Periostin facilitates ovarian cancer recurrence by enhancing cancer stemness

Ovarian cancer (OC) is the deadliest reproductive system cancer. Its high lethality is due to the high recurrence rate and the development of chemotherapeutic resistance, which requires synergy between cancer cells and non-cancerous cells of the tumor microenvironment (TME). Analysis of gene expression microarray data from paired primary and recurrent OC tissues revealed significantly elevated expression of the gene encoding periostin ( POSTN ) in recurrent OC compared to matched primary tumors (p=0.014). Finding POSTN primarily localized to the TME, we investigated the role of TME POSTN in OC cell viability, migration/invasion, and chemosensitivity. Conditioned media with high levels of POSTN (CM POSTNhigh ) was generated using POSTN -transfected fibroblastic preadipocyte 3T3-L1 cells. CM POSTNhigh -cultured OC cells exhibited faster migration, more invasiveness (p=0.006), and more chemoresistance (p<0.05) compared to OC cells cultured with control medium (CM CTL ). Furthermore, CM POSTNhigh -cultured HEYA8 cells demonstrated increased resistance to paxlitaxel-induced apoptosis. Multiple OC cell lines (HEYA8, CAOV2, and SKOV3) cultured with CM POSTNhigh showed increases in stem cell side population relative to CM CTL -cultured cells. POSTN -transfected 3T3-L1 cells exhibited more intracellular and extracellular lipids, and this was linked to increased cancer cell expression of the oncogene fatty acid synthetase (FASN). Additionally, POSTN functions in the TME were linked to Akt pathway activities. In a xenograft mouse model of OC, the mean tumor volume in mice injected with CM POSTNhigh -grown OC cells was larger than that in mice injected with CM CTL -grown OC cells (p=0.0023). Altogether, higher POSTN expression is present in recurrent OC and promotes a more aggressive and chemoresistant oncogenic phenotype in vitro. Within cancer TME fibroblasts, POSTN can stimulate lipid production and is associated with increased OC stem cell side population, consistent with its known role in maintaining stemness. Our results bolster the need for further study of POSTN as a potential therapeutic target in treatment and potential prevention of recurrent ovarian cancer. Author Summary Ovarian cancer has a high rate of recurrent disease that is often resistant to chemotherapy. Comparing primary and recurrent ovarian cancer tumors, we found that the gene POSTN , which encodes the protein periostin, is more highly expressed in recurrent tumors, and more highly expressed in the tumor microenvironment, outside of the cancer cells. We transfected cells with vectors encoding POSTN or with blank vectors to generate conditioned media with high POSTN or control media. Ovarian cancer cells cultured in the POSTN-high conditioned media showed faster wound healing, more invasiveness, and more resistance to apoptosis caused by chemotherapeutic agents, and increased stemness, an important trait in cancer cells, especially recurrent cells. POSTN-transfected cells showed higher expression of the enzyme fatty acid synthase and higher concentrations of lipids, indicating that POSTN may play a role in increasing the energy available to cancer cells. The Akt pathway, often activated in ovarian cancer growth, was activated more in cells cultured in the POSTN-high environment. Finally, we injected immunocompromised mice with ovarian cancer cells that were grown in either the POSTN-high media or the control media, and the average tumor size was higher in mice injected with the cells that were grown in the POSTN-high media.