isotretinoin and Endometrial-Neoplasms

We have shown that moderately differentiated endometrial adenocarcinoma (RL95-2) cells differentiate in response to retinoic acid treatment, illustrated by their reorganization of actin filaments and cell enlargement (Carter et al., Anticancer Res. 16, 17-24, 1996). Tyrphostin, an inhibitor of epidermal growth factor receptor (EGF-R)-associated protein tyrosine kinases, caused a dramatic reorganization of actin filaments in RL95-2 cells, similar to retinoic-acid-treated cells (Carter and Bellido, J. Cell. Physiol. 178, 320-332, 1999). We evaluated the possibility that the differentiating effects of retinoids are due to retinoic-acid-induced decreases in phosphorylation of EGF-R and changes in downstream effector proteins. Retinoic acid caused a decrease in tyrosine phosphorylation of EGF-R. Retinoic acid treatment induced a dramatic actin filament reorganization and cell enlargement. Treatment with EGF reversed this effect, because cells treated with retinoic acid followed by EGF only possessed disrupted actin aggregates and appeared small, thus resembling medium controls. Retinoic acid induced a relocalization and decrease in the amount of Shc protein, another actin-binding protein which is an adaptor protein for EGF-R signaling. In addition, retinoic acid induced a relocalization of gelsolin from the plasma membrane to the cytoplasm. Retinoic acid decreased cell detachment in detachment assays; one-half as many retinoic-acid-treated cells detached as in controls. These results are consistent with the idea that retinoic acid induces differentiation of RL95-2 cells by interfering with the EGF-R signaling pathway.

Topics: Actin Cytoskeleton; Actins; Adaptor Proteins, Signal Transducing; Adaptor Proteins, Vesicular Transport; Adenocarcinoma; Cell Adhesion; Cell Differentiation; Cell Membrane; Cyclic AMP-Dependent Protein Kinases; Cytoplasm; Cytoskeleton; Endometrial Neoplasms; Enzyme Activation; Epidermal Growth Factor; ErbB Receptors; Female; Gelsolin; GRB2 Adaptor Protein; Humans; Isotretinoin; Membrane Proteins; Neoplasm Proteins; Phosphorylation; Protein Processing, Post-Translational; Proteins; Shc Signaling Adaptor Proteins; Signal Transduction; Src Homology 2 Domain-Containing, Transforming Protein 1; Tetradecanoylphorbol Acetate; Tretinoin; Tumor Cells, Cultured

Transformed cells often express elevated levels of tyrosine-phosphorylated proteins. Inhibition of protein tyrosine kinases causes reversion of malignant cells to the normal phenotype. In the present study, we evaluated the possibility that the reversion of human endometrial adenocarcinoma RL95-2 cells to a stationary phenotype induced by retinoic acid was associated with inhibition of tyrosine phosphorylation of cellular proteins. We found that retinoic acid decreased the levels of tyrosine-phosphorylated proteins, as assessed by immunostaining and immunoprecipitations using specific anti-phosphotyrosine antibodies. In addition, the inhibitors of tyrosine kinases herbimycin A and tyrphostin mimicked retinoic acid, inducing F-actin reorganization and increasing the size of RL95-2 cells, as determined by measurement of cell perimeters. Because focal adhesions that connect actin filaments with the plasma membrane are major sites of tyrosine phosphorylation, we further investigated whether selected focal adhesion proteins were affected by retinoic acid. We found that retinoic acid altered the localization of focal adhesion kinase. All-trans retinoic acid was effective in reducing the levels of focal adhesion kinase and paxillin protein. Thirteen-cis retinoic acid increased the levels of vinculin protein in the cytosolic fraction of cells. These changes are consistent with actin reorganization and reversion toward a stationary phenotype induced by retinoic acid in endometrial adenocarcinoma RL95-2 cells. Our results indicate that the differentiating effects of retinoids on endometrial cells are associated with decreases in tyrosine phosphorylation and changes in the levels and distribution of focal adhesion proteins. These findings suggest that signaling pathways that involve tyrosine kinases are potential targets for drug design against endometrial cancer.

Topics: Actins; Adenocarcinoma; Analysis of Variance; Benzoquinones; Cell Adhesion Molecules; Endometrial Neoplasms; Enzyme Inhibitors; Female; Focal Adhesion Kinase 1; Focal Adhesion Protein-Tyrosine Kinases; Humans; Isotretinoin; Kinetics; Lactams, Macrocyclic; Phosphoproteins; Phosphorylation; Phosphotyrosine; Protein-Tyrosine Kinases; Quinones; Rifabutin; Tretinoin; Tumor Cells, Cultured

Phase II trials of the novel biologic combination of 13-cis-retinoic acid plus interferon (IFN)-alpha have achieved major activity in advanced squamous cell carcinomas of the skin and cervix, but not of the lung or head and neck. Very limited study of this combination has occurred in cancers other than those of squamous type. Although uncommon, cases of unresectable or metastatic endometrial adenocarcinoma are virtually incurable, and chemotherapy has had no impact on survival in these cases. This report describes our use of 13-cis-retinoic acid plus IFN-alpha to treat a case of cisplatin- and hormone-resistant, locally advanced and distantly metastatic adenocarcinoma of the endometrium. In this worst-prognosis case, the biologic therapy achieved a major response, which persisted for 4 months. Based on the dramatic activity in this case, we believe that depthful mechanistic and clinical study of this promising new biologic combination should be expanded to include non-squamous tumors of many different sites and histopathologic types.

Topics: Adenocarcinoma; Antineoplastic Combined Chemotherapy Protocols; Combined Modality Therapy; Endometrial Neoplasms; Female; Humans; Interferon-alpha; Isotretinoin; Lung Neoplasms; Middle Aged; Prognosis