ABSTRACT
Smooth muscle alpha-actin (SMA) is a cytoskeletal protein expressed in vascular smooth muscle cells, pericytes, hair follicle dermal sheaths and myofibroblasts which appear in the process of wound healing and tumor growth. To examine the effect of malignant melanoma on the expression of SMA in these non-neoplastic cells, we carried out immunohistochemical staining and a cell culture study. Conditioned medium prepared from a melanoma cell line M14 was incubated with a rat fibroblastic cell line 3Y1, which had been shown to express SMA. Human cells that had migrated from nevus tissue were also cultured either with or without M14 conditioned medium. Immuno-histochemical staining of human melanoma tissues suggested that the expression of SMA was low in the vicinity of the tumor as well as within the tumor nodules. The conditioned medium from melanoma, but not the medium from control non-neoplastic cells, suppressed the expression of SMA both in the 3Y1 cells and human cells that migrated from the nevus. Preincubation of the medium with anti-platelet-derived growth factor allowed 76% recovery of SMA expression. These data thus imply that melanoma cells release a platelet-derived growth factor-like substance which has a suppressive effect on the contractile elements in non-neoplastic cells.
Subject(s)
Actins/biosynthesis , Culture Media, Conditioned/pharmacology , Melanoma/metabolism , Muscle, Smooth, Vascular/drug effects , Muscle, Smooth, Vascular/metabolism , Animals , Humans , Neoplasm Proteins/pharmacology , Rats , Tumor Cells, CulturedABSTRACT
A normal rat fibroblast 3Y1 cell line expresses smooth muscle a actin and the expression of alpha actin is suppressed in the transformant (SR-3Y1-2) induced by a Raus sarcoma virus. Gene transfer with smooth muscle alpha actin into the SR-3Y1-2 cell line reduced growth and invasiveness in vitro, as well as tumor growth and experimental lung metastasis depending on the expression of the alpha actin. These results indicated that smooth muscle alpha actin is involved in the regulation of cell growth as well as cell motility and thus leads to the suppression of malignant phenotypes in transformed cells.
Subject(s)
Actins/biosynthesis , Actins/genetics , Animals , Cell Division , Cell Line, Transformed , Cell Movement , Female , Fluorescent Antibody Technique , Gene Transfer Techniques , Muscle Neoplasms/metabolism , Muscle Neoplasms/pathology , Neoplasm Metastasis , Phenotype , Polyomavirus , Rats , Thigh , Tumor Cells, CulturedABSTRACT
The cytolytic and/or cytostatic effects of hyperthermia, lymphokine-activated killer cells (LAK cells) and the combination of both were assayed using F1 and F10 B16 melanoma cell lines. F10 cells with a high metastatic potential showed a greater sensitivity to hyperthermia than F1 cells which have low metastatic potential. The F10 cells were lysed to a lesser extent by LAK cells than the F1-B16 cells. When the cell lines were subjected to hyperthermia at 43 degrees C for 3 h and then interacted with LAK cells, the maximum cytolysis reached almost 100%. When the interaction with LAK cells was followed by hyperthermia at 43 degrees C, the total release of 51Cr from the cell lines was 75-85%. The extent of 51Cr release from the B16 melanoma cell lines was inversely correlated with the survival rate as calculated by the plating efficiency of the incubated cells. The survival rate of mice intravenously injected with B16-F10 cells and subjected to hyperthermia at 41 degrees C for 3 h in vitro increased compared to that of controls. This was further increased by the simultaneous administration of LAK cells.
Subject(s)
Cytotoxicity, Immunologic/physiology , Hyperthermia, Induced , Killer Cells, Lymphokine-Activated/physiology , Melanoma, Experimental/therapy , Animals , Cell Death/immunology , Combined Modality Therapy , Melanoma, Experimental/mortality , Mice , Tumor Cells, CulturedABSTRACT
Expression of actin was examined in a cultured rat embryonic cell line 3Y1 and transformed cell lines that originated from 3Y1. An alpha-actin in addition to cytoplasmic beta- and gamma-actins was detected in 3Y1 by two-dimensional gel electrophoresis. This alpha-actin was hardly detected at all in the transformants induced by Rous sarcoma virus, v-H-ras oncogene or adenovirus type 12, while the alpha-actin was retained in the transformed cell lines induced by N-methyl-N'-nitro-N-nitrosoguanidine or in SV40, which are cell lines of relatively low malignancy. Western and Northern blot analyses established that this alpha-actin was a smooth muscle alpha-isoform. An immunofluorescence study revealed that smooth muscle alpha-actin in 3Y1 cells is present in stress fibers. Thus, smooth muscle alpha-actin is also a component of actin stress fibers, as beta- and gamma-actins are in 3Y1 cells. An alteration in the expression of this actin isoform may be related to phenotypical changes accompanying transformation.
