HER2 expression identifies dynamic functional states within circulating breast cancer cells

Abstract

Circulating tumor cells (CTCs) in women with advanced estrogen receptor-positive/HER2-negative breast cancer acquire a HER2-positive subpopulation following multiple courses of therapy1,2. In contrast to HER2-amplified primary breast cancer, which is highly sensitive to HER2-targeted therapy, the clinical significance of acquired HER2 heterogeneity during the evolution of metastatic breast cancer is unknown. Here, we analyzed CTCs from 19 ER+/HER2− patients, 84% of whom had acquired CTCs expressing HER2. Cultured CTCs maintain discrete HER2+ and HER2− subpopulations: HER2+ CTCs are more proliferative but not addicted to HER2, consistent with activation of multiple signaling pathways. HER2− CTCs show activation of Notch and DNA damage pathways, exhibiting resistance to cytotoxic chemotherapy, but sensitivity to Notch inhibition. HER2+ and HER2− CTCs interconvert spontaneously, with cells of one phenotype producing daughters of the opposite within four cell doublings. While HER2+ and HER2− CTCs have comparable tumor initiating potential, differential proliferation favors the HER2+ state, while oxidative stress or cytotoxic chemotherapy enhances transition to the HER2− phenotype. Simultaneous treatment with paclitaxel and Notch inhibitors achieves sustained suppression of tumorigenesis in orthotopic CTC-derived tumor models. Together, these results point to distinct yet interconverting phenotypes within patient-derived CTCs, contributing to progression of breast cancer and acquisition of drug resistance.

Phosphorylation-induced conformational dynamics in an intrinsically disordered protein and potential role in phenotypic heterogeneity

“…When CTCs from patients with estrogen receptor-positive/human epidermal growth factor receptor 2-negative (HER2 − ) breast cancer who developed metastatic multidrug-resistant disease were cultured in vitro, they maintained a discrete population of Her2 + and Her2 − cells that interconvert spontaneously with significant consequences for disease progression and drug response. Although the underlying mechanisms driving spontaneity in state switching were not elucidated, the study by Jordan et al (59) and several other studies in different types of cancer (60)(61)(62)(63) suggest that the phenomenon of state switching driven by nongenetic variability need not be restricted to bacterial "persisters" and may be fairly common in cancer. For example, cancer cells in a hybrid epithelial/mesenchymal state, when cultured, can give rise to epithelial and mesenchymal cells predominantly (64).…”

“…Interestingly, a recent study reported that a situation paralleling the preexistence of hormone-resistant cells in PCa is also encountered in breast cancer (59). When CTCs from patients with estrogen receptor-positive/human epidermal growth factor receptor 2-negative (HER2 − ) breast cancer who developed metastatic multidrug-resistant disease were cultured in vitro, they maintained a discrete population of Her2 + and Her2 − cells that interconvert spontaneously with significant consequences for disease progression and drug response.…”

Relationship between hepatocellular carcinoma circulating tumor cells and tumor volume

“…Other work with positive capture against the asialoglycoprotein receptor has reported detection as high as 89% (Xu et al, 2011;Li et al, 2014). However, these positive capture strategies often cannot utilize sophisticated methods for the study of CTCs including single cell RNA-sequencing and culturing, which we have demonstrated with the CTC-iChip for a variety of other epithelial cancers (Ting et al, 2014;Yu et al, 2014;Miyamoto et al, 2015;Jordan et al, 2016). Interestingly, our study has revealed the possibility that HCC CTC generation occurs when primary tumors are still relatively small.…”

Cancer, circulating tumor cells, and metastasis: could protein-derived peptide fragments impede brain metastases?

“…The Boral's report concluded that the CTC biomarker profile and knowledge of their signaling pathways could be valuable as screening tools for: (1) micro-and macro-metastatic cell characterization; (2) decision-making in treatment modalities; and (3) monitoring post-treatment responses in patients with metastatic disease. Previous literature reports have emerged which enumerated epithelial cell adhesion molecules (EpCAM) present on CTCs, thus providing an estimate of the overall metastatic cell burden present in BC patients [11][12][13] . Using previous EpCAM-related studies as a starting point, Boral et al…”

“…In addition, both full length AFP and GIP were both found capable of inhibiting platelet aggregation [36] , a process necessary for CTC survival in the bloodstream; this activity involved integrins α2β1, α5β1, and α2β3. CTCs are known to adhere to blood vessel inner walls and to platelets, thereby cloaking themselves from circulating cytotoxic lymphocyte destruction [13,35,36] . Furthermore, GIP was found to block both adhesion of extra-cellular matrix (ECM) proteins to substrata as well as tumor cell adhesion to ECM-coated wells of microtiter plates [35] .…”