Riluzole enhances ionizing radiation-induced cytotoxicity in human melanoma cells that ectopically express metabotropic glutamate receptor 1 in vitro and in vivo.

PURPOSE: Brain metastases are a common preterminal event in patients with metastatic melanoma and require radiation therapy. Our group has previously shown that human GRM1 (hGRM1) expressing melanoma cells release excess extracellular glutamate and are growth inhibited by riluzole, an inhibitor of glutamate release. Riluzole-treated cells accumulate in G(2)/M phase of the cell cycle at 24 hours, and then undergo apoptotic cell death. We evaluated whether riluzole enhanced radiosensitivity in melanoma cells. EXPERIMENTAL DESIGN: Clonogenic assays were performed to evaluate clonogenic survival after treatment in hGRM1 expressing and nonexpressing melanoma cells. Western immunoblots were performed to confirm apoptotic cell death. A xenograft mouse model was used to validate the in vitro experiments. Tumors harvested from the xenografts were fixed and stained for apoptosis and DNA damage markers. RESULTS: In the hGRM1-positive cell lines C8161 and UACC903, riluzole enhanced the lethal effects of ionizing radiation; no difference was seen in the hGRM1-negative UACC930 cell line. C8161 cells treated with riluzole plus irradiation also showed the highest levels of the cleaved forms of PARP and caspase-3; excised C8161 xenografts showed the greatest number of apoptotic cells by immunohistochemistry (P < 0.001). On cell cycle analysis, a sequence-dependent enrichment in the G(2)/M phase was shown with the combination of riluzole and irradiation. Xenografts treated with riluzole and weekly radiation fractions showed significant growth inhibition and revealed markedly increased DNA damage. CONCLUSIONS: We have shown, in vitro and in vivo, that the combination of riluzole and ionizing radiation leads to greater cytotoxicity. These results have clinical implications for patients with brain metastases receiving whole brain radiation therapy.

Evaluation of acute locoregional toxicity in patients with breast cancer treated with adjuvant radiotherapy in combination with bevacizumab.

PURPOSE: Preclinical studies have shown that bevacizumab combined with radiotherapy (RT) induces a radiosensitizing effect. Published reports regarding the safety of combination therapy involving bevacizumab and RT are lacking. The purpose of this study was to analyze acute locoregional toxicity in patients with breast cancer receiving concurrent bevacizumab plus RT. METHODS AND MATERIALS: After institutional review board approval was obtained, patients with breast cancer who received bevacizumab were identified; these patients were then cross-referenced with patients receiving RT. Toxicity was scored by the Common Terminology Criteria for Adverse Events. Patients were matched 1:1 with those who did not receive bevacizumab. Statistical analysis was performed to analyze toxicity between the two groups. RESULTS: Fourteen patients were identified to have received bevacizumab plus RT. All patients received bevacizumab during RT without delay or treatment breaks; there were no RT treatment breaks in all patients. No patient receiving bevacizumab plus RT experienced ≥Grade 3 toxicity; 3 matched control patients experienced a Grade 3 skin reaction. There was no difference in fatigue, radiation fibrosis, pneumonitis, or lymphedema between the two groups. Five patients (35%) developed reduction in ejection fraction; 2 with right-sided and 3 with left-sided treatment. Patients with left-sided treatment experienced a persistent reduction in ejection fraction compared with those receiving right-sided treatment. CONCLUSION: Concurrent bevacizumab and RT did not increase acute locoregional toxicity in comparison with matched control patients who did not receive RT alone. The addition of concurrent RT when treating the intact breast, chest wall, and associated nodal regions in breast cancer seems to be safe and well tolerated.

Evaluation of single nucleotide polymorphisms (SNPs) in the p53 binding protein 1 (TP53BP1) gene in breast cancer patients treated with breast-conserving surgery and whole-breast irradiation (BCS + RT).

PURPOSE: TP53BP1 is a key component of radiation-induced deoxyribonucleic acid damage repair. The purpose of this study was to evaluate the significance of a known common single nucleotide polymorphism in this gene (rs560191) in patients treated with breast-conserving surgery and whole-breast irradiation (BCS + RT). METHODS AND MATERIALS: The population consisted of 176 premenopausal women treated with BCS + RT (median follow-up, 12 years). Genomic deoxyribonucleic acid was processed by use of TaqMan assays. Each allele for rs560191 was either C or G, so each patient was therefore classified as CC, CG, or GG. Patients were grouped as GG if they were homozygous for the variant G allele or CC-CG if they carried at least one copy of the common C allele (CC or CG). RESULTS: Of the 176 women, 124 (71%) were CC-CG and 52 (29%) were GG. The mean age was 44 years for GG vs. 38 years for CC-CG (p < 0.001). GG was more common in African-American women than white women (69% vs. 13%, p < 0.001) and more commonly estrogen receptor negative (70% vs. 49%, p = 0.02). There were no significant correlations of rs560191 with other critical variables. Despite the fact that GG patients were older, the 10-year rate of local relapses was higher (22% for GG vs. 12% for CC-CG, p = 0.04). CONCLUSIONS: This novel avenue of investigation of polymorphisms in radiation repair/response genes in patients treated with BCS + RT suggests a correlation to local relapse. Additional evaluation is needed to assess the biological and functional significance of these single nucleotide polymorphisms, and larger confirmatory validation studies will be required to determine the clinical implications.

Clinicopathologic significance of excision repair cross-complementation 1 expression in patients treated with breast-conserving surgery and radiation therapy.

PURPOSE: The excision repair cross-complementation 1 (ERCC1) enzyme plays a rate-limiting role in the nucleotide excision repair pathway and is associated with resistance to platinum-based chemotherapy in cancers of the head and neck and the lung. The purpose of this study was to evaluate the clinicopathologic and prognostic significance of ERCC1 expression in a cohort of early-stage breast cancer patients treated with breast conservation therapy. METHODS AND MATERIALS: Paraffin specimens from 504 women with early-stage breast cancer treated with breast conservation therapy were constructed into tissue microarrays. The array was stained for estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) and ERCC1. This was then correlated with clinicopathologic factors and outcomes data. RESULTS: ERCC-1 expression was evaluable in 366 cases (72%). In this group, 32% and 38% of patients received adjuvant chemotherapy and hormonal therapy, respectively. Increased ERCC-1 expression was found to be correlated with ER positivity (p < 0.005), lower T stage (p < 0.017), nodal negativity (p < 0.013), age >50 (p < 0.006), reduced use of adjuvant chemotherapy (p < 0.02), and increased use of adjuvant hormonal therapy (p < 0.004). ERCC1 expression did not correlate with locoregional recurrence-free survival, distant metastasis-free survival, cause-specific survival, or overall survival. In patients who were both ERCC1-negative and -positive, the use of chemotherapy predicted for worse distant metastasis-free survival (p = 0.05 and p = 0.07, respectively) but not cause-specific survival or overall survival. CONCLUSIONS: Although ERCC1 expression did not predict for outcome measures in this dataset, overexpression correlated with favorable prognostic factors such as ER positivity, lower T stage, nodal negativity, and age >50. To our knowledge, this is the first study investigating ERCC1 expression in patients receiving adjuvant radiation therapy for breast cancer.