Expression of CD44 on two lines of transplantable melanoma cells--relationship with cytokine secretion and tumor progression.

In the present work it was investigated if a spontaneous alteration of the native melanotic transplantable melanoma form into amelanotic form, connected with the tumor progression, is accompanied by changes of CD44 surface glycoprotein expression. We also tried to find out if there exists any correlation between changes in CD44 expression and IL-6, TNF-alpha, and IL-10 secretion. Cells of two hamster transplantable melanoma lines: melanotic and amelanotic were used. The levels of TNF-alpha, IL-6, IL-10 in supernatants were determined by the ELISA test. For the detection of CD44 expression by flow cytometry, isolated melanoma cells were stained with the rat anti-mouse CD44 monoclonal antibody. The stained cells were also examined using a fluorescence microscope and a confocal microscopy system. The obtained results indicate that a spontaneous alteration of the native melanotic form into amelanotic form and the associated tumor progression was accompanied by a decrease in CD44 glycoprotein expression on the cell surface and a decrease in IL-6, TNF-alpha and especially IL-10 secretion by amelanotic melanoma cells. Our observations suggest a relationship between CD44 expression and locally secreted cytokines in the course of transplantable melanoma progression.

Estimation of macrophage IL-10 and NO secretion in the cytotoxicity against transplantable melanomas in relation to the progression of these tumours.

The relationship between the secretion of interleukin 10 (IL-10) and nitric oxide (NO) by hamster peritoneal macrophages and their cytotoxic effects on the cells of those two melanoma lines was studied. The nonuniform reaction of macrophages from hamsters bearing two transplantable melanoma lines has been observed. An increase in the cytotoxicity of macrophages from hamsters bearing the amelanotic melanoma line was accompanied by an inverse correlation between IL-10 and NO secretion. Such a relationship was not found in the case of macrophages from animals bearing the native-melanotic melanoma line. It is suggested that the phenotypical changes of melanomas connected with their progression modified the cytotoxic and secretory activity of the macrophages with regard to IL-10 and NO.

Heterogeneous susceptibility to spontaneous and induced apoptosis characterizes two related transplantable melanomas with different biological properties.

A family of phenotypically and biologically different transplantable hamster melanomas was derived from a single tumor more than 40 yr ago. In this work, we were seeking the differences between the abilities of the cells from two biologically heterogeneous (melanotic and amelanotic) members of this family to undergo spontaneous or camptothecin-induced apoptosis. We studied these differences by looking at three important features of the apoptotic process, i.e. binding of annexin V, DNA fragmentation and caspase-3 activity. Of these, annexin binding and DNA fragmentation were more pronounced in the parental, melanotic line while the activity of caspase-3 was stronger in the amelanotic tumor cells. We concluded that a spontaneous alteration of the original, melanotic melanoma line into an amelanotic one, associated with more aggressive tumor progression, was accompanied by significant decrease in ability to undergo spontaneous and camptothecin-induced apoptosis, and that apoptosis of these two cell types may not depend on the activity of caspase-3.