Sex-related changes in lactate dehydrogenase A expression differently impact the immune response in melanoma.

Melanoma is more aggressive in male patients than female ones and this is associated with sexual dimorphism in immune responses. Taking into consideration the impact tumour metabolic alterations in affecting the immune landscape, we aimed to investigate the effect of the sex-dependent metabolic profile of melanoma in re-shaping immune composition. Melanoma is characterised by Warburg metabolism, and secreted lactate has emerged as a key driver in the establishment of an immunosuppressive environment. Here, we identified lactate dehydrogenase A (LDH-A) as a crucial player in modulating sex-related differences in melanoma immune responses, both in vitro and in patient-derived specimens. LDH-A is associated with higher lactate secretion in male melanoma cells, which leads to a significant enrichment in pro-tumoural regulatory T cells (Treg) with a concurrent decrease in the number and activity of anti-tumour CD8 T cells. Remarkably, pharmacological and genetic impairment of LDH-A in male melanoma cells normalises Treg and CD8 infiltration. In keeping with this, in vivo pharmacological targeting of LDH-A in melanoma-bearing male mice impairs tumour growth and lung colonisation, with a concomitant modulation of Treg and CD8 T cells infiltration. Taken together, our findings highlight the sex-related differences promoted by LDH-A in immune reshaping in melanoma, and suggest that therapeutic targeting of LDH-A could be leveraged as an effective strategy to abolish the sex-gap in melanoma progression.