TPD52 represents a survival factor inERBB2‐amplified breast cancer cells

Abstract

TPD52 and ERBB2 co-expression has been persistently reported in human breast cancer and animal models of this disease, but the significance of this is unknown. We identified significant positive associations between relative TPD52 and ERBB2 transcript levels in human diagnostic breast cancer samples, and maximal TPD52 expression in the hormone receptor (HR)- and ERBB2-positive sub-group. High-level TPD52 expression was associated with significantly reduced metastasis-free survival, within the overall cohort (log rank test, P = 8.6 × 10(-4), n = 375) where this was an independent predictor of metastasis-free survival (hazard ratio, 2.69, 95% confidence interval 1.59-4.54, P = 2.2 × 10(-4), n = 359), and the HR- and ERBB2-positive sub-group (log rank test, P = 0.035, n = 47). Transient TPD52 knock-down in the ERBB2-amplified breast cancer cell lines SK-BR-3 and BT-474 produced significant apoptosis, both singly and in combination with transient ERBB2 knock-down. Unlike ERBB2 knock-down, transient TPD52 knock-down produced no reduction in pAKT levels in SK-BR-3 or BT-474 cells. We then derived multiple SK-BR-3 cell lines in which TPD52 levels were stably reduced, and measured significant inverse correlations between pERBB2 and TPD52 levels in viable TPD52-depleted and control cell lines, all of which showed similar proliferative capacities. Our results therefore identify TPD52 as a survival factor in ERBB2-amplified breast cancer cells, and suggest complementary cellular functions for TPD52 and ERBB2.

Heterogeneity of fatty acid metabolism in breast cancer cells underlies differential sensitivity to palmitate‐induced apoptosis

“…MTT assays were performed as described previously (Roslan et al ., 2014) at defined time points stated in figure legends. Viable cell were counted by trypan blue dye exclusion at indicated time points stated in figure legends.…”

TPD52 expression increases neutral lipid storage within cultured cells

“…To determine whether these phenotypes were confined to 3T3 cells, we examined a second stable TPD52-expressing cell line, derived from the breast cancer cell line MDA-MB-231 with low endogenous TPD52 expression levels (Roslan et al, 2014). Again, increased lipid droplets were detected in TPD52-transfected MDA-MB-231 cells (TPD52-H1D2) compared to vector control cells (supplementary material Fig.…”

“…Increased fatty acid synthase (FASN) expression has been noted in response to exogenous ERBB2 expression in breast cancer cells (Kumar-Sinha et al, 2003), and genes encoding other regulators of lipid metabolism might be coamplified with ERBB2 at chromosome 17q (Kourtidis et al, 2010). TPD52 expression has been reproducibly associated with ERBB2 expression in human breast cancer cell lines and tissues, and in mammary tissues from Erbb2 transgenic mice Kourtidis et al, 2010;Roslan et al, 2014). By contrast, knockdown of the Caenorhabditis elegans TPD52 orthologue F13E6.1 significantly reduces lipid storage as assessed by a genome-wide screening study (Ashrafi et al, 2003), and expression microarray analyses have identified increases in TPD52 levels in mouse and human adipose tissue from obese versus lean subjects (Clement et al, 2004;Keller et al, 2008;Nadler et al, 2000).…”

Dropping in on the lipid droplet- tumor protein D52 (TPD52) as a new regulator and resident protein

“…21 At the time, we were analyzing the effects of TPD52 knock-down in breast cell lines. 22 Like Kourtidis et al, 21 we noted that TPD52 knock-down decreased the survival of ERBB2-positive breast cancer cell lines, 22 which were characterized by higher levels of LD staining. 21 Breast and prostate cancers have been shown to accumulate cytoplasmic LDs, [23][24][25] and ERBB2 expression in breast cancer has been associated with a transcriptional program upregulating fatty acid synthase.…”

“…10 There is therefore no shortage of explanations for why cancer cells might benefit from TPD52 overexpression, but these explanations are relatively generic and would not be expected to favor one cancer cell type over others. Where knock-down studies have been conducted in different breast cell lines, reduced TPD52 expression commonly reduced the survival of ERBB2-positive breast cancer cell lines, 21,22 suggesting a particular function in this cell type. ERBB2-positive breast cancer cell lines are characterized by increased LDs, 21 and ERBB2-positive breast cancers more frequently express proteins associated with lipogenesis or lipid storage.…”