ABSTRACT
The objective of the present study was to determine the effects of retinoic acid on the growth of the mouse mammary cells HC11 and HC11ras, which are a model for in vitro breast cancer progression. The expression of the two classes (RARs and RXRs) of retinoic acid receptor mRNAs was determined by Northern blot analysis. Receptor functional integrity was determined by testing whether RAR á mRNA could be induced by retinoic acid. The effects of a 72-h exposure to 50 æM 13-cis retinoic acid on HC11 and HC11ras cell proliferation and HC11 cell differentiation were investigated by flow cytometric cell cycle analysis, and by determination of á-casein mRNA expression, respectively. The possibility that retinoic acid would induce the expression of the vitamin D receptor and synergize with vitamin D, a known inhibitor of HC11 cell growth, was also investigated. HC11 cells expressed higher mRNA levels of both RAR a and RAR g when compared to HC11ras cells. In contrast, RAR á, as well as RXR a, á and g expression was low in both HC11 and HC11ras cells. In addition, RAR á mRNA was induced by retinoic acid treatment in both cells. In spite of these observations, no effects were seen on cell proliferation or differentiation upon exposure to retinoic acid. Neither vitamin D receptor induction nor synergy with vitamin D on growth inhibition was observed. We conclude that the RAR expression profile could be related to the transformed state in HC11ras cells and that the retinoic acid resistance observed merits further investigation.
Subject(s)
Animals , Female , Mice , Breast Neoplasms , Cell Transformation, Neoplastic , Tretinoin , Blotting, Northern , Cell Transformation, Neoplastic , Disease Models, Animal , Gene Expression Regulation , Genes, ras , Mammary Glands, Animal , Receptors, Retinoic Acid , RNA, Messenger , Tumor Cells, Cultured , Vitamin DABSTRACT
The hormone 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3), the active form of vitamin D3, is an important regulator of calcium homeostasis, exerts antiproliferative effects on various cell systems and can induce differentiation in some kinds of hematopoietic cells. These effects are triggered by its receptor, vitamin D receptor (VDR), a phosphoprotein member of the nuclear receptor superfamily, which functions as a transcriptional factor. VDR binds as a heterodimer with retinoid X receptor (R X R) to hexameric repeats, characterized as vitamin D-responsive elements present in the regulatory region of target genes such as osteocalcin, osteopontin, calbindin-D28K, calbindin-D9K, p21WAF1/CIP1, TGF-ß2 and vitamin D 24-hydroxylase. Many factors such as glucocorticoids, estrogens, retinoids, proliferation rate and cell transformation can modulate VDR levels. VDR is expressed in mammary tissue and breast cancer cells, which are potential targets to hormone action. Besides having antiproliferative properties, vitamin D might also reduce the invasiveness of cancer cells and act as an anti-angiogenesis agent. All of these antitumoral features suggest that the properties of vitamin D could be explored for chemopreventive and therapeutic purposes in cancer. However, hypercalcemia is an undesirable side effect associated with pharmacological doses of 1,25-(OH)2D3. Some promising 1,25-(OH)2D3 analogs have been developed, which are less hypercalcemic in spite of being potent antiproliferative agents. They represent a new field of investigation
Subject(s)
Humans , Female , Antineoplastic Agents/pharmacology , Breast Neoplasms , Calcitriol , Cell Transformation, Neoplastic , Breast Neoplasms , Calcitriol , Cell Division , Receptors, CalcitriolABSTRACT
To understand relationiship between transforming growth factor beta-1 (TGF-ß1) and the integrin profile presented by chronic myeloid leukemia cells, we have studied, using Northen analysis, the expression of TGF-ß1 messenger RNA (TGF-ß mRNA) in myeloid cell lines and in patient with acute myeloid leukemia (AML) and chronic myeloid leukemia (CML). In addition we determined the positivity for alfa4 and alfa5 integrin moleculas in those cell using specific monoclonal antibodies and flow cytometry. CML patients (N=3) presented mean values of alfa4 higher (alfa4: 60 ñ 20 per cent); alfa5: 70 ñ 41 per cent) than AML (N=10) blast cells (alfa4: 25 ñ 23 per cent); alfa5: 18 ñ 16 per cent). Northern analysis revealed an almost four-fold higher expression of TGF-ß mRNA in K562 (derived from a patient with chronic myeloid leukemia) compared to the myeloblastic cell line HL60. The highest TGF-ß mRNA levels were seen in the U937 lineage. CML leukemic cells (N=3) showed high TGF-ß mRNA levels comparable to the levels expressed by K562 which was paralleled by high ß1 integrin mRNA. AML blast cells presented a variable degree of expression of TGF-ß mRNA when compared to HL60. One patient with acute megakaryoblastic leukemia (FAB subtype M7), usually associated with myelofibrosis, presented the highest TGF-ß mRNA levels. We conclude that studing TGF-ß1 and its mechanisms of action will help in understanding fibrosis in leukemic patients, and perhaps to design treatments for such conditions