Lapatinib for breast cancer: a review of the current literature

Copper-Catalyzed Consecutive Ullmann, Decarboxylation, Oxidation, and Dehydration Reaction for Synthesis of Pyrrolo or Pyrido[1,2-a]imidazo[1,2-c]quinazolines

A protocol for a copper-catalyzed intermolecular cross-coupling cascade between 2-(2-bromoaryl)-1H-benzo[d]imidazole analogues and proline or pipecolic acid has been developed. The developed protocol allows access to a variety of synthetically useful N-fused pyrrolo or pyrido[1,2-a]imidazo[1,2-c]quinazoline scaffolds with high efficiency and good functional group compatibility. Proline or pipecolic acid plays a dual role in the reaction: as ligand and reactants. A mechanistically consecutive approach for the Ullmann coupling, decarboxylation, oxidation, and dehydration reaction process was presented.

Inhibition of mutationally activated HER2

Human epidermal growth factor receptor 2 (HER2) is an oncogenic driver and key therapeutic target for human cancers. Current therapies targeting HER2 are primarily based on overexpression of the wild-type form of HER2. However, kinase domain mutations have been identified that can increase the activity of HER2 even when expressed at basal levels. Using purified enzymes, we confirmed the hyperactivity of two HER2 mutants (D769Y and P780insGSP). To identify small molecule inhibitors against these cancer-associated variants, we used a combined approach consisting of biochemical testing, similarity-based searching, and in silico modeling. These approaches resulted in the identification of a candidate molecule that inhibits mutant forms of HER2 in vitro and in cell-based assays. Our structural model predicts that the compound takes advantage of water-mediated interactions in the HER2 kinase binding pocket.

Conformation-tunable ATP-competitive kinase inhibitors

Small molecule kinase inhibitors have shown immense clinical utility for diverse indications. While >60 kinase inhibitors have been approved (and many more in clinical trials), it remains unclear whether the clinical efficacy of a kinase inhibitor is solely dependent on enzymatic inhibition, or whether non-catalytic functions play a role in the efficacy of some kinase inhibitors. Here, we designed and synthesized a series of pyrazolopyrimidine kinase inhibitors that modulate the global kinase conformation of c-Src kinase. Expanding upon our findings from the pyrazolopyrimidine inhibitor series, we designed, synthesized, and evaluated three pair of conformation-selective kinase inhibitors, each with a unique hinge-binding scaffold. We profiled each pair of kinase inhibitors across 468 kinases and identified 38 kinases that could be studied using these pair of conformation-selective inhibitors. We also explore the binding of conformation-selective kinase inhibitors to mutant kinases of EGFR, FLT3, and KIT. Together, these studies yield important insight into the design of conformation-tunable kinase inhibitors and provide a toolset of compounds to study the role of protein conformation on kinase signaling.

Discovery and Pharmacological Evaluation of STEAP4 as a Novel Target for HER2 Overexpressing Breast Cancer

Breast cancer (BC) is a highly heterogeneous disease encompassing multiple subtypes with different molecular and histopathological features, disease prognosis, and therapeutic responses. Among these, the Triple Negative BC form (TNBC) is an aggressive subtype with poor prognosis and therapeutic outcome. With respect to HER2 overexpressing BC, although advanced targeted therapies have improved the survival of patients, disease relapse and metastasis remains a challenge for therapeutic efficacy. In this study the aim was to identify key membrane-associated proteins which are overexpressed in these aggressive BC subtypes and can serve as potential biomarkers or drug targets. We leveraged on the development of a membrane enrichment protocol in combination with the global profiling GeLC-MS/MS technique, and compared the proteomic profiles of a HER2 overexpressing (HCC-1954) and a TNBC (MDA-MB-231) cell line with that of a benign control breast cell line (MCF-10A). An average of 2300 proteins were identified from each cell line, of which approximately 600 were membrane-associated proteins. Our global proteomic methodology in tandem with invigoration by Western blot and Immunofluorescence analysis, readily detected several previously-established BC receptors like HER2 and EPHA2, but importantly STEAP4 and CD97 emerged as novel potential candidate markers. This is the first time that the mitochondrial iron reductase STEAP4 protein up-regulation is linked to BC (HER2+ subtype), while for CD97, its role in BC has been previously described, but never before by a global proteomic technology in TNBC. STEAP4 was selected for further detailed evaluation by the employment of Immunohistochemical analysis of BC xenografts and clinical tissue microarray studies. Results showed that STEAP4 expression was evident only in malignant breast tissues whereas all the benign breast cases had no detectable levels. A functional role of STEAP4 intervention was established in HER2 overexpressing BC by pharmacological studies, where blockage of the STEAP4 pathway with an iron chelator (Deferiprone) in combination with the HER2 inhibitor Lapatinib led to a significant reduction in cell growth in vitro. Furthermore, siRNA mediated knockdown of STEAP4 also suppressed cell proliferation and enhanced the inhibition of Lapatinib in HER2 overexpressing BC, confirming its potential oncogenic role in BC. In conclusion, STEAP4 may represent a novel BC related biomarker and a potential pharmacological target for the treatment of HER2 overexpressing BC.

Treatment of cancer cells with Lapatinib negatively regulates general translation and induces stress granules formation

Stress granules (SG) are cytoplasmic RNA granules that form during various types of stress known to inhibit general translation, including oxidative stress, hypoxia, endoplasmic reticulum stress (ER), ionizing radiations or viral infection. Induction of these SG promotes cell survival in part through sequestration of proapoptotic molecules, resulting in the inactivation of cell death pathways. SG also form in cancer cells, but studies investigating their formation upon treatment with chemotherapeutics are very limited. Here we identified Lapatinib (Tykerb / Tyverb®), a tyrosine kinase inhibitor used for the treatment of breast cancers as a new inducer of SG in breast cancer cells. Lapatinib-induced SG formation correlates with the inhibition of general translation initiation which involves the phosphorylation of the translation initiation factor eIF2α through the kinase PERK. Disrupting PERK-SG formation by PERK depletion experiments sensitizes resistant breast cancer cells to Lapatinib. This study further supports the assumption that treatment with anticancer drugs activates the SG pathway, which may constitute an intrinsic stress response used by cancer cells to resist treatment.

HLA-DRB1*07:01 and lapatinib-induced hepatotoxicity: a systematic review and meta-analysis

Associations between HLA-DRB1*07:01 and lapatinib-induced hepatotoxicity have been reported. To consolidate the results from all available reports in scientific databases, systematic review and meta-analysis techniques were used to quantify these associations. Studies investigating associations between HLA-DRB1*07:01 and lapatinib-induced hepatotoxicity were systematically searched in PubMed, Human Genome Epidemiology Network, and the Cochrane Library. Primary outcomes were the associations between HLA-DRB1*07:01 and lapatinib-induced hepatotoxicity. Overall odds ratios (ORs) with the corresponding 95%CIs were calculated using a random-effect model to determine the associations between HLA-DRB1*07:01 and lapatinib-induced hepatotoxicity. A clear association between HLA-DRB1*07:01 and lapatinib-induced hepatotoxicity was identified in our analyses. The summary OR was 6.23 (95%CI = 4.11-9.45). Similar associations were also found in the subgroup analyses by lapatinib treatment regimens. ORs were 10.04 (95%CI = 6.15-16.39), 8.65 (95%CI = 4.52-16.58), and 3.88 (95%CI = 2.20-6.82) in the lapatinib group, lapatinib + trastuzumab group, and lapatinib + chemotherapy or lapatinib + trastuzumab + chemotherapy group, respectively. Since HLA-DRB1*07:01 is associated with lapatinib-induced hepatotoxicity, genetic screening of HLA-DRB1*07:01 in breast cancer patients prior to lapatinib therapy is warranted for patient safety. In addition, further studies should define the risk of HLA-DRB1*07:01 and lapatinib-induced hepatotoxicity in specific ethnicities.

DCZ3112, a novel Hsp90 inhibitor, exerts potent antitumor activity against HER2-positive breast cancer through disruption of Hsp90-Cdc37 interaction

Hsp90 regulates the stability of oncoproteins important in tumor development and progression, and represents a potential therapeutic target. However, all Hsp90 inhibitors currently in clinical trials target Hsp90 ATPase activity and exhibit low selectivity and high toxicity. In this study, we discovered a new Hsp90 inhibitor, DCZ3112, with a novel mechanism of action. DCZ3112 directly bound to the N-terminal domain of Hsp90 and inhibited Hsp90-Cdc37 interaction without inhibiting ATPase activity. DCZ3112 inhibited the proliferation predominantly in HER2-positive breast cancer cells, including those resistant to the classical Hsp90 inhibitor geldanamycin, which mainly targets ATPase. DCZ3112 produced synergistic in vitro activity in inhibiting cell proliferation, inducing G₁-phase arrest and apoptosis, and reducing AKT and ERK phosphorylation. Consistent with this, DCZ3112 alone inhibited the growth of HER2-positive BT-474 xenografts, and exhibited enhanced antitumor activity when combined with the anti-HER2 antibody trastuzumab. Importantly, DCZ3112 also significantly inhibited the growth of trastuzumab-resistant BT-474 cells, and combined treatment retained synergistic antitumor activity. Thus, our findings show that disrupting Hsp90-Cdc37 interaction may represent a promising strategy against HER2-positive breast cancer, especially those with acquired resistance to trastuzumab.

Structural investigations on mechanism of lapatinib resistance caused by HER-2 mutants

HER-2 belongs to the human epidermal growth factor receptor (HER) family. Via different signal transduction pathways, HER-2 regulates normal cell proliferation, survival, and differentiation. Recently, it was reported that MCF10A, BT474, and MDA-MB-231 cells bearing the HER2 K753E mutation were resistant to lapatinib. Present study revealed that HER-2 mutant K753E showed some contrasting behaviour as compared to wild, L768S and V773L HER-2 in complex with lapatinib while similar to previously known lapatinib resistant L755S HER-2 mutant. Lapatinib showed stable but reverse orientation in binding site of K753E and the highest binding energy among studied HER2-lapatinib complexes but slightly lesser than L755S mutant. Results indicate that K753E has similar profile as L755S mutant for lapatinib. The interacting residues were also found different from other three studied forms as revealed by free energy decomposition and ligplot analysis.

Lapatinib induces autophagic cell death and differentiation in acute myeloblastic leukemia

Lapatinib is an oral-form dual tyrosine kinase inhibitor of epidermal growth factor receptor (EGFR or ErbB/Her) superfamily members with anticancer activity. In this study, we examined the effects and mechanism of action of lapatinib on several human leukemia cells lines, including acute myeloid leukemia (AML), chronic myeloid leukemia (CML), and acute lymphoblastic leukemia (ALL) cells. We found that lapatinib inhibited the growth of human AML U937, HL-60, NB4, CML KU812, MEG-01, and ALL Jurkat T cells. Among these leukemia cell lines, lapatinib induced apoptosis in HL-60, NB4, and Jurkat cells, but induced nonapoptotic cell death in U937, K562, and MEG-01 cells. Moreover, lapatinib treatment caused autophagic cell death as shown by positive acridine orange staining, the massive formation of vacuoles as seen by electronic microscopy, and the upregulation of LC3-II, ATG5, and ATG7 in AML U937 cells. Furthermore, autophagy inhibitor 3-methyladenine and knockdown of ATG5, ATG7, and Beclin-1 using short hairpin RNA (shRNA) partially rescued lapatinib-induced cell death. In addition, the induction of phagocytosis and ROS production as well as the upregulation of surface markers CD14 and CD68 was detected in lapatinib-treated U937 cells, suggesting the induction of macrophagic differentiation in AML U937 cells by lapatinib. We also noted the synergistic effects of the use of lapatinib and cytotoxic drugs in U937 leukemia cells. These results indicate that lapatinib may have potential for development as a novel antileukemia agent.

Activated estrogen receptor-mitogen-activated protein kinases cross talk confer acquired resistance to lapatinib

Background

The efficacy of lapatinib is limited by the development of acquired resistance. The aim of this study was to investigate the role of estrogen receptor (ER) signaling compensatory activation in acquired resistance to lapatinib in breast cancer cells BT474 and the related mechanism.

Methods

Acquired resistant cell model resistant (r)BT474 was generated with an increasing concentration of lapatinib. Real-time polymerase chain reaction and Western blotting were used to determine the changes of human epidermal growth factor receptor (HER)2 and ER pathways in breast cancer cell BT474 after treatment with lapatinib and the distinction between BT474 and rBT474. Methyl thiazolyl tetrazolium and colony formation assays were employed to detect the proliferation of rBT474 and BT474 cells treated with lapatinib and/or an ER inhibitor, fulvestrant, respectively.

Results

Lapatinib could inhibit phosphorylation of HER2 and induce expression of forkhead-box protein O3a and progesterone receptor. Acquired resistant cell model rBT474 could grow in the presence of 5 μM lapatinib, with an apoptosis rate of only 5%. Significant inhibition of phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/protein kinase B (AKT) pathway and the activation of the mitogen-activated protein kinases (MAPK) and ER pathways were detected in rBT474, compared with BT474. Furthermore, the expressions of Src phosphorylation and caveolin-1 were also upregulated. The viability of rBT474 was markedly suppressed by the lapatinib/fulvestrant combination in vitro, confirmed by the BT474 xenograft model.

Conclusion

ER signaling compensatory activation may partly contribute to lapatinib acquired resistance in HER2-overexpressing/ERα-positive breast cancer cells, which might be related to PI3K/AKT inhibition and MAPK pathway activation.

Lapatinib induces autophagic cell death and inhibits growth of human hepatocellular carcinoma

Lapatinib, an orally administered small-molecule tyrosine kinase inhibitor targeting epidermal growth factor receptors (EGFR) and Her2/Neu, has been widely accepted in the treatment of breast cancer. In this study, we found that lapatinib induced cytotoxicity in human hepatoma Huh7, HepG2 and HA22T cells. For the mode of cell death, we found lapatinib induced a higher percent of dead cells and a lower percent of hypodiploid cells, suggesting non-apoptotic cell death in lapatinib-treated hepatoma cells. Moreover, lapatinib-induced autophagy in hepatoma cells was confirmed by the detection of autophagic LC3-II conversion, the up-regulation of autophagy-related proteins, and the down-regulation of p62 by immunoblotting. Autophagic cell death was demonstrated by images of punctuated LC3 patterns, a higher percent of acridine orange positive cells, as well as a partial rescue of cell death by autophagy inhibitor 3-methyladenine or chloroquine. We also found massive vacuoles in lapatinib-treated hepatoma cells by electronic microscopy. In addition, the shRNA of knocked-down autophagy-related proteins rescued the hepatoma cells from lapatinib-induced growth inhibition. We also demonstrated a reduction of tumorigenesis by lapatinib in vivo. In conclusion, lapatinib induced autophagic cell death and the growth of human hepatoma cells. Our study provides potential cancer therapies by using lapatinib as a treatment for hepatoma.

TIMP-1 overexpression does not affect sensitivity to HER2-targeting drugs in the HER2-gene-amplified SK-BR-3 human breast cancer cell line

Tissue inhibitor of metalloproteinases-1 (TIMP-1) has been suggested as a marker of prognosis and response to treatment in breast cancer. In vitro, TIMP-1 can regulate shedding of the extracellular domain of HER2 and signalling via the Akt pathway, and we hypothesize that TIMP-1 therefore can affect sensitivity to the HER2-targeting drugs trastuzumab and lapatinib. SK-BR-3 human breast cancer cells were stably transfected with TIMP-1, characterized with regard to TIMP-1 protein expression, proliferation, and functionality of the secreted TIMP-1, and the sensitivity to trastuzumab and lapatinib was studied in five selected single-cell subclones expressing TIMP-1 protein at various levels plus the parental SK-BR-3 cell line. Both trastuzumab and lapatinib reduced cell viability, as determined by MTT assay, but the sensitivity to the drugs was not associated with the expression level of TIMP-1 protein. Western blotting showed that the activation of Akt, PTEN, and HER2 as well as ADAM10 was similar in all clones. In conclusion, in this model, TIMP-1 overexpression does not affect HER2 cleavage by ADAM10 or signalling via the Akt pathway, and TIMP-1 does not influence sensitivity to trastuzumab and lapatinib.

Predictive value of HER2 serum levels in patients treated with lapatinib or trastuzumab -- a translational project in the neoadjuvant GeparQuinto trial

BACKGROUND

We were able to demonstrate a predictive value of serum HER2 (sHER2) in patients receiving trastuzumab in the neoadjuvant GeparQuattro trial. However, the role of sHER2 in patients receiving neoadjuvant therapy (NT) with lapatinib is still unclear.

METHODS

The neoadjuvant GeparQuinto trial compared trastuzumab vs lapatinib in addition to chemotherapy in HER2-positive primary breast cancer patients. The sHER2 levels were measured by enzyme-linked immunosorbant assay in 210 patients, of whom 109 (52%) patients received trastuzumab and 101 (48%) lapatinib at three different time points.

RESULTS

Twenty-two percent of patients had elevated baseline sHER2 levels (>15 ng ml⁻¹). A decrease of sHER2 levels (>20%) in the trastuzumab and lapatinib-treated group during NT was seen in 44% and 24% of the patients, an increase of sHER2 levels (>20%) was seen in 6% and 41% of patients, respectively. Higher pre-chemotherapy sHER2 levels were associated with higher pathological complete remission (pCR) rates in the entire study cohort (OR 1.8, 95% CI 1.02-3.2, P=0.043). A decline of sHER2 levels (>20%) during NT was a predictor for pCR in the lapatinib-treated patient group (OR: 11.7, 95% CI 1.3-110, P=0.031).

CONCLUSION

Results of this study demonstrate that sHER2 levels change differently during NT depending on the anti-HER2 treatment strategy. Elevated baseline sHER2 levels (>15 ng ml⁻¹) and a decrease of sHER2 levels (>20%) early after therapy initiation are both relevant criteria to predict response to lapatinib-based treatment.

Targeting epidermal growth factor receptor in tumors: from conventional monoclonal antibodies via heavy chain-only antibodies to nanobodies

The discovery of naturally occurring heavy chain only antibodies and their further development into small recombinant 'nanobodies' offers attractive applications in drug targeting. Here, we describe the properties of nanobodies that have been developed to target the epidermal growth factor receptor (EGFR) and contrast these to the characteristics of heavy chain only antibodies and conventional antibodies. EGFR is overexpressed in many tumors and is an attractive target for tumor-directed drug targeting.

YB-1 drives preneoplastic progression: Insight into opportunities for cancer prevention

Surprisingly little is known about the underlying genetic events that trigger the progression of a normal cell into a cancerous cell. We recently developed a YB-1-driven model of pre-malignancy where we uncovered that the oncogene promotes genomic instability through cell cycle checkpoint slippage and centrosome amplification. In this research perspective, we describe a possible mechanism by which YB-1 instigates preneoplastic transformation. Using Kinex antibody microarrays with coverage of 800 proteins, we discovered that pre-malignant cells exhibit deregulated signal transduction along the HER2-MAPK-RSK axis. We will discuss the implications of these finding in regard to early intervention strategies.

Modular anti-EGFR and anti-Her2 targeting of SK-BR-3 and BT474 breast cancer cell lines in the presence of ErbB receptor-specific growth factors

Over the last decade, a number of monoclonal antibodies and small molecule inhibitors emerged as potent therapeutic agents in the treatment of Her2/neu overexpressing breast cancer. Numerous patients, however, do not adequately respond to anti-epidermal growth factor receptor (EGFR)/Her2 receptor targeting. Receptor- and, in turn, growth-stimulating effects, which potentially hamper antiproliferative cell treatment, have barely been investigated. BT474 and SK-BR-3 breast cancer cell lines were treated with Trastuzumab, Pertuzumab, and Lapatinib alone using different combinations and concentrations. Moreover, epidermal growth factor (EGF) or heregulin (HRG) was added to reveal potential growth factor-mediated compensatory effects. Receptor and intracellular signaling were analyzed as a function of cell treatment. Read-out parameters were cell proliferation and apoptosis. BT474 cells were efficiently driven into quiescence by Trastuzumab, but not by Pertuzumab treatment. Simultaneous EGF or HRG administration, however, restored the BT474 cell proliferation capacity. In contrast, neither therapeutic antibody treatment caused a profound inhibition of SK-BR-3 cell-cycle progress. Lapatinib turned out to be the most potent cell-cycle inhibitor in both cell lines even though its impact was significantly abrogated in the presence of EGF and HRG. The compensatory effect of EGF on Lapatinib-induced cell-cycle inhibition was reversed by Trastuzumab as well as by Pertuzumab treatment. Most importantly, HRG-caused compensation of Lapatinib-induced cell-cycle exit was reversed by Pertuzumab but not by Trastuzumab. Apparently, multiple anti-EGFR/Her2 targeting by using Trastuzumab, Pertuzumab, and Lapatinib more efficiently affects receptor function (interaction and activation) and consequently enhances their antiproliferative capacity. Growth inhibition by anticancer drugs targeted to Her/ErbB receptors, however, can be significantly undermined in the presence of EGF and in particular by HRG treatment, which suggests that specific therapeutic growth factor sequestration might further enhance anti-EGFR/Her2 targeting.

Autophagy facilitates the Lapatinib resistance of HER2 positive breast cancer cells

ErbB2 receptor (HER2) tyrosine kinase was overexpressed in about 25% breast cancers, and was correlated with extremely aggressive phenotype and poor prognosis. Lapatinib, an oral, reversible inhibitor of both ErbB2 and EGFR tyrosine kinases, was approved in combination with capecitabine for treating advanced stage ErbB2 positive breast cancers. However, the clinical response of Lapatinib was seriously limited by the drug resistance. We established the Lapatinib resistant breast cancer cell lines and the preliminary data demonstrated the increased autophagosome formation in the stable resistant cells. The resistant cells were re-sensitized to Lapatinib after treated with autophagy inhibitor. According to our preliminary data and related reference, we hypothesized that autophagy could facilitate the ErbB2 positive breast cancer cells to be Lapatinib resistant and promoted the survival of the resistant cells. The abrogation of autophagy might restore the drug sensitivity. Autophagy might be one of the targets to overcome the Lapatinib resistance.