Fibronectin Regulates the Dynamic Formation of Ovarian Cancer Multicellular Aggregates and the Expression of Integrin Receptors

Insights into high-grade serous carcinoma pathobiology using three-dimensional culture model systems

Epithelial ovarian cancer (EOC) research has become more complex as researchers try to fully understand the metastatic process. Especially as we delve into the concept of tumour dormancy, where cells transition between proliferative and dormant states to survive during disease progression. Thus, the in vitro models used to conduct this research need to reflect this vast biological complexity. The innovation behind the many three-dimensional (3D) spheroid models has been refined to easily generate reproducible spheroids so that we may understand the various molecular signaling changes of cells during metastasis and determine therapeutic efficacy of treatments. This ingenuity was then used to develop the 3D ex vivo patient-derived organoid model, as well as multiple co-culture model systems for EOC research. Although, researchers need to continue to push the boundaries of these current models for in vitro and even in vivo work in the future. In this review, we describe the 3D models already in use, where these models can be developed further and how we can use these models to gain the most knowledge on EOC pathogenesis and discover new targeted therapies.

Lysophosphatidic acid modulates ovarian cancer multicellular aggregate assembly and metastatic dissemination

Epithelial ovarian cancer (EOC) metastasis occurs by exfoliation of cells and multicellular aggregates (MCAs) from the tumor into the peritoneal cavity, adhesion to and retraction of peritoneal mesothelial cells and subsequent anchoring. Elevated levels of lysophosphatidic acid (LPA) have been linked to aberrant cell proliferation, oncogenesis, and metastasis. LPA disrupts junctional integrity and epithelial cohesion in vitro however, the fate of free-floating cells/MCAs and the response of host peritoneal tissues to LPA remain unclear. EOC MCAs displayed significant LPA-induced changes in surface ultrastructure with the loss of cell surface protrusions and poor aggregation, resulting in increased dissemination of small clusters compared to untreated control MCAs. LPA also diminished the adhesive capacity of EOC single cells and MCAs to murine peritoneal explants and impaired MCA survival and mesothelial clearance competence. Peritoneal tissues from healthy mice injected with LPA exhibited enhanced mesothelial surface microvilli. Ultrastructural alterations were associated with restricted peritoneal susceptibility to metastatic colonization by single cells as well as epithelial-type MCAs. The functional consequence is an LPA-induced dissemination of small mesenchymal-type clusters, promoting a miliary mode of peritoneal seeding that complicates surgical removal and is associated with worse prognosis.

Circulating Tumor Cell Migration Requires Fibronectin Acting through Integrin B1 or SLUG

Fibronectin (FN1) is an extracellular matrix protein gaining increasing attention for its multifaceted roles in cancer progression. Using our recently established circulating tumor cell (CTC) lines, we had demonstrated increased FN1 expression and enhanced migration in CTC lines, in comparison to primary tumor cell lines. Whether increased FN1 expression is directly required for CTC migration, and the specific role of FN1’s regulation of integrin B1 (ITGB1) and SLUG (SNAI2) in CTC migration remains unclear. Here, for the first time, we report that the knockdown of FN1, ITGB1, or SLUG expression in CTCs leads to a significant decrease in CTC migration. Knocking down two or all three of these proteins simultaneously did not further inhibit migration. We observed a corresponding increase in CTC migration when recombinant FN1 was added to CTCs. This effect was significantly impeded by prior knockdown of ITGB1 or SLUG. Using knock down experiments and western blotting analysis, we confirmed FN1’s regulation of ITGB1 and SLUG to occur via two separate, independent pathways. Consequently, we can conclude that FN1-dependent enhanced migration of CTCs requires downstream signaling through either ITGB1 or SLUG and that FN1 regulation of ITGB1 and SLUG may have important implications for cancer progression and metastasis.

Expression Changes and Impact of the Extracellular Matrix on Etoposide Resistant Human Retinoblastoma Cell Lines

Retinoblastoma (RB) represents the most common malignant childhood eye tumor worldwide. Several studies indicate that the extracellular matrix (ECM) plays a crucial role in tumor growth and metastasis. Moreover, recent studies indicate that the ECM composition might influence the development of resistance to chemotherapy drugs. The objective of this study was to evaluate possible expression differences in the ECM compartment of the parental human cell lines WERI-RB1 (retinoblastoma 1) and Y79 and their Etoposide resistant subclones via polymerase chain reaction (PCR). Western blot analyses were performed to analyze protein levels. To explore the influence of ECM molecules on RB cell proliferation, death, and cluster formation, WERI-RB1 and resistant WERI-ETOR cells were cultivated on Fibronectin, Laminin, Tenascin-C, and Collagen IV and analyzed via time-lapse video microscopy as well as immunocytochemistry. We revealed a significantly reduced mRNA expression of the proteoglycans Brevican, Neurocan, and Versican in resistant WERI-ETOR compared to sensitive WERI-RB1 cells. Also, for the glycoproteins α1-Laminin, Fibronectin, Tenascin-C, and Tenascin-R as well as Collagen IV, reduced expression levels were observed in WERI-ETOR. Furthermore, a downregulation was detected for the matrix metalloproteinases MMP2, MMP7, MMP9, the tissue-inhibitor of metalloproteinase TIMP2, the Integrin receptor subunits ITGA4, ITGA5 and ITGB1, and all receptor protein tyrosine phosphatase β/ζ isoforms. Downregulation of Brevican, Collagen IV, Tenascin-R, MMP2, TIMP2, and ITGA5 was also verified in Etoposide resistant Y79 cells compared to sensitive ones. Protein levels of Tenascin-C and MMP-2 were comparable in both WERI cell lines. Interestingly, Fibronectin displayed an apoptosis-inducing effect on WERI-RB1 cells, whereas an anti-apoptotic influence was observed for Tenascin-C. Conversely, proliferation of WERI-ETOR cells was enhanced on Tenascin-C, while an anti-proliferative effect was observed on Fibronectin. In WERI-ETOR, cluster formation was decreased on the substrates Collagen IV, Fibronectin, and Tenascin-C. Collectively, we noted a different ECM mRNA expression and behavior of Etoposide resistant compared to sensitive RB cells. These findings may indicate a key role of ECM components in chemotherapy resistance formation of RB.

The Extracellular Matrix Influences Ovarian Carcinoma Cells' Sensitivity to Cisplatinum: A First Step towards Personalized Medicine

The development of personalized therapies for ovarian carcinoma patients is still hampered by several limitations, mainly the difficulty of predicting patients’ responses to chemotherapy in tumor cells isolated from peritoneal fluids. The main reason for the low predictive power of in vitro assays is related to the modification of the cancer cells’ phenotype induced by the culture conditions, which results in changes to the activation state and drug sensitivity of tumor cells compared to their in vivo properties. We have defined the optimal culture conditions to set up a prognostic test to predict high-grade serous ovarian carcinoma (HGSOC) patients’ responses to platinum chemotherapy. We evaluated the effects of hyaluronic acid (HA) and fibronectin matrices and the contribution of freezing/thawing processes to the cell response to platinum-based treatment, collecting spheroids from the ascitic fluids of 13 patients with stage II or III HGSOC. Our findings indicated that an efficient model used to generate predictive data for in vivo sensitivity to platinum is culturing fresh spheroids on HA, avoiding the use of previously frozen primary tumor cells. The establishment of this easy, reproducible and standardized testing method can significantly contribute to an improvement in therapeutic effectiveness, thus bringing the prospect of personalized therapy closer for ovarian carcinoma patients.

Diagnostic and prognostic values of integrin α subfamily mRNA expression in colon adenocarcinoma

The integrin α (ITGA) subfamily genes play a fundamental role in various cancers. However, the potential mechanism and application values of ITGA genes in colon adenocarcinoma (COAD) remain elusive. The present study investigated the significance of the expression of ITGA genes in COAD from the perspective of diagnosis and prognosis. A COAD RNA-sequencing dataset was obtained from The Cancer Genome Atlas. The present study investigated the biological function of the ITGA subfamily genes through bioinformatics analysis. Reverse transcription-quantitative polymerase chain reaction was applied to investigate the distribution of integrin α8 (ITGA8) expression in COAD tumors and adjacent normal tissues. Bioinformatics analysis indicated that ITGA genes were noticeably enriched in cell adhesion and the integrin-mediated signaling pathway, and co-expressed with each other. It was also revealed through observation that the majority of gene expression was significantly low in tumor tissues (P<0.05), and diagnostic receiver operating characteristic curves revealed that most of the genes could serve as significant diagnostic markers in COAD (P<0.05), especially ITGA8 which had a high diagnostic value with an area under curve (AUC) of 0.989 [95% confidence interval (CI) 0.980–0.997] in COAD (P<0.0001). In addition, ITGA8 expression was verified in clinical samples and it was revealed that it was higher in adjacent normal tissues (P=0.041) compared to COAD tissues, and the AUC was 0.704 (95% CI, 0.577–0.831; P<0.0085). Multivariate survival analysis indicated that integrin α (ITGA5) may be an independent prognostic indicator for COAD overall survival. Gene set enrichment analysis indicated that ITGA5 may participate in multiple biological processes and pathways. The present study revealed that ITGA genes were associated with the diagnosis and prognosis of COAD. The mRNA expression of ITGA8 may be a potential diagnosis biomarker and ITGA5 may serve as an independent prognosis indicator for COAD.