MicroRNAs (miRNAs) are a class of non-coding small RNA molecules that regulate gene expression at the post-transcriptional level by interacting with 3′ untranslated regions (UTRs) of their target mRNAs. The invention relates to the application of miR-192 and miR-215. Both of these miRNAs impact cellular proliferation through the p53-miRNA circuit, and interact with dihydrofolate reductase (DHFR) and thymidylate synthase (TS). Particularly, upregulation of these miRNAs reduces cellular proliferation. The invention relates to this discovery. For example, inhibiting miR-192 and/or miR-215 sensitizes a neoplasm or a subject with a neoplasm to chemotherapeutic agents. Furthermore, measuring the levels of miR-192 and/or miR-215 provides one with information regarding whether the neoplasm or subject will respond to chemotherapeutic agents. Accordingly, the invention relates to composition and methods relating to the identification, characterization and modulation of the expression of miR-192 and miR-215.