Dynamic integrin expression, atypical nuclear localization, and spatial distribution changes during ovarian cancer progression and metastasis

Nazia Bano¹Jack Browning¹Isabelle Lewis¹Malaika Amin²Piper Zimmerman¹Lina Lee¹Eva M Schmelz^1*

• ¹Virginia Tech, Blacksburg, United States
• ²Hollins University, Roanoke, United States

Aggregation and adhesion of ovarian cancer cells are facilitated by integrins, key adhesion receptors in ovarian cancer. Here we identify changes in the expression of integrins (ITG), their ligands and regulators during ovarian cancer progression and metastatic dissemination that support adaptation of the cellular phenotype to aggregation and adhesion and promote cancer cell survival and metastatic outgrowth. We mimicked the stages of peritoneal dissemination of ovarian metastases by using benign cells and ovarian cancer cells representing slow-and fast developing disease and generated adherent, spheroid, and adherent-spheroid mouse cell cultures adjusted for oxygen and glucose levels as reported for malignant ascites. We determined changes in integrin expression, other adhesion receptors, ECM and their regulators by qPCR PCR arrays and Western blotting. Spatial and intracellular protein expression in 3D spheroids were determined by confocal microscopy and quantitated by IMARIS software. Relevance of integrins for aggregation, adherence, and outgrowth was determined using specific inhibitors. Increased integrin expression during aggregation, adhesion and reoxygenation was accompanied by increases in their ligands (fibronectin, collagens) and regulators. This was especially apparent in the stem-like MOSE-LTICv and may contribute to their aggressive phenotype. 3D spatial analysis of adherent spheroids revealed distinct spatial integrin expression in the periphery of the non-adherent spheroids or a uniform expression. Most integrins and CD44 were localized in the nucleus where they may affect gene transcription. Only the inhibition of ITGaVβ1 and ITGa2β1 effectively suppressed spheroid adhesion and outgrowth, highlighting their importance as stage-specific target to block peritoneal metastasis. Our studies show that integrin expression and localization are dynamic, spatially regulated, and functionally compartmentalized during ovarian cancer progression and dissemination. The coordinated upregulation of integrins, other adhesion molecules (CD44, NCAM1, VCAM), ECM (FN1, collagens) and their regulators (SPP1, TIMP2,3) in response to the culture conditions indicate a complex reprogramming of adhesion networks that can facilitate different steps of ovarian cancer progression and dissemination. Nuclear localization of integrins and CD44 point to dual roles in adhesion, survival, and proliferation by activating adhesion-mediated signaling pathways and directly affect gene transcription that support a switch from a more dormant phenotype to active proliferation and invasion after adhesion.