NC or between the indicated two groups (n?=?3) To investigate whether IL-1 was actually involved in the regulation of other SASP factors in senescent A375 cells, the neutralisation antibody of IL-1 (anti-IL-1) was added to the growth medium on the fourth day after the CDDP treatment. sequential activation of the DNA damage Schisantherin B response and the P53/P21 pathway. All the senescent melanoma cells induced by CDDP alone or the combination of CDDP and dacarbazine developed robust senescence-associated secretory phenotype (SASP), that is, the secretion of multiple cytokines. IL-1 was an early component Rabbit polyclonal to STAT3 and an upstream regulator of SASP. Similarly, CDDP either alone or combined with dacarbazine could induce melanoma cell senescence and SASP in either A375 or B16F10 melanoma xenograft mice. The supernatant of senescent A375 cells promoted the growth of normal non-senescent A375 cells and enhanced their expression and secretion of IL-8 through the activation of the ERK1/2-RSK1 pathway. The transplantation of non-senescent and senescent A375 cells together into nude mice showed accelerated tumour growth compared with transplanting non-senescent cells alone; no tumours developed when transplanting senescent cells alone. Following CDDP administration in A375-bearing mice, the intratumour injection of neutralisation antibodies targeting the SASP factors IL-1 or IL-8 evidently delayed tumour growth. The results suggest that the CDDP-induced senescent melanoma cells promote non-senescent cells proliferation through the activation of ERK1/2-RSK1 pathway by the SASP factors. Cell senescence and concomitant SASP may be Schisantherin B the particular mechanisms for melanoma to resist chemotherapeutics. Introduction Melanoma consistently shows increased incidence almost all over the world1. The established risk factors for melanoma include family history, multiple moles, fair skin, ultraviolet radiation and immunosuppression2. Some of the risk factors, especially ultraviolet radiation, can lead to somatic base mutation. BRAFV600E is the most common mutation site, occurring in about 50% of patients and resulting in the hyperactivation of the MAPK pathway. Drug therapy is essential for metastatic melanoma. The traditional chemotherapeutic drugs, such as cisplatin, dacarbazine and paclitaxel (PTX), are generally low in efficiency. In recent years, Schisantherin B the targeted inhibitors of BRAF (vemurafenib) or MEK (binimetinib) have shown improved survival and response rates in metastatic melanoma3C5. Alternatively, immunotherapies have made great breakthroughs. Immune checkpoint inhibitors, such as PD-1 antibody and CTLA-4 antibody, produce striking durable responses and curative outcomes2,6. Nevertheless, both targeted therapies and immunotherapies have obvious limitations, such as drug resistance and improved but still low response rates7,8. Immunotherapies can even hasten the spread of cancer in some patients9. Therefore, traditional chemotherapies are still indispensable in melanoma therapy 10. Cisplatin (CDDP, cis-Diaminodichloroplatinum) is one of the most widely used chemotherapeutic agents11,12. In the latest guideline recommended by the National Comprehensive Cancer Network, CDDP is consistently regarded as the first-line agent Schisantherin B against lung cancer and cervical cancer, among others. However, melanoma is inherently resistant to CDDP, and the mechanisms are not fully understood. In this study, we investigated the effect of CDDP on several types of tumour cells and revealed that melanoma is particularly inclined to enter into senescence. The cell senescence and concomitant senescence-associated secretory phenotype (SASP) may be the usual mechanisms underlying the resistance of melanoma to chemotherapy. Results CDDP-induced robust cell senescence in melanoma A375 cells through the P53/P21 pathway To observe the effect on melanoma, CDDP was added to the growth medium of A375 cells (defined as Schisantherin B 0?h) at various final concentrations. 24?h later, CDDP was removed and detections were performed at different time points (Fig.?1a). After the CDDP treatment, an enlargement of the cellular morphology was observed, thus implying cell senescence. Thus, the activity of senescence-associated -galactosidase (-gal), a canonical marker of cell senescence, was evaluated. 4 days after the CDDP treatment, the -gal-positive (blue-stained) cells were observed when CDDP was greater than 2?M (Supplementary Fig.?1A). On the seventh day, the blue colour deepened, which implied a stable cell cycle arrest in the stained cells (Supplementary Fig.?1B). Note that in 2?M CDDP, a few cells escaped from senescence and formed proliferative clones on the seventh day. In 4 or 10?M CDDP, most of the survival cells became senescent and few clones were observed..