Disclosed is the discovery that the mTORC2 complex plays a role in the regulation of PKN3 phosphorylation at the turn motif threonine and the use of the phosphorylation status of the turn motif threonine of PKN3 as a biomarker. In some embodiments, the phosphorylation status of the turn motif threonine of PKN3 is determined using an antibody that specifically binds to the turn motif threonine of a PKN3 protein, such as an anti-phosphoT860 antibody. In some embodiments, the invention relates to methods for screening compounds that have cancer therapeutic potential, methods for diagnosing cancer, methods for determining the prognosis of a patient suffering from cancer, methods for stratifying patients in a clinical trial, methods for treating a patient suffering from cancer, and methods for determining the effectiveness of a particular treatment regimen.
