Given that multiple clinical trials involving mTOR inhibitors as monotherapy or in combination with HDAC inhibitors are being tested in advanced cancers (NCT01058707, NCT02719691, NCT01087554, and NCT00918333), our findings suggest that incorporating the analysis of Snail and 4E-BP1 expression in primary tumors may help to prospectively identify resistance to mTOR inhibitors in the clinic studies. This evidence concerns the gene HDAC9 and cancer.