Important in this context is the observation that, after disregarding nonangiogenic subsets of NSCLC (which tend to obscure the association Foretinib research buy of Oct-4 with tumor angiogenesis), a subset of NSCLC tumors does not induce

angiogenesis, but instead co-opts the normal vasculature for further growth. On the basis of the previous finding that Oct-4 may be a major contributor to the maintenance of self-renewal in embryonic stem cells, we investigated the association of Oct-4 expression with self-renewal of NSCLC cells. The immunohistochemical analyses presented here showed clear Oct-4 staining in most sections, and RT-PCR showed Oct-4 mRNA in all NSCLC cell lines. Our data extend the previous report of Oct-4 overexpression in lung adenocarcinoma [20], providing the first demonstration that Oct-4 is also present in lung squamous cell carcinoma specimens, exhibiting an apparent difference in the degree of expression among sections analyzed. One possible explanation for these findings is that the genesis of lung buy Salubrinal adenocarcinoma and squamous cell carcinoma may be different. The former arises from mucous glands or the cells of bronchoalveolar duct junction and the latter grows most commonly in or around major bronchi. Further studies designed

to address the relationship between Oct-4 expression in endothelial precursors and the sites of origin of adenocarcinoma and squamous cell carcinoma are required to confirm this. Our data also showed that the degree of immunohistochemical staining was positively

correlated with poor differentiation of tumor cells and Ki-67 expression; this latter marker provides an opportunity to analyze the proliferative cell fraction in preserved tumor specimens. High levels of Oct-4 have been shown to increase the malignant potential of tumors, whereas inactivation of Oct-4 induces a regression of the malignant component [22]; moreover, knockdown of Oct-4 expression in lung cancer cells has been shown to facilitate differentiation of CD133-positive cells into CD133-negative cells [23]. These findings, taken together with our data, indicate that overexpression of Oct-4 in NSCLC tissues may maintain the second poorly differentiated state by contributing to tumor cell proliferation. On the other hand, down-regulation of Oct-4 expression has been shown to induce apoptosis of tumor-initiating-cell-like cells through an Oct-4/Tcl1/Akt1 pathway, implying that Oct-4 might maintain the survival of tumor-initiating cells, at least in part, by inhibiting apoptosis [13]. Whether an Oct-4-dependent pathway modulates apoptosis in clinical NSCLC samples or NSCLC cell lines has not yet been tested. Previous reports have indicated that tumor-induced angiogenesis is important in maintaining the poorly differentiated state and promoting metastasis in NSCLC [23, 24].