Progesterone potentiates the growth inhibitory effects of calcitriol in endometrial cancer via suppression of CYP24A1.

Here, we evaluated the expression of CYP24A1, a protein that inactivates vitamin D in tissues. CYP24A1 expression was increased in advanced-stage endometrial tumors compared to normal tissues. Similarly, endometrial cancer cells expressed higher levels of CYP24A1 than immortalized endometrial epithelial cells. RT-PCR and Western blotting were used to examine CYP24A1 mRNA and protein levels in endometrial cancer cells after 8, 24, 72, and 120 h of exposure to progesterone, progestin derivatives and calcitriol, either alone or in combination. Progestins inhibited calcitriol-induced expression of CYP24A1 and splice variant CYP24SV mRNA and protein in cancer cells. Furthermore, actinomycin D, but not cycloheximide, blocked calcitriol-induced CYP24A1 splicing. siRNA-induced knockdown of CYP24A1 expression sensitized endometrial cancer cells to calcitriol-induced growth inhibition. These data suggest that CYP24A1 overexpression reduces the antitumor effects of calcitriol in cancer cells and that progestins may be beneficial for maintaining calcitriol's anti-endometrial cancer activity.

Nestin suppression attenuates invasive potential of endometrial cancer cells by downregulating TGF-ß signaling pathway.

Nestin, an intermediate filament protein and a stem cell marker is expressed in several tumors. Until recently, little was known about the expression levels and the role of Nestin in endometrial cancer. Compared to the immortalized endometrial epithelial cell line EM-E6/E7-TERT, endometrial cancer cell lines express high to moderate levels of Nestin. Furthermore, endometrial tumors and tumor cell lines have a cancer stem-like cell subpopulation expressing CD133. Among the cancer lines, AN3CA and KLE cells exhibited both a significantly higher number of CD133+ cells and expressed Nestin at higher levels than Ishikawa cells. Knockdown of Nestin in AN3CA and KLE increased cells in G0/G1 phase of the cell cycle, whereas overexpression in Ishikawa decreased cells in G0/G1 phase and increased cells in S-phase. Nestin knockdown cells showed increased p21, p27, and PNCA levels and decreased expression of cyclin-D1 and D3. In contrast, Nestin overexpression revealed an inverse expression pattern of cell cycle regulatory proteins. Nestin knockdown inhibited cancer cell growth and invasive potential by downregulating TGF-ß signaling components, MMP-2, MMP-9, vimentin, SNAIL, SLUG, Twist, N-cadherin, and upregulating the epithelial cell marker E-cadherin whereas the opposite was observed with Nestin overexpressing Ishikawa cells. Nestin knockdown also inhibited, while overexpression promoted invadopodia formation and pFAK expression. Knockdown of Nestin significantly reduced tumor volume in vivo. Finally, progesterone inhibited Nestin expression in endometrial cancer cells. These results suggest that Nestin can be a therapeutic target for cancer treatment.

Inhibition of Transforming Growth Factor-ß (TGF-ß) Signaling by Scutellaria baicalensis and Fritillaria cirrhosa Extracts in Endometrial Cancer.

Transforming growth factor-ß (TGF-ß), regulates cell proliferation, angiogenesis, metastasis, and is an inducer of epithelial-mesenchymal transition (EMT). Cancer cells exhibit activated TGF-ß/SMAD signaling pathway and its inhibition is an attractive strategy for cancer treatment. The Chinese Herbs Scutellaria baicalensis (SB) and Fritillaria cirrhosa (FC) have been shown to be beneficial to cancer patients, but the mechanisms by which the extracts of two herbs elicit the beneficial effects are unclear. In this study, we have used human endometrial cancer cells to assess the anticancer efficacy of SB and FC on TGF-ß signaling pathway components. SB and FC treatment of cancer cells resulted in a significant decrease in expression of TGF-ß isoforms, TGF-ß receptors, and SMADs. Both herbs effectively inhibited basal and TGF-ß1-induced cancer cell proliferation and invasion, which was accompanied with abrogation of Snail, Slug, matrix metalloproteinases (MMPs), αvß3 integrin, focal adhesion kinase (FAK), and p-FAK expression. An inhibitor of TGF-ßRI blocked TGF-ß1-induced cell invasion and significantly diminished antitumor effects of SB and FC. These results suggest that SB and FC block endometrial cancer growth by downregulating TGF-ß/SMAD signaling pathway.

The Chinese herbs Scutellaria baicalensis and Fritillaria cirrhosa target NFκB to inhibit proliferation of ovarian and endometrial cancer cells.

The herbs Scutellaria baicalensis (SB) and Fritillaria cirrhosa (FC) are widely used in Chinese medicine to treat several aliments and as an adjuvant to chemotherapy of lung cancer. No information is available regarding the two herbs' influence on ovarian and endometrial cancer. To fill this data gap we compared cell growth responses to SB and FC in ovarian and endometrial cancer cell lines. Dose-dependent cell growth inhibition was observed following higher doses in all cell lines while lower doses stimulated growth in only endometrial cell lines. Higher doses of SB and FC significantly decreased cell growth on soft agar and decreased the invasive potential of cancer cells. Treatment of cells with both herbs resulted in activation of caspase-3, G0 /G1 phase cell cycle arrest, downregulation of cyclins D1 and D3 and induction of p27. Both herbs decreased NFκB DNA binding, reduced expression of phosphorylated IκBα, abrogated NFκB activation, and downregulated NFκB-regulated metastasis-promoting proteins in cancer cells. Furthermore, knockdown of NFκB attenuated SB- and FC-induced cell growth inhibition. These results suggest that inhibition of NFκB activation may be an important mechanism for growth suppression by SB and FC. Data indicate that these herbs may represent a new source of agents for NFκB inhibition in cancer therapy.

Progesterone inhibits endometrial cancer invasiveness by inhibiting the TGFß pathway.

Increased expression of TGFß isoforms in human endometrial cancer correlates with decreased survival and poor prognosis. Progesterone has been shown to exert a chemoprotective effect against endometrial cancer, and previous animal models have suggested that these effects are accompanied by changes in TGFß. The goal of this study was to characterize the effect of progesterone on TGFß signaling pathway components and on TGFß-induced protumorigenic activities in endometrial cancer cell lines. Progesterone significantly decreased expression of three TGFß isoforms at 72 hours after treatment except for TGFß2 in HEC-1B and TGFß3 in Ishikawa cells. Progesterone treatment for 120 hours attenuated expression of the three isoforms in all cell lines. Progesterone exposure for 72 hours reduced expression of TGFß receptors in HEC-1B cells and all but TGFßR1 in Ishikawa cells. Progesterone reduced TGFßR3 expression in RL-95 cells at 72 hours, but TGFßR1 and ßR2 expression levels were not affected by progesterone at any time point. SMAD2/3 and pSMAD2/3 were substantially reduced at 72 hours in all cell lines. SMAD4 expression was reduced in RL-95 cells at 24 hours and in HEC-1B and Ishikawa cells at 72 hours following progesterone treatment. Furthermore, progesterone effectively inhibited basal and TGFß1-induced cancer cell viability and invasion, which was accompanied by increased E-cadherin and decreased vimentin expression. An inhibitor of TGFßRI blocked TGFß1-induced effects on cell viability and invasion and attenuated antitumor effects of progesterone. These results suggest that downregulation of TGFß signaling is a key mechanism underlying progesterone inhibition of endometrial cancer growth.