However, the wild-type RB1 existence should also be taken into consideration, for instance, the IC50 value of SKPin C1 in lung squamous cell carcinoma cell line H520 with wild-type RB1 was higher than that in SCLC cell line H69 with deficient RB1 (Zhao et al., 2020). Here, RB1 is linked to small cell lung carcinoma.