LAG3 and cancer: Persistent stimulation from cancer antigens leads to T lymphocytes (T cells) exhaustion, with up‐regulated expression of co‐inhibitory receptors, including programmed death‐1 (PD‐1), cytotoxic T lymphocyte‐associated antigen‐4 (CTLA‐4), lymphocyte‐activation gene 3 (LAG‐3), T cell immunoglobulin and mucin domain 3 (TIM‐3) and T cell immunoreceptor with Ig and ITIM domains (TIGIT).