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The extracellular matrix to which cancer cells adhere affects cellular sensitivity to anticancer drugs. We sought to examine the changes in sensitivity of colorectal cancer cells carrying the BRAF V600E mutation to vemurafenib cultured in three‐dimensional (3D) collagen‐I gels, while also identifying the signaling pathways involved in these changes. HT29 colorectal cancer cells were cultured in conventional tissue culture (TC) plastic plates or in collagen‐I gels. The HT29 cells demonstrated approximately 10‐fold higher sensitivity to vemurafenib in 3D‐collagen‐I gels compared with those cultured on conventional TC plastic plates. Furthermore, in cells cultured on TC plastic, vemurafenib was found to augment tyrosine phosphorylation of focal adhesion kinase (FAK), while 3D‐cultured cells expressed lower levels of FAK and vemurafenib did not affect its tyrosine phosphorylation, suggesting that FAK contributes to vemurafenib resistance. However, pharmacological inhibition of FAK did not sensitize the cells to vemurafenib. Also, the level of tyrosine‐phosphorylated epidermal growth factor receptor (EGFR)/ERBB2 family proteins was found to be lower in cells cultured in 3D‐collagen gel compared with those in cells cultured on TC plastic. Afatinib, an inhibitor of the EGFR/ERBB family of kinases, sensitized the cells to higher concentrations of vemurafenib, implying their participation in vemurafenib resistance. Adhesion to collagen‐I gel but not to the collagen‐I‐coated plastic surface sensitized the cells, suggesting that the rigidity of the media rather than adherence to collagen‐I may be important for cellular sensitivity to vemurafenib. [ABSTRACT FROM AUTHOR]

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer in the world. The evolution and progression of HNSCC are considered to result from multiple stepwise alterations of cellular and molecular pathways in squamous epithelium. Recently, inhibitor of growth gene (ING) family consisting of five genes, ING1 to ING5, was identified as a new tumor suppressor gene family that was implicated in the downregulation of cell cycle and chromatin remodeling. In contrast, it has been shown that ING1 and ING2 play an oncogenic role in some cancers, this situation being similar to TGF-β. In HNSCC, the ING family has been reported to be downregulated, and ING translocation from the nucleus to the cytoplasm may be a critical event for carcinogenesis. In this paper, we describe our recent results and briefly summarize current knowledge regarding the biologic functions of ING in HNSCC. [ABSTRACT FROM AUTHOR]

Telomerase activity is correlated with the immortality of various cultured cells and cancer cells. The activity, however, is also demonstrated in various normal regenerating cells which normally have a finite life span in vivo and in vitro, though its biological implication remains unclear. Using cultured normal human epithelial cells, we show that telomerase activity is associated with epithelial cell subsets which actively proliferate in vitro. Unlike in most cancer cell lines, telomerase activity was evidently up-regulated when the cells entered into S phase in primary human epithelial cells. To characterize the cells which have telomerase activity, the primary human epithelial cell population of uterine cervix was dissociated into several distinctive cellular subsets by means of immunocytochemical cell fractionation. Telomerase activity was found to be closely associated with the subset which expressed predominantly integrin β1 and epidermal growth factor receptor. We further identified the telomerase-negative subpopulation which contained a small subset that strongly coexpresses p75NGFR low affinity nerve growth factor receptor, integrin β4 and bcl-2 protein. The location of the p75NGFR-expressing cells contrasts to that of the Ki-67 positive cells in vivo and is distinctive of telomerase positive cycling cells, indicating that these cells remain at the G0 phase. The present study supports the notion that telomerase activity is linked to cell cycle regulation, implying that telomerase is activated upon cell proliferation in regenerating normal human epithelial cells. [ABSTRACT FROM AUTHOR]

The epithelial cell type- specific enhancer of the human papillomavirus (HPV) type 16 termed the long control region (LCR) carries three AP-1 binding sites. We investigated the roles of the AP-1 sites for transactivation of the LCR by Jun-B that may be a cell type specific- transactivator for the HPVs in human fibroblasts in which expression of the endogenous jun-B gene is low. Transient expression of Jun-B alone poorly activated transcriptional activity of the LCR. However, when combined with c- Fos, Jun-B activated the LCR. The promoter-proximal AP-1 site was required for transactivation of the LCR by Jun-B:c- Fos, but the site itself was not sufficient for the maximal response. The proposed cell type specific- regulatory element that harbors binding sites for NF1 as well as TEF-1 and PEA3 motifs, but neither other AP-1 sites nor the proximal enhancer region, could augment the transcriptional response of the promoter-proximal AP-1 site to Jun-B:c- Fos. [ABSTRACT FROM AUTHOR]

Proteolytic cleavage of membrane proteins can alter their functions depending on the cleavage sites. We recently demonstrated that membrane type 1 matrix metalloproteinase (MT1-MMP ) converts the tumor suppressor EphA2 into an oncogenic signal transducer through EphA2 cleavage. The cleaved EphA2 fragment that remains at the cell surface may be a better target for cancer therapy than intact EphA2. To analyze the cleavage site(s) of EphA2, we purified the fragments from tumor cells expressing MT1-MMP and Myc- and 6× His-tagged EphA2 by two-step affinity purification . The purified fragment was digested with trypsin to generate proteolytic peptides , and the amino acid sequences of these peptides were determined by nano-LC-mass spectrometry to identify the MT1-MMP-mediated cleavage site(s) of EphA2.

The autogenic lens tumors induced by the Simian vacuolating virus 40 (SV40) T antigen in α-crystallin/SV40 T antigen transgenic (TG) mice, provide a tool to screen anti-tumor reagents in vivo and to clarify the underlying mechanisms. Juzen-taiho-to, a Chinese medicine composed of 10 herbs, was frequently used as an alternative medicine for cancer patients by clinicians and occasionally it was demonstrated to have beneficial effects on the prognosis and general condition of cancer patients. However, it was not scientifically verified. In the present study, the anti-tumor effects and underlying mechanisms of Juzen-taiho-to in the TG mice model was examined using cDNA microarray analysis and the results were confirmed by real-time PCR. The TG mice demonstrated a higher cumulative survival rate after treatment with the drug compared with the control group (P<0.05). Gene chip profiles demonstrated that cell functions involving the membrane, glycoprotein, cell membrane, signal and ionic channel for the lens tumor, the cell cycle, DNA replication, homeobox, mitosis and cell division for the spleen and the acetylation, mitochondrion, ribosomal protein, ribonucleoprotein for the liver, were altered by the administration of Juzen‑taiho-to. The important canonical pathways were those of the mitogen-activated protein kinase (MAPK), the cell cycle and the ribosome for the altered genes of the lens tumor, spleen and liver after drug administration, respectively. From real-time PCR, in the eyeball, epidermal growth factor receptor (Egfr), Rasgrf1 and heat shock protein 1B (Hspa1b) mRNAs were found to be significantly lower in treated lenses than in those not exposed to the drug, while Rps25 mRNA demonstrated the opposite association in the liver. It was suggested that Juzen-taiho-to may prolong the survival time of SV40 T antigen TG mice by improving their nutritional condition, inhibiting the MAPK pathway and strengthening the immune system without causing hepatic toxicity.

To clarify the role of p33ING1b in tumorigenesis and progression of head and neck squamous cell carcinoma (HNSCC), we examined the expression and subcellular localization of p33ING1b in 214 HNSCC cases in parallel with 60 dysplasia samples and 48 normal epithelium samples by immunohistochemistry, and analyzed correlations of expression of p33ING1b in HNSCC cases with clinicopathological variables, apototic index and expression of 14-3-3η, p300, p21 and PCNA. Although 12% of HNSCC cases lost expression of p33ING1b, most cases of HNSCC retained expression of p33ING1b with levels similar to those in non-cancerous epithelia. Nuclear expression of p33ING1b was significantly decreased in HNSCC compared to normal epithelia. In contrast, cytoplasmic expression of p33ING1b was found to be significantly higher in HNSCC. An abundance of p33ING1b in cytoplasm positively correlated with poor differentiation and tumor progression. Corresponding to those clinicopathogical features, high expression of p33ING1b in the cytoplasm correlated with PCNA labelling index but in contrast, that in the nuclei correlated with apoptosis. In nuclei, p33ING1b is coexpressed with p300 and p21, implying its roles in tumor suppression. Elevated expression of 14-3-3η was associated with cytoplasmic expression of p33ING1b and immunofluorescence study suggested association of p33ING1b and 14-3-3η. Among three cell lines derived from oral SCC, poorly-differentiated SAS cells showed a relatively high expression of p33ING1b in cytoplasm with increased level of 14-3-3η. The results obtained here suggest that relocation of p33ING1b from the nucleus to the cytoplasm, where the protein is tethered by 14-3-3η, participates in tumorigenesis and progression in HNSCC.