Targeted therapy: comprehensive review

Targeting RSK2 in human malignancies

IMPORTANCE OF THE FIELD

p90 ribosomal S6 kinase 2 (RSK2) belongs to a Ser/Thr kinase family containing four members, RSK1 - 4, which play an essential role in a number of cellular functions including cell cycle, survival and proliferation. Recent advances reveal a crucial role of RSK2 in oncogenesis and tumor progression, making RSK2 an attractive therapeutic target for cancer treatment.

AREA COVERED IN THIS REVIEW

Recent findings identifying the role of RSK2 in human cancers, including hematopoietic malignancies and solid tumors. Therapeutic implications of targeting RSK2 are also discussed with regard to clinical circumstance.

WHAT THE READER WILL GAIN

A better understanding of molecular mechanisms underlying RSK2 activation and its contribution to human cancers and also insight into the development of novel targeted cancer therapy.

TAKE HOME MESSAGE

The significance of RSK2 in cancer cell survival, proliferation, invasion and tumor metastasis varies amongst human malignancies and depends on the signaling properties of the oncogenes and cellular microenvironment of the transformed cells. Thus, further exploitation of RSK2 signaling and its dynamic interaction with other crucial oncogenic and pro-metastatic pathways in different human malignancies is needed for more effective therapeutic interventions.

Rapamycin sensitizes Akt inhibition in malignant human breast epithelial cells

Akt and mTOR are therapeutic targets for the treatment of cancer. The effects of inhibiting mTOR, with rapamycin, and Akt, with A-443654, concurrently, on cell morphology, cell proliferation, the cell cycle, and apoptosis were examined using the benign MCF10A and malignant MCF10CA1a human breast epithelial cells. Rapamycin and A-443654 in combination produced the greatest morphological changes and inhibited cell proliferation by G2/M arrest. Rapamycin and A-443654 in combination induced apoptosis at earlier times and at lower A-443654 concentrations in MCF10CA1a tumor cells than in the benign MCF10A cells. Rapamycin and A-443654 increased p53 and p15(INK4B) protein levels, decreased anti-apoptotic Bcl-2 levels, and increased Bad levels in the MCF10CA1a tumor cells by approximately 5-fold. These results suggest that the combined inhibition of Akt and mTOR may have beneficial therapeutic and safety margin effects.