exposure. We tested the potency of a novel inhibitor of Chk1 and Chk2, XL-844 (provided by Exelixis Inc., CA, USA), to radiosensitize human cancer cells grown in culture and investigated the underlying mechanisms. HT-29 cells (a human colon cancer line) were exposed to XL-844, radiation, or both, and assessed for clonogenic cell survival. Treatment-dependent effects on phosphorylated forms of Chk proteins were assessed by Western blots. Further mechanistic investigations in HT-29 cells included cell cycle analysis by flowcytometry and assessment of DNA repair kinetics by immuno-cytochemistry (ICC) for nuclear appearance of the phosphorylated form of histone 2AX protein (γ-H2AX) staining. Cells undergoing mitotic catastrophe were identified by irregular pattern of mitotic spindle markers α and γ-tubulin staining by ICC. XL-844 enhanced radiosensitivity in a dose and schedule-dependent manner and the enhancement factor was 1.42 at 0.5 survival fraction. Mechanistically XL-844 abrogated radiation-induced Chk2 phosphorylation, induced pan-nuclear γ-H2AX, and prolonged the presence of radiation-induced γ-H2AX foci, and promoted mitotic catastrophe. In conclusion, our data showed that inhibition of Chk2 activity by XL-844 enhanced cancer cell radiosensitivity that was associated with inhibition of DNA repair and induction of mitotic catastrophe.

Combination of anti-IGF-1R antibody A12 and ionizing radiation in upper respiratory tract cancers.

PURPOSE: The IGF1/IGF-1R signaling pathway has emerged as a potential determinant of radiation resistance in human cancer cell lines. Therefore we investigated the potency of monoclonal anti-IGF-1R antibody, A12, to enhance radiation response in upper respiratory tract cancers. METHODS AND MATERIALS: Cell lines were assessed for IGF-1R expression and IGF1-dependent response to A12 or radiation using viability and clonogenic cancer cell survival assays. In vivo response of tumor xenografts to 10 or 20 Gy and A12 (0.25-2 mg × 3) was assessed using growth delay assays. Combined treatment effects were also analyzed by immunohistochemical assays for tumor cell proliferation, apoptosis, necrosis, and vascular endothelial growth factor expression at Days 1 and 6 after start of treatment. RESULTS: A12 enhanced the radiosensitivity of HN5 and FaDu head-and-neck carcinomas in vitro (p < 0.05) and amplified the radioresponse of FaDu xenografts in a dose-dependent manner, with enhancement factors ranging from 1.2 to 1.8 (p < 0.01). Immunohistochemical analysis of FaDu xenografts demonstrated that A12 inhibited tumor cell proliferation (p < 0.05) and vascular endothelial growth factor expression. When A12 was combined with radiation, this resulted in apoptosis induction that persisted until 6 days from the start of treatment and in increased necrosis at Day 1 (p < 0.01, respectively). Combined treatment with A12 and radiation resulted in additive or subadditive growth delay in H460 or A549 xenografts, respectively. CONCLUSIONS: The results of this study strengthen the evidence for investigating how anti-IGF-1R strategies can be integrated into radiation and radiation-cetuximab regimen in the treatment of cancer of the upper aerodigestive tract cancers.

Epithelial-to-mesenchymal transition and c-myc expression are the determinants of cetuximab-induced enhancement of squamous cell carcinoma radioresponse.

PURPOSE: Radiation therapy cures malignant tumors of the head and neck region more effectively when it is combined with application of the anti-EGFR monoclonal antibody cetuximab. Despite the successes achieved, we still do not know how to select patients who will respond to this combination of anti-EGFR monoclonal antibody and radiation. This study was conducted to elucidate possible mechanisms which cause the combined treatment with cetuximab and irradiation to fail in some cases of squamous cell carcinomas. METHODS AND MATERIALS: Mice bearing FaDu and A431 squamous cell carcinoma xenograft tumors were treated with cetuximab (total dose 3 mg, intraperitoneally), irradiation (10 Gy) or their combination at the same doses. Treatment was applied when tumors reached 8mm in size. To collect samples for further protein analysis (two-dimensional differential gel electrophoresis (2-D DIGE), mass spectrometry MALDI-TOF/TOF, Western blot analysis, and ELISA), mice from each group were sacrificed on the 8th day after the first injection of cetuximab. Other mice were subjected to tumor growth delay assay. RESULTS: In FaDu xenografts, treatment with cetuximab alone was nearly as effective as cetuximab combined with ionizing radiation, whereas A431 tumors responded to the combined treatment with significantly enhanced delay in tumor growth. Tumors extracted from the untreated FaDu and A431 xenografts were analysed for protein expression, and 34 proteins that were differently expressed in the two tumor types were identified. The majority of these proteins are closely related to intratumoral angiogenesis, cell adhesion, motility, differentiation, epithelial-to-mesenchymal transition (EMT), c-myc signaling and DNA repair. CONCLUSIONS: The failure of cetuximab to enhance radiation response in FaDu xenografts was associated with the initiation of the program of EMT and with c-myc up-regulation in the carcinoma cells. For this reason, c-myc and EMT-related proteins (E-cadherin, vimentin) may be considered as potential biomarkers to predict squamous cell carcinoma response after treatment with cetuximab in combination with radiation.

Imexon augments sensitivity of human lymphoma cells to ionizing radiation: in vitro experimental study.

BACKGROUND: Imexon is an aziridine-containing small pro-oxidant molecule with promising antitumor activity in myeloma, lymphoma and lung and pancreatic cancer. Imexon is already in clinical trials in patients with advanced solid tumors. The present study examined the effects of imexon on H9 and Raji lymphoma cell lines in vitro when given in combination with ionizing radiation. MATERIALS AND METHODS: H9 and Raji lymphoma cells were grown in culture and exposed to imexon, radiation, or both. Cells were assessed for cell viability, glutathione content, induction of apoptosis, cell cycle distribution and also subject to Western blot analysis. RESULTS: Imexon inhibited cell proliferation in a dose-dependent manner. Imexon, given for 48 h prior to irradiation at a clinically achievable dose of 40 muM, potently enhanced the cell radiosensitivity. Imexon enhanced radiation-induced apoptosis and accumulated cells in G2/M phase of the cell cycle. Imexon induced caspase-3 activation and PARP cleavage. Alterations in glutathione levels were not observed at 40 microM of imexon. CONCLUSION: In conclusion, imexon efficiently augmented lymphoma cell radiosensitivity independently of glutathione and the underlying mechanisms include induction of apoptosis and cell cycle redistribution.