The possible mechanisms may be AMPK (5′-AMP-activated protein kinase) mediated cell cycle arrest17, inhibition of reactive oxygen species generation by inhibiting the Electron Transport Chain18, promotion of apoptosis and autophagy of tumor cells19, and inhibition of leptin induced T cell exhaustion20 and increased number of CD3+ and CD8+ tumor infiltrating lymphocytes21 by metformin. Here, CD8A is linked to neoplasm.