Protein markers of cancer-associated fibroblasts and tumor-initiating cells reveal subpopulations in freshly isolated ovarian cancer ascites

Abstract

BackgroundIn ovarian cancer, massive intraperitoneal dissemination is due to exfoliated tumor cells in ascites. Tumor-initiating cells (TICs or cancer stem cells) and cells showing epithelial-mesenchymal-transition (EMT) are particularly implicated. Spontaneous spherical cell aggregates are sometimes observed, but although similar to those formed by TICs in vitro, their significance is unclear.MethodsCells freshly isolated from malignant ascites were separated into sphere samples (S-type samples, n=9) and monolayer-forming single-cell suspensions (M-type, n=18). Using western blot, these were then compared for expression of protein markers of EMT, TIC, and of cancer-associated fibroblasts (CAFs).ResultsS-type cells differed significantly from M-type by expressing high levels of E-cadherin and no or little vimentin, integrin-β3 or stem cell transcription factor Oct-4A. By contrast, M-type samples were enriched for CD44, Oct-4A and for CAF markers. Independently of M- and S-type, there was a strong correlation between TIC markers Nanog and EpCAM. The CAF marker α-SMA correlated with clinical stage IV. This is the first report on CAF markers in malignant ascites and on SUMOylation of Oct-4A in ovarian cancer.ConclusionsIn addition to demonstrating potentially high levels of TICs in ascites, the results suggest that the S-type population is the less tumorigenic one. Nanoghigh/EpCAMhigh samples represent a TIC subset which may be either M- or S-type, and which is separate from the CD44high/Oct-4Ahigh subset observed only in M-type samples. This demonstrates a heterogeneity in TIC populations in vivo which has practical implications for TIC isolation based on cell sorting. The biological heterogeneity will need to be addressed in future therapeutical strategies.

Human Mesenchymal Stroma/Stem Cells Exchange Membrane Proteins and Alter Functionality During Interaction with Different Tumor Cell Lines

“…However, co-culture of the ovarian cancer cells with MSC was associated with EpCAM mRNA and protein induction, which suggested certain differentiation processes by adding epithelial celllike properties to the MSC. Such heterogenic functionality was also discussed in vivo with EpCAM-positive subsets of tumor-initiating cells (cancer stem cells) in patient ovarian cancer ascites also carrying markers of cancer-associated fibroblasts [44]. Other in vivo studies demonstrated crosstalk of MSC with tumor cells and promotion of tumor growth in patients with head and neck cancer, whereby MSC isolated from these patient tumors constitutively produced high levels of IL-6, IL-8, and stromal cell-derived factor (SDF)-1a [45].…”

Cancer-associated fibroblasts: A multifaceted driver of breast cancer progression

“…They are also morphologically identified as spindleshaped cells scattered in the tumor stroma [28]. Although a series of molecular markers have been identified, none are unique to CAFs [29]. However, increasing evidence has revealed the association between mCAFs and poorer survival in breast cancer patients or an aggressive tumor phenotype (Table 1).…”

Cancer-associated fibroblasts enhance the migration ability of ovarian cancer cells by increasing EZH2 expression

“…Numerous studies have found that cancer-associated fibroblasts (CAFs) play an important role in a wide variety of tumors, such as breast, prostate, esophageal, pancreatic and lung cancer by promoting the initiation, proliferation, invasion and metastasis of cancer cells; however, the underlying mechanisms are not yet fully understood (6)(7)(8)(9). In our previous studies, we found that the abundance of CAFs in ovarian cancer is associated with the advanced stage of the tumor, lymph node metastasis and omental metastasis.…”