The role of Piezo1 mechanotransduction in high-grade serous ovarian cancer: Insights from an in vitro model of collective detachment.

Slowing peritoneal spread in high-grade serous ovarian cancer (HGSOC) would improve patient prognosis and quality of life. HGSOC spreads when single cells and spheroids detach, float through the peritoneal fluid and take over new sites, with spheroids thought to be more aggressive than single cells. Using our in vitro model of spheroid collective detachment, we determine that increased substrate stiffness led to the detachment of more spheroids. We identified a mechanism where Piezo1 activity increased MMP-1/MMP-10, decreased collagen I and fibronectin, and increased spheroid detachment. Piezo1 expression was confirmed in omental masses from patients with stage III/IV HGSOC. Using OV90 and CRISPR-modified PIEZO1-/- OV90 in a mouse xenograft model, we determined that while both genotypes efficiently took over the omentum, loss of Piezo1 significantly decreased ascitic volume, tumor spheroids in the ascites, and the number of macroscopic tumors in the mesentery. These results support that slowing collective detachment may benefit patients and identify Piezo1 as a potential therapeutic target.

Oral Carbon Monoxide Enhances Autophagy Modulation in Prostate, Pancreatic, and Lung Cancers.

Modulation of autophagy, specifically its inhibition, stands to transform the capacity to effectively treat a broad range of cancers. However, the clinical efficacy of autophagy inhibitors has been inconsistent. To delineate clinical and epidemiological features associated with autophagy inhibition and a positive oncological clinical response, a retrospective analysis of patients is conducted treated with hydroxychloroquine, a known autophagy inhibitor. A direct correlation between smoking status and inhibition of autophagy with hydroxychloroquine is identified. Recognizing that smoking is associated with elevated circulating levels of carbon monoxide (CO), it is hypothesized that supplemental CO can amplify autophagy inhibition. A novel, gas-entrapping material containing CO in a pre-clinical model is applied and demonstrated that CO can dramatically increase the cytotoxicity of autophagy inhibitors and significantly inhibit the growth of tumors when used in combination. These data support the notion that safe, therapeutic levels of CO can markedly enhance the efficacy of autophagy inhibitors, opening a promising new frontier in the quest to improve cancer therapies.

Model of collective detachment in high-grade serous ovarian cancer demonstrates that tumor spheroids produce ECM to support metastatic processes.

High-grade serous ovarian cancer (HGSOC) metastasizes through transcoelomic spread, with both single cells and spheroids of tumor cells observed in patient ascites. These spheroids may form through single cells that detach and aggregate (Sph-SC) or through collective detachment (Sph-CD). We developed an in vitro model to generate and separate Sph-SC from Sph-CD to enable study of Sph-CD in disease progression. In vitro-generated Sph-CD and spheroids isolated from ascites were similar in size (mean diameter 51 vs 55 µm, p > 0.05) and incorporated multiple ECM proteins. Using the in vitro model, nascent protein labeling, and qRT-PCR, we determined that ECM was produced after detachment. As fibronectin plays a key role in many cell adhesion events, we confirmed that inhibiting RGD-based adhesion or fibronectin assembly reduced Sph-CD-mesothelial adhesion strength under shear stress. Our model will enable future studies to determine factors that favor formation of Sph-CD, as well as allow investigators to manipulate Sph-CD to better study their effects on HGSOC progression.