Lapatinib and HER2 status: results of a meta-analysis of randomized phase III trials in metastatic breast cancer

Human Blood Serum Counteracts EGFR/HER2-Targeted Drug Lapatinib Impact on Squamous Carcinoma SK-BR-3 Cell Growth and Gene Expression

Lapatinib is a targeted therapeutic inhibiting HER2 and EGFR proteins. It is used for the therapy of HER2-positive breast cancer, although not all the patients respond to it. Using human blood serum samples from 14 female donors (separately taken or combined), we found that human blood serum dramatically abolishes the lapatinib-mediated inhibition of growth of the human breast squamous carcinoma SK-BR-3 cell line. This antagonism between lapatinib and human serum was associated with cancelation of the drug induced G1/S cell cycle transition arrest. RNA sequencing revealed 308 differentially expressed genes in the presence of lapatinib. Remarkably, when combined with lapatinib, human blood serum showed the capacity of restoring both the rate of cell growth, and the expression of 96.1% of the genes expression of which were altered by the lapatinib treatment alone. Co-administration of EGF with lapatinib also restores the cell growth and cancels alteration of expression of 95.8% of the genes specific to lapatinib treatment of SK-BR-3 cells. Differential gene expression analysis also showed that in the presence of human serum or EGF, lapatinib was unable to inhibit the Toll-Like Receptor signaling pathway and alter expression of genes linked to the Gene Ontology term of Focal adhesion.

Screening of phytochemicals as potential anti-breast cancer agents targeting HER2: an in-silico approach

Breast cancer is the most common cancer among women around the world. Human Epidermal growth factor Receptor-2 (HER2) is a membrane tyrosine kinase overexpressed in 30% of human breast cancers; thus, it serves as an important drug target. Currently available HER2 inhibitor lapatinib targets the ATP binding site of the cytoplasmic kinase domain, blocking autophosphorylation and activation of HER-2. However, it causes side effects like diarrhea, nausea, rash and possible liver toxicity. As phytochemicals have fewer side effects and are relatively affordable, they offer an effective alternative. Hence, we aimed to identify potential phytochemicals that could act as HER2 inhibitors employing computational methods such as molecular docking, molecular dynamic simulation, and ADMET prediction. Out of 1500 phytochemicals docked to the ATP binding site of the HER2 kinase domain, luxenchalcone, rhinacanthin Q, subtrifloralacton D, and 7,7″-dimethyllanaraflavone exhibited higher binding affinity than the reference inhibitor and satisfied the Lipinski's rule of five. Analysis of molecular dynamics simulation trajectory showed that Rhinacanthin Q, subtrifloralacton D, and 7,7″-dimethyllanaraflavone formed a stable and compact complex without vast conformational fluctuations. MM/PBSA binding free energy analysis revealed that Rhinacanthin Q, subtrifloralacton D, and 7,7″-dimethyllanaraflavone have high binding affinity to HER2. Therefore, Rhinacanthin Q, subtrifloralacton D, and 7,7″-dimethyllanaraflavone could be potential bioactive molecules to act as inhibitor of HER2 protein. Eventually, experimental studies are needed to evaluate the potentials of these phytochemicals further. The development of drug for HER2 positive breast cancer could be accelerated with the findings of our research. Communicated by Ramaswamy H. Sarma.

Comparative review of pharmacological therapies in individuals with HER2-positive advanced breast cancer with focus on hormone receptor subgroups

Breast cancer is the fifth leading cause of cancer-related deaths worldwide. The randomized controlled trials (RCTs) of targeted therapies in human epidermal receptor 2 (HER2)-positive advanced breast cancer (ABC) have provided an evidence base for regulatory and reimbursement agencies to appraise the use of cancer therapies in clinical practice. However, a subset of these patients harbor additional biomarkers, for example, a positive hormone receptor status that may be more amenable to therapy and improve overall survival (OS). This review seeks to explore the reporting of evidence for treatment effects by the hormone receptor status using the RCT evidence of targeted therapies for HER2-positive ABC patients. Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines were followed to identify published RCTs. Extracted data were synthesized using network meta-analysis to obtain the relative effects of HER2-positive-targeted therapies. We identified a gap in the reporting of the effectiveness of therapies by the hormone receptor status as only 15 out of 42 identified RCTs reported hormone receptor subgroup analyses; the majority of which reported progression-free survival but not OS or the overall response rate. In conclusion, we recommend that future trials in ABC should report the effect of cancer therapies in hormone receptor subgroups for all outcomes.

A novel treatment strategy for lapatinib resistance in a subset of HER2-amplified gastric cancer

Background

Gastric cancer (GC) is one of the leading causes of cancer-related deaths worldwide. Human epidermal growth factor receptor 2 (HER2) amplification occurs in approximately 13–23% of all GC cases and patients with HER2 overexpression exhibit a poor prognosis. Lapatinib, a dual EGFR/HER2 tyrosine kinase inhibitor, is an effective agent to treat HER2-amplified breast cancer but it failed in gastric cancer (GC) clinical trials. However, the molecular mechanism of lapatinib resistance in HER2-amplified GC is not well studied.

Methods

We employed an unbiased, genome-scale screening with pooled CRISPR library on HER2-amplified GC cell lines to identify genes that are associated with resistance to lapatinib. To validate the candidate genes, we applied in vitro and in vivo pharmacological tests to confirm the function of the target genes.

Results

We found that loss of function of CSK or PTEN conferred lapatinib resistance in HER2-amplified GC cell lines NCI-N87 and OE19, respectively. Moreover, PI3K and MAPK signaling was significantly increased in CSK or PTEN null cells. Furthermore, in vitro and in vivo pharmacological study has shown that lapatinib resistance by the loss of function of CSK or PTEN, could be overcome by lapatinib combined with the PI3K inhibitor copanlisib and MEK inhibitor trametinib.

Conclusions

Our study suggests that loss-of-function mutations of CSK and PTEN cause lapatinib resistance by re-activating MAPK and PI3K pathways, and further proved these two pathways are druggable targets. Inhibiting the two pathways synergistically are effective to overcome lapatinib resistance in HER2-amplified GC. This study provides insights for understanding the resistant mechanism of HER2 targeted therapy and novel strategies that may ultimately overcome resistance or limited efficacy of lapatinib treatment for subset of HER2 amplified GC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08283-9.

Development of acquired resistance to lapatinib may sensitise HER2-positive breast cancer cells to apoptosis induction by obatoclax and TRAIL

Background

Lapatinib has clinical efficacy in the treatment of trastuzumab-refractory HER2-positive breast cancer. However, a significant proportion of patients develop progressive disease due to acquired resistance to the drug. Induction of apoptotic cell death is a key mechanism of action of lapatinib in HER2-positive breast cancer cells.

Methods

We examined alterations in regulation of the intrinsic and extrinsic apoptosis pathways in cell line models of acquired lapatinib resistance both in vitro and in patient samples from the NCT01485926 clinical trial, and investigated potential strategies to exploit alterations in apoptosis signalling to overcome lapatinib resistance in HER2-positive breast cancer.

Results

In this study, we examined two cell lines models of acquired lapatinib resistance (SKBR3-L and HCC1954-L) and showed that lapatinib does not induce apoptosis in these cells. We identified alterations in members of the BCL-2 family of proteins, in particular MCL-1 and BAX, which may play a role in resistance to lapatinib. We tested the therapeutic inhibitor obatoclax, which targets MCL-1. Both SKBR3-L and HCC1954-L cells showed greater sensitivity to obatoclax-induced apoptosis than parental cells. Interestingly, we also found that the development of acquired resistance to lapatinib resulted in acquired sensitivity to TRAIL in SKBR3-L cells. Sensitivity to TRAIL in the SKBR3-L cells was associated with reduced phosphorylation of AKT, increased expression of FOXO3a and decreased expression of c-FLIP. In SKBR3-L cells, TRAIL treatment caused activation of caspase 8, caspase 9 and caspase 3/7. In a second resistant model, HCC1954-L cells, p-AKT levels were not decreased and these cells did not show enhanced sensitivity to TRAIL. Furthermore, combining obatoclax with TRAIL improved response in SKBR3-L cells but not in HCC1954-L cells.

Conclusions

Our findings highlight the possibility of targeting altered apoptotic signalling to overcome acquired lapatinib resistance, and identify potential novel treatment strategies, with potential biomarkers, for HER2-positive breast cancer that is resistant to HER2 targeted therapies.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4852-1) contains supplementary material, which is available to authorized users.

Novel Systemic Therapies for Advanced Gastric Cancer

Gastric cancer (GC) is the second leading cause of cancer mortality and the fourth most commonly diagnosed malignant diseases. While continued efforts have been focused on GC treatment, the introduction of trastuzumab marked the beginning of a new era of target-specific treatments. Considering the diversity of mutations in GC, satisfactory results obtained from various target-specific therapies were expected, yet most of them were unsuccessful in controlled clinical trials. There are several possible reasons underlying the failures, including the absence of patient selection depending on validated predictive biomarkers, the inappropriate combination of drugs, and tumor heterogeneity. In contrast to targeted agents, immuno-oncologic agents are designed to regulate and boost immunity, are not target-specific, and may overcome tumor heterogeneity. With the successful establishment of predictive biomarkers, including Epstein-Barr virus pattern, microsatellite instability status, and programmed death-ligand 1 (PD-L1) expression, as well as ideal combination regimens, a new frontier in the immuno-oncology of GC treatment is on the horizon. Since the field of immuno-oncology has witnessed innovative, practice-changing successes in other cancer types, several trials on GC are ongoing. Among immuno-oncologic therapies, immune checkpoint inhibitors are the mainstay of clinical trials performed on GC. In this article, we review target-specific agents currently used in clinics or are undergoing clinical trials, and highlight the future clinical application of immuno-oncologic agents in inoperable GC.

Evaluation of the EGFR polymorphism R497K in two cohorts of neoadjuvantly treated breast cancer patients

Pathological response of breast cancer to neoadjuvant chemotherapy (NAC) presents great variability, and new prognostic biomarkers are needed. Our aim was to evaluate the association of the epidermal growth factor receptor gene (EGFR) polymorphism R497K (rs2227983) with prognostic features and clinical outcomes of breast cancer, including the pathological response to NAC and the recurrence-free survival (RFS). Tumoral complete response (tCR) was defined by no remaining invasive cancer in the excised breast, whereas pathological complete response (pCR) was defined by no remaining invasive cancer both in the excised breast and lymph nodes. Two independent cohorts were analyzed: one from Brazil (INCA, n = 288) and one from The Netherlands (NKI-AVL, n = 255). In the INCA cohort, the variant (Lys-containing) genotypes were significantly associated with lower proportion of tCR (ORadj = 0.92; 95%CI = 0.85-0.99), whereas in the NKI-AVL cohort they were associated with tumor grade 3 (p = 0.035) and with triple-negative subtype (p = 0.032), but not with clinical outcomes. Such distinct prognostic associations may have arisen due to different neoadjuvant protocols (p < 0.001), or to lower age at diagnosis (p < 0.001) and higher proportion of tumor grade 3 (p = 0.018) at the NKI-AVL cohort. Moreover, NKI-AVL patients achieved better proportion of pCR (21.2% vs 8.3%, p < 0.001) and better RFS (HRadj = 0.48; 95% adjCI = 0.26-0.86) than patients from INCA. In conclusion, large scale studies comprehending different populations are needed to evaluate the impact of genome variants on breast cancer outcomes.

Challenges and future of biomarker tests in the era of precision oncology: Can we rely on immunohistochemistry (IHC) or fluorescence in situ hybridization (FISH) to select the optimal patients for matched therapy?

Molecular techniques have improved our understanding of the pathogenesis of cancer development. These techniques have also fueled the rational development of targeted drugs for patient populations stratified by their genetic characteristics. These novel methods have changed the classic paradigm of diagnostic pathology; among them are IHC, FISH, polymerase chain reaction (PCR) and microarray technology. IHC and FISH detection methods for human epidermal growth factor receptor-2 (HER2), epidermal growth factor receptor (EGFR) and programmed death ligand-1 (PD-L1) were recently approved by the Food and Drug Administration (FDA) as routine clinical practice for cancer patients. Here, we discuss general challenges related to the predictive power of these molecular biomarkers for targeted therapy in cancer medicine. We will also discuss the prospects of utilizing new biomarkers for fibroblast growth factor receptor (FGFR) and hepatocyte growth factor receptor (cMET/MET) targeted therapies for developing new and robust predictive biomarkers in oncology.

Increased life expectancy as a result of non-hormonal targeted therapies for HER2 or hormone receptor positive metastatic breast cancer: A systematic review and meta-analysis

This article aimed to assess the clinical effectiveness of non-hormonal targeted therapies (TTs) in terms of increase of median progression-free survival (PFS) and overall survival (OS) in receptor-positive metastatic breast cancer (MBC) patients by performing a systematic review and meta-analysis. We systematically searched relevant randomized controlled trials and extracted data about number of patients on targeted and comparator therapy, receptor status, line of treatment, median PFS and OS, p values, hazard ratios (HRs) and 95% confidence intervals (CI). Inverse variance was used to estimate pooled HRs, chi-square test for heterogeneity and Jadad scale for quality were applied. Thirty-eight studies (n=17,192 patients) were eligible for inclusion. TTs added 3.3months to the median PFS [0.7-9.6; HRs 0.74, 95% CI 0.71-0.77] of receptor-positive MBC patients and prolonged their median OS with 3.5months [0-4.7; HRs 0.90, 95% CI 0.82-0.98]. The highest increase in median PFS of 3.6months was found in HER2-/hormone receptor(HR)+ patients, while the highest increase in median OS of 7.2months was observed in HER2+/HRmixed status patients. First-line TTs were most effective in increasing the median PFS in the HR+/HER2- group with 2.0months, and in the HER2+/HRmixed group by adding 4.7months to the median OS. Second-line TTs were most effective for HER2-/HR+ patients by adding 2.6months to their PFS, and for HER2+/HRmixed patients by adding 3.1months to their median OS. Albeit small, the gain in months of median PFS and median OS was significant. Importantly, the results reported show large variation, and thus routinely applying a personalized approach seems warranted.

Phase II studies of two different schedules of dasatinib in bone metastasis predominant metastatic breast cancer: SWOG S0622

Bone metastases from breast cancer are common, causing significant morbidity. Preclinical data of dasatinib, an oral small molecule inhibitor of multiple oncogenic tyrosine kinases, suggested efficacy in tumor control and palliation of bone metastases in metastatic breast cancer (MBC). This clinical trial aimed to determine whether treatment with either of 2 dose schedules of dasatinib results in a progression-free survival (PFS) >50 % at 24 weeks in bone metastasis predominant MBC, to evaluate the toxicity of the 2 dosing regimens, and explore whether treatment results in decreased serum bone turnover markers and patient-reported "worst pain." Subjects with bone metastasis predominant MBC were randomly assigned to either 100 mg of dasatinib once daily, or 70 mg twice daily, with treatment continued until time of disease progression or intolerable toxicity. Planned accrual was 40 patients in each arm. The primary trial endpoint was PFS, defined as time from registration to progression or death due to any cause. Median PFS for all eligible patients (79) was 12.6 weeks (95 % CI 9.1-16.7). Neither cohort met the threshold for further clinical interest. There were no significant differences in PFS by randomized treatment arm (p = 0.85). Toxicity was similar in both cohorts, with no clear trend in serum biomarkers of bone turnover or patient-reported pain. Dasatinib was ineffective in controlling bone-predominant MBC in a patient population, unselected by molecular markers. Further study of dasatinib in breast cancer should not be pursued unless performed in molecularly determined patient subsets, or rational combinations.

Changing strategies for target therapy in gastric cancer

In spite of a worldwide decrease in the incidence of gastric cancer, this malignancy still remains one of the leading causes of cancer mortality. Great efforts have been made to improve treatment outcomes in patients with metastatic gastric cancer, and the introduction of trastuzumab has greatly improved the overall survival. The trastuzumab treatment took its first step in opening the era of molecular targeted therapy, however several issues still need to be resolved to increase the efficacy of targeted therapy. Firstly, many patients with metastatic gastric cancer who receive trastuzumab in combination with chemotherapeutic agents develop resistance to the targeted therapy. Secondly, many clinical trials testing novel molecular targeted agents with demonstrated efficacy in other malignancies have failed to show benefit in patients with metastatic gastric cancer, suggesting the importance of the selection of appropriate indications according to molecular characteristics in application of targeted agents. Herein, we review the molecular targeted agents currently approved and in use, and clinical trials in patients with metastatic gastric cancer, and demonstrate the limitations and future direction in treatment of advanced gastric cancer.

Lapatinib combined with neoadjuvant paclitaxel-trastuzumab-based chemotherapy in patients with human epidermal growth factor receptor 2-positive breast cancer: A meta-analysis of randomized controlled trials

The purpose of the present study was to quantify the cumulative randomized evidence for the efficacy and safety of lapatinib combined with neoadjuvant therapy in human epidermal growth factor receptor (HER) 2-positive breast cancer. Three electronic databases, MEDLINE, Embase and Cochrane Central Register of Controlled Trials, and the abstracts of major international conferences between inception and 15 December 2013 were searched. Two evaluators independently extracted data. The end-points assessed consisted of the pathological complete response (pCR) rate, breast-conserving surgery (BCS) rate and the occurrence of adverse events. Four randomized controlled trials were assessed in the present study, involving a total of 779 participants. Compared with the patients who did not receive lapatinib, the pCR rate was higher in the hormone receptor (HR)-positive [risk ratio (RR), 1.39; 95% confidence interval (CI), 1.12–1.72; P=0.002) and HR-negative (RR, 1.38; 95% CI, 1.14–1.68; P=0.0009) patients that received lapatinib. No significant difference between the BCS rate of the two treatment arms was observed in two trials (n=382; RR, 1.14; 95% CI, 0.89–1.47; P=0.31). The primary adverse events, including diarrhea, dermatological toxicity, hepatic toxicity and neutropenia, were statistically more frequent in patients that received lapatinib (RR, 2.46; 95% CI, 1.97–3.07; P<0.00001). The present analysis revealed that the addition of lapatinib to neoadjuvant chemotherapy for HER2-positive breast cancer improves the probability of achieving a higher pCR rate, but the use of lapatinib is associated with a higher risk of adverse events.

Optimal sequencing of anti-HER2 therapy throughout the continuum of HER2-positive breast cancer: evidence and clinical considerations

With the advent of the monoclonal antibody trastuzumab over 2 decades ago for breast cancer therapy, the outcome of patients with human epidermal growth factor receptor (HER) 2-positive disease has improved dramatically. Based on its substantial efficacy and good tolerability, trastuzumab has become the therapeutic gold standard for early as well as advanced breast cancer. Nevertheless, despite adjuvant trastuzumab, patients do experience recurrence and require further anti-HER2-targeted therapy. Next to the small molecule tyrosine kinase inhibitor lapatinib, which was the first approved therapy option after trastuzumab failure, several new anti-HER2 agents are currently already available for clinical use [i.e. pertuzumab, T-DM1 (trastuzumab emtansine)] or are still being evaluated (e.g. afatinib, neratinib). Recent evidence from neoadjuvant as well as metastatic therapy suggests that dual blockade may be superior to single-agent HER2 blockade. While the number of available or potential therapies has increased considerably, no additional predictive biomarkers beyond HER2 have been validated for the use of the different anti-HER2 therapies. Moreover, novel therapeutic concepts such as the antibody-drug conjugate T-DM1 warrant excellent determination methodology for HER2 and suggest re-evaluation of tumor biology upon first metastasis. The clinical challenge remains to optimally choose, utilize, and sequence anti-HER2 therapy in early as well as metastatic breast cancer. This article will provide evidence-based guidance for sequencing anti-HER2 therapy throughout the continuum of breast cancer therapy.

Emerging EGFR antagonists for breast cancer

INTRODUCTION

The EGFR has been associated with the pathogenesis and progression of breast cancer. Treatment based on an EGFR target is emerging as a promising option, especially in combination with conventional therapies. Unfortunately, there are no validated predictor biomarkers, and combinatorial treatments are meeting new resistance.

AREAS COVERED

The purpose of this review is to summarize the existing treatments and the current research based on targeting the EGFR pathway.

EXPERT OPINION

The existing EGFR treatments in breast cancer have shown limited benefit. The combination of the monoclonal antibody cetuximab and platinum salts achieves a 15 - 20% response rate. The effectiveness of tyrosine kinase inhibitors is not completely clear, showing modest or no benefits. Gefitinib treatment has offered some promising results in estrogen receptor + breast cancer. However, it has not been identified as a predictive factor for the appropriate selection of patients. Radioimmunotherapy with anti-EGFR radiolabeled antibodies is a promising strategy in BRCA-mutated breast cancer, but it still requires clinical confirmation. Nevertheless, the crosstalk between pathways frequently leads to treatment resistance. Current research is focused on increasing knowledge about the mechanisms of response and the discovery of predictive markers. Targeting several pathways simultaneously and a correct selection of patients seem essential.

Unraveling trastuzumab and lapatinib inefficiency in gastric cancer: Future steps (Review)

The newly developed concept of oncogene addiction provides a rationale for the use of targeted therapies. In sharp contrast to the field of breast cancer treatment, attempts to target human epidermal growth factor receptor 2 (HER2) among gastric cancer (GC) patients have been unsatisfactory. The ToGA trial reported only a modest prolongation of progression-free survival (PFS) with trastuzumab and the subsequent TYTAN and LOGiC trials failed to demonstrate any survival advantage with lapatinib. These results suggest that a response to the molecular-targeted therapies is achieved in only a fraction of the patients; in addition, even responders may experience secondary resistance, with the efficacy of the treatment being decreased or abrogated over a short period of time. Considering the increased recognition of primary or acquired resistance, recent investigations on targeted therapies have been primarily focused on determining in advance the mechanisms that may mediate resistance to treatment and the methods through which such obstacles may be circumvented. The proposed molecules or mechanisms that may be responsible for the development of resistance to single HER2-targeted therapy include a dimerization partner or crosstalk with HER2, such as HER3 and MET, as well as any subsequent activation of their downstream pathways, which exhibit a partial overlap with those of HER2. Furthermore, genetic alterations that stimulate the aberrant activation of the pathways downstream of HER2 may be the underlying mechanisms that restore prosurvival signaling. These mechanisms generate a complex signaling network with a significant potential for signal amplification and diversification. Although in the early stages of description, several compounds have been suggested as next generation treatments for GC, with expectations for their delineating the function of such receptors or molecules, with subsequent contributions of specific survival signaling blockades. This review focuses on the current achievements of anti-HER2 therapies in GC and the plausible mechanisms of resistance to these therapies. Elucidating these mechanisms of resistance may provide valuable information pertinent to the design of future strategies to improve molecular-targeted therapies.

Trichostatin A suppresses EGFR expression through induction of microRNA-7 in an HDAC-independent manner in lapatinib-treated cells

Lapatinib, a dual EGFR/HER2 tyrosine kinase inhibitor, has been shown to improve the survival rate of patients with advanced HER2-positive breast cancers. However, the off-target activity of lapatinib in inducing EGFR expression without tyrosine kinase activity was demonstrated to render HER2-negative breast cancer cells more metastatic, suggesting a limitation to the therapeutic effectiveness of this dual inhibitor in HER2-heterogeneous tumors. Therefore, targeting EGFR expression may be a feasible approach to improve the anticancer efficiency of lapatinib-based therapy. Inhibition of HDAC has been previously reported to epigenetically suppress EGFR protein expression. In this study, however, our data indicated that treatment with HDAC inhibitors trichostatin A (TSA), but not suberoylanilide hydroxamic acid (SAHA) or HDAC siRNA, can attenuate both protein and mRNA expressions of EGFR in lapatinib-treated triple-negative breast cancer cells, suggesting that TSA may suppress EGFR expression independently of HDAC inhibition. Nevertheless, TSA reduced EGFR 3′UTR activity and induced the gene expression of microRNA-7, a known EGFR-targeting microRNA. Furthermore, treatment with microRNA-7 inhibitor attenuated TSA-mediated EGFR suppression. These results suggest that TSA induced microRNA-7 expression to downregulate EGFR expression in an HDAC-independent manner.

shRNA kinome screen identifies TBK1 as a therapeutic target for HER2+ breast cancer

HER2(+) breast cancer is currently treated with chemotherapy plus anti-HER2 inhibitors. Many patients do not respond or relapse with aggressive metastatic disease. Therefore, there is an urgent need for new therapeutics that can target HER2(+) breast cancer and potentiate the effect of anti-HER2 inhibitors, in particular those that can target tumor-initiating cells (TIC). Here, we show that MMTV-Her2/Neu mammary tumor cells cultured as nonadherent spheres or as adherent monolayer cells select for stabilizing mutations in p53 that "immortalize" the cultures and that, after serial passages, sphere conditions maintain TICs, whereas monolayer cells gradually lose these tumorigenic cells. Using tumorsphere formation as surrogate for TICs, we screened p53-mutant Her2/Neu(+) tumorsphere versus monolayer cells with a lentivirus short hairpin RNA kinome library. We identified kinases such as the mitogen-activated protein kinase and the TGFβR protein family, previously implicated in HER2(+) breast cancer, as well as autophagy factor ATG1/ULK1 and the noncanonical IκB kinase (IKK), TANK-binding kinase 1 (TBK1), which have not been previously linked to HER2(+) breast cancer. Knockdown of TBK1 or pharmacologic inhibition of TBK1 and the related protein, IKKε, suppressed growth of both mouse and human HER2(+) breast cancer cells. TBK1/IKKε inhibition promoted cellular senescence by suppressing p65-NF-κB and inducing p16(Ink4a). In addition, TBK1/IKKε inhibition cooperated with lapatinib, a HER2/EGFR1-targeted drug, to accelerate apoptosis and kill HER2(+) breast cancer cells both in culture and in xenografts. Our results suggest that patients with HER2(+) breast cancer may benefit from anti-TBK1/IKKε plus anti-HER2 combination therapies and establish conditions that can be used to screen for additional TIC-specific inhibitors of HER2(+) breast cancer.

Emerging approaches for treating HER2-positive metastatic breast cancer beyond trastuzumab

Because metastatic breast cancer (MBC) is incurable in most cases, the goals of treatment are improvement in quality of life, management of symptoms, and prolonged survival. The human epidermal growth factor receptor 2 (HER2) is overexpressed in up to 30% of breast tumors, and before the development of HER-targeted therapy, HER2 positivity was predictive of poorer clinical outcomes. Trastuzumab and pertuzumab (anti-HER2 monoclonal antibodies), lapatinib (a small molecule inhibitor of HER2 and the epidermal growth factor receptor [EGFR]) are approved for treating HER2-positive MBC in the United States. Although trastuzumab plus chemotherapy is currently regarded as the first-line standard of care for HER2-positive MBC, it is not without shortcomings; these include its association with certain adverse events (e.g. cardiotoxic effect) and development of resistance. A number of investigational agents that target HER2 and other members of that receptor family are in clinical development for patients with HER2-positive MBC whose disease has progressed on trastuzumab. In addition, in an effort to overcome treatment resistance, clinical trials are evaluating combination therapy (investigational HER-targeted agents with trastuzumab or lapatinib). This review discusses recently completed and ongoing phase II and III clinical trials of investigational HER-targeted agents in the setting of trastuzumab-progressive, HER2-positive MBC.

Development of acneiform rash does not predict response to lapatinib treatment in patients with breast cancer

STUDY OBJECTIVE

To determine if development of acneiform rash is a predictor of objective response rate with lapatinib.

DESIGN

Subanalysis of data from a prospective, phase II study.

SETTING

Academic breast care clinic.

PATIENTS

Forty-nine treatment-naïve patients with human epidermal growth factor receptor-2 (HER2)-positive locally advanced breast cancer, who were treated with neoadjuvant lapatinib monotherapy for 6 weeks; 47 patients were included in the final analysis.

MEASUREMENTS AND MAIN RESULTS

Of the 49 patients enrolled, 33 (67%) developed a rash of any type, and 26 (55%) had acneiform rash. Of the 26 evaluable patients with acneiform rash (55%), 19 (73%) responded to lapatinib and 7 (27%) did not. Of the 21 evaluable patients without acneiform rash, 11 (67%) responded to treatment and 7 (33%) did not. Thus, no association was found between the occurrence of acneiform rash and response to lapatinib monotherapy.

CONCLUSION

This study does not support the development of the acneiform rash as a predictor of clinical efficacy of lapatinib in the treatment of breast cancer.

Lapatinib-mediated cyclooxygenase-2 expression via epidermal growth factor receptor/HuR interaction enhances the aggressiveness of triple-negative breast cancer cells

Lapatinib, a dual epidermal growth factor receptor (EGFR)/human epidermal growth factor receptor 2 (HER2) kinase inhibitor, showed clinical benefits in advanced HER2-positive breast cancer patients. Because some triple-negative breast cancers (TNBCs) frequently overexpress EGFR, the antitumor activity of lapatinib in such diseases was also tested. However, the results showed a worse event-free survival rate. It remains unknown whether and how lapatinib elicits the aggressiveness of such cancer cells. In this study, our results demonstrated that lapatinib facilitated axillary and lung metastases of triple-negative MDA-MB-231 breast cancer cells without affecting their viability, leading to worse survival in orthotopic xenograft mice. The lapatinib-increased motility was attributed by the elevation of EGFR through the downregulation of microRNA-7 and by the subsequent overexpression of cyclooxygenase-2 (COX-2). Strikingly, independent of its kinase activity, the elevated EGFR at least partly stabilized COX-2 expression by enhancing the binding of HuR to COX-2 mRNA. Our results suggest that lapatinib may increase the migration and invasion of MDA-MB-231 cells by upregulating EGFR and COX-2 through the downregulation of microRNA-7, providing a potential explanation for the worse clinical outcome of TNBC patients who receive lapatinib-based treatment. These findings also shed new light on the molecular mechanism of COX-2 mRNA stabilization by EGFR in a kinase-independent manner.

Advances in the management of HER2-positive advanced gastric and gastroesophageal junction cancer

In the past, patients with advanced or metastatic gastric or gastroesophageal junction cancer have had few treatment options and generally poor survival rates. The human epidermal growth factor receptor 2 (HER2) has been identified as a potential therapeutic target because of its overexpression or gene amplification in 6% to 35% of gastric or gastroesophageal junction cancers, although the methods of assessment and prognostic value of HER2 have been subject to debate. The phase III Trastuzumab for Gastric Cancer (ToGA) trial showed that adding the HER2-targeted humanized monoclonal antibody trastuzumab to chemotherapy significantly improves survival without negatively impacting quality of life in patients with advanced gastric or gastroesophageal junction cancer. As a result, trastuzumab is now the sole HER2-targeted therapy approved in several countries for this indication. The ToGA trial also demonstrated that patients who expressed higher levels of HER2 (determined by immunohistochemical screening) received the greatest benefit from trastuzumab therapy. This finding underlines the importance of accurate HER2 testing. Because of the unique characteristics of gastric cancer, a new gastric cancer-specific scoring system for HER2 expression was proposed during the ToGA trial. The aim of this review is to inform the gastroenterologist of the potential role of HER2-targeted therapy, to discuss the importance of accurate and reliable HER2 testing, and to discuss ongoing studies with HER2-targeted therapies that may have an impact on the future treatment of HER2-positive gastric cancer.