Carbon-Ion Beam Irradiation and the miR-200c Mimic Effectively Eradicate Pancreatic Cancer Stem Cells Under in vitro and in vivo Conditions

Abstract

Purpose The study investigated the molecular mechanisms that killed pancreatic cancer cells, including cancer stem cells (CSCs), by carbon ion beam irradiation alone or in combination with miRNA-200c under in vitro and in vivo conditions. Methods Human pancreatic cancer (PC) cells, PANC1 and PK45, were treated with carbon-ion beam irradiation alone or in combination with microRNA-200c (miR-200c) mimic. Cell viability assay, colony and spheroid formation assay, quantitative real-time PCR analysis of apoptosis-, autophagy-, and angiogenesis-related gene expression, xenograft tumor control and histopathological analyses were performed. Results The cell viability assay showed that transfection of the miRNA-200c (10 nM) mimic into pancreatic CSC (CD44+/ESA+) and non-CSC (CD44-/ESA-) significantly suppressed proliferation of both types of cell populations described above. Combining carbon-ion beam irradiation with the miRNA-200c mimic significantly reduced the colony as well as spheroid formation abilities compared to that observed with the treatment of carbon-ion beam alone or X-ray irradiation combined with the miRNA-200c mimic. Moreover, the combination of carbon ion beam irradiation and miRNA-200c mimic increased the expression of apoptosis-related gene BAX, autophagy-related genes Beclin-1 and p62 , addition of gemcitabine (GEM) further enhanced the expression of these genes. In vivo data showed that carbon-ion beam irradiation in combination with the miRNA-200c mimic effectively suppressed xenograft tumor growth and significantly induced tumor necrosis and cavitation. Conclusion The combination of miRNA-200c mimic and carbon ion beam irradiation may be powerful radiotherapy that significantly kills pancreatic cancer cells containing CSCs and enhances the effect of carbon-ion beam irradiation compared to carbon-ion beam irradiation alone.

Role of autophagy in tumor response to radiation: Implications for improving radiotherapy

“…In radio-resistant cancer cells, like pancreatic ductal adenocarcinoma cells and NSCLC stem cells, autophagy has found to be essential in promoting tumor growth and invasiveness ( 120 ) as well as maintaining the stem cell-like properties ( 121 ) of the cells. as a result autophagy inhibitors, either individually or with combination with other traditional methods of cancer therapy, have been able to block proliferation, colony and, spheroid formation (in pancreatic CSC populations) in cancer cells ( 122 ). Similarly, silencing of prominent autophagic genes like Atg5 was able to induce radio sensitivity within radio-resistant cancer stem cell populations (prostate CSCs) ( 111 ).…”