Accumulating studies have provided concrete evidence that p90 ribosomal S6 kinase 2 (RSK2) is a key
signaling molecule involved in cell proliferation, transformation, and cancer development. RSK2 is known to be
an etiological gene of Coffin-Lowry Syndrome (CLS). Recently, signaling analysis and molecular biological
approaches have provided concrete evidence that RSK2 plays an essential role in human cancers. Here, we will
extensively discuss signaling pathways regulating RSK2 activity, the role of RSK2 in human cancer development,
inhibitors suppressing RSK2 activity, and why RSK2 is an important target to develop drugs for human cancers.