Figure 6.

Expression of LARP6 in Cancer Is Triggered by EMT and Acts to Enhance Protein Synthesis

(A) Analysis of LARP6 expression in a panel of 33 human breast tumors by IHC. Three distinct patterns of LARP6 expression were detected among the tumor samples: “negative,” “weakly positive,” and “strongly positive.” Representative images for each category are shown. Scale bars, 50 μm.

(B) LARP6 strongly positive tumors are significantly enriched among metaplastic carcinomas. Categorizing tumors based on their LARP6 IHC staining status as in (A) reveals a significant enrichment of LARP6 strongly positive tumors among metaplastic carcinomas (n = 7 out of 33). The p value was calculated using Fisher’s exact test.

(C) Induction of EMT by human TGF-β1 upregulates LARP6. Left, morphology of MCF10AT cells following mock treatment or TGF-β1 (5 ng/mL) treatment for 7 days, reveals EMT induction. Scale bars, 50 μm. Right, immunoblot (IB) analysis of EMT markers (CDH1, ZEB1, and VIM) and LARP6, on the cells shown in left. GAPDH was used as loading control.

(D) Quantification of changes in LARP6 and EMT marker proteins relative to GAPDH, from experiments shown in (C). IBs from 4 independent experiments as in (C) were quantified. Error bars are SD. p values were calculated using two-tailed, homoscedastic t test. ^∗∗∗p < 0.001; ^∗∗p < 0.01; ^∗p < 0.05.

(E) EMT enhances overall protein synthesis in a LARP6-dependent manner. MCF10AT parental and EMT pairs from (C) were treated with indicated siRNAs for 72 h before being subjected to OPP staining.

(F) Quantification of OPP staining from experiments shown in (D). Normalized OPP averages were calculated from 7–11 field of view images from two independent experiments. Error bars are SD. p values were calculated using two-tailed, homoscedastic t test. n.s., non-significant; ^∗p < 0.05.