Apoptosis inhibitor 5 (API-5; AAC-11; FIF) is upregulated in human carcinomas in vivo.

Apoptosis inhibitor 5 (API-5) is a 55 kDa nuclear protein with potent anti-apoptotic signaling in tumor cells in vitro. In this study, we analyzed the expression of the API-5 protein in vivo in a broad spectrum of human carcinomas, including those of the colon, lung, liver, kidney, pancreas, stomach and esophagus using tumor tissues obtained during tumor resection. The results showed significant upregulation of API-5 expression in biopsies of lung (23%, n=13) and colorectal tumors (33%, n=27) in comparison with biopsies from the adjacent normal tissue. Colon cancer biopsies were used to study the cell populations with an upregulated level of expression of API-5 more closely. Using a magnetic bead-based selection for the epithelial cell marker EpCAM, we purified epithelial cells from the tumor and control tissues and analyzed these cells for API-5 expression by western immunoblotting. We observed that EpCAM-positive tumor cells expressed API-5 in all three colorectal cancer cases tested, in contrast to the control EpCAM-positive and EpCAM-negative cells isolated from the control or tumor tissues. These data suggest that the expression of the API-5 protein is upregulated in tumor epithelial cells and may serve as a prognostic marker in colorectal cancer.

Detachment-mediated resistance to TRAIL-induced apoptosis is associated with stimulation of the PI3K/Akt pathway in fetal and adenocarcinoma epithelial colon cells.

The resistance of transformed epithelial cells to a detachment-induced apoptosis (anoikis) can significantly affect their susceptibility to anticancer therapy. We showed that detachment of both fetal (FHC) and adenocarcinoma (HT-29) human colon epithelial cells resulted in the activation of the pro-survival Akt pathway, and significant changes in integrin-linked kinase (ILK) and focal adhesive kinase (FAK) phosphorylation. We demonstrated a detachment-induced and PI3K/Akt-mediated resistance to apoptotic effects of TRAIL, which was not associated with any changes in the cell surface TRAIL death receptor levels. Instead, a modulation of downstream intracellular signaling events was suggested to be involved. Our results may have important implications for optimization of new strategies in treatment of cancers at different stages of development.

Lower sensitivity of FHC fetal colon epithelial cells to photodynamic therapy compared to HT-29 colon adenocarcinoma cells despite higher intracellular accumulation of hypericin.

Preferential uptake of photosensitizer by tumour tissue is an elementary prerequisite of effective and successful photodynamic therapy (PDT). Therefore intracellular concentration of photosensitizer is one of the limiting factors affecting PDT efficiency. Hypericin (HY) has found applications in photodynamic diagnostics solely due to its high specificity for tumour cells and tissues. However, here we suggest that not only HY uptake, but importantly also the cell ability to manage oxidative stress induced by HY-PDT can be important decisive factors finally affecting the cell death response. We showed that despite the higher accumulation of HY in FHC human fetal colon epithelial cells compared to HT-29 colon adenocarcinoma cells, the cytotoxic effects of this photosensitizer were more pronounced in the latter cell line, and this was associated with enhanced accumulation of HY-PDT-induced reactive oxygen species (ROS).

Fetal colon cell line FHC exhibits tumorigenic phenotype, complex karyotype, and TP53 gene mutation.

Stable cell lines obtained by spontaneous immortalization might represent early stages of malignant transformation and be useful experimental models for studies of mechanisms of cancer development. The FHC (fetal human cells) cell line has been established from normal fetal colonic mucosa. Detailed characterization of this cell line and mechanism of spontaneously acquired immortality have not been described yet. Therefore, we characterized the FHC cell line in terms of its tumorigenicity, cytogenetics, and TP53 gene mutation analysis. FHC cells displayed capability for anchorage-independent growth in semisolid media in vitro and formed solid tumors after transplantation into SCID (severe combined immunodeficiency) mice. This tumorigenic phenotype was associated with hypotriploidy and chromosome number ranging from 66 to 69. Results of comparative genetic hybridization arrays showed that most chromosomes included regions of copy number gains or losses. Region 8q23 approximately 8q24.3 (containing, e.g., MYC proto-oncogene) was present in more than 20 copies per nucleus. Moreover, we identified mutation of TP53 gene in codon 273; triplet CGT coding Arg was changed to CAG coding His. Expression of Pro codon 72 polymorphic variant of p53 was also detected. Mutation of TP53 gene was associated with abolished induction of p21(Waf1/Cip1) and MDM-2 proteins and resistance to apoptosis after genotoxic treatment. Because of their origin from normal fetal colon and their relative resistance to the induction of apoptosis, FHC cells can be considered a valuable experimental model for various studies.