Paola Spessotto

Serum- and glucocorticoid- inducible kinase 2, SGK2, is a novel autophagy regulator and modulates platinum drugs response in cancer cells

AbstractFor many tumor types chemotherapy still represents the therapy of choice and many standard treatments are based on the use of platinum (PT) drugs. However, de novo or acquired resistance to platinum is frequent and leads to disease progression. In Epithelial Ovarian Cancer (EOC) patients, PT-resistant recurrences are very common and improving the response to treatment still represents an unmet clinical need. To identify new modulators of PT-sensitivity, we performed a loss-of-function screening targeting 680 genes potentially involved in the response of EOC cells to platinum. We found that SGK2 (Serum-and Glucocorticoid-inducible kinase 2) plays a key role in PT-response. We show here that EOC cells relay on the induction of autophagy to escape PT-induced death and that SGK2 inhibition increases PT sensitivity inducing a block in the autophagy cascade due to the impairment of lysosomal acidification. Mechanistically we demonstrate that SGK2 controls autophagy in a kinase-dependent manner by binding and inhibiting the V-ATPase proton pump. Accordingly, SGK2 phosphorylates the subunit V1H (ATP6V1H) of V-ATPase and silencing or chemical inhibition of SGK2, affects the normal autophagic flux and sensitizes EOC cells to platinum. Hence, we identified a new pathway that links autophagy to the survival of cancer cells under platinum treatment in which the druggable kinase SGK2 plays a central role. Our data suggest that blocking autophagy via SGK2 inhibition could represent a novel therapeutic strategy to improve patients’ response to platinum.

Probe-based confocal laser endomicroscopy intra-operative evaluation in ovarian cancer: definition of in vivo architectural patterns to determine resection strategies.

Probe-based confocal laser endomicroscopy (pCLE) is a novel real-time imaging technique that is potentially useful for accurately distinguishing between normal and cancerous tissues. The aim of this study was to describe the pCLE patterns of areas suggestive of tumors and evaluate the ability of the method to differentiate between normal and cancerous tissue during cytoreductive surgery for epithelial ovarian cancer. In vivo pCLE images and subsequent biopsies were acquired from various anatomical sites including the parietal and visceral peritoneum, ovaries, and omentum. Each endomicroscopic sequence was analyzed by highly experienced investigators using pCLE imaging for cancer diagnosis. Each pCLE sequence was compared with the histology of the corresponding specimens. We enrolled 18 women with International Federation of Gynecology and Obstetrics stage III/IV high-grade serous epithelial ovarian cancer referred for primary or interval debulking surgery. A total of 112 biopsies were obtained for histologic analysis. The pCLE images of normal tissue showed a regular distribution of stromal fibers and consistent cellular architecture, regardless of the anatomical region, with vascularized areas characterized by regular vessels. Conversely, the extravasation of fluorescein, used as a contrast agent, was a distinguishing feature of malignant nodules, which were easily recognized by leakage and are typical of tumor-associated vessels. The leakage often surrounded the dark clusters of neoplastic cells. A substantial agreement between pCLE and histology emerged (k = 0.66), whereas only a fair concordance between the surgeon's intra-operative assessment and histology was found (k = 0.30). Our results suggest that pCLE is a promising intra-operative technique to assist surgeons in accurately detecting peritoneal metastases in patients with advanced epithelial ovarian cancer, enhancing surgical radicality while avoiding unnecessary resection.

Platinum-induced upregulation of ITGA6 promotes chemoresistance and spreading in ovarian cancer

Abstract Platinum (PT)-resistant Epithelial Ovarian Cancer (EOC) grows as a metastatic disease, disseminating in the abdomen and pelvis. Very few options are available for PT-resistant EOC patients, and little is known about how the acquisition of PT-resistance mediates the increased spreading capabilities of EOC. Here, using isogenic PT-resistant cells, genetic and pharmacological approaches, and patient-derived models, we report that Integrin α6 (ITGA6) is overexpressed by PT-resistant cells and is necessary to sustain EOC metastatic ability and adhesion-dependent PT-resistance. Using in vitro approaches, we showed that PT induces a positive loop that, by stimulating ITGA6 transcription and secretion, contributes to the formation of a pre-metastatic niche enabling EOC cells to disseminate. At molecular level, ITGA6 engagement regulates the production and availability of insulin-like growth factors (IGFs), over-stimulating the IGF1R pathway and upregulating Snail expression. In vitro data were recapitulated using in vivo models in which the targeting of ITGA6 prevents PT-resistant EOC dissemination and improves PT-activity, supporting ITGA6 as a promising druggable target for EOC patients.