The HER3/ErbB3 receptor: a promising target in cancer drug therapy

Inhibiting HER3 Hyperphosphorylation in HER2-Overexpressing Breast Cancer through Multimodal Therapy with Branched Gold Nanoshells

Treatment failure in breast cancers overexpressing human epidermal growth factor receptor 2 (HER2) is associated mainly to the upregulation of human epidermal growth factor receptor 3 (HER3) oncoprotein linked to chemoresitence. Therefore, to increase patient survival, here a multimodal theranostic nanoplatform targeting both HER2 and HER3 is developed. This consists of doxorubicin-loaded branched gold nanoshells functionalized with the near-infrared (NIR) fluorescent dye indocyanine green, a small interfering RNA (siRNA) against HER3, and the HER2-specific antibody Transtuzumab, able to provide a combined therapeutic outcome (chemo- and photothermal activities, RNA silencing, and immune response). In vitro assays in HER2+ /HER3+ SKBR-3 breast cancer cells have shown an effective silencing of HER3 by the released siRNA and an inhibition of HER2 oncoproteins provided by Trastuzumab, along with a decrease of the serine/threonine protein kinase Akt (p-AKT) typically associated with cell survival and proliferation, which helps to overcome doxorubicin chemoresistance. Conversely, adding the NIR light therapy, an increment in p-AKT concentration is observed, although HER2/HER3 inhibitions are maintained for 72 h. Finally, in vivo studies in a tumor-bearing mice model display a significant progressively decrease of the tumor volume after nanoparticle administration and subsequent NIR light irradiation, confirming the potential efficacy of the hybrid nanocarrier.

Comprehensive Genomic Analysis Reveals the Prognostic Role of LRRK2 Copy-Number Variations in Human Malignancies

Genetic alterations of leucine-rich repeat kinase 2 (LRRK2), one of the most important contributors to familial Parkinson’s disease (PD), have been hypothesized to play a role in cancer development due to demographical and preclinical data. Here, we sought to define the prevalence and prognostic significance of LRRK2 somatic mutations across all types of human malignancies by querying the publicly available online genomic database cBioPortal. Ninety-six different studies with 14,041 cases were included in the analysis, and 761/14,041 (5.4%) showed genetic alterations in LRRK2. Among these, 585 (76.9%) were point mutations, indels or fusions, 168 (22.1%) were copy number variations (CNVs), and 8 (1.0%) showed both types of alterations. One case showed the somatic mutation R1441C. A significant difference in terms of overall survival (OS) was noted between cases harboring somatic LRRK2 whole deletions, amplifications, and CNV-unaltered cases (median OS: 20.09, 57.40, and 106.57 months, respectively; p = 0.0008). These results suggest that both LRRK2 amplifications and whole gene deletions could play a role in cancer development, paving the way for future research in terms of potential treatment with LRRK2 small molecule inhibitors for LRRK2-amplified cases.

Somatic Mutations in HER2 and Implications for Current Treatment Paradigms in HER2-Positive Breast Cancer

In one of every four or five cases of breast cancer, the human epidermal growth factor receptor-2 (HER2) gene is overexpressed. These carcinomas are known as HER2-positive. HER2 overexpression is linked to an aggressive phenotype and a lower rate of disease-free and overall survival. Drugs such as trastuzumab, pertuzumab, lapatinib, neratinib, and the more recent afatinib target the deregulation of HER2 expression. Some authors have attributed somatic mutations in HER2, a role in resistance to anti-HER2 therapy as differential regulation of HER2 has been observed among patients. Recently, studies in metastatic ER + tumors suggest that some HER2 mutations emerge as a mechanism of acquired resistance to endocrine therapy. In an effort to identify possible biomarkers of the efficacy of anti-HER2 therapy, we here review the known single-nucleotide polymorphisms (SNPs) of the HER2 gene found in HER2-positive breast cancer patients and their relationship with clinical outcomes. Information was recompiled on 11 somatic HER2 SNPs. Seven polymorphisms are located in the tyrosine kinase domain region of the gene contrasting with the low number of mutations found in extracellular and transmembrane areas. HER2-positive patients carrying S310F, S310Y, R678Q, D769H, or I767M mutations seem good candidates for anti-HER2 therapy as they show favorable outcomes and a good response to current pharmacological treatments. Carrying the L755S or D769Y mutation could also confer benefits when receiving neratinib or afatinib. By contrast, patients with mutations L755S, V842I, K753I, or D769Y do not seem to benefit from trastuzumab. Resistance to lapatinib has been reported in patients with L755S, V842I, and K753I. These data suggest that exploring HER2 SNPs in each patient could help individualize anti-HER2 therapies. Advances in our understanding of the genetics of the HER2 gene and its relations with the efficacy of anti-HER2 treatments are needed to improve the outcomes of patients with this aggressive breast cancer.

The Under-Appreciated Promiscuity of the Epidermal Growth Factor Receptor Family

Each member of the epidermal growth factor receptor (EGFR) family plays a key role in normal development, homeostasis, and a variety of pathophysiological conditions, most notably in cancer. According to the prevailing dogma, these four receptor tyrosine kinases (RTKs; EGFR, ERBB2, ERBB3, and ERBB4) function exclusively through the formation of homodimers and heterodimers within the EGFR family. These combinatorial receptor interactions are known to generate increased interactome diversity and therefore influence signaling output, subcellular localization and function of the heterodimer. This molecular plasticity is also thought to play a role in the development of resistance toward targeted cancer therapies aimed at these known oncogenes. Interestingly, many studies now challenge this dogma and suggest that the potential for EGFR family receptors to interact with more distantly related RTKs is much greater than currently appreciated. Here we discuss how the promiscuity of these oncogenic receptors may lead to the formation of many unexpected receptor pairings and the significant implications for the efficiency of many targeted cancer therapies.

Heregulin-1ß and HER3 in hepatocellular carcinoma: status and regulation by insulin

Background

The heregulin-1ß/HER3-driven pathway is implicated in several epithelial malignancies and its blockade is currently undergoing clinical investigation. Paradoxically, the status and the regulation of this pathway is poorly known in hepatocellular carcinoma (HCC).

Methods

Using 85 HCC obtained after tumour resection, heregulin-1ß and HER3 expression was evaluated by real-time RT-PCR, ELISA and/or immunohistochemistry. Statistics were performed to analyze associations between gene expression and clinicopathological parameters. The effects of insulin on the heregulin-1ß/HER3 pathway was investigated in four HCC cell lines.

Results

HER3 mRNA was upregulated in 52 % of tumours, while heregulin-1ß mRNA was downregulated in 82 %. Hepatitis B and C viral infections were respectively associated with high and low HER3 mRNA expression. No association was seen between neither HER3 or heregulin-1ß mRNA and prognostic factors, survival or recurrence. Immunohistochemistry showed predominant cytoplasmic staining of HER3 in tumours but the staining was nonreproducible. HER3 mRNA and protein levels were not correlated in liver tissues. In HCC cells, insulin promoted HER3 proteasomal degradation and inhibited heregulin-1ß stimulation of cell migration. HER3 and insulin receptor co-immunoprecipitated in these cells. The loss of insulin receptor expression by RNA interference sensitized cells to heregulin-1ß-induced AKT phosphorylation.

Conclusions

Autocrine heregulin-1ß loop is uncommon in HCC and HER3 mRNA expression is differentially influenced by hepatitis viruses. Insulin is a negative regulator of HER3 protein expression and function in HCC cells. Altogether these data may explain why HER3 and heregulin-1ß expression have no prognostic value and suggest that HCC patients are unlikely to derive benefit from HER3-targeted monotherapies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-016-0402-3) contains supplementary material, which is available to authorized users.

VERO stable cell lines expressing full-length human epidermal growth factor receptors 2 and 3: platforms for subtractive phage display

Cross-talk between human epidermal growth factor receptor 2 and 3 (HER2 and HER3) may potentially contribute to therapeutic resistance in human breast cancer. Subtractive phage display allows highly specific selection for antibody fragments directed against cells surface HER2 and HER3. The strategies to select conformation- and activation-specific antibodies against HER2 and HER3 require tightly regulated HER2 and HER3 expressing cells that allow controlled activation/inactivation of these receptors during panning procedures. To achieve this, first, we found that the VERO cell line is an appropriate cell line for heterogeneous expression of HER2 and HER3, and then we established a panel of VERO stable cell lines expressing high levels of HER2 and HER3 alone and in combination. We also showed that HER2 and HER3 expressed in VERO cells were biologically active and could form heterodimer following neuregulin1 treatment. The cell line established here not only provided platforms for phage display-based methods but also could be used in any HER-related studies.

HER2/HER3 heterodimers and p21 expression are capable of predicting adjuvant trastuzumab response in HER2+ breast cancer

Human epidermal growth factor receptor 2 (HER2) plays an important role in breast cancer progression and provides predictive information for response to targeted therapy including trastuzumab although this is limited. Downstream pathways, such as PI3K/Akt, are associated with HER2/HER3 heterodimerization promoting survival and proliferation amongst cancer cells. Thus, patient outcome and trastuzumab therapy effectiveness might be further characterised by HER2/HER3 dimerisation and its signalling pathways. HER2/HER3 dimerisation status was assessed, using chromogenic in situ Proximity Ligation Assay, in two breast cancer series: early stage primary breast cancer, including 224 HER2+ patients that were not submitted to trastuzumab, and HER2+ breast cancer where patients were treated with adjuvant trastuzumab (n = 143). Levels of biomarkers including PI3K, pAKT, ER, PgR, HER3, BCL2, p53, PTEN and p21 were measured using immunohistochemistry. Levels of HER2/HER3 heterodimers were compared with biomarker expression and patient outcome. An association between high levels of HER2/HER3 dimerisation and absence of hormone receptors, ER and PgR, was observed. We further show for the first time the presence of HER2/HER3 heterodimers and the loss of p21 expression in HER2+ breast cancer predicts a significantly poorer outcome when submitted to adjuvant trastuzumab. Breast cancer patients that reveal high levels of HER2/HER3 dimerisation and loss of p21 are associated with poor survival prognosis in patients with HER2+ breast cancer treated with adjuvant trastuzumab. Further quantification analysis of HER dimer/ligand complexes and downstream signalling pathways will begin to unravel the complex associations with patient outcome and its relationship with sensitivity to targeted treatment.

Downregulation of both EGFR and ErbB3 improves the cellular response to pemetrexed in an established pemetrexed‑resistant lung adenocarcinoma A549 cell line

Epidermal growth factor receptor (EGFR) and ErbB3 (HER3) play important roles in the regulation of cell proliferation, differentiation, anti-apoptosis and chemoresistance; however, their dysregulation in pemetrexed (PEM) resistance remains unclear. The aim of the present study was to clarify the relationship between PEM resistance and gene expression of EGFR and ErbB3, by establishing the PEM-resistant lung adenocarcinoma A549 cell line, A549/PEM. Compared with A549 cells, the A549/PEM cells were significantly more resistant to PEM (P=0.0024). The downregulation of S phase and arrest at G1 stage were detected in the A549/PEM cell line when compared to the A549 cells (P<0.05). The apoptosis rate of A549/PEM cells was much lower than that of the A549 cells after a 24 h continuous exposure to PEM (P<0.001). Real-time PCR and western blotting demonstrated the overexpression of EGFR and ErbB3 in A549/PEM cells. However, downregulation of EGFR or ErbB3 by lentiviral delivered shRNAs in A549/PEM cells showed no significant correlation with PEM sensitivity while silencing both EGFR and ErbB3 increased the cellular response to PEM in the A549/PEM cells and significantly decreased phosphorylation of STAT3, AKT and ERK. Together, these data suggest that either high expression of EGFR or ErbB3 plays a critical role in the cellular response to PEM in human lung adenocarcinoma cells though EGFR/ErbB3-dependent pathways.

HER3 status by immunohistochemistry is correlated with poor prognosis in hormone receptor-negative breast cancer patients

Breast cancer is a highly heterogeneous malignancy. The triple-negative breast cancer (TNBC) and human epidermal growth factor receptor 2 (HER2) breast cancer subtypes are highly aggressive and are associated with a poor prognosis. The therapeutic targets for TNBC remain undefined, and many patients with the HER2 subtype acquire resistance to therapy after prolonged treatment. The objective of this study was to evaluate the prognostic significance of HER3 expression in invasive breast carcinoma. We established matched tissue microarray (TMA) blocks and clinical data from 950 cases of invasive breast carcinoma with long-term clinical follow-up data (median 109.7 months). Using the TMAs, we characterized the expression of ER, PR, HER2, EGFR, and HER3 by immunohistochemistry. Each case was classified as one of four IHC-based subtypes based on the expression of hormonal receptor (HR) and HER2. The clinicopathological characteristics and survival of 950 patients were analyzed by subtype. In the TNBC subtype, the HER3(+) group showed poorer disease-free survival (DFS, P = 0.010) and overall survival (OS, P = 0.015) than the HER3(-) group. In the HER2 subtype, the HER3(+) group also showed poorer DFS (P = 0.022) and OS (P = 0.077) than the HER3(-) group. However, there was no difference in patients with HR-positive breast cancer. HER3 expression was associated with poor DFS in both the TNBC and HER2 subtypes and poor OS in the TNBC subtype. HER3 overexpression is an important prognostic marker in hormone receptor-negative breast cancer, and further study is needed to clarify the role of HER-3 targeted treatment.