The present invention relates to the roles played by the TBC1D7 genes in cancer, in particular, lung cancer or esophageal cancer, or carcinogenesis and features a method for treating and/or preventing cancer, in particular, lung cancer or esophageal cancer by administering a double-stranded molecule against one or more of the TBC1D7 genes or a composition, vector or cell containing such a double stranded molecule. The present invention also features methods for diagnosing lung or assessing/determining the prognosis of a patient with lung, especially NSCLC or SCLC, or esophageal cancer, using one or more over-expressed genes selected from among TBC1D7. To that end, TBC1D7 may serve as a novel biomarker for lung cancer or esophageal cancer. Also, disclosed are methods of identifying compounds for treating and preventing lung or esophageal cancer, using as an index for their effect on the over-expression of one or more of TBC1D7 in the lung cancer or esophageal cancer.