Kdm1a promotes SCLC progression by transcriptionally silencing the tumor suppressor Rest

Small cell lung carcinoma (SCLC) is one of the deadliest cancer types, with a 5-year survival rate less than 10%. Kdm1a/Lsd1 has recently been implicated as a potential therapeutic target for SCLC. However, the underlying molecular mechanism by which Kdm1a promotes the oncogenesis of SCLC has not been fully understood. Kdm1a is significantly elevated in most human SCLC specimens, whereas Rest, a tumor suppressor and neuronal repressive transcriptional factor, is typically inactivated. Knock-out of Kdm1a (Kdm1a-KO) in mouse SCLC cell lines resulted in the suppression of cell growth and soft agar colony formation. RNA-Seq analysis of the Kdm1a-KO cells revealed significant repression of a program of neuroendocrine signature genes, and conversely, a significant upregulation of a network of genes capable of inhibiting tumor cell growth. Rest was identified among the top 10 upregulated genes in Kdm1a-KO cells. The treatment of the SCLC cells with Kdm1a demethylase inhibitors resulted in a dramatic up-regulation of Rest similar to the extent of that in Kdm1a-KO cells. Importantly, accompanying the restored expression of the SCLC signature genes, knock-out of Rest in Kdm1a-KO cells rescued the restricted cell growth and soft agar colony formation. Taken together, these novel findings show that Kdm1a is a key transcriptional repressor of Rest, and that suppression of SCLC progression by the targeted inhibition of Kdm1a depends on the reactivation of Rest, suggesting a new strategy for effective SCLC treatment by targeting the Kdm1a/Rest molecular pathway.