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In situ single-cell analysis identifies heterogeneity for PIK3CA mutation and HER2 amplification in HER2-positive breast cancer.

ABSTRACT: Detection of minor, genetically distinct subpopulations within tumors is a key challenge in cancer genomics. Here we report STAR-FISH (specific-to-allele PCR-FISH), a novel method for the combined detection of single-nucleotide and copy number alterations in single cells in intact archived tissues. Using this method, we assessed the clinical impact of changes in the frequency and topology of PIK3CA mutation and HER2 (ERBB2) amplification within HER2-positive breast cancer during neoadjuvant therapy. We found that these two genetic events are not always present in the same cells. Chemotherapy selects for PIK3CA-mutant cells, a minor subpopulation in nearly all treatment-naive samples, and modulates genetic diversity within tumors. Treatment-associated changes in the spatial distribution of cellular genetic diversity correlated with poor long-term outcome following adjuvant therapy with trastuzumab. Our findings support the use of in situ single cell-based methods in cancer genomics and imply that chemotherapy before HER2-targeted therapy may promote treatment resistance.

SUBMITTER: Janiszewska M

PROVIDER: S-EPMC4589505 | biostudies-literature | 2015 Oct

REPOSITORIES: biostudies-literature

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In situ single-cell analysis identifies heterogeneity for PIK3CA mutation and HER2 amplification in HER2-positive breast cancer.

Janiszewska Michalina M Liu Lin L Almendro Vanessa V Kuang Yanan Y Paweletz Cloud C Sakr Rita A RA Weigelt Britta B Hanker Ariella B AB Chandarlapaty Sarat S King Tari A TA Reis-Filho Jorge S JS Arteaga Carlos L CL Park So Yeon SY Michor Franziska F Polyak Kornelia K

Nature genetics 20150824 10

Detection of minor, genetically distinct subpopulations within tumors is a key challenge in cancer genomics. Here we report STAR-FISH (specific-to-allele PCR-FISH), a novel method for the combined detection of single-nucleotide and copy number alterations in single cells in intact archived tissues. Using this method, we assessed the clinical impact of changes in the frequency and topology of PIK3CA mutation and HER2 (ERBB2) amplification within HER2-positive breast cancer during neoadjuvant ther ...[more]

PMID: 26301495

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Project description:PurposeWe used targeted capture sequencing to analyze TP53-mutated circulating tumor DNA (ctDNA) in metastatic breast cancer patients and to determine whether TP53 mutation has predictive value for anti-human epidermal growth factor receptor 2 (HER2) treatment for in HER2 amplification-positive patients (HER2+) and HER2 mutation-positive, amplification-negative (HER2-/mut) patients.Patients and methodsTP53 mutation features were analyzed in the Geneplus cohort (n = 1184). The MSK-BREAST cohort was used to explore the value of TP53 mutation in predicting anti-HER-2 antibody efficacy. Sequencing of ctDNA in phase Ib, phase Ic, phase II clinical trials of pyrotinib (HER2+ patients), and an investigator-initiated phase II study of pyrotinib (HER2-/mut patients) were performed to analyze the relationships between TP53 mutation and prognosis for HER2 TKIs. The MSK-BREAST cohort, MutHER, and SUMMIT cohort were used for verification.ResultsTP53 mutations were detected in 53.1% (629/1184) of patients in the Geneplus cohort. The TP53 mutation rate was higher in HR-negative (p < 0.001) and HER2 amplification-positive (p = 0.015) patients. Among patients receiving anti-HER2 antibody therapy, those whose tumors carried TP53 mutations had a shorter PFS (p = 0.004). However, the value of TP53 mutation in predicting HER2 TKI response was inconsistent. In HER2+ patients, no difference in PFS was observed among patients with different TP53 statuses in the combined analysis of the pyrotinib phase Ib, phase Ic, and phase II clinical trials (p = 1.00) or in the MSK-BREAST cohort (p = 0.62). In HER2-/mut patients, TP53 mutation-positive patients exhibited a trend toward worse prognosis with anti-HER2 TKI treatment than TP53-wild-type patients in our investigator-initiated phase II study (p = 0.15), and this trend was confirmed in the combined analysis of the MutHER and SUMMIT cohorts (p = 0.01).ConclusionsTP53 mutation can be used to identify biomarkers of anti-HER2 antibody drug resistance in HER2+ patients and HER2 TKI resistance in HER2-/mut patients.

Project description:BackgroundThis study aimed to comprehensively explore the clinical significance of PIK3CA mutation in human epidermal growth factor receptor 2 (HER2)-positive breast cancer treated with anti-HER2 therapy.MethodsWe systematically searched PubMed, Embase, and the Cochrane databases for eligible studies assessing the association between PIK3CA mutation and outcomes in patients with HER2-positive breast cancer receiving anti-HER2 therapy. The main outcomes included: (1) pathological complete response (pCR) or disease-free survival (DFS) for the neoadjuvant setting; (2) DFS or invasive DFS for the adjuvant setting; (3) objective response rate (ORR), progression-free survival (PFS), time-to-progression (TTP), or overall survival (OS) for the metastatic setting. The mutational landscape of HER2-positive breast cancer according to PIK3CA mutation status was examined based on TCGA breast cancer dataset.ResultsTotally, 43 eligible studies, covering 11,099 patients with available data on PIK3CA mutation status, were identified. In the neoadjuvant setting, PIK3CA mutation was significantly associated with a lower pCR rate (OR=0.23, 95% CI 0.19-0.27, p<0.001). This association remained significant irrespective of the type of anti-HER2 therapy (single-agent or dual-agent) and hormone receptor status. There were no significant differences in DFS between PIK3CA mutated and wild-type patients in either the neoadjuvant or adjuvant settings. In the metastatic setting, PIK3CA mutation predicted worse ORR (OR=0.26, 95%CI 0.17-0.40, p<0.001), PFS (HR=1.28, 95%CI 1.03-1.59, p = 0.024) and TTP (HR=2.27, 95%CI 1.54-3.34, p<0.001). However, no significant association was observed between PIK3CA mutation status and OS. Distinct mutational landscapes were observed in HER2-positive breast cancer between individuals with PIK3CA mutations and those with wild-type PIK3CA.ConclusionsPIK3CA mutation was significantly associated with a lower pCR rate in HER2-positive breast cancer treated with neoadjuvant anti-HER2 therapy. In the metastatic setting, PIK3CA mutation was predictive of worse ORR, PFS and TTP. These results suggest the potential for developing PI3K inhibitors as a therapeutic option for these patients.

Dataset Information

In situ single-cell analysis identifies heterogeneity for PIK3CA mutation and HER2 amplification in HER2-positive breast cancer.

Publications

In situ single-cell analysis identifies heterogeneity for PIK3CA mutation and HER2 amplification in HER2-positive breast cancer.

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