Unmasking by soluble IL-6 receptor of IL-6 effect on metastatic melanoma: growth inhibition and differentiation of B16-F10.9 tumor cells

Abstract

Interleukin-6 (IL-6) inhibits the growth of melanocytes and of early stage melanoma cells, but not that of advanced melanoma cells. The in vitro IL-6 response can be restored in the highly metastatic melamona B16-F10.9 by addition of recombinant soluble IL-6 receptor a-chain (sIL-6R). The F10.9 cells then undergo irreversible growth-arrest and show increased adherence with changes from epithelioid to spindleoid morphology. The sIL-6R is required for IL-6 to induce a sustained activation of the various Stat transcription factors which bind to speci®c IL-6 inducible enhancers. The sIL-6R and IL-6 combination causes an increase in the level of the anti-oncogenic transcription factor IRF-1 protein and DNA-binding, which remain elevated for 24 h. The promoter activity of the anti-oncogenic p21/Waf-1/Cip-1 gene is induced and accumulation of the p21 protein is observed. These results illustrate the potent agonist activity of sIL-6R on molecular pathways which could mediate the growth-arrest and di erentiation of the metastatic melanoma cells. Previously observed antimetastatic e ects of IL-6 therapy in mice bearing F10.9 tumors may be at least partly due to direct growth inhibition and di erentiation elicited by sIL-6R present in biological¯uids.

Interleukin-6 and oncostatin M-induced growth inhibition of human A375 melanoma cells is STAT-dependent and involves upregulation of the cyclin-dependent kinase inhibitor p27/Kip1

“…Similar observations have been made for other tumor cells growth-inhibited by IL-6 such as murine B16 melanoma cells (Oh et al, 1997), human non-small cell lung carcinoma cells (Ganapathi et al, 1996) or human osteosarcoma cells (Bellido et al, 1998). Thus, loss of receptors may provide a possibility for tumor cells to evade the action of inhibitory cytokines.…”

“…Other cyclin-dependent kinase inhibitors have been reported to be subject of regulation by IL-6-type cytokines: p21/Cip1/Waf1 was found to be upregulated by IL-6/sIL-6R complexes during growth inhibition and di erentiation of murine B16.F12 melanoma cells (Oh et al, 1997) and of human MG63 osteosarcoma cells (Bellido et al, 1998). Induction of di erentiation of B cells by IL-6 coincided with increased levels of p21 and p18 (Morse et al, 1997).…”

Interleukin-6 dependent induction of the cyclin dependent kinase inhibitor p21WAF1/CIP1 is lost during progression of human malignant melanoma

“…Consistent with this ®nding, an increased level of p21 WAF1/CIP1 along with accumulation of hypophosphorylated pRb protein, have been detected in M1 leukemia cells induced to di erentiate by IL-6 treatment (Resnitzky et al, 1992). Furthermore, treatment of B16 ± F10.9 mouse metastatic melanoma cells with IL-6 in the presence of exogenously added soluble IL-6R alpha subunit (gp 80) was shown recently to induce growth arrest, differentiation and expression of p21 WAF1/CIP1 (Oh et al, 1997).…”

The designer cytokine hyper-IL-6 mediates growth inhibition and GM–CSF-dependent rejection of B16 melanoma cells

“…The observed reduction of melanogenesis might be explained by cytokine-induced activation of NF-kB which has been shown to be responsible for the inhibition of tyrosinase expression in B16 cells (Englaro et al, 1999). Growth inhibition of B16 cells and morphological alteration towards a dendrite-like shape were also observed by other groups after exposing B16-F10.9 cells to IL-6 in combination with sIL-6R or to a recombinant IL-6/sIL-6R fusion protein Oh et al, 1997).…”

“…Examples for experimental systems are human nonsmall cell lung carcinoma cell lines (Ganapathi et al, 1996), human breast carcinoma cells (Novick et al, 1992) and B-78 and B16 murine melanoma cells (Mackiewicz et al, 1995b;Oh et al, 1997). The low immunogenic B16 melanoma was shown to undergo growth inhibition after transfection with IL-6 cDNA (Sun et al, 1992).…”