ErbB-3 mediates phosphoinositide 3-kinase activity in gefitinib-sensitive non-small cell lung cancer cell lines

SIBP-03, a novel anti-HER3 antibody, exerts antitumor effects and synergizes with EGFR- and HER2-targeted drugs

HER3 (human epidermal growth factor receptor 3) acts through heterodimerization with EGFR (epidermal growth factor receptor) or HER2 to play an essential role in activating phosphoinositide 3-kinase (PI3K) and AKT signaling-a crucial pathway that promotes tumor cell survival. HER3 is a promising target for cancer therapy, and several HER3-directed antibodies have already entered into clinical trials. In this study we characterized a novel anti-HER3 monoclonal antibody, SIBP-03. SIBP-03 (0.01-10 μg/mL) specifically and concentration-dependently blocked both neuregulin (NRG)-dependent and -independent HER3 activation, attenuated HER3-mediated downstream signaling and inhibited cell proliferation. This antitumor activity was dependent, at least in part, on SIBP-03-induced, cell-mediated cytotoxicity and cellular phagocytosis. Importantly, SIBP-03 enhanced the antitumor activity of EGFR- or HER2-targeted drugs (cetuximab or trastuzumab) in vitro and in vivo. The mechanisms underlying this synergy involve increased inhibition of HER3-mediated downstream signaling. Collectively, these results demonstrated that SIBP-03, which is currently undergoing a Phase I clinical trial in China, may offer a new treatment option for patients with cancers harboring activated HER3, particularly as part of a combinational therapeutic strategy.

Clinical advances in EGFR-TKI combination therapy for EGFR-mutated NSCLC: a narrative review

Background and Objective

Mutations located in epidermal growth factor receptor (EGFR) tyrosine kinase domains have been described as the 'Achilles heel' of non-small cell lung cancer (NSCLC) and can be targeted by epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs). However, the clinical benefits of EGFR-TKIs are limited, and drug resistance inevitably occurs in NSCLC patients after long-term exposure to certain drugs. EGFR-TKI combination therapies, including combined targeted therapy, radiotherapy, chemotherapy, and immunotherapy, have shown promise in addressing this issue. This literature review analyzed the rationale and controversies of clinical research related to various EGFR-TKI combination therapies.

Methods

The PubMed database was searched to retrieve articles published from January 1, 2001 to April 15, 2023 using the following Medical Subject Headings (MeSH) terms: "EGFR-mutated non-small cell lung cancer" and "clinical trial". Google Scholar was also reviewed to retrieve additional articles. The search was limited to articles published in English.

Key Content and Findings

In this review, we summarized EGFR-TKI combination therapies, including combined targeted therapy, radiotherapy, chemotherapy, and immunotherapy, most of which have shown efficacy and safety in patients with EGFR-mutated NSCLC. A number of clinical studies with large sample sizes have analyzed the activity and toxicity of combined therapies and explored potential and well-tolerated treatment options.

Conclusions

EGFR mutations have been detected in many NSCLC patients and can be targeted by EGFR-TKIs. However, drug resistance after long-term exposure remains a significant challenge for this type of treatment. Most clinical trials have shown that the combination of EGFR-TKIs and targeted therapy, chemotherapy, radiotherapy or immunotherapy is efficacious and safe in the treatment of EGFR-mutated NSCLC. It should be noted that in some instances, serious adverse events have led to the termination of trials. However, EGFR-TKI combination therapy is indeed an effective approach for the treatment of patients with EGFR-mutated NSCLC and deserves further development.

Therapeutic target biomarkers of patient-derived xenograft models of gastric-type cervical adenocarcinoma

Background

Most cervical adenocarcinomas are associated with human papillomavirus (HPV). Gastric-type cervical adenocarcinoma (GAS), an HPV-independent adenocarcinoma, shows an aggressive clinical feature, resulting in a poor prognosis. Resistance to chemotherapy poses a difficulty in managing patients with metastatic GAS. We aimed to establish patient-derived xenografts (PDXs) of tumors from two patients with GAS and evaluated protein biomarkers for drug development using immunohistochemistry.

Methods

Two PDXs were established 78 and 48 days after transplanting the patient's tumor tissues into immunodeficient mice, respectively. PDX and patient's tumor samples were stained for HER2, HER3, PMS2, MSH6, PanTrk, and ARID1A to evaluate biomarkers for therapeutic targets. In addition, whole exome sequencing and RNA sequencing were performed on available samples.

Results

The pathological findings in morphological features and immunohistochemical profiles from the established PDXs were similar to those from the patients' surgical tumor specimens. HER3 was overexpressed in the patient's tumors, and the corresponding PDX tumors and HER2 was weakly stained in both types of tumor samples. In all PDX and patient tumor samples, PMS2, MSH6, and ARID1A were retained, and PanTrk was not expressed. In addition, a total of 10 samples, including tumor tissue samples from 8 other GAS patients, were evaluated for HER3 expression scores, all of which were 2 + or higher.

Conclusions

In summary, we evaluated biomarkers for therapeutic targets using newly established PDX models of GAS. Frequent HER3 overexpression and HER2 expression in GAS tumors suggest the possibility of new treatments for patients with GAS by targeting HER3 and HER2.

PLEKHS1 drives PI3Ks and remodels pathway homeostasis in PTEN-null prostate

The PIP3/PI3K network is a central regulator of metabolism and is frequently activated in cancer, commonly by loss of the PIP3/PI(3,4)P2 phosphatase, PTEN. Despite huge research investment, the drivers of the PI3K network in normal tissues and how they adapt to overactivation are unclear. We find that in healthy mouse prostate PI3K activity is driven by RTK/IRS signaling and constrained by pathway feedback. In the absence of PTEN, the network is dramatically remodeled. A poorly understood YXXM- and PIP3/PI(3,4)P2-binding PH domain-containing adaptor, PLEKHS1, became the dominant activator and was required to sustain PIP3, AKT phosphorylation, and growth in PTEN-null prostate. This was because PLEKHS1 evaded pathway-feedback and experienced enhanced PI3K- and Src-family kinase-dependent phosphorylation of Y258XXM, eliciting PI3K activation. hPLEKHS1 mRNA and activating Y419 phosphorylation of hSrc correlated with PI3K pathway activity in human prostate cancers. We propose that in PTEN-null cells receptor-independent, Src-dependent tyrosine phosphorylation of PLEKHS1 creates positive feedback that escapes homeostasis, drives PIP3 signaling, and supports tumor progression.

Peptide G-Protein-Coupled Receptors and ErbB Receptor Tyrosine Kinases in Cancer

The ErbB RTKs (EGFR, HER2, HER3, and HER4) have been well-studied in cancer. EGFR, HER2, and HER3 stimulate cancer proliferation, principally by activating the phosphatidylinositol-3-kinase and extracellular signal-regulated kinase (ERK) pathways, resulting in increased cancer cell survival and proliferation. Cancer cells have high densities of the EGFR, HER2, and HER3 causing phosphorylation of tyrosine amino acids on protein substrates and tyrosine amino acids near the C-terminal of the RTKs. After transforming growth factor (TGF) α binds to the EGFR, homodimers or EGFR heterodimers form. HER2 forms heterodimers with the EGFR, HER3, and HER4. The EGFR, HER2, and HER3 are overexpressed in lung cancer patient tumors, and monoclonal antibodies (mAbs), such as Herceptin against HER2, are used to treat breast cancer patients. Patients with EGFR mutations are treated with tyrosine kinase inhibitors, such as gefitinib or osimertinib. Peptide GPCRs, such as NTSR1, are present in many cancers, and neurotensin (NTS) stimulates the growth of cancer cells. Lung cancer proliferation is impaired by SR48692, an NTSR1 antagonist. SR48692 is synergistic with gefitinib at inhibiting lung cancer growth. Adding NTS to lung cancer cells increases the shedding of TGFα, which activates the EGFR, or neuregulin-1, which activates HER3. The transactivation process is impaired by SRC, matrix metalloprotease, and reactive oxygen species inhibitors. While the transactivation process is complicated, it is fast and occurs within minutes after adding NTS to cancer cells. This review emphasizes the use of tyrosine kinase inhibitors and SR48692 to impair transactivation and cancer growth.

Features of tumor-microenvironment images predict targeted therapy survival benefit in patients with EGFR-mutant lung cancer

Tyrosine kinase inhibitors (TKIs) targeting epidermal growth factor receptor (EGFR) are effective for many patients with lung cancer with EGFR mutations. However, not all patients are responsive to EGFR TKIs, including even those harboring EGFR-sensitizing mutations. In this study, we quantified the cells and cellular interaction features of the tumor microenvironment (TME) using routine H&E-stained biopsy sections. These TME features were used to develop a prediction model for survival benefit from EGFR TKI therapy in patients with lung adenocarcinoma and EGFR-sensitizing mutations in the Lung Cancer Mutation Consortium 1 (LCMC1) and validated in an independent LCMC2 cohort. In the validation data set, EGFR TKI treatment prolonged survival in the predicted-to-benefit group but not in the predicted-not-to-benefit group. Among patients treated with EGFR TKIs, the predicted-to-benefit group had prolonged survival outcomes compared with the predicted not-to-benefit group. The EGFR TKI survival benefit positively correlated with tumor-tumor interaction image features and negatively correlated with tumor-stroma interaction. Moreover, the tumor-stroma interaction was associated with higher activation of the hepatocyte growth factor/MET-mediated PI3K/AKT signaling pathway and epithelial-mesenchymal transition process, supporting the hypothesis of fibroblast-involved resistance to EGFR TKI treatment.

To Investigate Growth Factor Receptor Targets and Generate Cancer Targeting Inhibitors

Receptor tyrosine kinase (RTK) regulates multiple pathways, including Mitogenactivated protein kinases (MAPKs), PI3/AKT, JAK/STAT pathway, etc. which has a significant role in the progression and metastasis of tumor. As RTK activation regulates numerous essential bodily processes, including cell proliferation and division, RTK dysregulation has been identified in many types of cancers. Targeting RTK is a significant challenge in cancer due to the abnormal upregulation and downregulation of RTK receptors subfamily EGFR, FGFR, PDGFR, VEGFR, and HGFR in the progression of cancer, which is governed by multiple RTK receptor signalling pathways and impacts treatment response and disease progression. In this review, an extensive focus has been carried out on the normal and abnormal signalling pathways of EGFR, FGFR, PDGFR, VEGFR, and HGFR and their association with cancer initiation and progression. These are explored as potential therapeutic cancer targets and therefore, the inhibitors were evaluated alone and merged with additional therapies in clinical trials aimed at combating global cancer.

HER3 Alterations in Cancer and Potential Clinical Implications

In recent years, the third member of the HER family, kinase impaired HER3, has become a target of interest in cancer as there is accumulating evidence that HER3 plays a role in tumor growth and progression. This review focuses on HER3 activation in bladder, breast, colorectal, and lung cancer disease progression. HER3 mutations occur at a rate up to ~10% of tumors dependent on the tumor type. With patient tumors routinely sequenced for gene alterations in recent years, we have focused on HER3 mutations in bladder, breast, colon, and lung cancers particularly in response to targeted therapies and the potential to become a resistance mechanism. There are currently several HER3 targeting drugs in the pipeline, possibly improving outcomes for cancer patients with tumors containing HER3 activation and/or alterations.

Targeting the EGF receptor family in non-small cell lung cancer-increased complexity and future perspectives

Lung cancer remains the leading cause of cancer-associated mortality worldwide, but with the emergence of oncogene targeted therapies, treatment options have tremendously improved. Owing to their biological relevance, members of the ERBB receptor family, including the EGF receptor (EGFR), HER2, HER3 and HER4, are among the best studied oncogenic drivers. Activating EGFR mutations are frequently observed in non-small cell lung cancer (NSCLC), and small molecule tyrosine kinase inhibitors (TKIs) are the established first line treatment option for patients whose tumors bear "typical/classical" EGFR mutations (exon 19 deletions, L858R point mutations). Additionally, new TKIs are rapidly evolving with better efficacy to overcome primary and secondary treatment resistance (e.g., that due to T790M or C797S resistance mutations). Some atypical EGFR mutations, such as the most frequent exon 20 insertions, exhibit relative resistance to earlier generation TKIs through steric hindrance. In this subgroup, newer TKIs, such as mobocertinib and the bi-specific antibody amivantamab have recently been approved, whereas less frequent atypical EGFR mutations remain understudied. In contrast to EGFR, HER2 has long remained a challenging target, but better structural understanding has led to the development of newer generations of TKIs. The recent FDA approval of the antibody-drug conjugate trastuzumab-deruxtecan for pretreated patients with HER2 mutant NSCLC has been an important therapeutic breakthrough. HER3 and HER4 also exert oncogenic potential, and targeted treatment approaches are being developed, particularly for HER3. Overall, strategies to inhibit the oncogenic function of ERBB receptors in NSCLC are currently evolving at an unprecedented pace; therefore, this review summarizes current treatment standards and discusses the outlook for future developments.

EGFR Inhibition Potentiates FGFR Inhibitor Therapy and Overcomes Resistance in FGFR2 Fusion-Positive Cholangiocarcinoma

FGFR inhibitors are approved for the treatment of advanced cholangiocarcinoma harboring FGFR2 fusions. However, the response rate is moderate, and resistance emerges rapidly due to acquired secondary FGFR2 mutations or due to other less-defined mechanisms. Here, we conducted high-throughput combination drug screens, biochemical analysis, and therapeutic studies using patient-derived models of FGFR2 fusion-positive cholangiocarcinoma to gain insight into these clinical profiles and uncover improved treatment strategies. We found that feedback activation of EGFR signaling limits FGFR inhibitor efficacy, restricting cell death induction in sensitive models and causing resistance in insensitive models lacking secondary FGFR2 mutations. Inhibition of wild-type EGFR potentiated responses to FGFR inhibitors in both contexts, durably suppressing MEK/ERK and mTOR signaling, increasing apoptosis, and causing marked tumor regressions in vivo. Our findings reveal EGFR-dependent adaptive signaling as an important mechanism limiting FGFR inhibitor efficacy and driving resistance and support clinical testing of FGFR/EGFR inhibitor therapy for FGFR2 fusion-positive cholangiocarcinoma.

SIGNIFICANCE

We demonstrate that feedback activation of EGFR signaling limits the effectiveness of FGFR inhibitor therapy and drives adaptive resistance in patient-derived models of FGFR2 fusion-positive cholangiocarcinoma. These studies support the potential of combination treatment with FGFR and EGFR inhibitors as an improved treatment for patients with FGFR2-driven cholangiocarcinoma.

Claudin1 decrease induced by 1,25-dihydroxy-vitamin D3 potentiates gefitinib resistance therapy through inhibiting AKT activation-mediated cancer stem-like properties in NSCLC cells

Claudins, the integral tight junction proteins that regulate paracellular permeability and cell polarity, are frequently dysregulated in cancer; however, their roles in regulating EGFR tyrosine kinase inhibitors (EGFR-TKIs) resistance in non-small cell lung cancer (NSCLC) are unknown. To this end, we performed GEO dataset analysis and identified that claudin1 was a critical regulator of EGFR-TKI resistance in NSCLC cells. We also found that claudin1, which was highly induced by continuous gefitinib treatment, was significantly upregulated in EGFR-TKI-resistant NSCLC cells. By knocking down claudin1 in cell lines and xenograft models, we established that gefitinib resistance was decreased. Moreover, claudin1 knockdown suppressed the expression levels of pluripotency markers (Oct4, Nanog, Sox2, CD133, and ALDH1A1). Claudin1 loss inhibited phosphorylated AKT (p-AKT) expression and reduced cancer cell stemness by suppressing AKT activation. Furthermore, SKL2001, a β-catenin agonist, upregulated the expression levels of claudin1, p-AKT, and pluripotency markers, and 1,25-dihydroxy-vitamin D3 (1,25(OH)₂D₃) reduced claudin1 expression, AKT activation, and cancer cell stemness by inhibiting β-catenin, and suppressed claudin1/AKT pathway mediated cancer stem-like properties and gefitinib resistance. Collectively, inhibition of claudin1-mediated cancer stem-like properties by 1,25(OH)₂D₃ may decrease gefitinib resistance through the AKT pathway, which may be a promising therapeutic strategy for inhibiting gefitinib resistance in EGFR-mutant lung adenocarcinoma.

Probing altered enzyme activity in the biochemical characterization of cancer

Enzymes have evolved to catalyze their precise reactions at the necessary rates, locations, and time to facilitate our development, to respond to a variety of insults and challenges, and to maintain a healthy, balanced state. Enzymes achieve this extraordinary feat through their unique kinetic parameters, myriad regulatory strategies, and their sensitivity to their surroundings, including substrate concentration and pH. The Cancer Genome Atlas (TCGA) highlights the extraordinary number of ways in which the finely tuned activities of enzymes can be disrupted, contributing to cancer development and progression often due to somatic and/or inherited genetic alterations. Rather than being limited to the domain of enzymologists, kinetic constants such as k_cat, K_m, and k_cat/K_m are highly informative parameters that can impact a cancer patient in tangible ways—these parameters can be used to sort tumor driver mutations from passenger mutations, to establish the pathways that cancer cells rely on to drive patients’ tumors, to evaluate the selectivity and efficacy of anti-cancer drugs, to identify mechanisms of resistance to treatment, and more. In this review, we will discuss how changes in enzyme activity, primarily through somatic mutation, can lead to altered kinetic parameters, new activities, or changes in conformation and oligomerization. We will also address how changes in the tumor microenvironment can affect enzymatic activity, and briefly describe how enzymology, when combined with additional powerful tools, and can provide us with tremendous insight into the chemical and molecular mechanisms of cancer.

Targeting PI3K/Akt signal transduction for cancer therapy

The phosphatidylinositol 3-kinase (PI3K)/Akt pathway plays a crucial role in various cellular processes and is aberrantly activated in cancers, contributing to the occurrence and progression of tumors. Examining the upstream and downstream nodes of this pathway could allow full elucidation of its function. Based on accumulating evidence, strategies targeting major components of the pathway might provide new insights for cancer drug discovery. Researchers have explored the use of some inhibitors targeting this pathway to block survival pathways. However, because oncogenic PI3K pathway activation occurs through various mechanisms, the clinical efficacies of these inhibitors are limited. Moreover, pathway activation is accompanied by the development of therapeutic resistance. Therefore, strategies involving pathway inhibitors and other cancer treatments in combination might solve the therapeutic dilemma. In this review, we discuss the roles of the PI3K/Akt pathway in various cancer phenotypes, review the current statuses of different PI3K/Akt inhibitors, and introduce combination therapies consisting of signaling inhibitors and conventional cancer therapies. The information presented herein suggests that cascading inhibitors of the PI3K/Akt signaling pathway, either alone or in combination with other therapies, are the most effective treatment strategy for cancer.

The role of miRNA-377 as a tumor suppressor in lung cancer by negative regulation of genes belonging to ErbB signaling pathway

BACKGROUND

The ErbB signaling pathway plays important role in the pathogenesis of lung cancer. We explored the role of miRNA-377 as a tumor suppressor in NSCLC through silencing of some genes in the ErbB pathway.

METHODS AND RESULTS

The targeting effect of miRNA-377 on EGFR, MAPK1, ABL2, and PAK2 was evaluated. The expression levels of these genes and miRNA-377 were surveyed in NSCLC and normal human tissues, Calu-6, and A549 cells. Real-time PCR was used to figure out whether miRNA-377 could decrease the target genes mRNAs in transfected lung cancer cell lines. The effects of miRNA-377 on apoptosis cell and proliferation were analyzed. We showed that miRNA-377 targets EGFR, MAPK1, and PAK2 mRNAs in in-silico and luciferase reporter assay. The expression of miRNA-377 was significantly downregulated in human NSCLC tissues, Calu-6 and A549 cells compared to their controls. We observed a negative correlation between EGFR, MAPK1, PAK2, and miRNA-377 expression in human NSCLC tissues. A significant reduction in EGFR, MAPK1, and PAK2 mRNA levels was detected, following miRNA-377 transfection in Calu-6 and A549 cells. The higher levels of miRNA-377 in Calu-6, and A549 cells induced apoptosis and reduced proliferation, significantly.

CONCLUSIONS

All these data reveal that miRNA-377 functions as a tumor suppressor in NSCLC and may serve as a potential therapeutic target for the treatment of NSCLC.

DGG-100629 inhibits lung cancer growth by suppressing the NFATc1/DDIAS/STAT3 pathway

DNA damage-induced apoptosis suppressor (DDIAS) promotes the progression of lung cancer and hepatocellular carcinoma through the regulation of multiple pathways. We screened a chemical library for anticancer agent(s) capable of inhibiting DDIAS transcription. DGG-100629 was found to suppress lung cancer cell growth through the inhibition of DDIAS expression. DGG-100629 induced c-Jun NH(2)-terminal kinase (JNK) activation and inhibited NFATc1 nuclear translocation. Treatment with SP600125 (a JNK inhibitor) or knockdown of JNK1 restored DDIAS expression and reversed DGG-100629-induced cell death. In addition, DGG-100629 suppressed the signal transducer and activator of transcription (STAT3) signaling pathway. DDIAS or STAT3 overexpression restored lung cancer cell growth in the presence of DGG-100629. In a xenograft assay, DGG-100629 inhibited tumor growth by reducing the level of phosphorylated STAT3 and the expression of STAT3 target genes. Moreover, DGG-100629 inhibited the growth of lung cancer patient-derived gefitinib-resistant cells expressing NFATc1 and DDIAS. Our findings emphasize the potential of DDIAS blockade as a therapeutic approach and suggest a novel strategy for the treatment of gefitinib-resistant lung cancer.

HER3 expression and MEK activation in non-small-cell lung carcinoma

Aim:

We explore HER3 expression in lung adenocarcinoma (adeno-NSCLC) and identify potential mechanisms of HER3 expression.

Materials & methods:

Tumor samples from 45 patients with adeno-NSCLC were analyzed. HER3 and HER2 expression were identified using immunohistochemistry and bioinformatic interrogation of The Cancer Genome Atlas (TCGA).

Results:

HER3 was highly expressed in 42.2% of cases. ERBB3 copy number did not account for HER3 overexpression. Bioinformatic analysis of TCGA demonstrated that MEK activity score (a surrogate of functional signaling) did not correlate with HER3 ligands. ERBB3 RNA expression levels were significantly correlated with MEK activity after adjusting for EGFR expression.

Conclusion:

HER3 expression is common and is a potential therapeutic target by virtue of frequent overexpression and functional downstream signaling.

HER3 expression is common in adeno-NSCLC and is a potential therapeutic target by virtue of frequent overexpression and functional downstream signaling.

Antitumour immunity regulated by aberrant ERBB family signalling

Aberrant signalling of ERBB family members plays an important role in tumorigenesis and in the escape from antitumour immunity in multiple malignancies. Molecular-targeted agents against these signalling pathways exhibit robust clinical efficacy, but patients inevitably experience acquired resistance to these molecular-targeted therapies. Although cancer immunotherapies, including immune checkpoint inhibitors (ICIs), have shown durable antitumour response in a subset of the treated patients in multiple cancer types, clinical efficacy is limited in cancers harbouring activating gene alterations of ERBB family members. In particular, ICI treatment of patients with non-small cell lung cancers with epidermal growth factor receptor (EGFR) alterations and breast cancers with HER2 alterations failed to show clinical benefits, suggesting that EGFR and HER2 signalling may have an essential role in inhibiting antitumour immune responses. Here, we discuss the mechanisms by which the signalling of ERBB family members affects not only autonomous cancer hallmarks, such as uncontrolled cell proliferation, but also antitumour immune responses in the tumour microenvironment and the potential application of immune-genome precision medicine into immunotherapy and molecular-targeted therapy focusing on the signalling of ERBB family members.

Thirty Years of HER3: From Basic Biology to Therapeutic Interventions

HER3 is a pseudokinase member of the EGFR family having a role in both tumor progression and drug resistance. Although HER3 was discovered more than 30 years ago, no therapeutic interventions have reached clinical approval to date. Because the evidence of the importance of HER3 is accumulating, increased amounts of preclinical and clinical trials with HER3-targeting agents are emerging. In this review article, we discuss the most recent HER3 biology in tumorigenic events and drug resistance and provide an overview of the current and emerging strategies to target HER3.

Randomized Phase II Study of 3 Months or 2 Years of Adjuvant Afatinib in Patients With Surgically Resected Stage I-III EGFR-Mutant Non-Small-Cell Lung Cancer

For patients with surgically resected disease, multiple studies suggest a benefit of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in delaying cancer recurrence. The necessary duration of therapy for benefit is unknown.

MATERIALS AND METHODS

This randomized phase II study enrolled patients with completely resected stage IA-IIIB EGFR-mutant non-small-cell lung cancer (American Joint Committee on Cancer 7th edition) after stage-appropriate standard-of-care adjuvant therapy. Patients were randomly assigned 1:1 to 3 months or 2 years of adjuvant afatinib starting at 30 mg by mouth daily. Computed tomography imaging was performed every 6 months for 3 years and then annually. The primary study end point for this planned 92-patient trial was recurrence rate at 2 years from randomization. A 20% improvement (from 70% with 3 months to 90% with 2 years) was targeted.

RESULTS

Forty-six patients enrolled and 45 were treated. The assigned course of afatinib treatment was completed by 96% (22/23) of patients in the 3-month group and only 41% (9/22) in the 2-year group. The 2-year recurrence-free survival (RFS) rates were 70% in the 3-month group and 81% in the 2-year group (P = .55). The median RFS was 42.8 months in the 3-month group and 58.6 months in the 2-year group. Side effects were consistent with those previously described for afatinib.

CONCLUSION

Recurrences at 2 years were 11% less common with 2 years versus 3 months of adjuvant afatinib. This difference did not meet the 20% primary study target, likely because of underaccrual and early drug discontinuation on the 2-year group. With the availability of osimertinib with better efficacy and tolerability than earlier-generation agents, the optimal duration of adjuvant EGFR TKI therapy remains an important question.

The Resurgence of Antibody Drug Conjugates in Cancer Therapeutics: Novel Targets and Payloads

Antibody drug conjugates (ADCs) are an emerging class of therapeutics that consist of a cytotoxic agent linked covalently to an antibody, which is directed toward a specific cell surface target expressed by tumor cells and/or the microenvironment. ADCs leverage the specificity of the antibody such that it functions as a carrier to deliver the cytotoxic payload into the tumor. Four parameters are considered critical for this class of complex engineered therapeutics: target selection, antibody, cytotoxic payload, as well as conjugation and linker technology. The development of this class of drugs has proven more complex than expected. Several challenges have arisen, including a lack of true tumor antigen specificity, early release of the cytotoxic payload into the bloodstream due to linker instability, and low potency of the payload, resulting in either greater toxicity or lack of improved efficacy compared with unconjugated cytotoxics. The approval of trastuzumab emtansine in 2013 for HER2-positive breast cancer served as a proof of concept that ADCs have therapeutic application in solid tumors. Two novel ADCs have recently been approved: trastuzumab deruxtecan for HER2-positive breast cancer and enfortumab vedotin for locally advanced or metastatic urothelial cancer. Trastuzumab deruxtecan is distinguished by a unique biochemical structure with a novel cytotoxic payload, deruxtecan-a highly potent, topoisomerase I inhibitor. Enfortumab vedotin is directed toward nectin-4 and represents an example of successful and strategic target selection. This review focuses on the concepts underlying the choice of suitable targets and novel payloads, discusses specific examples of ADCs in preclinical and clinical development, and provides future directions related to this unique class of therapeutics.

New insights into ErbB3 function and therapeutic targeting in cancer

INTRODUCTION

The importance of ErbB3 receptor tyrosine kinase in cancer progression, primary and acquired drug resistance, has become steadily evident since its discovery in 1989. ErbB3 overexpression in various solid organ malignancies is associated with shorter survival of patients. However, initial strategies to therapeutically target ErbB3 have not been rewarding.

AREAS COVERED

Here, we provide an overview of ErbB3 biology in carcinogenesis. We outline the role of ErbB3 as a critical pathway for resistance to other anti-cancer drugs. We focus on emerging clinical data, which will steer the potential future development of ErbB3 directed therapies.

EXPERT OPINION

Initial approaches to ErbB3 targeting have been challenging. However, the lack of success of anti-ErbB3 therapies in ongoing clinical trials may relate more to the complex biology of the receptor and challenges with the biomarkers used to date. Furthermore, it seems certain that the expression of the receptor per se is necessary but not sufficient for the response to ErbB3 therapies. Emerging data suggest that more sophisticated biomarkers are needed. Nonetheless, it is also likely that ErbB3 therapies may have the most efficacy in combination therapy, and their favorable toxicity profile makes this feasible.

Exploring the radiosensitizing potential of AZD8931: a pilot study on the human LoVo colorectal cancer cell line

AIM

To explore the radiosensitizing effect of AZD8931, a novel equipotent and reversible inhibitor of signaling by EGFR (HER1), HER2 and HER3 receptors, focusing on cell cycle progression, apoptosis and clonogenic capacity in the human LoVo colorectal cancer (CRC) cell line, also in comparison with the EGFR-blocking monoclonal antibody Cetuximab or the EGFR tyrosine kinase selective small molecular inhibitor Gefitinib.

MATERIALS AND METHODS

Cells were pretreated with EGFR inhibitors for 5 consecutive days and then exposed or not to ionizing radiation (IR) (2 Gy daily for 3 consecutive days). Cell proliferation, cell cycle progression and apoptosis were evaluated by flow cytometry and enzyme-linked immunosorbent assay (ELISA), clonogenic potential and radiosensitivity were studied by colony formation assay.

RESULTS

AZD8931 induced cell cycle arrest and apoptosis more effectively than Gefitinib and Cetuximab and, more importantly, it was significantly more potent than Gefitinib and Cetuximab in radiosensitizing cells. This radiosensitizing action by AZD8931 mainly occurred by markedly reducing cell cycle progression into S phase, the most radioresistant phase of cell cycle, secondly by inducing apoptosis and reducing clonogenic survival.

CONCLUSIONS

Our results show that AZD8931 increases IR efficacy in LoVo cells, suggesting that it works as a potent radiosensitizer, even more efficient than Gefitinib and Cetuximab, opening new pathways of investigation for further in vitro and in vivo studies aimed at confirming its potential to improve local radiotherapy in CRC.

Recent updates on the resistance mechanisms to epidermal growth factor receptor tyrosine kinase inhibitors and resistance reversion strategies in lung cancer

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) have led to a substantial improvement in the prognosis of lung cancer patients by explicitly targeting the activating mutations within the EGFR. Initially, patients harboring tumors with EGFR mutations show progression-free survival and improvement in the response rates toward all-generation EGFR-TKIs; however, these agents fail to deliver the intended results in the long-term due to drug resistance. Therefore, it is necessary to recognize specific cardinal mechanisms that regulate the resistance phenomenon. Understanding the intricate mechanisms underlying EGFR-TKIs resistance in lung cancer could provide cognizance for more advanced targeted therapeutics. The present review features insights into current updates on the discrete mechanisms, including secondary or tertiary mutations, parallel and downstream signaling pathways, acquiring an epithelial-to-mesenchymal transition (EMT) signature, microRNAs (miRNAs), and epigenetic alterations, which lead to intrinsic and acquired resistance against EGFR-TKIs in lung cancer. In addition, this paper also reviews current possible strategies to overcome this issue using combination treatment of recently developed MET inhibitors, allosteric inhibitors or immunotherapies, transformation of EMT, targeting miRNAs, and epigenetic alterations in intrinsic and acquired EGFR-TKIs resistant lung cancer. In conclusion, multiple factors are responsible for intrinsic and acquired resistance to EGFR-TKIs and understanding of the detailed molecular mechanisms, and recent advancements in pharmacological studies are needed to develop new strategies to overcome intrinsic and acquired EGFR-TKIs resistance in lung cancer.

Plasma DNA as a "liquid biopsy" incompletely complements tumor biopsy for identification of mutations in a case series of four patients with oligometastatic breast cancer

PURPOSE

Circulating tumor DNA in plasma may present a minimally invasive opportunity to identify tumor-derived mutations to inform selection of targeted therapies for individual patients, particularly in cases of oligometastatic disease where biopsy of multiple tumors is impractical. To assess the utility of plasma DNA as a "liquid biopsy" for precision oncology, we tested whether sequencing of plasma DNA is a reliable surrogate for sequencing of tumor DNA to identify targetable genetic alterations.

METHODS

Blood and biopsies of 1-3 tumors were obtained from 4 evaluable patients with advanced breast cancer. One patient provided samples from an additional 7 tumors post-mortem. DNA extracted from plasma, tumor tissues, and buffy coat of blood were used for probe-directed capture of all exons in 149 cancer-related genes and massively parallel sequencing. Somatic mutations in DNA from plasma and tumors were identified by comparison to buffy coat DNA.

RESULTS

Sequencing of plasma DNA identified 27.94 ± 11.81% (mean ± SD) of mutations detected in a tumor(s) from the same patient; such mutations tended to be present at high allelic frequency. The majority of mutations found in plasma DNA were not found in tumor samples. Mutations were also found in plasma that matched clinically undetectable tumors found post-mortem.

CONCLUSIONS

The incomplete overlap of genetic alteration profiles of plasma and tumors warrants caution in the sole reliance of plasma DNA to identify therapeutically targetable alterations in patients and indicates that analysis of plasma DNA complements, but does not replace, tumor DNA profiling.

TRIAL REGISTRATION

Subjects were prospectively enrolled in trial NCT01836640 (registered April 22, 2013).

Reduced expression of CYLD promotes cell survival and inflammation in gefitinib-treated NSCLC PC-9 cells: Targeting CYLD may be beneficial for acquired resistance to gefitinib therapy

The application of tyrosine kinase inhibitors (TKIs) to the epidermal growth factor receptor (EGFR) has been proven to be highly effective for non-small-cell lung cancer (NSCLC). However, patients often evolve into acquired resistance. The secondary mutations in EGFR account for nearly half of the acquired resistance. While the remaining 50% of patients exhibit tolerance to EGFR-TKIs with unclear mechanism(s). Cylindromatosis (CYLD), a deubiquitinase, functions as a tumor suppressor to regulate cell apoptosis, proliferation, and immune response, and so on. The role of CYLD in NSCLC EGFR-TKI resistance remains elusive. Here, we found CYLD was upregulated in PC-9 cells, whereas downregulated in PC-9 acquired gefitinib-resistant (PC-9/GR) cells in response to the treatment of gefitinib, which is consistent with the results in the Gene Expression Omnibus database. Overexpression of CYLD promoted a more apoptotic death ratio in PC-9/GR cells than that in PC-9 cells. In addition, silencing the expression of CYLD resulted in an increase of the expression level of interleukin-6, transforming growth factor-β and tumor necrosis factor-α, which may contribute to acquired resistance of PC-9 cells to gefitinib. Taken together, our data in vitro demonstrate that PC-9/GR cells downregulated CYLD expression, enhanced subsequent CYLD-dependent antiapoptotic capacity and inflammatory response, which may provide a possible target for acquired gefitinib-resistant treatment in NSCLC.

The emerging treatment landscape of targeted therapy in non-small-cell lung cancer

Lung cancer is one of the most common cancer in the world. In 2018, there were over 2 million new cases of lung cancer and over 1.7 million deaths were attributed to lung cancer. Targeted therapy has emerged as an important mean of the disease management for patients with non-small-cell lung cancer (NSCLC). Herein, we review and analyze recent literature, discuss the targeting pathways and ongoing clinical trials in lung cancer. Chemotherapy is no longer the best available treatment for all patients. Therapeutic decisions should be guided by an understanding of the molecular features of patient's tumor tissues. The future gains will likely emerge from finding optimal ways of combining targeted therapy, immunotherapy, and chemotherapy.

Neuropeptide bombesin receptor activation stimulates growth of lung cancer cells through HER3 with a MAPK-dependent mechanism

Despite recent advances in treatment of non-small cell lung cancer (NSCLC), prognosis still remains poor and new therapeutic approaches are needed. Studies demonstrate the importance of the EGFR/HER-receptor family in NSCLC growth, as well as that of other tumors. Recently, HER3 is receiving increased attention because of its role in drug resistance and aggressive growth. Activation of overexpressed G-protein-coupled receptors (GPCR) can also initiate growth by transactivating EGFR/HER-family members. GPCR transactivation of EGFR has been extensively studied, but little is known of its ability to transactivate other EGFR/HER-members, especially HER3. To address this, we studied the ability of bombesin receptor (BnR) activation to transactivate all EGFR/HER-family members and their principal downstream signaling cascades, the PI3K/Akt- and MAPK/ERK-pathways, in human NSCLC cell-lines. In all three cell-lines studied, which possessed EGFR, HER2 and HER3, Bn rapidly transactivated EGFR, HER2 and HER3, as well as Akt and ERK. Immunoprecipitation studies revealed Bn-induced formation of both HER3/EGFR- and HER3/HER2-heterodimers. Specific EGFR/HER3 antibodies or siRNA-knockdown of EGFR and HER3, demonstrated Bn-stimulated activation of EGFR/HER members is initially through HER3, not EGFR. In addition, specific inhibition of HER3, HER2 or MAPK, abolished Bn-stimulated cell-growth, while neither EGFR nor Akt inhibition had an effect. These results show HER3 transactivation mediates all growth effects of BnR activation through MAPK. These results raise the possibility that targeting HER3 alone or with GPCR activation and its signal cascades, may be a novel therapeutic approach in NSCLC. This is especially relevant with the recent development of HER3-blocking antibodies.

CXCR7 Reactivates ERK Signaling to Promote Resistance to EGFR Kinase Inhibitors in NSCLC

Although EGFR mutant-selective tyrosine kinase inhibitors (TKI) are clinically effective, acquired resistance can occur by reactivating ERK. We show using in vitro models of acquired EGFR TKI resistance with a mesenchymal phenotype that CXCR7, an atypical G protein-coupled receptor, activates the MAPK-ERK pathway via β-arrestin. Depletion of CXCR7 inhibited the MAPK pathway, significantly attenuated EGFR TKI resistance, and resulted in mesenchymal-to-epithelial transition. CXCR7 overexpression was essential in reactivation of ERK1/2 for the generation of EGFR TKI-resistant persister cells. Many patients with non-small cell lung cancer (NSCLC) harboring an EGFR kinase domain mutation, who progressed on EGFR inhibitors, demonstrated increased CXCR7 expression. These data suggest that CXCR7 inhibition could considerably delay and prevent the emergence of acquired EGFR TKI resistance in EGFR-mutant NSCLC. SIGNIFICANCE: Increased expression of the chemokine receptor CXCR7 constitutes a mechanism of resistance to EGFR TKI in patients with non-small cell lung cancer through reactivation of ERK signaling.

PTPRK suppresses progression and chemo-resistance of colon cancer cells via direct inhibition of pro-oncogenic CD133

Receptor‐type protein tyrosine phosphatase κ (PTPRK) is considered to be a candidate tumor suppressor. PTPRK dephosphorylates CD133, which is a stem cell marker; phosphorylated CD133 accelerates xenograft tumor growth of colon cancer cells through the activation of AKT, but the functional significance of this has remained elusive. In this study, we have demonstrated that knockdown of PTPRK potentiates the pro‐oncogenic CD133–AKT pathway in colon cancer cells. Intriguingly, depletion of PTPRK significantly reduced sensitivity to the anti‐cancer drug oxaliplatin and was accompanied by up‐regulation of phosphorylation of Bad, a downstream target of AKT. Together, our present observations strongly suggest that the CD133–PTPRK axis plays a pivotal role in the regulation of colon cancer progression as well as drug resistance.

Principles of Resistance to Targeted Cancer Therapy: Lessons from Basic and Translational Cancer Biology

Identification of the genomic drivers of cancer has led to the clinical development of targeted therapies that strike at the heart of many malignancies. Nonetheless, many cancers outsmart such precision-medicine efforts, and thus therapeutic resistance contributes significantly to cancer mortality. Attempts to understand the basis for resistance in patient samples and laboratory models has yielded two major benefits: one, more effective chemical inhibitors and rational combination therapies are now employed to prevent or circumvent resistance pathways; and two, our understanding of how oncogenic mutations drive cancer cell survival and oncogene addiction is deeper and broader, highlighting downstream or parallel cellular programs that shape these phenotypes. This review discusses emerging principles of resistance to therapies targeted against key oncogenic drivers.

Anti-tumor effect of neratinib against lung cancer cells harboring HER2 oncogene alterations

Human epidermal growth factor receptor 2 (HER2) is a member of the ErbB family of receptor tyrosine kinases. Numerous studies have reported the amplification and overexpression of HER2 in several types of cancer, including non-small cell lung cancer (NSCLC). However, the benefits of HER2-targeted therapy have not been fully established. In the present study, the anti-tumor effect of neratinib, an irreversible pan-HER tyrosine kinase inhibitor (TKI), against NSCLC cells harboring HER2 alterations was investigated. The sensitivity of normal bronchial epithelial cells (BEAS-2B) ectopically overexpressing wild-type or mutant HER2 to neratinib was assessed. Furthermore, the anti-tumor activity of neratinib in several NSCLC cell lines harboring HER2 alterations was determined in vitro and in vivo, and the association between their genetic alterations and sensitivity to neratinib treatment was investigated. BEAS-2B cells ectopically overexpressing wild-type HER2 or mutants (A775insYVMA, G776VC, G776LC, P780insGSP, V659E, G660D and S310F) exhibited constitutive autophosphorylation of HER2, as determined by western blotting. While these BEAS-2B cells were sensitive to neratinib, they were insensitive to erlotinib, a first-generation epidermal growth factor receptor-TKI. Neratinib also exerted anti-proliferative effects on HER2-altered (H2170, Calu-3 and H1781) NSCLC cell lines. Neratinib was also demonstrated to exert strong tumor growth inhibitory activity in mouse xenograft models using HER2-altered lung cancer cells. The results of the present study strongly suggest that neratinib has potential as a promising therapeutic option for the treatment of HER2-altered NSCLC.

The Role of PI3K in Met Driven Cancer: A Recap

The Receptor Tyrosine Kinase (RTK) Met, overexpressed or mutated in cancer, plays a major role in cancer progression and represents an attractive target for cancer therapy. However RTK inhibitors can lead to drug resistance, explaining the necessity to develop therapies that target downstream signaling. Phosphatidylinositide 3-kinase (PI3K) is one of the most deregulated pathways in cancer and implicated in various types of cancer. PI3K signaling is also a major signaling pathway downstream of RTK, including Met. PI3K major effectors include Akt and "mechanistic Target of Rapamycin" (mTOR), which each play key roles in numerous and various cell functions. Advancements made due to the development of molecular and pharmaceutical tools now allow us to delve into the roles of each independently. In this review, we summarize the current understanding we possess of the activation and role of PI3K/Akt/mTOR, downstream of Met, in cancer.

An HER3-targeting antibody-drug conjugate incorporating a DNA topoisomerase I inhibitor U3-1402 conquers EGFR tyrosine kinase inhibitor-resistant NSCLC

EGFR tyrosine kinase inhibitors (TKIs) are standard therapy for EGFR-mutant non-small cell lung cancer (NSCLC); however, these tumours eventually acquire chemoresistance. U3-1402 is an anti-HER3 antibody-drug conjugate with a novel topoisomerase I inhibitor, DXd. In the current study, we evaluated the anticancer efficacy of U3-1402 in EGFR-mutant NSCLC cells with acquired resistance to EGFR-TKIs. HCC827GR5 and PC9AZDR7 are EGFR-TKI-resistant clones for gefitinib and osimertinib, respectively. U3-1402 alone or in combination with the EGFR-TKI erlotinib demonstrated potent anticancer efficacy in HCC827GR5 cells using an in vitro growth inhibition assay and in vivo xenograft mouse model. U3-1402 induced apoptosis in HCC827GR5 cells accompanying phosphorylation of histone H2A.X, a marker of DNA damage, but did not block HER3/PI3K/AKT signalling. Further, we found using flow cytometry that the cell surface HER3 expression level in HCC827GR5 cells was twice that found in HCC827 cells, indicating internalization of U3-1402 was increased in resistant cells. In addition, administration of U3-1402 notably repressed growth of EGFR-TKI osimertinib-resistant PC9AZDR7 xenograft tumours, and that PC9AZDR7 cells expressed five times greater cell surface HER3 than PC9 cells. Furthermore, using immunofluorescent microscopy, HER3 was observed predominantly in the nucleus of PC9 cells, but was localized in the cytoplasm of PC9AZDR7 cells. This finding indicates that altered trafficking of the HER3-U3-1402 complex may accelerate linker payload cleavage by cytoplasmic lysosomal enzymes, resulting in DNA damage. Our results indicate that administration of U3-1402 alone or in combination with an EGFR-TKI may have potential as a novel therapy for EGFR-TKI-resistant EGFR-mutant NSCLC.

Inducible SHP-2 activation confers resistance to imatinib in drug-tolerant chronic myeloid leukemia cells

BCR-ABL kinase mutations, accounting for clinical resistance to tyrosine kinase inhibitor (TKI) such as imatinib, frequently occur in acquired resistance or in advanced phases of chronic myeloid leukemia (CML). Emerging evidence implicates a critical role for non-mutational drug resistance mechanisms underlying the survival of residual cancer 'persister' cells. Here, we utilized non-mutational imatinib-resistant K562/G cells to reveal SHP-2 as a resistance modulator of imatinib treatment response during the early phase. SHP-2 phosphorylation was significantly higher in K562/G cells than in sensitive K562 cells. In K562 cells, both short-term and long-term exposure to imatinib induced SHP-2 phosphorylation. Consistently, gain- and loss-of-function mutants in SHP-2 proved its regulation of imatinib resistance. SHP-2 inhibitor and imatinib exhibited a strong antitumor synergy in in vitro and in vivo K562/G models. Mechanistically, dual SHP-2 and BCR-ABL inhibition blocked RAF/MEK/ERK and PI3K/AKT/mTOR pathways, respectively, leading to dramatic apoptotic death of K562/G cells. In conclusion, our results highlight that SHP-2 could be exploited as a biomarker and therapeutic target during the early phase of imatinib resistance development in CML.

MicroRNA and HER2-overexpressing cancer

The discovery of microRNAs (miRNAs) has opened up new avenues for studying cancer at the molecular level, featuring a post-genomic era of biomedical research. These non-coding regulatory RNA molecules of ~22 nucleotides have emerged as important cancer biomarkers, effectors, and targets. In this review, we focus on the dysregulated biogenesis and function of miRNAs in cancers with an overexpression of the proto-oncogene HER2. Many of the studies reviewed here were carried out in breast cancer, where HER2 overexpression has been extensively studied and HER2-targeted therapy practiced for more than a decade. MiRNA signatures that can be used to classify tumors with different HER2 status have been reported but little consensus can be established among various studies, emphasizing the needs for additional well-controlled profiling approaches and meta-analyses in large and well-balanced patient cohorts. We further discuss three aspects of microRNA dysregulation in or contribution to HER2-associated malignancies or therapies: (a) miRNAs that are up- or down-regulated by HER2 and mediate the downstream signaling of HER2; (b) miRNAs that suppress the expression of HER2 or a factor in HER2 receptor complexes, such as HER3; and (c) miRNAs that affect responses to anti-HER2 therapies. The regulatory mechanisms are elaborated using mainly examples of miR-205, miR-125, and miR-21. Understanding the regulation and function of miRNAs in HER2-overexpressing tumors shall shed new light on the pathogenic mechanisms of microRNAs and the HER2 proto-oncogene in cancer, as well as on individualized or combinatorial anti-HER2 therapies.

Association of Tumor HER3 Messenger RNA Expression With Panitumumab Efficacy in Advanced Colorectal Cancer

IMPORTANCE

Epidermal growth factor receptor (EGFR) (HER1) signaling depends on ligand binding and dimerization with itself or other HER receptors. We previously showed in a randomized trial that high EGFR ligand expression is predictive of panitumumab benefit in advanced colorectal cancer. Tumor expression of HER3 may further refine the RAS wild-type (wt) population benefitting from anti-EGFR agents.

OBJECTIVE

To examine HER3 messenger RNA expression as a prognostic and predictive biomarker for anti-EGFR therapy in a randomized clinical trial of panitumumab.

DESIGN, SETTING, AND PARTICIPANTS

The study was a prospectively planned retrospective biomarker study of pretreatment samples from the PICCOLO trial that tested the addition of panitumumab to irinotecan therapy in patients with KRAS wt advanced colorectal cancer who experienced failure with prior fluoropyrimidine treatment. HER3 was assessed as a prognostic marker, then as a predictive biomarker in patients with RAS wt, first as a continuous variable and then as a binary (high vs low) variable. Relationship with MEK-AKT pathway mutations and EGFR ligands epiregulin and amphiregulin (EREG/AREG) were also assessed.

MAIN OUTCOMES AND MEASURES

Primary end point was progression-free survival (PFS); secondary end points were response rate and overall survival (OS).

RESULTS

In 308 patients (mean age at randomization, 61.6 years; 193 men) higher HER3 was weakly prognostic for OS (hazard ratio [HR] per 2-fold change, 0.91; 95% CI, 0.83-0.99; P = .04) but not PFS (HR, 0.93; 95% CI, 0.83-1.05; P = .25). Higher HER3 was predictive, being associated with prolonged PFS on irinotecan plus panitumumab (IrPan) (HR, 0.71; 95% CI, 0.61-0.82; P < .001), but not irinotecan (HR, 0.96; 95% CI, 0.82-1.13; P = .65) in patients with RAS wt, with significant interaction between biomarker and treatment (P = .001). Similar interaction was seen for OS (P = .004). In an exploratory binary model, dividing the population at the 66th percentile, HER3 was predictive of panitumumab benefit: in patients with high HER3 expression, median PFS was 8.2 months (IrPan) vs 4.4 months (irinotecan) (HR, 0.33; 95% CI, 0.19-0.58; P < .001). Patients with low HER3 expression gained no benefit in PFS: 3.3 months (IrPan) vs 4.3 months (irinotecan) (HR, 0.96; 95% CI, 0.67-1.38; P = .84), with significant interaction (P = .002). The binary model was also predictive for OS, with significant interaction (P = .01). Combining HER3 and ligand data, patients with HER3-high, AREG/EREG-high tumors gained markedly from panitumumab (PFS HR, 0.24; 95% CI, 0.11-0.51; P < .005 and OS HR, 0.36; 95% CI, 0.18-0.73; P = .004). Conversely, patients with HER3-low, AREG/EREG-low tumors did not benefit (PFS HR, 1.14; 95% CI, 0.73-1.79; P = .57 and OS HR, 1.44; 95% CI, 0.92-2.26; P = .11).

CONCLUSIONS AND RELEVANCE

High HER3 expression identified patients with RAS wt who gained markedly from panitumumab, and those who did not, with statistically significant biomarker-treatment interactions for PFS and OS. This finding provides insight into the mechanism of anti-EGFR agents and is of potential clinical utility.

HER3 expression is enhanced during progression of lung adenocarcinoma without EGFR mutation from stage 0 to IA1

Background

Activating EGFR mutations, HER2, and HER3 are implicated in lung cancer; however, with the exception of EGFR gene amplification in lung adenocarcinoma harboring EGFR mutations, their involvement in disease progression during the early stages is poorly understood. In this paper, we focused on which receptor is correlated with lung adenocarcinoma progression in the presence or absence of EGFR mutation from stage 0 to IA1.

Methods

HER2 and HER3 expression and activating EGFR mutations in surgically resected lung adenocarcinoma exhibiting ground glass nodules on chest computed tomography and re‐classified to stage 0 and IA1 were examined by immunohistochemistry and peptide nucleic acid‐locked nucleic acid PCR clamp method, respectively.

Results

HER2 and HER3 expression was detected in 22.2% and 86.1% of samples, respectively. The frequency of EGFR mutation was 45.7% and was not significantly different between stage 0 and IA1 (40.0% and 48.0%, respectively), suggesting that EGFR mutation does not correlate with cancer progression from stage 0 to IA1. HER2 expression also did not correlate to progression. However, not only the frequency, but also the intensity of HER3 expression was increased in stage IA1 lung adenocarcinoma, particularly in lung adenocarcinoma without EGFR mutation.

Conclusion

HER3 tends to be intensively expressed during the progression of lung adenocarcinoma without EGFR mutation from carcinoma in situ to invasive carcinoma.

Mechanisms of receptor tyrosine kinase activation in cancer

Receptor tyrosine kinases (RTKs) play an important role in a variety of cellular processes including growth, motility, differentiation, and metabolism. As such, dysregulation of RTK signaling leads to an assortment of human diseases, most notably, cancers. Recent large-scale genomic studies have revealed the presence of various alterations in the genes encoding RTKs such as EGFR, HER2/ErbB2, and MET, amongst many others. Abnormal RTK activation in human cancers is mediated by four principal mechanisms: gain-of-function mutations, genomic amplification, chromosomal rearrangements, and / or autocrine activation. In this manuscript, we review the processes whereby RTKs are activated under normal physiological conditions and discuss several mechanisms whereby RTKs can be aberrantly activated in human cancers. Understanding of these mechanisms has important implications for selection of anti-cancer therapies.

Surrogate Predictive Biomarkers for Response to Anti-EGFR Agents: State of the Art and Challenges

The epidermal growth factor receptor (EGFR) plays a key role in cancer development and progression in several human malignancies including non-small cell lung cancer (NSCLC). Several strategies aimed at inhibiting the EGFR have been investigated in the last years, including the use of small tyrosine kinase inhibitors (TKIs) directed against the intracellular domain of the receptor and monoclonal antibodies targeting its extracellular portion. Subgroups of patients who are more likely to respond to TKIs have been identified based on both clincal and biological features. Never-smoking history has emerged as the most relevant clinical characteristic predictive of response to TKIs in NSCLC, while presence of drug-sensitive EGFR mutations and EGFR gene gain represent critical biological variables associated with an improved outcome for patients exposed to these agents. Recent studies have highlighted the existence of biological factors involved in intrinsic and acquired resistance to TKIs, including k-ras, HER-2 and EGFR exon 20 mutations. Increasing knowledge of EGFR biology and drug-receptor interactions will allow to identify individuals who are likely to derive a clinical benefit from the proposed targeted therapy, sparing refractory patients expensive and potentially toxic treatment.

Estrogen receptor alpha drives mTORC1 inhibitor-induced feedback activation of PI3K/AKT in ER+ breast cancer

The mTORC1 inhibitor RAD001 (everolimus) is approved for treatment of recurrent/metastatic estrogen receptor (ER)-positive breast cancer in combination with the aromatase inhibitor (AI) exemestane. The benefits of A) continued anti-estrogen therapy for anti-estrogen-resistant disease in the context of mTORC1 inhibition, and B) adjuvant everolimus in combination with anti-estrogen therapy for early-stage disease are being tested clinically, but molecular rationale remains unclear. We hypothesized that mTORC1 inhibition activates the IGF-1R/InsR/IRS-1/2 axis in an ER-dependent manner to drive PI3K/AKT and promote cancer cell survival, implicating ER in survival signaling induced by mTORC1 inhibition. Anti-estrogen treatment synergized with RAD001 to inhibit ER+ breast cancer cell growth. Inhibition of ER, IGF-1R/InsR, or IRS-1/2 suppressed AKT activation induced by mTORC1 inhibition. RAD001 primed IGF-1R/InsR for activation, which was enhanced by ER signaling. Post-menopausal patients with early-stage ER+ breast cancer were treated presurgically +/- the AI letrozole. Viable tumor fragments from surgical specimens were treated with RAD001 and/or OSI-906 ex vivo; RAD001 increased AKT activation, which was abrogated by presurgical letrozole. Letrozole decreased IGF-1R and IRS-1/2 tumor levels. These data suggest that ER drives PI3K/AKT activation in response to mTORC1 inhibition, providing molecular rationale for therapeutic combinations of anti-estrogens and mTORC1 inhibitors in endocrine-sensitive disease.

Positive prognostic value of HER2-HER3 co-expression and p-mTOR in gastric cancer patients

Background

The HER2-HER3 heterodimer significantly decreases survival in breast cancer patients. However, the prognostic value of HER2-HER3 overexpression remains unknown in gastric cancer (GC).

Methods

The expression levels of HER2, HER3, Akt, p-Akt, mTOR and p-mTOR were examined in specimens from 120 GC patients by immunohistochemistry and quantitative reverse transcription-PCR. The associations of HER proteins, PI3K/Akt/mTOR pathway-related proteins, clinicopathological features of GC, and overall survival (OS) were assessed. To comprehensively evaluate the prognostic values of pathway-related proteins, meta-analyses were conducted with STATA 11.0.

Results

HER2 overexpression was significantly associated with HER3 levels (P = 0.02). HER3 was highly expressed in gastric cancer tissues. High HER2 and HER3 levels were associated with elevated p-Akt and p-mTOR amounts (P < 0.05). Furthermore, HER2-HER3 co-expression was associated with high p-Akt and p-mTOR (P < 0.05) levels. Meanwhile, p-mTOR overexpression was tightly associated with differentiation, depth of invasion, lymph node metastasis, TNM stage and OS (P < 0.05). By meta-analyses, Akt, p-Akt, and mTOR levels were unrelated to clinicopathological characters. HER3 overexpression was associated with depth of invasion (OR = 2.39, 95%CI 1.62–3.54, P < 0.001) and lymph node metastasis (OR = 2.35, 95%CI 1.34–4.11, P = 0.003). Further, p-mTOR overexpression was associated with patient age, tumor location, depth of invasion (OR = 1.63, 95%CI 1.08–2.45, P = 0.02) and TNM stage (OR = 1.73, 95%CI 1.29–2.32, P < 0.001). In addition, HER2-HER3 overexpression corresponded to gradually shortened 5-year OS (P < 0.05), and significant relationships were shown among HER3, p-mTOR overexpression, and 1-, 3-, 5-year OS (P < 0.05).

Conclusions

HER2-HER3 co-expression may potentially enhance mTOR phosphorylation. HER2-HER3 co-expression and p-mTOR are both related to the prognosis of GC patients.

Electronic supplementary material

The online version of this article (10.1186/s12885-017-3851-y) contains supplementary material, which is available to authorized users.

Hepatocyte growth factor reduces sensitivity to the epidermal growth factor receptor-tyrosine kinase inhibitor, gefitinib, in lung adenocarcinoma cells harboring wild-type EGFR

Epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) therapy is an option for lung cancers harboring wild-type EGFR when chemotherapeutic reagents have failed. In this study, we found that the EGFR-TKI, gefitinib, modestly suppressed proliferation of the lung cancer cell lines, A549 and H358, which both harbor wild-type EGFR. Treatment with hepatocyte growth factor (HGF) reduced the sensitivity to gefitinib, whereas sensitivity was restored by treatment with an HGF antibody, a MET inhibitor, or depletion of MET but not ErbB3 gene. Moreover, both PI3K/mTOR inhibitors and MEK inhibitors suppressed proliferation of A549 cells, whereas only PI3K/mTOR inhibitors effectively suppressed cell viability of EGFR mutant PC-9 cells. Our findings suggest that HGF reduced the gefitinib sensitivity through MET and downstream PI3K and MAPK pathways. Combined use of EGFR-TKI and MET inhibitors or inhibition of downstream signaling molecules might be a better second or third line choice for a group of patients with advanced lung cancer harboring wild-type EGFR.

Upregulation of Bcl2 in NSCLC with acquired resistance to EGFR-TKI

Lung cancer has the highest incidence and mortality rate worldwide among all malignancy-associated mortalities, of which non-small cell lung cancer accounts for 80% of all cases. Resistance against epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) develops following 8–12 months of disease progression, and is a critical issue. HCC827 cell lines with resistance to EGFR-TKIs were successfully screened. The half maximal inhibitory concentration values were 1,000-fold higher than the values for the parental HCC827 cell line, thereby demonstrating cross-resistance against the same family of TKIs. The expression of B-cell lymphoma 2 (Bcl2) was markedly increased in the resistant clones, as well as in the patient biopsies. The phosphatase and tensin homolog phosphoinositide 3-kinase signaling axis is a potential mechanism for acquiring resistance, and therefore targeting Bcl2 may be a useful strategy for further investigations.

Recent advances of bispecific antibodies in solid tumors

Cancer immunotherapy is the most exciting advancement in cancer therapy. Similar to immune checkpoint blockade and chimeric antigen receptor T cell (CAR-T), bispecific antibody (BsAb) is attracting more and more attention as a novel strategy of antitumor immunotherapy. BsAb not only offers an effective linkage between therapeutics (e.g., immune effector cells, radionuclides) and targets (e.g., tumor cells) but also simultaneously blocks two different oncogenic mediators. In recent decades, a variety of BsAb formats have been generated. According to the structure of Fc domain, BsAb can be classified into two types: IgG-like format and Fc-free format. Among these formats, bispecific T cell engagers (BiTEs) and triomabs are commonly investigated. BsAb has achieved an exciting breakthrough in hematological malignancies and promising outcome in solid tumor as showed in various clinical trials. In this review, we focus on the preclinical experiments and clinical studies of epithelial cell adhesion molecule (EpCAM), human epidermal growth factor receptor (HER) family, carcinoembryonic antigen (CEA), and prostate-specific membrane antigen (PSMA) related BsAbs in solid tumors, as well as discuss the challenges and corresponding approaches in clinical application.

ErbB3 drives mammary epithelial survival and differentiation during pregnancy and lactation

Background

During pregnancy, as the mammary gland prepares for synthesis and delivery of milk to newborns, a luminal mammary epithelial cell (MEC) subpopulation proliferates rapidly in response to systemic hormonal cues that activate STAT5A. While the receptor tyrosine kinase ErbB4 is required for STAT5A activation in MECs during pregnancy, it is unclear how ErbB3, a heterodimeric partner of ErbB4 and activator of phosphatidyl inositol-3 kinase (PI3K) signaling, contributes to lactogenic expansion of the mammary gland.

Methods

We assessed mRNA expression levels by expression microarray of mouse mammary glands harvested throughout pregnancy and lactation. To study the role of ErbB3 in mammary gland lactogenesis, we used transgenic mice expressing WAP-driven Cre recombinase to generate a mouse model in which conditional ErbB3 ablation occurred specifically in alveolar mammary epithelial cells (aMECs).

Results

Profiling of RNA from mouse MECs isolated throughout pregnancy revealed robust Erbb3 induction during mid-to-late pregnancy, a time point when aMECs proliferate rapidly and undergo differentiation to support milk production. Litters nursed by ErbB3^KO dams weighed significantly less when compared to litters nursed by ErbB3^WT dams. Further analysis revealed substantially reduced epithelial content, decreased aMEC proliferation, and increased aMEC cell death during late pregnancy. Consistent with the potent ability of ErbB3 to activate cell survival through the PI3K/Akt pathway, we found impaired Akt phosphorylation in ErbB3^KO samples, as well as impaired expression of STAT5A, a master regulator of lactogenesis. Constitutively active Akt rescued cell survival in ErbB3-depleted aMECs, but failed to restore STAT5A expression or activity. Interestingly, defects in growth and survival of ErbB3^KO aMECs as well as Akt phosphorylation, STAT5A activity, and expression of milk-encoding genes observed in ErbB3^KO MECs progressively improved between late pregnancy and lactation day 5. We found a compensatory upregulation of ErbB4 activity in ErbB3^KO mammary glands. Enforced ErbB4 expression alleviated the consequences of ErbB3 ablation in aMECs, while combined ablation of both ErbB3 and ErbB4 exaggerated the phenotype.

Conclusions

These studies demonstrate that ErbB3, like ErbB4, enhances lactogenic expansion and differentiation of the mammary gland during pregnancy, through activation of Akt and STAT5A, two targets crucial for lactation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-017-0893-7) contains supplementary material, which is available to authorized users.

α-Catenin homodimers are recruited to phosphoinositide-activated membranes to promote adhesion

A unique feature of α-catenin localized outside the cadherin-catenin complex is its capacity to form homodimers, but the subcellular localization and functions of this form of α-catenin remain incompletely understood. We identified a cadherin-free form of α-catenin that is recruited to the leading edge of migrating cells in a phosphatidylinositol 3-kinase-dependent manner. Surface plasmon resonance analysis shows that α-catenin homodimers, but not monomers, selectively bind phosphatidylinositol-3,4,5-trisphosphate-containing lipid vesicles with high affinity, where three basic residues, K488, K493, and R496, contribute to binding. Chemical-induced dimerization of α-catenin containing a synthetic dimerization domain promotes its accumulation within lamellipodia and elaboration of protrusions with extended filopodia, which are attenuated in the α-catenin^KKR<3A mutant. Cells restored with a full-length, natively homodimerizing form of α-catenin^KKR<3A display reduced membrane recruitment, altered epithelial sheet migrations, and weaker cell-cell adhesion compared with WT α-catenin. These findings show that α-catenin homodimers are recruited to phosphoinositide-activated membranes to promote adhesion and migration, suggesting that phosphoinositide binding may be a defining feature of α-catenin function outside the cadherin-catenin complex.