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. 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.

尽管已开发出有效的治疗策略，HER2阳性（HER2+）乳腺癌的治疗耐药仍是一项临床挑战。甲羟戊酸通路（Mevalonate pathway, MVA）被证实可促进细胞生长与存活，在HER2阳性肿瘤模型中亦发挥类似作用，但其在抗HER2靶向治疗耐药中的潜在功能尚未明确。本研究以HER2阳性乳腺癌亲本（P）细胞模型（AU565、SKBR3及UACC812）为研究对象，构建了对拉帕替尼（lapatinib, LR）耐药，或对拉帕替尼联合曲妥珠单抗（lapatinib plus trastuzumab, LTR）耐药的抗HER2耐药衍生细胞株。随后，我们对上述耐药模型，以及经拉帕替尼或拉帕替尼联合曲妥珠单抗处理24小时的亲本细胞开展RNA测序（RNA-seq）。研究结果显示，以通路关键基因的平均表达量作为通路活性的替代指标，短期药物处理的亲本细胞中甲羟戊酸通路关键基因的平均表达水平显著降低；与之相反，所有三株耐药（LR/LTR）模型中，该通路基因的表达水平均得以恢复，甚至较亲本细胞进一步上调。通过亲脂性他汀类药物（而非亲水性他汀类药物）以及n-双膦酸盐类药物唑来膦酸（zoledronic acid）对该通路进行特异性阻断，可诱导耐药细胞发生凋亡并显著抑制其增殖。该抑制效应可被甲羟戊酸或其中间代谢产物法尼基焦磷酸（farnesyl pyrophosphate, FPP）、香叶基香叶基焦磷酸（geranylgeranyl pyrophosphate, GGPP）逆转，但胆固醇无法逆转该效应。甲羟戊酸通路阻断可抑制活化的YAP/TAZ及mTORC1信号通路及其下游靶基因产物生存素（Survivin），该抑制效应在LR/LTR耐药模型中尤为显著。过表达组成型活化的YAP，可在甲羟戊酸通路被阻断的情况下，恢复生存素及磷酸化S6的表达水平。上述研究结果表明，当HER2靶点被阻断时，甲羟戊酸通路可通过激活YAP/TAZ-mTORC1-生存素信号通路，为细胞提供存活与耐药的替代信号途径，提示该通路可作为新型治疗靶点。甲羟戊酸通路抑制剂（包括亲脂性他汀类药物及n-双膦酸盐类药物）或可克服抗HER2治疗耐药，有待开展进一步的临床研究。本数据集包含三株HER2阳性乳腺癌抗HER2耐药细胞模型的RNA-seq数据，涵盖经短期抗HER2治疗处理的亲本（P）细胞，以及对拉帕替尼（LR）或拉帕替尼联合曲妥珠单抗（LTR）耐药的衍生细胞株，测序采用Illumina HiSeq平台，采用双端100bp读长策略。