TP53 and squamous cell carcinoma: In comparison to lung adenocarcinomas (ADC) and squamous cell carcinomas (SqCC), where co-occurring somatic alterations of TP53 and RB1 are less frequent and rather rare25,26, SCLC tumors exhibited significantly higher expression levels of genes controlling cell cycle regulation and DNA replication, as well as pathways that emphasize the neuroendocrine features of this lung cancer subtype (Fig. 1A).