Selective Anti-Proliferation of HER2-Positive Breast Cancer Cells by Anthocyanins Identified by High-Throughput Screening

Overexpressed Human epidermal growth factor receptor 2 (HER2) drives the biology of 20% breast cancer and is a prediction of a poor prognosis for patients. HER2-targeted therapies significantly improve outcomes for HER2-positive patients. Traditional Chinese herbs/medicines have been used to treat breast cancer patients including HER2-positive patients in Asia for decades. Although the traditional medicines demonstrate efficacy in clinics for HER2-positive patients, the mechanism is largely unknown. In this article, we screened a 10,000 natural product library in 6 different cell lines representing breast cancer, and assessed the ability of each drug to cause cytotoxicity through a high-throughput screening approach. We have identified eight natural compounds that selectively inhibit the proliferation of HER2-positive cells. Two of the hit compounds, peonidin-3-glucoside and cyaniding-3-glucoside, are both extracts from black rice. They inhibit the phospho-HER2 and phospho-AKT and were confirmed to induce HER2-psotive breast cancer cells apoptosis both in vitro and in vivo. Peonidin-3-glucoside and cyaniding-3-glucoside treatments significantly reduced the tumor size and volume in vivo compared to the control group. There is no significant difference of antitumorgenic effects between peonidin-3-glucoside and cyaniding-3-glucoside treatments.     

Determining Duration of HER2-Targeted Therapy Using Stem Cell Extinction Models

Introduction

Trastuzumab dramatically improves survival in breast cancer patients whose tumor overexpresses HER2. A subpopulation of cells in human breast tumors has been identified with characteristics of cancer stem cells. These breast cancer stem-like cells (BCSCs) rely on HER2 signaling for self-renewal, suggesting that HER2-targeted therapy targets BCSCs even when the bulk of the tumor does not overexpress HER2. In order to guide clinical trials examining HER2-targeted therapy in the adjuvant setting, we propose a mathematical model to examine BCSC population dynamics and predict optimal duration of therapy.

Methods

Varying the susceptibility of BCSCs to HER2-targeted therapy, we quantify the average time to extinction of BCSCs. We expand our model using stochastic simulation to include the partially differentiated tumor cells (TCs) that represent bulk tumor population and examine effects of plasticity on required duration of therapy.

Results

Lower susceptibility of BCSCs and increased rates of dedifferentiation entail longer extinction times, indicating a need for prolonged administration of HER2-targeted therapy. We predict that even when therapy does not appreciably reduce tumor size in the advanced cancer setting, it will eventually eradicate the tumor in the adjuvant setting as long as there is at least a modest effect on BCSCs.

Conclusions

We anticipate that our results will inform clinical trials of targeted therapies in planning the duration of therapy needed to eradicate BCSCs. Our predictions also address safety, as longer duration of therapy entails a greater potential impact on normal stem cells that may also be susceptible to stem cell-targeted therapies.     

Efficacy and Safety of HER2-Targeted Agents for Breast Cancer with HER2-Overexpression: A Network Meta-Analysis

BackgroundClinical trials of human epidermal growth factor receptor 2 (HER2)-targeted agents added to standard treatment have been efficacious for HER2-positive (HER2+) advanced breast cancer. To our knowledge, no meta-analysis has evaluated HER2-targeted therapy including trastuzumab emtansine (T-DM1) and pertuzumab for HER2-positive breast caner and ranked the targeted treatments. We performed a network meta-analysis of both direct and indirect comparisons to evaluate the effect of adding HER2-targeted agents to standard treatment and examined side effects.MethodsWe performed a Bayesian-framework network meta-analysis of randomized controlled trials to compare 6 HER2-targeted treatment regimens and 1 naïve standard treatment (NST, without any-targeted drugs) in targeted treatment of HER2+ breast cancer in adults. These treatment regimens were T-DM1, LC (lapatinib), HC (trastuzumab), PEC (pertuzumab), LHC (lapatinib and trastuzumab), and PEHC (pertuzumab and trastuzumab). The main outcomes were overall survival and response rates. We also examined side effects of rash, LVEF (left ventricular ejection fraction), fatigue, and gastrointestinal disorders, and performed subgroup analysis for the different treatment regimens in metastatic or advanced breast cancer.ResultsWe identified 25 articles of 21 trials, with data for 11,276 participants. T-DM1 and PEHC were more efficient drug regimens with regard to overall survival as compared with LHC, LC, HC and PEC. The incidence of treatment-related rash occurs more frequently in the patients who received LC treatment regimen than PEHC and T-DM1 and HC. In subgroup analysis, T-DM1 was associated with increased overall survival as compared with LC and HC. PEHC was associated with increased overall response as compared with LC, HC, and NST.ConclusionsOverall, the regimen of T-DM1 as well as pertuzumab in combination with trastuzumab and docetaxel is efficacious with fewer side effects as compared with other regimens, especially for advanced HER2+ breast cancer.ImpactThis study suggests that both T-DM1 and PEHC therapy are potentially and equally useful treatments for HER2+ breast cancer.     

曲妥珠单抗治疗HER2阳性乳腺癌的耐药机制及新疗法探索

研究表明大约有20％的乳腺癌患者存在HER2过表达现象。HER2的异常表达及异常信号通路与乳腺癌的侵袭转移、治疗抵抗及不良预后密切相关。在临床上,对于HER2阳性的初期乳腺癌患者常联合曲妥珠单抗及化学药物治疗,但部分患者对曲妥珠单抗产生耐药。因此,研究其耐药机制对于HER2阳性乳腺癌患者的治疗、预后及新疗法的探索具有重要的临床意义。目前引起曲妥珠单抗抵抗的主要机制有：p95-HER2累积、P13K／AKT／mTOR信号异常激活、HER家族受体和IGF-1R信号增加、非受体酪氨酸激酶c-SRC活性增加等。将对上述机制及治疗HER2阳性乳腺癌的新疗法进行综述。     

A novel mutant PIK3R1EY451delinsD breast cancer patient resistant to HER2-targeted therapy treated with everolimus: a case report

Molecular Biology Reports - Resistance to HER2-targeted therapy is a critical issue in breast cancer that must be addressed immediately. PIK3R1 mutations are more common in Chinese breast cancer...     

Targeting of HER3 with Functional Cooperative miRNAs Enhances Therapeutic Activity in HER2-Overexpressing Breast Cancer Cells

Background

The HER3 receptor functions as a major cause of drug resistance in cancer treatment. It is believed that therapeutic targeting of HER3 is required to improve patient outcomes. It is not clear whether a novel strategy with two functional cooperative miRNAs would effectively inhibit erbB3 expression and potentiate the anti-proliferative/anti-survival effects of a HER2-targeted therapy (trastuzumab) and chemotherapy (paclitaxel) on HER2-overexpressing breast cancer cells.

Results

Combination of miR-125a and miR-205, as compared to either miRNA alone, potently inhibited expression of HER3 in HER2-overexpressing breast cancer BT474 cells. Co-expression of the two miRNAs not only reduced the levels of phosphorylated erbB3 (P-erbB3), Akt (P-Akt), and Src (P-Src), it also inhibited cell proliferation and increased cells at G1 phase. A multi-miRNA lentiviral vector - the cluster of miR-125a and miR-205 - was constructed to simultaneously express the two miRNAs in HER2-overexpressing breast cancer cells. Concurrent expression of miR-125a and miR-205 via the miRNA cluster transfection significantly enhanced trastuzumab-mediated growth inhibition and cell cycle G1 arrest in BT474 cells and markedly increased paclitaxel-induced apoptosis in another HER2-overexpressing breast cancer cell line HCC1954.

Conclusions

Here, we showed that functional cooperative miRNAs effectively suppressed erbB3 expression. This novel approach targeting of HER3 was able to enhance the therapeutic efficacy of trastuzumab and paclitaxel against HER2-overexpressing breast cancer.

     

Switching addictions between HER2 and FGFR2 in HER2-positive breast tumor cells: FGFR2 as a potential target for salvage after lapatinib failure

Agents that target HER2 have improved the prognosis of patients with HER2-amplified breast cancers. However, patients who initially respond to such targeted therapy eventually develop resistance to the treatment. We have established a line of lapatinib-resistant breast cancer cells (UACC812/LR) by chronic exposure of HER2-amplified and lapatinib-sensitive UACC812 cells to the drug. The mechanism by which UACC812/LR acquired resistance to lapatinib was explored using comprehensive gene hybridization. The FGFR2 gene in UACC812/LR was highly amplified, accompanied by overexpression of FGFR2 and reduced expression of HER2, and a cell proliferation assay showed that the IC₅₀ of PD173074, a small-molecule inhibitor of FGFR tyrosine kinase, was 10,000 times lower in UACC812/LR than in the parent cells. PD173074 decreased the phosphorylation of FGFR2 and substantially induced apoptosis in UACC812/LR, but not in the parent cells. FGFR2 appeared to be a pivotal molecule for the survival of UACC812/LR as they became independent of the HER2 pathway, suggesting that a switch of addiction from the HER2 to the FGFR2 pathway enabled cancer cells to become resistant to HER2-targeted therapy. The present study is the first to implicate FGFR in the development of resistance to lapatinib in cancer, and suggests that FGFR-targeted therapy might become a promising salvage strategy after lapatinib failure in patients with HER2-positive breast cancer.     

A systematic analysis of the resistance and sensitivity of HER2YVMA receptor tyrosine kinase mutant to tyrosine kinase inhibitors in HER2-positive lung cancer

Human epidermal growth factor receptor 2 (HER2) has become a well-established target for the treatment of HER2-positive lung cancer. However, a frequently observed in-frame mutation that inserts amino acid quadruplex Tyr776-Val777-Met778-Ala779 at G776 (G776^YVMA) in HER2 kinase domain can cause drug resistance and sensitivity, largely limiting the application of reversible tyrosine kinase inhibitors in lung cancer therapy. A systematic investigation of the intermolecular interactions between the HER2^YVMA mutant and clinical small-molecule inhibitors would help to establish a complete picture of drug response to HER2 G776^YVMA insertion in lung cancer, and to design new tyrosine kinase inhibitors with high potency and selectivity to target the lung cancer-related HER2^YVMA mutant. Here, we combined homology modeling, ligand grafting, structure minimization, molecular simulation and binding affinity analysis to profile a number of tyrosine kinase inhibitors against the G776^YVMA insertion in HER2. It is found that the insertion is far away from HER2 active pocket and thus cannot contact inhibitor ligand directly. However, the insertion is expected to induce marked allosteric effect on some regions around the pocket, including A-loop and hinges connecting between the N- and C-lobes of HER2 kinase domain, which may exert indirect influence to inhibitor binding. Most investigated inhibitors exhibit weak binding strength to both wild-type and mutant HER2, which can be attributed to steric hindrance that impairs ligand compatibility with HER2 active pocket. However, the cognate inhibitor lapatinib and the non-cognate inhibitor bosutinib were predicted to have low affinity for wild-type HER2 but high affinity for HER2^YVMA mutant, which was confirmed by subsequent kinase assay experiments; the inhibitory potencies of bosutinib against wild-type and mutant HER2 were determined to be IC₅₀?>?1000 and =27?nM, respectively, suggesting that the bosutinib might be exploited as a selective inhibitor for mutant over wild-type HER2. Structural examination revealed that formation of additional non-bonded interactions such as hydrogen bonds and hydrophobic contacts with HER2 A-loop region due to G776^YVMA insertion is the primary factor to improve bosutinib affinity upon the mutation.     

HER2 阳性乳腺癌转移患者最佳治疗方案的研究进展

针对人表皮生长因子受体HER2 的靶向制剂曲妥珠单抗,显著改善了HER2 阳性乳腺癌转移患者疾病的发展状况,提高了 患者的总体生存期（OS）,然而耐药现象时有发生。其它靶向制剂如帕妥珠单抗,酪氨酸激酶受体抑制剂拉帕替尼和ado-transtusumab emtansine等克服了其耐药性,为治疗提供了更多选择。这些HER2 靶向制剂单用或联用已显示出良好的临床功效,但最 佳治疗次序依然未知。随着新型靶向制剂的出现,最佳治疗方案的研究成为热点。本篇综述重点阐述了目前HER2 阳性乳腺癌转 移患者最佳治疗方案的研究进展,以及新型靶向制剂的现有状况。     

Prevalence and Clinicopathological Characteristics of HER2 and BRAF Mutation in Chinese Patients with Lung Adenocarcinoma

Aims

To determine the prevalence and clinicopathological characteristics of BRAF V600E mutation and HER2 exon 20 insertions in Chinese lung adenocarcinoma (ADC) patients.

Methods

Given the fact that the driver mutations are mutually exclusive in lung ADCs, 204 EGFR/KRAS wild-type cases were enrolled in this study. Direct Sanger sequencing was performed to examine BRAF V600E and HER2 exon 20 mutations. The association of BRAF and HER2 mutations with clinicopathological characteristics was statistically analyzed.

Results

Among the 204 lung ADCs tested, 11 cases (5.4%) carried HER2 exon 20 insertions and 4 cases (2.0%) had BRAF V600E mutation. HER2 mutation status was identified to be associated with a non-smoking history (p<0.05). HER2 mutation occurs in 9.4% of never smokers (10/106), 8.7% of female (8/92) and 2.7% of male (3/112) in this selected cohort. All four BRAF mutated patients were women and three of them were never-smokers. No HER2 mutant patients harbor BRAF mutation.

Conclusions

HER2 and BRAF mutations identify a distinct subset of lung ADCs. Given the high prevalence of lung cancer and the availability of targeted therapy, Chinese lung ADC patients without EGFR and KRAS mutations are recommended for HER2 and BRAF mutations detection, especially for those never smokers.     

Simultaneous Inhibition of Estrogen Receptor and the HER2 Pathway in Breast Cancer: Effects of HER2 Abundance

The estrogen receptor (ER) pathway and the epidermal growth factor receptor (EGFR) pathway play pivotal roles in breast cancer progression. Targeted therapies able to intercept ER or signaling downstream to EGFR and its kin, HER2, are routinely used to treat distinct groups of breast cancer patients. However, patient responses are limited by resistance to endocrine therapy, which may be due to compensatory HER2/EGFR signaling. This raises the possibility that simultaneous interception of HER2 and ER may enhance therapeutic efficacy. To address the question, we treated breast cancer cells with both fulvestrant (ICI 182780), an ER antagonist with no agonist effects, and lapatinib, an orally available tyrosine kinase inhibitor specific to EGFR and HER2. Our results indicate that the combination of drugs is especially effective when applied to HER2-overexpressing, ER-positive cancer cells. Interestingly, fulvestrant activated the mitogen-activated protein kinase (MAPK) pathway of these cells, but complete inhibition of MAPK signaling was observed on cotreatment with lapatinib. Taken together, our observations reinforce the possibility that the effectiveness of combining anti-ER and anti-HER2/EGFR drugs may be especially effective on a relatively small subtype of HER2-overexpressing, ER-positive tumors of the breast.     

Immunoproteomics of HER2-positive and HER2-negative breast cancer patients with positive lymph nodes

Identification of more and more novel tumor antigens and autoantibodies will lead to the earlier diagnosis, better prognosis prediction, and more efficient therapy of cancer in the future. Immunoproteomics techniques have successfully been used for finding novel cancer biomarkers in different subgroups of cancer patients. HER2 is a marker for an aggressive breast cancer, particularly in node-positive (NP) cases. The aim of our study was to identify antigens eliciting a humoral immune response in HER2+ and HER2- NP breast cancers by two-dimensional electrophoresis (2D), Western blotting, and mass spectrometry. Sera from 18 women with newly diagnosed NP breast cancer (9 HER2+ and 9 HER2-) and 9 healthy volunteers were individually investigated for the presence of antibodies to MCF7 breast cancer cell line proteome. Reactive spots in 2D blots were matched to stained 2D gels. Twenty-eight of matched spots were identified by mass spectrometry. Among them were LDH-A, glyceraldehydes-3-phosphate dehydrogenase, enolase-α, phosphoglycerate dehydrogenase, proteasome 26S non-ATPase subunit 13, triosephosphate isomerase, hnRNP K, hsp27, hsp90, prohibitin, nucleophosmin, 14-3-3?, PP2A regulatory subunit, and ribonuclease inhibitor-angiogenin. The five former antigens were more commonly reacted with sera from HER2+ cases, and the three latter antigens were more commonly reacted with sera from HER2- cases. Noteworthy, the antigenicity of the 28 spots showed a few differences when SBR3 cell line was used as the source of antigens. Although some of the identified antigens were previously defined as tumor antigens, others were novel. Further investigations for their utilizations as markers for breast cancer diagnosis, progression, and therapy are warranted.     

Implementation of Next-Generation Sequencing in Saudi Arabia for HER2-Positive Breast Cancer

Breast cancer is a common malignancy that poses a hazard to women's health. In 2021, around 2.3 million new cases are predicted to be discovered, with a mortality rate of 6.9% on average. Breast cancer accounts for 14.8% of malignancies among the Saudis with an 8.5% fatality rate. Breast cancers that are HER2 positive account for 15 to 20% of all breast cancers. We intended to investigate the genetic mutations and the clinicopathological aspects of HER2 positive breast cancer patients. We used TruSight Tumor 15 using Next-Generation Sequencing (NGS) to look at genetic changes in 126 Saudi women with stage I to IV breast cancer. c-MET (p = 0.001), c-KIT (p = 0.001), and PIK3CA (p = 0.0001), were shown to be substantially linked with HER2 positive patients. We also detected mutations in other genes, including BRAF, EGFR, and KRAS. Tumor size, grade, stage, and nodal status were all associated with increased levels of HER2 expression. Our results recommend that patients with HER2 positive breast cancer in Saudi Arabia have a high mutational burden, which may be related to trastuzumab resistance. We expect that in the future, targeting these mutations will be a promising therapeutic method for the treatment of breast cancer.     

HER2/HER3 signaling regulates NK cell-mediated cytotoxicity via MHC class I chain-related molecule A and B expression in human breast cancer cell lines

Overexpression of the receptor tyrosine kinases HER2 and HER3 is associated with a poor prognosis in several types of cancer. Presently, HER2- as well as HER3-targeted therapies are in clinical practice or evaluated within clinical trials, including treatment with mAbs mediating growth inhibition and/or activation of Ab-induced innate or adaptive cellular immunity. A better understanding of how HER2/HER3 signaling in tumors influences cellular immune mechanisms is therefore warranted. In this study, we demonstrate that HER2/HER3 signaling regulates the expression of MHC class I-related chain A and B (MICA and MICB) in breast cancer cell lines. The MICA and MICB (MICA/B) molecules act as key ligands for the activating receptor NK group 2, member D (NKG2D) and promote NK cell-mediated recognition and cytolysis. Genetic silencing of HER3 but not HER2 downregulated the expression of MICA/B, and HER3 overexpression significantly enhanced MICA expression. Among the major pathways activated by HER2/HER3 signaling, the PI3K/AKT pathway was shown to predominantly regulate MICA/B expression. Treatment with the HER3-specific ligand neuregulin 1β promoted the expression in a process that was antagonized by pharmacological and genetic interference with HER3 but not by the ataxia-telangiectasia-mutated (ATM) and ATM and Rad3-related protein kinases inhibitor caffeine. These observations further emphasize that HER2/HER3 signaling directly, and not via genotoxic stress, regulates MICA/B expression. As anticipated, stimulating HER2/HER3 enhanced the NKG2D-MICA/B-dependent NK cell-mediated cytotoxicity. Taken together, we conclude that signaling via the HER2/HER3 pathway in breast carcinoma cell lines may lead to enhanced NKG2D-MICA/B recognition by NK cells and T cells.     

Targeting the autophagy promoted antitumor effect of T-DM1 on HER2-positive gastric cancer

Trastuzumab emtansine (T-DM1), an antibody-drug conjugate consisted of the HER2-targeted monoclonal antibody trastuzumab and the tubulin inhibitor emtansine, has shown potent therapeutic value in HER2-positive breast cancer (BC). However, a clinical trial indicated that T-DM1 exerts a limited effect on HER2-positive gastric cancer (GC), but the underlying mechanism is inconclusive. Our research attempted to reveal the probable mechanism and role of autophagy in T-DM1-treated HER2-positive GC. In this study, our results showed that T-DM1 induced apoptosis and exhibited potent therapeutic efficacy in HER2-positive GC cells. In addition, autophagosomes were observed by transmission electron microscopy. Autophagy was markedly activated and exhibited the three characterized gradations of autophagic flux, consisting of the formation of autophagosomes, the fusion of autophagosomes with lysosomes, and the deterioration of autophagosomes in autolysosomes. More importantly, autophagic inhibition by the suppressors 3-methyladenine (3-MA) and LY294002 significantly potentiated cytotoxicity and apoptosis in HER2-positive GC cells in vitro, while the combined use of LY294002 and T-DM1 elicited potent anti-GC efficacy in vivo. In mechanistic experiments, immunoblot analysis indicated the downregulated levels of Akt, mTOR, and P70S6K and confocal microscopy analysis clearly showed that autophagic inhibition promoted the fusion of T-DM1 molecules with lysosomes in GC cells. In conclusion, our research demonstrated that T-DM1 induced apoptosis as well as cytoprotective autophagy, and autophagic inhibition could potentiate the antitumor effect of T-DM1 on HER2-positive GC. Furthermore, autophagic inhibition might increase the fusion of T-DM1 with lysosomes, which might accelerate the release of the cytotoxic molecule emtansine from the T-DM1 conjugate. These findings highlight a promising therapeutic strategy that combines T-DM1 with an autophagy inhibitor to treat HER-positive GC more efficiently.Subject terms: Targeted therapies, Tumour biomarkers     

Profiling signalling pathways in formalin-fixed and paraffin-embedded breast cancer tissues reveals cross-talk between EGFR, HER2, HER3 and uPAR

In the last few years, new approaches and developments in patient-tailored cancer therapies have raised the need to select, more precisely, those patients who will respond to personalized treatments. Therefore, the most efficient way for optimal therapy and patient selection is to provide a tumour-specific protein network portrait prior to treatment. The aim of our study was to monitor protein networks in formalin-fixed and paraffin-embedded (FFPE) breast cancer tissues, with special emphasis on epidermal growth factor receptor 2 (HER2)-mediated signalling pathways, to identify and validate new disease markers. For this purpose we used a recently developed technology to extract full-length proteins from FFPE tissues and analysed 23 molecules involved in HER2-related signalling by reverse phase protein microarray (RPPA) in a series of 106 FFPE breast cancer tissue samples. We found a significant correlation of HER2 with human epidermal growth factor receptor 3 (HER3/erbB3), epidermal growth factor receptor 1 (EGFR/HER1/erbB1) and urokinase plasminogen receptor (uPAR) in routinely used FFPE breast cancer tissues. Thus, targeting HER2, EGFR, HER3 and uPAR together may offer a more efficient treatment option for patients with breast cancer.     

The influence of HER2 genotypes as molecular markers on breast cancer outcome

Alterations of the human epidermal growth factor receptor 2 (HER2) protooncogene have been implicated in the carcinogenesis and prognosis of breast cancer. A polymorphism has been identified at codon 655 (ATC/isoleucine to GTC/valine [I655V]) in the transmembrane domain-coding region of this gene, which may be associated with the risk of breast cancer. In this study we aimed to determine whether the risk of breast cancer is associated with the I655V polymorphism of HER2 transmembrane domain-coding region at codon 655. The genomic DNA from breast cancer patients and control subjects underwent analysis by the polymerase chain reaction-fragment length polymorphism. We observed no overall association between HER2 genotype and breast cancer (p = 0.53). However, an elevated positive association was observed for Ile/Val+Val/Val versus Ile/Ile genotypes in women >age 60 years (p = 0.02). Further, other risk factors--namely, the body mass index and family history--were found to be risk factors for developing breast cancer (p = 0.006 and p = 0.00, respectively). In conclusion, results of this study suggest that polymorphisms of the HER2 gene may be important susceptibility biomarkers for breast cancer risk among older women.     

Basal/HER2 breast carcinomas

High rates of inherent primary resistance to the humanized monoclonal antibody trastuzumab (Herceptin) are frequent among HER2 gene-amplified breast carcinomas in both metastatic and adjuvant settings. The clinical efficacy of trastuzumab is highly correlated with its ability to specifically and efficiently target HER2-driven populations of breast cancer stem cells (CSCs). Intriguingly, many of the possible mechanisms by which cancer cells escape trastuzumab involve many of the same biomarkers that have been implicated in the biology of CS-like tumor-initiating cells. In the traditional, one-way hierarchy of CSCs in which all cancer cells descend from special self-renewing CSCs, HER2-positive CSCs can occur solely by self-renewal. Therefore, by targeting CSC self-renewal and resistance, trastuzumab is expected to induce tumor shrinkage and further reduce breast cancer recurrence rates when used alongside traditional therapies. In a new, alternate model, more differentiated non-stem cancer cells can revert to trastuzumab-refractory, CS-like cells via the activation of intrinsic or microenvironmental paths-to-stemness, such as the epithelial-to-mesenchymal transition (EMT). Alternatively, stochastic transitions of trastuzumab-responsive CSCs might also give rise to non-CSC cellular states that lack major attributes of CSCs and, therefore, can remain “hidden” from trastuzumab activity. Here, we hypothesize that a better understanding of the CSC/non-CSC social structure within HER2-overexpressing breast carcinomas is critical for trastuzumab-based treatment decisions in the clinic. First, we decipher the biological significance of CSC features and the EMT on the molecular effects and efficacy of trastuzumab in HER2-positive breast cancer cells. Second, we reinterpret the genetic heterogeneity that differentiates trastuzumab-responders from non-responders in terms of CSC cellular states. Finally, we propose that novel predictive approaches aimed at better forecasting early tumor responses to trastuzumab should identify biological determinants that causally underlie the intrinsic flexibility of HER2-positive CSCs to “enter” into or “exit” from trastuzumab-sensitive states. An accurate integration of CSC cellular states and EMT-related biomarkers with the currently available breast cancer molecular taxonomy may significantly improve our ability to make a priori decisions about whether patients belonging to HER2 subtypes differentially enriched with a “mesenchymal transition signature” (e.g., luminal/HER2 vs. basal/HER2) would distinctly benefit from trastuzumab-based therapy ab initio.     

HER2+ mCRC patients with exon 20 R784G substitution mutation do not respond to the cetuximab therapy

The human epidermal growth factor 2 (HER2) gene undergoes various mutations that could alter its activity or respond to the antibody therapies. Cetuximab, a known anti-EGFR monoclonal antibody (mAB), is widely administered in metastatic colorectal cancer (mCRC) cases. Here we identified mCRC patients who did not respond to cetuximab (500 mg/m², q2w) after fluoropyrimidine/oxaliplatin regimen failure. Tumor samples were examined with immunohistochemistry for protein distribution, polymerase chain reaction (PCR) sequencing for mutation detection and real-time PCR for mRNA expression pattern analysis between cetuximab sensitive and resistance patients. The conformational differences of normal and mutated protein structures were predicted by bioinformatics analysis. The 5-year survival rates of target groups were estimated using the Kaplan–Meier method. Immunohistochemistry showed that all cases had high level of HER2 protein. No K-Ras or B-Raf mutation was observed among the study population; however, cetuximab resistance patients harbored a somatic mutation R784G at the exon 20 region of HER2 coding sequence. According to bioinformatics analysis, this mutation caused a notable misfold in protein conformation. Meanwhile, survival analysis showed R784G mutated mCRC patients had shortened survival rate compared with the mCRC cases with wild-type HER2. Collectively, these data report a new mechanism of resistance to cetuximab and might be applicable in modifying new therapeutic strategies for HER2 involved cancers.