CD38 and neoplasm: The study conducted by Ng et al. 31 investigated the pre-treatment expression of CD38 in tumor tissues of 49 HCC patients treated with PD-1 or PD-L1 ICI combined with or without CTLA-4 ICI and showed that high CD38-positive (CD38+) cell proportion (≥ 5%) was associated with higher ORR (43% vs. 4%, P value = 0.019) and longer median OS (19.1 vs. 9.6 months, P value = 0.0295) and PFS (8.2 vs. 1.6 months, P value = 0.0065) than low CD38+ cell proportion (< 5%).