Project description:Transcriptional profiling of human HER2-positive BT474 breast cancer cells comparing control untreated cancer cells with lapatinib-resistant clone established by chronic treatment with lapatinib Two-condition experiment, parental cells vs. lapatinib-resistant (LR) clone.
Project description:Transcriptional profiling of human HER2-positive BT474 breast cancer cells comparing control untreated cancer cells with lapatinib-resistant clone established by chronic treatment with lapatinib
Project description:These studies are aimed at understanding gene expression chnages in a Her2 positive breast cancer cell line that has developed acquired resistance to lapatinib. Samples include SKBR3 parental and resistant (SKBR3-R) under basal conditions and in response to 0.1 and 1uM lapatinib treatment after 24 hours.
Project description:Ablation of ERRalpha significantly delays ERBB2-induced mammary tumorigenesis and ERRalpha regulates genes of the ERBB2 amplicon. To further investigate the relationship between ERRalpha activity and RTK signaling, we mapped ERRalpha binding sites in SKBr3 cells upon EGF treatment or heregulin treatment. Inhibition of ERBB2 signaling using the RTK inhibitor lapatinib impacts on ERRalpha stability, while cells resistant to lapatinib treatment exhibit restored ERRalpha expression. We therefore mapped ERRalpha binding sites in parental (sensitive) cells (pSKBr3) as well as in lapatinib-resistant cells (LRSKBr3). ChIP-Seq analysis of ERRalpha binding profile in SKBr3 or BT-474 breast cancer cells.
Project description:Ablation of ERRalpha significantly delays ERBB2-induced mammary tumorigenesis and ERRalpha regulates genes of the ERBB2 amplicon. To further investigate the relationship between ERRalpha activity and RTK signaling, we depleted ERRalpha in SKBr3 cells upon serum starvation, EGF treatment or heregulin treatment. Inhibition of ERBB2 signaling using the RTK inhibitor lapatinib impacts on ERRalpha stability. Since we have shown that the development of lapatinib-resistance restaures the expression of ERRalpha in breast cancer cells, we performed depletion of ERRalpha in SKBr3 cells that have developped resistance to lapatinib treatment in order to identify a potential reprogramming of ERRa transcriptional activity associated to lapatinib resistance, For the study of growth factor effec on ERRalpha activity, total RNA was obtained from human SKBr3 breast cancer cells cultured in DMEM deprived of FBS (starved) for 24 hours and treated with PBS, EGF (100uM) or Heregulin (100uM) for an additional 24h. Cells were transfected with siRNA against ERRalpha or with siControl for 60 hours prior to harvesting. For the effect of ERRalpha in lapatinib resistance cells, parental SKBr3 cells (pSKBr3) and Lapatinib-resistant cells (LRSKBr3, maintained in 2uM lapatinib) were transfected with siControl (siC) or siERRalpha for 60 hours prior to harvesting and RNA extraction
Project description:Targeting HER2 with lapatinib (L), trastuzumab (T), or the LT combination, is effective in HER2+ breast cancer (BC), but de novo and acquired resistance commonly occur. The purpose of this experiment was to investigate the somatic alterations found in Lapatinib and/or Trastuzumab resistant cells lines.
Project description:HER2 targeting with trastuzumab has changed the prognosis of breast cancer patients carrying amplification and/or overexpression of this oncogene. Despite this progress, however, resistance to trastuzumab occurs in the vast majority of patients. Newer anti-HER2 therapies, like the dual tyrosine-kinase inhibitor (TKI) lapatinib, show antitumor activity in a limited proportion of patients, indicating that HER2 can be still exploited as a target after trastuzumab failure. However, due to the high proportion of patients that fail to respond to these alternative strategies, it is reasonable to assume that cells escaping HER2 targeting may rely on alternative pathways not involving HER2 to sustain their growth. Their knowledge is relevant for exploiting new therapies. To investigate this hypothesis we generated a human HER2 overexpressing breast cancer cell line resistant to trastuzumab and lapatinib (T100) and we have characterized it genetically and molecularly. In T100 cells, the previously proposed mechanisms of resistance to HER2 inhibitors did not explain cell escape. Notably, silencing HER2 by shRNA did not affect the growth of T100 cells, suggesting loss of reliance upon HER2. Among the alternative pathways that we explored, altered levels of the antiapoptoptic proteins Mcl-1 and Survivin were observed. This suggested the possibility of targeting resistant cells with the multitarget inhibitor sorafenib. Moreover, sorafenib, nearly inactive in parental cells, strongly inhibited the in vitro growth of T100 cells. In conclusion, we provide a new model where the activation of HER2 independent mechanisms sustains the growth of tumor cells, significantly increasing the sensitivity to sorafenib. Keywords: HER2, breast cancer, resistance, trastuzumab, lapatinib, sorafenib
Project description: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.