Replication Study: The microRNA miR-34a inhibits prostate cancer stem cells and metastasis by directly repressing CD44.

Abstract

As part of the Reproducibility Project: Cancer Biology, we published a Registered Report (Li et al., 2015), that described how we intended to replicate selected experiments from the paper 'The microRNA miR-34a inhibits prostate cancer stem cells and metastasis by directly repressing CD44' (Liu et al., 2011). Here we report the results. We found the microRNA, miR-34a, was expressed at twice the level in CD44⁺ prostate cancer cells purified from xenograft tumors (LAPC4 cells) compared to CD44^- LAPC4 cells, whereas the original study reported miR-34a was underexpressed in CD44⁺ LAPC4 cells (Figure 1B; Liu et al., 2011). When LAPC4 cells engineered to express miR-34a were injected into mice, we did not observe changes in tumor growth or CD44 expression; however, unexpectedly miR-34a expression was lost <i>in vivo</i>. In the original study, LAPC4 cells expressing miR-34a had a statistically significant reduction in tumor regeneration and reduced CD44 expression compared to control (Figure 4A and Supplemental Figures 4A,B and 5C; Liu et al., 2011). Furthermore, when we tested if miR-34a regulated CD44 through binding sites in the 3'UTR we did not find a statistically significant difference, whereas the original study reported miR-34a decreased CD44 expression that was partially abrogated by mutation of the binding sites in the <i>CD44</i> 3'UTR (Figure 4D; Liu et al., 2011). Finally, where possible, we report meta-analyses for each result.