In Reply: In response to Drs Kida and Han, we found an increased expression of miR-335 in colon tumors based on our microarray experiments, while a recent study reports miR-335 to be decreased in breast tumors with implications for a role for miR-335 suppressing metastasis.1 There are many possibilities that can account for this. MicroRNA function is dependent on the cellular context in which it is expressed. The transcriptome of colon cells is different from breast cells; therefore, cellular consequence of increased expression of miR-335 in colon cells could be quite different from in breast cells. In our study, we identified 37 micro RNAs that were differentially expressed in tumors and we selected 5 microRNAs to validate. We validated all 5, which gave us confidence in the accuracy of our list of micro RNAs. Because we did not specifically test miR-335 by quantitative reverse transcriptase–polymerase chain reaction in a second cohort, we encourage validation of these specific results before continuing to speculate further.
Schetter AJ, Harris CC. MicroRNA Expression in Colon Adenocarcinoma—Reply. JAMA. 2008;299(22):2628-2629. doi:10.1001/jama.299.22.2628-b