The mTOR inhibitor RAD001 augments radiation-induced growth inhibition in a hepatocellular carcinoma cell line by increasing autophagy.

Treatment of hepatocellular carcinoma (HCC) is a major concern for physicians as its response to chemotherapy and radiotherapy remains generally poor, due, in part, to intrinsic resistance to either form of treatment. We previously reported that an irradiation with fast neutrons, which are high-linear energy transfer (LET) particles, massively induced autophagic cell death in the human HCC SK-Hep1 cell line. In the present study, we tested the capacity of the mammalian target of rapamycin (mTOR) inhibitor RAD001 to augment the cytotoxicity of low and high-LET radiation in these cells. As mTOR is a key component in a series of pathways involved in tumor growth and development, it represents a potential molecular target for cancer treatment. Results indicate that RAD001, at clinically relevant nanomolar concentrations, enhances the efficacy of both high- and low-LET radiation in SK-Hep1 cells, and that the induction of autophagy may account for this effect. However, fast neutrons were found to be more efficient at reducing tumor cell growth than low-LET radiation.

Cell death after high-LET irradiation in orthotopic human hepatocellular carcinoma in vivo.

Hepatocellular carcinoma (HCC) represents the sixth most common cancer worldwide and a major health problem since the choice of treatment is limited due to chemo- and radio-resistance. It was previously reported that high linear energy transfer (LET) radiation induced massive autophagic cell death in the human HCC SK-Hep1 cell line in vitro. This study analyzed the effects of high-LET radiation on the same HCC tumor model, orthotopically transplanted into nude mice. For this purpose, after surgical xenograft in the liver, animals were irradiated with fast neutrons and cell death occurring in the tumors was assessed with various techniques, including electron microscopy and probe-based confocal laser endomicroscopy. Results indicate that considerable autophagy and only limited apoptosis took place in the tumor xenografts after high-LET irradiation. These data confirm the previous in vitro results, suggesting that autophagy may act as a predominant mode of cell death in the efficacy of high-LET radiation.

Pharmacological enhancement of autophagy induced in a hepatocellular carcinoma cell line by high-LET radiation.

The aim of the present study was to determine the cytotoxic consequences of high-linear energy transfer (LET) irradiation in the presence of oxaliplatin on hepatocellular carcinoma (HCC) cells in vitro. We attempted to correlate the induction of apoptosis and autophagy with the formation of DNA double-strand breaks (DSBs). SK-Hep1 cells were irradiated by 65 MeV neutrons in the presence of oxaliplatin and/or the poly(ADP-ribose) polymerase (PARP) inhibitor PJ34. DSBs were measured by the formation of gammaH2AX foci. Results show that in SK-Hep1 cells exposed to fast neutrons in the presence of oxaliplatin, DSBs occurred and persisted with time after irradiation. While apoptosis remained low in co-treated cells, autophagy was considerably increased after irradiation and augmented by the addition of oxaliplatin. Thus, autophagic cell death appears to play a prominent role in the cytotoxicity of the combined treatment and may be linked to the generation of heavy damage to DNA.

Feasibility and reliability of pancreatic cancer staging using fiberoptic confocal fluorescence microscopy in rats.

BACKGROUND & AIMS: Surgical management of pancreatic cancer depends on tumor resectability and staging. This study evaluated a new in vivo technique, fiberoptic confocal fluorescence microscopy (FCFM), for detection and staging of pancreatic tumors in rats. METHODS: FCFM was used with a protease-activated fluorescent marker (ProSense; VisEn Medical Inc, Woburn, MA) for in vivo imaging of solid organs (1.8-microm resolution) in a rat model of pancreatic ductal adenocarcinoma. A preliminary study described the FCFM rendering of normal and pathologic tissues. Subsequently, 2 double-blind studies compared FCFM to standard histology in (1) detection of tumors in rat models of cancer and controls and (2) detection of nodal involvement (splenic, celiac, mesenteric, and colic) 4, 5, and 6 weeks after tumor induction vs controls. RESULTS: Tumor cells displayed a fluorescent ductal pattern compared with non-fluorescent normal pancreas or normal follicular pattern of lymph nodes (LNs). FCFM detected all the pancreatic tumors (1.7-mm mean diameter) and identified 23 LNs that contained metastases of 99 LNs examined. Standard histologic analyses resulted in 1 false-negative result in tumor detection and 2 false negatives in LN detection, whereas FCFM produced no false-negative results. Additional serial sectioning confirmed all tumors and 16 metastatic LNs; FCFM had a negative predictive value of 100% and a positive predictive value of 69.6%. CONCLUSIONS: Real-time "virtual biopsy" using FCFM detects tumors and LN metastases with 100% sensitivity and 92.2% specificity in rats, making it a reliable technique for detection and staging of pancreatic cancer.

Radiosensitising agents for the radiotherapy of cancer: novel molecularly targeted approaches.

BACKGROUND: The efficacy of radiotherapy (RT) for cancer treatment is limited by normal tissue toxicity and by the intrinsic or acquired radioresistance of many tumours. Therefore, continuing efforts are conducted to identify radiosensitising agents that preferentially sensitise tumour cells to the cytotoxic action of RT. Recent progresses in molecular oncology have uncovered an array of novel targets, which may be exploited for RT enhancement. OBJECTIVE: To survey the patent literature of the past 4 years pertaining to the development of molecularly targeted agents as potential tumour radiosensitisers. METHODS: Patents were searched with a set of relevant keywords using several search engines. A Medline search on the same topics was performed in parallel. RESULTS/CONCLUSION: A total of 48 patents/applications were selected. These concerned agents target molecular components of pathways involved in DNA damage repair, cell growth and survival signalling, apoptosis modulation and tumour angiogenesis. Current trials of some of these agents may reveal their value as clinical radiosensitisers.

Radiosensitising agents for the radiotherapy of cancer: advances in traditional and hypoxia targeted radiosensitisers.

BACKGROUND: Radiotherapy is utilised for the treatment of approximately 50% of patients with solid tumours, but its efficacy is limited by normal tissue toxicity and by the intrinsic or acquired radioresistance of many tumours. The combination of radiotherapy with chemotherapeutic agents that preferentially sensitise tumour cells to its cytotoxic effects has thus long been considered as a strategy to enhance cancer therapy. However, current chemoradiotherapy protocols remain highly unsatisfactory. Therefore, continuing efforts are being conducted to identify improved radiosensitising agents. OBJECTIVE: To survey the patent literature and associated peer-reviewed publications of the past 4 years pertaining to the development of novel radiosensitising agents, with a focus on anticancer drugs traditionally used as radiosensitisers and on agents targeting radioresistant hypoxic tumour cells. METHODS: Patents were searched with a set of relevant keywords using several search engines ( ep.espacenet.com/ , www.freepatentsonline.com/ , patft.uspto.gov/ ). A Medline search on the same topics was performed in parallel. RESULTS/CONCLUSION: A total of 37 patents/applications were retrieved. Of these, 14 concern the use of conventional anticancer cytotoxic drugs for tumour radiosensitisation. The other patents mostly disclose novel hypoxic radiosensitisers, bioreductive drugs and inhibitors of hypoxia-inducible factor-1. Whether these advances will translate into clinically valuable radiosensitisers is, however, unclear.

High-LET radiation combined with oxaliplatin induce autophagy in U-87 glioblastoma cells.

Modern protocols of concomitant chemo/radiotherapy provide a very effective strategy to treat certain types of tumors. High-linear energy transfer (LET) radiations, on the other hand, have an increased efficacy against cancer with low radiosensibility and critical localization. We previously reported that oxaliplatin, a third generation platinum drug, was able to reinforce the cytotoxicity of an irradiation by fast neutrons towards human glioblastoma U-87 cells in culture. We show here that such a combination has the capacity to enhance the number of double strand breaks in DNA and to induce autophagy in these cells. Xenografts experiments were further performed in nude mice subcutaneously transplanted with U-87 cells. When injected shortly before a single irradiation by fast neutrons, oxaliplatin causes a marked reduction of tumor growth compared with the irradiation alone. Overall, our data indicate the unique cytotoxic mechanism of a combined high-LET irradiation and oxaliplatin treatment modality and suggest its potential application in anticancer therapy.