GSE132055
Targeting the mevalonate pathway to overcome acquired anti-HER2 treatment resistance in breast cancer [RNA-seq]
Despite effective strategies, therapy resistance in HER2+ breast cancer remains a challenge. While the Mevalonate pathway (MVA) is suggested to promote cell growth and survival, including in HER2+ models, its potential role in resistance to HER2-targeted therapy is unknown. Using HER2+ breast cancer parental (P) cell models (AU565, SKBR3, and UACC812), we have established anti-HER2-resistant derivatives made resistant to lapatinib (LR) or lapatinib plus trastuzumab (LTR). We performed RNA-seq on these resistant models and the P cells treated with lapatinib or lapatinib plus trastuzumaba for 24 h. We found that the average expression of the key genes in the MVA pathway, as a surrogate for pathway activity, was dramatically reduced in P cells with short-term treatment. In contrast, expression was restored or further upregulated relative to P cells in all three resistant (LR/LTR) models. Specific blockade of this pathway with lipophilic but not hydrophilic statins and with the n-bisphosphonate zoledronic acid led to apoptosis and substantial growth inhibition of resistant cells. Inhibition was rescued by mevalonate or the intermediate metabolites farnesyl pyrophosphate (FPP) or geranylgeranyl pyrophosphate (GGPP), but not by cholesterol. Activated YAP/TAZ and mTORC1 signaling and their downstream target gene product Survivin were inhibited by MVA blockade especially in the LR/LTR models. Overexpression of constitutively active YAP rescued Survivin and phosphorylated S6 levels despite blockade of the MVA. The MVA may provide alternative signaling leading to cell survival and resistance when HER2 is blocked by activating YAP/TAZ-mTORC1-Survivin signaling suggesting novel therapeutic targets. MVA inhibitors including lipophilic statins and N-bisphosphonates may circumvent resistance to anti-HER2 therapy and warrant further clinical investigation. Overall design: RNA-seq of three HER2+ breast cancer anti-HER2-resistant cell models, including parental (P) cells treated with short-term anti-HER2 therapy and their derivatives made resistant to lapatinib (LR) or lapatinib plus trastuzumab (LTR), using Illumina HiSeq with paired-end 100 bp reads.