Regulation of BMI1 Polycomb gene expression in histological grades of invasive ductal breast carcinomas and its correlation with hormone receptor status

In vitro characterization of spheres derived from colorectal cancer cell lines

Spherical cultures (SCs) can be regarded in cancer research as a link between in vitro investigations on cancer lines and in vivo studies of tumor development. SCs are believed to mimic tumor architecture and to be enriched in cancer stem cell-like cells (CSC-like cells). In the present study we characterized colonospheres derived from colorectal cancer (CRC) cell lines, and we confirmed the ability of HCT116 and HT29 cell lines to form spheres within serum-free medium, however, the detailed analysis presented the major differences concerning their characteristics including morphology, phenotype, proliferative potential, distribution in the cell cycle phases and spherogenicity. Moreover, after we magnetically separated CD133+ and CD133- cells we could conduct the analogical analysis as we performed for the original cells. We observed that all cellular fractions unveiled sphere formation capacity, even when cultured in limited number of cells per well and only SCs originated from CD133+ fraction resembled morphologically the parental spheres. Both CD133+ and CD133- subsets derived from HCT116 line were more enriched in cells in G0/G1 phase of the cell cycle in comparison to their HT29 analogues. Additionally, proliferative potential also varied amongst all studied fractions. Surprisingly, 3-D invasion assay revealed that only HCT116-derived populations were able to migrate into extended regions of Matrigel Matrix confirming their higher aggressiveness. Our results provided comprehensive characterization of CRC cell lines culture in adherent and spherical forms and, what seems to be the most advantageous, the comparison of two distinct fractions after magnetic separation. As we found the specific features of cells presented line- and expansion mode-dependency, thus, such complete description might appear crucial before CRC lines would be involved into sophisticated assays, especially focused on potentially novel therapeutic agents targeting CSC-like cells.

TWIST1 and BMI1 in Cancer Metastasis and Chemoresistance

Purpose Increasing evidences revealed that cancer cells with the characteristics of epithelial-mesenchymal transition (EMT) or cancer stem cells (CSC) have high ability of progression, invasion, metastasis and chemoresistance. TWIST1 and BMI1 are crucial transcription factors required for EMT and CSC. Both TWIST1 and BMI1 are up-regulated in various cancers and have a positive correlation with poor prognosis. Although recent results showed that the two molecules function in promoting cancer metastasis and chemoresistance respectively, the correlation of TWIST1 and BMI1 is not well understood. Methods In this review, we summarize recent advance in cancer research focus on TWIST1 and BMI1 in cancer metastasis and chemoresistance, and emphasize the possible link between EMT and CSC. Results Further investigation of TWIST1 and BMI1 cooperately promote CSC proliferation due to EMT-associated effect will help to understand the mechanism of tumor cells metastasis and chemoresistance. Conclusions TWIST1 and BMI1 in cancer cells will be effective targets for treating chemoresistant metastatic lesions.

Downregulated miR-495 [Corrected] Inhibits the G1-S Phase Transition by Targeting Bmi-1 in Breast Cancer

Bmi-1 (B cell-specific Moloney murine leukemia virus integration site 1) is upregulated in breast cancer and was involved in many malignant progressions of breast cells, including cell proliferation, stem cell pluripotency, and cancer initiation. However, the epigenetic regulatory mechanism of Bmi-1 in breast cancer remains unclear. After analysis of the ArrayExpress dataset GSE45666, we comparatively detected the expression levels of miR-495 in 9 examined breast cancer cell lines, normal breast epithelial cells and 8 pairs of fresh clinical tumor samples. Furthermore, to evaluate the effect of miR-495 on the progression of breast cancer, MCF-7 and MDA-MB-231 were transduced to stably overexpress miR-495. The 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assay, colony formation assays, 5-Bromo-2-deoxyUridine labeling and immunofluorescence, anchorage-independent growth ability assay, flow cytometry analysis, and luciferase assays were used to test the effect of miR-495 in MCF-7 and MDA-MB-231 cells in vitro. Xenografted tumor model was also used to evaluate the effect of miR-495 in breast cancer. Herein, we found that miR-495, a predicted regulator of Bmi-1, was frequently downregulated in malignant cells and tissues of breast. Upregulation of miR-495 significantly suppressed breast cancer cell proliferation and tumorigenicity via G1-S arrest. Further analysis revealed that miR-495 targeted Bmi-1 through its 3' untranslated region. Moreover, Bmi-1 could neutralize the suppressive effect of miR-495 on cell proliferation and tumorigenicity of breast cancer in vivo. These data suggested that miR-495 could inhibit the G1-S phase transition that leads to proliferation and tumorigenicity inhibition by targeting and suppressing Bmi-1 in breast cancer.