Growth, morphologic, and invasive characteristics of early and late passages of a human endometrial carcinoma cell line (RL95-2)

Adaptation to chronic acidic extracellular pH elicits a sustained increase in lung cancer cell invasion and metastasis

Acidic extracellular pH (pH_e) is an important microenvironment for cancer cells. This study assessed whether adaptation to acidic pH_e enhances the metastatic phenotype of tumor cells. The low metastatic variant of Lewis lung carcinoma (LLCm1) cells were subjected to stepwise acidification, establishing acidic pH_e-adapted (LLCm1A) cells growing exponentially at pH 6.2. These LLCm1A cells showed increased production of matrix metalloproteinases (MMPs), including MMP-2, -3, -9, and -13, and pulmonary metastasis following injection into mouse tail veins. Although LLCm1A cells exhibited a fibroblastic shape, keratin-5 expression was increased and α-smooth muscle actin expression was reduced. Despite serial passage of these cells at pH 7.4, high invasive activity through Matrigel^® was sustained for at least 28 generations. Thus, adaptation to acidic pH_e resulted in a more invasive phenotype, which was sustained during passage at pH 7.4, suggesting that an acidic microenvironment at the primary tumor site is important in the acquisition of a metastatic phenotype.

Side population cells from long-term passage non-small cell lung cancer cells display loss of cancer stem cell-like properties and chemoradioresistance

The side population (SP) assay is a widely used method for isolating stem cell-like cells from cancer cell lines and primary cells. The cancer cells used in different laboratories have been passaged for different generations. Emerging evidence revealed that repeated passaging of cell lines for multiple generations frequently leads to change of characteristics. Thus, it is worth investigating the effects of repeated passaging on the biological and functional properties of the enriched SP fraction from early- and late-passage cells. The present study reports that the cancer stem cell (CSC) characteristics, including increased frequency of tumor-initiating and self-renewal capacity, and resistance to the chemotherapy agent doxorubicin and ionizing radiation, was diminished in SP cells from late-passage non-small cell lung cancer (NSCLC) cells. This finding revealed that the SP from long-term passage NSCLC cells was not consistently enriched for stem cell-like cancer cells, and low-passage cell lines and primary cancer cells are therefore recommended in the CSCs field.

Dichloroacetate induces apoptosis in endometrial cancer cells

PURPOSE

A recent landmark study demonstrated that Dichloroacetate (DCA) treatment promoted apoptosis in lung, breast, and glioblastoma cancer cell lines by shifting metabolism from aerobic glycolysis to glucose oxidation coupled with NFAT-Kv1.5 axis remodeling. The objective of this study was to determine whether DCA induces apoptosis in endometrial cancer cells and to assess apoptotic mechanism.

METHODS

A panel of endometrial cancer cell lines with varying degrees of differentiation was treated with DCA and analyzed for apoptosis via flow cytometry. Biological correlates such as gene expression, intracellular Ca(2+), and mitochondrial membrane potential were examined to assess apoptotic mechanism.

RESULTS

Initiation of apoptosis was observed in five low to moderately invasive cancer cell lines including Ishikawa, RL95-2, KLE, AN3CA, and SKUT1B while treatment had no effect on non-cancerous 293T cells. Two highly invasive endometrial adenocarcinoma cell lines, HEC1A and HEC1B, were found to be resistant to DCA-induced apoptosis. Apoptotic responding cell lines had a significant increase in early and late apoptotis, a decrease in mitochondrial membrane potential, and decreased Survivin transcript abundance, which are consistent with a mitochondrial-regulated mechanism. DCA treatment decreased intracellular calcium levels in most apoptotic responding cell lines which suggests a contribution from the NFAT-Kv1.5-mediated pathway. DCA treatment increased p53 upregulated modulator of apoptosis (PUMA) transcripts in cell lines with an apoptotic response, suggesting involvement of a p53-PUMA-mediated mechanism.

CONCLUSIONS

Dichloroacetate effectively sensitizes most endometrial cancer cell lines to apoptosis via mitochondrial, NFAT-Kv1.5, and PUMA-mediated mechanisms. Further investigation of the cancer therapeutic potential of DCA is warranted.

Characterization and phenotypic variation with passage number of cultured human endometrial adenocarcinoma cells

Despite numerous endometrial cancer cell lines, little is know about the progression and transition of primary cultured endometrial tumours. Herein, a stage I grade III endometrial adenocarcinoma was maintained in primary culture and the phenotypic and protein expression changes were observed in relation to passage number. At early passage numbers, cultured human endometrial cancer (CHEC) cells displayed classic epithelial cell morphology, growing in groups in a glandular structure and staining positive for cytokeratin. However, with increasing passage number, CHEC cells changed in morphology to display a stromal phenotype which was accompanied by a significant reduction in cytokeratin and increases in alpha-actin and vimentin expression. Simultaneous culture of stromal cells isolated from the original tumour failed to show the same morphological characteristics or protein expression patterns. We further characterised CHEC cells through a screening of cancer related proteins, among others, caveolin-1 and Tissue factor in comparison with established cancer cell lines and corresponding non-cancerous cells. This report demonstrates that endometrial adenocarcinoma cells in culture can undergo phenotypic and protein expression changes reminiscent of epithelial-mesenchymal transition. This work suggests that primary tumours and cell lines displaying stromal morphologies may have undergone epithelial-mesenchymal transition from an adenocarcinoma origin.

Adrenomedullin promotes formation of xenografted endometrial tumors by stimulation of autocrine growth and angiogenesis

The angiogenic peptide adrenomedullin (ADM) has been implicated as a mediator of the increased risk of endometrial hyperplasia and cancer resulting from the use of tamoxifen for the treatment and prevention of breast cancer. ADM has been shown to be induced by tamoxifen in the endometrium and to be a growth factor for endometrial endothelial cells in vitro. We have now shown ADM to be strongly angiogenic in the mouse subcutaneous sponge angiogenesis assay. To examine the role of ADM in tumor growth, the ADM cDNA was transfected into endometrial carcinoma cells followed by xenografting into athymic mice. Two endometrial cancer cell lines were employed, those in which transfection and expression of ADM resulted in no effect on growthin vitro (Ishikawa cells) and those in which expressionof exogenous ADM stimulated in vitro growth (RL95.2 cells). A clear enhancement of tumor growth was seen with both cell lines but the effect was far greater with the RL95.2 cells. We conclude that ADM is pro-tumorigenic by stimulating either angiogenesis alone or by stimulating angiogenesis and carcinoma cell growth directly. The combined activities lead to a striking increase in tumor growth. These results provide the first direct evidence of tumorigenic activity of ADM and provide further support for ADMs involvement in tamoxifen induced endometrial neoplasia.

12(S)-hydroxyeicosatetraenoic acid increases the actin microfilament content in B16a melanoma cells: a protein kinase-dependent process

12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE], a lipoxygenase metabolite of arachidonic acid, has been shown to be involved in a wide variety of cellular activities (i.e., adhesion, spreading, motility, invasion) which promote metastasis to occur in tumor cells. In this study, several techniques (Western blotting, flow cytometry and DNase I assay) were performed to examine the alterations in the distribution of G- and F-actin expressed in B16a melanoma cells. Each of these methods independently revealed that 12(S)-HETE treatment (0.1 mM, 15 min) resulted in an increase in the F-actin content in the cytoskeletal preparations. Since the integrity of cytoskeletal networks (i.e., actin filaments) can be dynamically regulated through protein phosphorylation, we investigated the potential role of several protein kinases in the 12(S)-HETE-induced actin polymerization. By flow cytometric analysis, 12(S)-HETE was found to increase the actin filament contents. This effect could be inhibited by protein kinase C (PKC) inhibitors (calphostin C and staurosporine) as well as by protein tyrosine kinase (PTK) inhibitor (genistein) but not by protein kinase A inhibitor (H8), suggesting that the 12(S)-HETE effect involves PKC and PTK. This conclusion is consistent with the observations that phorbol 12-myristate-13-acetate (PMA) mimics the biological effect of 12(S)-HETE in promoting the F-actin formation in B16a cells. As a final analysis, direct protein phosphorylation studies indicate that 12(S)-HETE treatment led to enhanced phosphorylation of myosin light chain, which may contribute to the increased stress fiber formation following 12(S)-HETE stimulation.

Regulation of the expression of the angiogenic enzyme platelet-derived endothelial cell growth factor/thymidine phosphorylase in endometrial isolates by ovarian steroids and cytokines

The angiogenic enzyme platelet-derived endothelial cell growth factor/thymidine phosphorylase (PD-ECGF/TP) was strongly expressed in the endometrial glands in the luteal and menstrual, but not the proliferative, phases of the cycle. The converse was seen in the stroma, where expression was strong in the proliferative, but not the luteal or menstrual, phases. Inflammatory cytokines induced PD-ECGF/TP expression in primary cultures of human normal endometrial epithelial (NEE) and normal endometrial stromal cells. The profile of cytokine induction of PD-ECGF/TP was cell dependent. Thus, in NEE cells, PD-ECGF/TP expression was strongly induced by the combination tumor necrosis factor-a and interferon-gamma. In contrast, in normal endometrial stromal cells, interferon-gamma gave, by far, the strongest induction of PD-ECGF/TP. Expression of the enzyme was not regulated by ovarian hormones alone. Although treatment of NEE cells with a physiological concentration of progesterone (5 X 10[-8] M) or transforming growth factor-beta1 (10 ng/ml) alone had no effect on PD-ECGF/TP expression, when delivered together at the same dose they induced a 48-fold increase in expression. This expression correlates with cyclic changes in progesterone and transforming growth factor-beta1 levels in the uterus.

Transcriptional regulation of estrogen receptor in breast carcinomas

An important transcriptional regulatory element of the estrogen receptor (ER) gene that binds a protein expressed in ER-positive breast carcinomas has been identified. Using a transient expression assay, we identified a 75-bp region of the 5' untranslated leader of the ER gene which augments expression from the ER promoter. This region contains two binding sites for a protein, estrogen receptor factor 1 (ERF-1), which is expressed in ER-positive breast carcinomas. A concatenated ERF-1 binding site probe identified a 30,000-Da protein. Low-level ERF-1 expression was detected in normal human mammary epithelial cells. Abundant ERF-1 expression was also found in endometrial carcinoma cell lines that express the ER-positive phenotype. These results indicate that ERF-1 expression represents a common mechanism of ER regulation in hormonally responsive carcinomas.