The present invention provides methods for detecting and/or diagnosing cancer through the determination of the expression level of the STC2 gene. The gene was discovered to discriminate cancer cells from normal cells. Furthermore, the present invention provides methods of screening for therapeutic agents useful in the treatment of cancer, methods for treating cancer. Moreover, the present invention provides double-stranded molecules targeting the STC2 gene, which are suggested to be useful in the treatment of cancer. The compositions and methods of the present invention find particular applicability to prostate cancer, more specifically, castration-resistant prostate cancer and aggressive prostate cancer.