To the Editor: Dr Schetter and colleagues1 demonstrated that high microRNA miR-21 expression in colon adenocarcinoma tissue was associated with a low survival rate and resistance to chemotherapy. Table 2 of their article listed microRNAs with significantly higher expression in tumors, including miR-335. Recently, miR-335 was reported to be a metastasis-suppressor microRNA in breast cancer, indicating that miR-335 may prevent tumor progression.2 It is possible that miR-335 has an opposite function in breast cancer vs colon cancer.3 The expression of miR-335 might be secondary during inhibition of tumor metastasis. We would be interested in the authors' interpretation of these differing findings.
Kida Y, Han Y. MicroRNA Expression in Colon Adenocarcinoma. JAMA. 2008;299(22):2628-2629. doi:10.1001/jama.299.22.2628-a