Suppression of HIF-1α expression and radiation resistance in acute hypoxic conditions.

Recently, it has become clear that acute hypoxia affecting radioresistance exists widely in tumor tissues. Concurrently, hypoxia-inducible factor-1α (HIF-1α) is recognized as an essential transcriptional factor, enabling cells to survive through hypoxia. However, it is unclear as to whether HIF-1α plays a direct role in the radioresistance caused by acute hypoxia. Therefore, in this study, we investigated the in vitro response of the human lung adenocarcinoma cell line, A549, to ionizing radiation in an experimental model that imitates acute hypoxia in the presence and absence of HIF-1α expression, using the HIF-1α inhibitor 5-[1-(phenylmethyl)-1H-indazol-3-yl]-2-furanmethanol (YC-1). Cells were treated with or without 10 µM YC-1 for 2 h. Cells were exposed to either 95% N(2) and 5% CO(2) (hypoxic condition of <0.1 mmHg) or atmospheric air (normoxic condition) for 1 h, and irradiated with 2, 5 and 10 Gy. Western blot analysis revealed that, without YC-1, cells exposed to hypoxic conditions expressed increased levels of HIF-1α compared with those exposed to normoxic conditions. Under hypoxic conditions, HIF-1α expression was suppressed by YC-1 to the same extent as that observed in cells exposed to normoxic conditions without YC-1. Clonogenic survival assay revealed that under hypoxic conditions there was no significant difference between the surviving fraction of cells treated with YC-1 and without YC-1 at any dose point examined. The oxygen enhancement ratio at 10% surviving fraction was calculated as 2.7 and 2.6 in the presence and the absence of YC-1, respectively. These results indicate that HIF-1α itself is not an immediate cause of acute hypoxia-induced radioresistance in A549 cells.

Reduction of nitric oxide level enhances the radiosensitivity of hypoxic non-small cell lung cancer.

The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (E-TKI) resistance has emerged as an important clinical issue. To overcome this resistance, researchers have examined different modalities, either for use as a monotherapy or in combination with E-TKI therapy. In the present study, we investigated whether a decrease in nitric oxide (NO) levels affects the radiosensitization of non-small cell lung cancer (NSCLC) cell lines. A549 and H3255 NSCLC cells were examined. They were subjected to hypoxic conditions and monotherapy, or combined therapy using radiation and N(G) -monomethyl-l-arginine, monoacetate (LNMMA). Reductions in nitric oxide levels enhanced the radiosensitivity of both cell lines and significantly reduced the expression of both hypoxia-inducible factor-1α (HIF-1α) and EGFR in H3255 cells compared to A549 cells. Since NO is significantly associated with cell metabolism, we measured the levels of pyruvate dehydrogenase kinase-1 (PDK-1), reactive oxygen species, and oxygen and observed that the expression of PDK-1 was significantly reduced. This reduction was seen simultaneously after the silencing of HIF-1α; however, not following LNMMA treatment. The oxygen concentration was significantly increased in the treated cells, and their viability decreased in parallel. Reactive oxygen species were decreased after LNMMA and radiation treatment. Adding EGFR-TKI to cells with reduced NO levels further suppressed cell viability when combined with radiation. This study suggests that a reduction in the NO level might substantially overcome the radioresistance of mutant NSCLC cells.

MK615, a prospective anti-proliferative agent, enhances CD4/CD8 ratio after exposure to irradiation.

PURPOSE: Recently, it was found that MK615 possessed an anti-proliferative ability on treated cancer cells as a consequence of triterpenoid compounds. It is well known that radiation affects cellular-mediated immunity in cancer patients who are treated with radiotherapy. Similarly, the ability of triterpenoid compounds to enhance the cellular-mediated immunity has been observed. Therefore, in the present study, we attempted to investigate the effect of MK615 on both cancer cells and cellular-mediated immunity after irradiation. MATERIALS AND METHODS: After mice were inoculated with mouse mammary carcinoma (FM3A) cells, they were categorised as follows: Non-treated, irradiated with 5 Gy, treated with 660 µg/day MK615 (MK615, an extract from the Japanese apricot) and lastly exposed to both irradiation and MK615. Afterward, mice were sacrificed and spleens were utilised to measure the cluster of differentiation 4 and 8 (CD4 and CD8) using flowcytometry. Simultaneously, in vitro study, human alveolar basal epithelial carcinomic (A549), mouse lymphoma (EL4) and FM3A cell lines were examined. Growth inhibition was assessed via colony, cell viability and apoptotic assays. RESULTS: The median survival was in favour of the MK615-treated group (26.1 ±â€Š1.9 days) compared with non-treated group (22.3 ±â€Š2.3 days) (p < 0.05). Approximately 50% reduction of the CD4/CD8 ratio was observed following the exposure to irradiation alone. However, this ratio was comparable between the non-treated and both MK615-treated groups. Additionally, only the dual treatment was associated with tumour volume reduction. In contrast, in vitro study showed that MK615 had no significant (p ≥ 0.1) effect on the selected cell lines with or without irradiation. CONCLUSION: MK615 has a potential to reduce tumour volume and may normalise cellular-mediated immunity level following the exposure to irradiation.

Cost-effectiveness of carbon ion radiation therapy for locally recurrent rectal cancer.

The aim of this study was to evaluate the cost-effectiveness of carbon ion radiotherapy compared with conventional multimodality therapy in the treatment of patients with locally recurrent rectal cancer. Direct costs for diagnosis, recurrent treatment, follow-up, visits, supportive therapy, complications, and admission were computed for each individual using a sample of 25 patients presenting with local recurrent rectal cancer at the National Institute of Radiological Science (NIRS) and Gunma University Hospital (GUH). Patients received only radical surgery for primary rectal adenocarcinoma and had isolated unresectable pelvic recurrence. Fourteen and 11 patients receiving treatment for the local recurrence between 2003 and 2005 were followed retrospectively at NIRS and GUH, respectively. Treatment was carried out with carbon ion radiotherapy (CIRT) alone at NIRS, while multimodality therapy including three-dimensional conformal radiotherapy, chemotherapy, and hyperthermia was performed at GUH. The 2-year overall survival rate was 85% and 55% for CIRT and multimodality treatment, respectively. The mean cost was yen4 803 946 for the CIRT group and yen4 611 100 for the multimodality treatment group. The incremental cost-effectiveness ratio for CIRT was yen6428 per 1% increase in survival. The median duration of total hospitalization was 37 days for CIRT and 66 days for the multimodality treatment group. In conclusion, by calculating all direct costs, CIRT was found to be a potential cost effective treatment modality as compared to multimodality treatment for locally recurrent rectal cancer.

Higher pAkt expression predicts a significant worse prognosis in glioblastomas.

phosphorylated-Akt (pAkt) plays an important role in tumorigenesis through promotion of cell survival by inhibiting apoptosis and mediating cell proliferation. Higher expression of pAkt has been reported to be associated with an unfavorable prognosis in several malignant tumors. In this study, the prognostic value of pAkt expression was investigated in glioblastomas by using immunohistochemical methods. Tissue sections obtained from 64 patients with glioblastoma were evaluated. The mean and median follow-up period was 16.2 +/- 12.4 and 12 months, respectively (range: from 1 to 62 months). pAkt expression levels were determined by immunohistochemical staining and evaluated for cell positivity. Positive staining was defined when more than 50% of the tumor cells were stained in each section. The correlation between expression of pAkt and overall survival rate was assessed. Glioblastomas showed either or both cytoplasmic and nuclear positive findings for pAkt. A total of 29.7% (19/64) of tissue specimens had greater than 50% positivity. The median survival periods of the patients with pAkt positive and negative tumor were 10 and 14 months, respectively. Two years overall survival rate of the pAkt positive and negative patients were 0% and 24.4%, respectively. Survival rate of the patients with pAkt positive tumor was significantly lower than that of the patients with pAkt negative tumors (p = 0.004). Multivariate analysis showed that extent of surgery was the strongest factor for survival (p = 0.01) and the pAkt expression was the secondly strongest factor (p = 0.06). These results suggest that the higher expression of pAkt the poorer prognosis in patients with glioblastoma.