A significant proportion of ovarian cancer cells within the peritoneal ascites exist as multicellular aggregates or spheroids which have the capacity to invade nearby organs [2]. ability, adhesion and the activities of matrix metalloproteinases 9/2 (MMP-9/2) was measured by in vitro functional assays and gelatin zymography. These observations were further validated in in vivo mouse models using Balb/c nu/nu mice. Results We report significantly elevated expression of Oct4A in high-grade serous ovarian tumors compared to normal ovarian tissues. The expression of Oct4A in ovarian cancer cell lines correlated with their CSC-related sphere forming abilities. The suppression of Oct4A in HEY cells resulted in a significant diminution of integrin 1 expression and associated 5 and 2 subunits compared to vector control cells. This was associated with a reduced adhesive ability on collagen and fibronectin and decreased secretion of pro-MMP2 in Oct4A KD cells compared to vector control cells. In vivo, Oct4A knock down (KD) cells produced tumors which were significantly smaller in size and weight compared to tumors derived from vector control cells. Immunohistochemical analyses of Oct4A KD tumor xenografts demonstrated a significant TG 100572 loss of cytokeratin 7 (CK7), Glut-1 as well as CD34 and CD31 compared to vector control cell-derived xenografts. Conclusion The expression of Oct4A may be crucial to promote and sustain integrin-mediated extracellular matrix (ECM) remodeling requisite for tumor metastasis in ovarian cancer patients. Keywords: Ovarian carcinoma, Cancer stem cells, Metastasis, Integrins, Chemoresistance, Recurrence, Oct4A Background Ovarian cancer is a major gynaecological malignancy worldwide with 125,000 deaths reported each year [1]. The development of ascites and peritoneal metastases is a major clinical issue in the prognosis and management of ovarian cancer. A significant proportion of ovarian cancer cells within the peritoneal ascites exist as multicellular aggregates or spheroids which have the capacity to invade nearby organs [2]. The pathology of peritoneal-based metastasis includes the attachment of shed primary ovarian tumor cells onto the mesothelial-lined spaces of the peritoneum in the form of spheroids resulting in Rabbit polyclonal to USP22 multiple tumor masses necessary for secondary growth. Current treatment strategies for advanced-stage ovarian cancer patients results in initial remission in up to 80?% of patients [3]. However, TG 100572 following a short remission period (usually 16C22 months), recurrence occurs in almost all patients ultimately resulting in patient mortality. This high rate of recurrence is largely due to the ability of tumor cells to evade the cytotoxic effects of chemotherapy associated with intrinsic or acquired chemoresistance, a property commonly associated with CSCs [4, 5]. The concept of CSCs supports the existence of a sub-population of tumor cells which drive tumor growth and progression, while also TG 100572 sustaining the cytotoxic pressure imposed by therapy to promote the re-growth of therapy-resistant tumors [6, 7]. In this scenario, it can be postulated that the development of an effective therapy for recurrent ovarian tumors will depend on the identification of tumor specific CSCs, as well as the pathways/regulators controlling their survival and sustenance. Oct4 (Oct3/4 or POU5F1) is a member of the POU-domain family of transcription factors and has been shown to play an important role in the maintenance of self-renewal and pluripotency in embryonic stem cells (ESCs). It is commonly expressed in unfertilized oocytes, the inner cell mass (ICM) of a blastocyst, germ cells, embryonic carcinoma cells and embryonic germ cells [8]. Up regulation of Oct4 expression has been shown to sustain an undifferentiated pluripotent stem cell state, while a loss of Oct4 expression results in the induction of differentiation in stem cells, producing a heterogeneous population of highly specialized daughter cells [8]. Additionally, Oct4 has consistently been shown to be an integral factor necessary for the reprogramming of somatic cells into induced pluripotent stem cells (iPSCs). Although a cocktail of transcription factors TG 100572 are typically involved in this process (eg Oct4, Sox2, Klf4 and c-Myc), reprogramming efficiency is reduced if Oct4 is not present, thus indicating an absolute requirement for Oct4 in maintaining a stem cell-like state [9]. Importantly however, Oct4 is highly expressed in many tumor types, suggesting that the reprogramming of somatic cells as well as tumor development and progression may share common cellular mechanisms [10]. The Oct4 gene encodes for three isoforms, generated by alternative splicing of genes, known as Oct4A, Oct4B and Oct4B1 [11, 12]. At the nucleotide level, both Oct4A and Oct4B share exons 2C5. However, exon 1 is missing in.