In vivo selection reveals autophagy promotes adaptation of metastatic ovarian cancer cells to abdominal microenvironment

Peritoneal dissemination is the most frequent metastatic route of ovarian cancer. However, due to the high heterogeneity in ovarian cancer, most conventional studies lack parental tumor controls relevant to metastases and, thus, it is difficult to trace the molecular changes of cancer cells along with the selection by the abdominal microenvironment. Here, we established an in vivo mouse peritoneal dissemination scheme that allowed us to select more aggressive sublines from parental ovarian cancer cells, including A2780 and SKOV-3. Microarray and gene profiling analyses indicated that autophagy-related genes were enriched in selected malignant sublines. Detection of LC3-II, p62 and autophagic puncta demonstrated that these malignant variants were more sensitive to autophagic induction when exposed to diverse stress conditions, such as high cell density, starvation and drug treatment. As compared with parental A2780, the selected variant acquired the ability to grow better under high-density stress; however, this effect was reversed by addition of autophagic inhibitors or knockdown of ATG5. When analyzing the clinical profiles of autophagy-related genes identified to be enriched in malignant A2780 variant, 73% of them had prognostic significance for the survival of ovarian cancer patients. Taken together, our findings indicate that an increase in autophagic potency among ovarian cancer cells is crucial for selection of metastatic colonies in the abdominal microenvironment. In addition, the derived autophagic gene profile can not only predict prognosis well but can also be potentially applied to precision medicine for identifying those ovarian cancer patients suitable for taking anti-autophagy cancer drugs.