26. Ma, R., et al., Metformin and cancer immunity . Acta Pharmacol Sin, 2020. 41(1 1): p. 1403-1409. 27. W u, Z., C. Zhang, and M. Najafi, Targeting of the tumor immune microenvironment by metformin. J Cell Commun Signal, 2022. 16(3): p. 333-348. 28. Afzal, M.Z., R.R.