Combination of EGFR Inhibitor Lapatinib and MET Inhibitor Foretinib Inhibits Migration of Triple Negative Breast Cancer Cell Lines

Targeting Receptor Tyrosine Kinases as a Novel Strategy for the Treatment of Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) comprises a group of aggressive and heterogeneous breast carcinoma. Chemotherapy is the mainstay for the treatment of triple-negative tumors. Nevertheless, the success of chemotherapeutic treatments is limited by their toxicity and development of acquired resistance leading to therapeutic failure and tumor relapse. Hence, there is an urgent need to explore novel targeted therapies for TNBC. Receptor tyrosine kinases (RTKs) are a family of transmembrane receptors that are key regulators of intracellular signaling pathways controlling cell proliferation, differentiation, survival, and motility. Aberrant activity and/or expression of several types of RTKs have been strongly connected to tumorigenesis. RTKs are frequently overexpressed and/or deregulated in triple-negative breast tumors and are further associated with tumor progression and reduced survival in patients. Therefore, targeting RTKs could be an appealing therapeutic strategy for the treatment of TNBC. This review summarizes the current evidence regarding the antitumor activity of RTK inhibitors in preclinical models of TNBC. The review also provides insights into the clinical trials evaluating the use of RTK inhibitors for the treatment of patients with TNBC.

Combinations of EGFR and MET inhibitors reduce proliferation and invasiveness of mucosal melanoma cells

Mucosal melanoma (MM) is a very rare and aggressive type of cancer for which immunotherapy or targeted therapy such as BRAF/MEK inhibitors, used in cutaneous melanoma, usually fail. Due to our earlier experience showing the high effectiveness of epidermal growth factor receptor (EGFR) and hepatocyte growth factor receptor (MET) inhibitors in reducing the activation of the MAPK and PI3K/AKT signalling pathways, we aim to test whether these drugs would also be effective for mucosal melanoma. Cells representing two commercially available mucosal melanoma cell lines (GAK and HMVII) and one cell line obtained from a patient's vaginal melanoma were treated with MET or EGFR inhibitors, or combinations of these agents. The dual-inhibitor treatment strategy resulted in a decrease of cell proliferation, migration and invasion. Moreover, combinations of inhibitors led to reduction of pEGFR/EGFR and pMET/MET ratio and downregulation of PI3K/AKT and MEK/ERK1/2-based signalling pathways. Our findings indicate a potential therapeutic strategy based on EGFR and MET inhibitors in mucosal melanoma, which should be further evaluated in vivo and in clinical experiments. They also suggest that targeting multiple receptor tyrosine kinases may block signalling crosstalk and possibly delay the appearance of resistance to kinase inhibitors in mucosal melanoma cells.

Cooperative regulation of coupled oncoprotein synthesis and stability in triple-negative breast cancer by EGFR and CDK12/13

Evidence has long suggested that epidermal growth factor receptor (EGFR) may play a prominent role in triple-negative breast cancer (TNBC) pathogenesis, but clinical trials of EGFR inhibitors have yielded disappointing results. Using a candidate drug screen, we identified that inhibition of cyclin-dependent kinases 12 and 13 (CDK12/13) dramatically sensitizes diverse models of TNBC to EGFR blockade. This combination therapy drives cell death through the 4E-BP1-dependent suppression of the translation and translation-linked turnover of driver oncoproteins, including MYC. A genome-wide CRISPR/Cas9 screen identified the CCR4-NOT complex as a major determinant of sensitivity to the combination therapy whose loss renders 4E-BP1 unresponsive to drug-induced dephosphorylation, thereby rescuing MYC translational suppression and promoting MYC stability. The central roles of CCR4-NOT and 4E-BP1 in response to the combination therapy were further underscored by the observation of CNOT1 loss and rescue of 4E-BP1 phosphorylation in TNBC cells that naturally evolved therapy resistance. Thus, pharmacological inhibition of CDK12/13 reveals a long-proposed EGFR dependence in TNBC that functions through the cooperative regulation of translation-coupled oncoprotein stability.

PELI1 and EGFR cooperate to promote breast cancer metastasis

Pellino-1 (PELI1) is an E3 ubiquitin ligase acting as a key regulator for the inflammation and autoimmunity via the ubiquitination of the substrate proteins. There is increasing evidence to support that PELI1 functions as an oncoprotein in tumorigenesis and metastasis. However, the molecular mechanism underlying the high expression and oncogenic roles of PELI1 in cancers remains limited. Herein, we revealed a novel regulation mechanism by which PELI1 and EGFR cooperate to promote breast cancer metastasis. EGFR is positively correlated with PELI1 expression in breast cancers, and its activation led to the phosphorylation of PELI1 at Tyr154 and Thr264, which subsequently activated its E3 ubiquitin ligase. Simultaneously, PELI1 physically interacted with and enhanced the stability of EGFR via the K63-linked polyubiquitination in reverse. The co-inhibition of the PELI1-EGFR showed synergetic effect to repress breast cancer metastasis. Furthermore, we identified a compound S62 as a small molecule disruptor of PELI1/EGFR that effectively repressed breast cancer metastasis. Our study not only uncovered the emerging roles of PELI1/EGFR interaction in the progression of breast cancer, but also provided an effective strategy for the inhibition of metastasis in breast cancer.

Foretinib Is Effective against Triple-Negative Breast Cancer Cells MDA-MB-231 In Vitro and In Vivo by Down-Regulating p-MET/HGF Signaling

This study investigated the antitumor effects of foretinib on triple-negative breast cancer cells MDA-MB-231 xenograft tumors in vivo underlying phosphorylated mesenchymal to epithelial transition (p-MET)/ hepatocyte growth factor (HGF)-related mechanism, as well as its pharmacokinetic characteristics. The MDA-MB-231 human breast cancer cell line was used for in vitro experiments, and the tumor xenograft model was established for in vivo experiments. MDA-MB-231 xenograft mice received oral foretinib (15 or 50 mg/kg/day) or vehicle for 18 days. The xenograft tumors were collected. Protein expressions of p-MET and HGF were examined with Western blotting and immunohistochemical staining. The mRNA expression of MET was examined with real-time PCR. Blood samples were collected from the mice treated with foretinib under different doses of 2, 10, and 50 mg/kg, and the pharmacokinetic profiles of foretinib were evaluated. We found that foretinib treatment caused a significant inhibition in tumor growth in a dose-dependent manner, whereas the continuous administration did not result in weight loss in treated nude mice. In both MDA-MB-231 cells and xenograft tumors, foretinib suppressed the expression of p-MET and HGF. These findings reveal that the decrease of p-MET and HGF may play an important role in the anti-breast cancer properties of foretinib.

Breast Cancer Antiestrogen Resistance 3 (BCAR3) promotes tumor growth and progression in triple-negative breast cancer

Triple-Negative Breast Cancers (TNBCs) constitute roughly 10-20% of breast cancers and are associated with poor clinical outcomes. Previous work from our laboratory and others has determined that the cytoplasmic adaptor protein Breast Cancer Antiestrogen Resistance 3 (BCAR3) is an important promoter of cell motility and invasion of breast cancer cells. In this study, we use both in vivo and in vitro approaches to extend our understanding of BCAR3 function in TNBC. We show that BCAR3 is upregulated in ductal carcinoma in situ (DCIS) and invasive carcinomas compared to normal mammary tissue, and that survival of TNBC patients whose tumors contained elevated BCAR3 mRNA is reduced relative to individuals whose tumors had less BCAR3 mRNA. Using mouse orthotopic tumor models, we further show that BCAR3 is required for efficient TNBC tumor growth. Analysis of publicly available RNA expression databases revealed that MET receptor signaling is strongly correlated with BCAR3 mRNA expression. A functional role for BCAR3-MET coupling is supported by data showing that both proteins participate in a single pathway to control proliferation and migration of TNBC cells. Interestingly, the mechanism through which this functional interaction operates appears to differ in different genetic backgrounds of TNBC, stemming in one case from potential differences in the strength of downstream signaling by the MET receptor and in another from BCAR3-dependent activation of an autocrine loop involving the production of HGF mRNA. Together, these data open the possibility for new approaches to personalized therapy for individuals with TNBCs.

TNBC: Potential Targeting of Multiple Receptors for a Therapeutic Breakthrough, Nanomedicine, and Immunotherapy

Triple-negative breast cancer (TNBC) is a heterogeneous, recurring cancer associated with a high rate of metastasis, poor prognosis, and lack of therapeutic targets. Although target-based therapeutic options are approved for other cancers, only limited therapeutic options are available for TNBC. Cell signaling and receptor-specific targets are reportedly effective in patients with TNBC under specific clinical conditions. However, most of these cancers are unresponsive, and there is a requirement for more effective treatment modalities. Further, there is a lack of effective biomarkers that can distinguish TNBC from other BC subtypes. ER, PR, and HER2 help identify TNBC and are widely used to identify patients who are most likely to respond to diverse therapeutic strategies. In this review, we discuss the possible treatment options for TNBC based on its inherent subtype receptors and pathways, such as p53 signaling, AKT signaling, cell cycle regulation, DNA damage, and programmed cell death, which play essential roles at multiple stages of TNBC development. We focus on poly-ADP ribose polymerase 1, androgen receptor, vascular endothelial growth factor receptor, and epidermal growth factor receptor as well as the application of nanomedicine and immunotherapy in TNBC and discuss their potential applications in drug development for TNBC.

Potentiating Therapeutic Effects of Epidermal Growth Factor Receptor Inhibition in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is a subset of breast cancer with aggressive characteristics and few therapeutic options. The lack of an appropriate therapeutic target is a challenging issue in treating TNBC. Although a high level expression of epidermal growth factor receptor (EGFR) has been associated with a poor prognosis among patients with TNBC, targeted anti-EGFR therapies have demonstrated limited efficacy for TNBC treatment in both clinical and preclinical settings. However, with the advantage of a number of clinically approved EGFR inhibitors (EGFRis), combination strategies have been explored as a promising approach to overcome the intrinsic resistance of TNBC to EGFRis. In this review, we analyzed the literature on the combination of EGFRis with other molecularly targeted therapeutics or conventional chemotherapeutics to understand the current knowledge and to provide potential therapeutic options for TNBC treatment.

Effects of Lapatinib on HER2-Positive and HER2-Negative Canine Mammary Carcinoma Cells Cultured In Vitro

HER2 is a prognostic and predictive marker widely used in breast cancer. Lapatinib is a tyrosine kinase inhibitor that works by blocking the phosphorylation of the receptor HER2. Its use is related to relatively good results in the treatment of women with HER2+ breast cancer. Thus, this study aimed to verify the effects of lapatinib on four canine primary mammary gland carcinoma cell cultures and two paired metastatic cell cultures. Cultures were treated with lapatinib at concentrations of 100, 500, 1000 and 3000 nM for 24 h and the 50% inhibitory concentration (IC₅₀) for each cell culture was determined. In addition, a transwell assay was performed to assess the ability of lapatinib to inhibit cell migration. Furthermore, we verified HER2 expression by RT-qPCR analysis of cell cultures and formalin-fixed paraffin-embedded tissues from samples corresponding to those used in cell culture. Lapatinib was able to inhibit cell proliferation in all cell cultures, but it was not able to inhibit migration in all cell cultures. The higher the expression of HER2 in a culture, the more sensitive the culture was to treatment. This relationship may be an indication that the expression of HER2 may be a predictive factor and opens a new perspective for the treatment of primary and metastatic mammary gland cancer.

MET and FASN as Prognostic Biomarkers of Triple Negative Breast Cancer: A Systematic Evidence Landscape of Clinical Study

Background

To know the expression of Mesenchymal–Epithelial Transition factor (MET) and Fatty Acid Synthase (FASN) in Triple Negative Breast Cancer (TNBC) patients, as well as its relationship with clinical pathological characteristic and prognosis.

Methods

we used immunohistochemistry staining to detect the expression of MET and FASN for those 218 TNBC patients, and analyze their relationship with the clinical pathological characteristic and prognosis.

Results

130 and 65 out of 218 TNBC patients were positive for MET in the cancer and adjacent tissues respectively. 142 and 30 out of 218 TNBC patients were positive for FASN in the cancer and adjacent tissues respectively. Positive expression of MET and FASN were significantly correlated with lymph node metastasis, pathological TNM, and pathological Stage. In addition, the positive expression of MET and FASN were correlated with recurrence and metastasis. The combined use of MET and FASN can better predict the survival condition.

Conclusions

Our results indicated that MET and FASN showed good predictive ability for TNBC. Combined use of MET and FASN were recommended in order to make a more accurate prognosis for TNBC.

Recent Progress in the Development of Quinoline Derivatives for the Exploitation of Anti-Cancer Agents

BACKGROUND

Along with the progress in medicine and therapies, the exploitation of anti-cancer agents focused more on the vital signaling pathways and key biological macromolecules. With rational design and advanced synthesis, quinoline derivatives have been utilized frequently in medicinal chemistry, especially in developing anti-cancer drugs or candidates.

METHODS

Using DOI searching, articles published before 2020 all over the world have been reviewed as comprehensively as possible.

RESULTS

In this review, we selected the representative quinoline derivate drugs in market or clinical trials, classified them into five major categories with detailed targets according to their main mechanisms, discussed the relationship within the same mechanism, and generated a summative discussion with prospective expectations. For each mechanism, the introduction of the target was presented, with the typical examples of quinoline derivate drugs.

CONCLUSION

This review has highlighted the quinoline drugs or candidates, suited them into corresponding targets in their pathways, summarized and discussed. We hope that this review may help the researchers who are interested in discovering quinoline derivate anti-cancer agents obtain considerable understanding of this specific topic. Through the flourishing period and the vigorous strategies in clinical trials, quinoline drugs would be potential but facing new challenges in the future.

Dual Inhibition of AKT and MEK Pathways Potentiates the Anti-Cancer Effect of Gefitinib in Triple-Negative Breast Cancer Cells

There is an unmet medical need for the development of new targeted therapeutic strategies for triple-negative breast cancer (TNBC). With drug combination screenings, we found that the triple combination of the protein kinase inhibitors (PKIs) of the epidermal growth factor receptor (EGFR), v-akt murine thymoma viral oncogene homolog (AKT), and MAPK/ERK kinase (MEK) is effective in inducing apoptosis in TNBC cells. A set of PKIs were first screened in combination with gefitinib in the TNBC cell line, MDA-MB-231. The AKT inhibitor, AT7867, was identified and further analyzed in two mesenchymal stem-like (MSL) subtype TNBC cells, MDA-MB-231 and HS578T. A combination of gefitinib and AT7867 reduced the proliferation and long-term survival of MSL TNBC cells. However, gefitinib and AT7867 induced the activation of the rat sarcoma (RAS)/ v-raf-1 murine leukemia viral oncogene homolog (RAF)/MEK/ extracellular signal-regulated kinase (ERK) pathway. To inhibit this pathway, MEK/ERK inhibitors were further screened in MDA-MB-231 cells in the presence of gefitinib and AT7867. As a result, we identified that the MEK inhibitor, PD-0325901, further enhanced the anti-proliferative and anti-clonogenic effects of gefitinib and AT7867 by inducing apoptosis. Our results suggest that the dual inhibition of the AKT and MEK pathways is a novel potential therapeutic strategy for targeting EGFR in TNBC cells.

Foretinib induces G2/M cell cycle arrest, apoptosis, and invasion in human glioblastoma cells through c-MET inhibition

PURPOSE

Glioblastoma multiforme (GBM) is one of the most aggressive human cancers. The c-MET receptor tyrosine kinase (RTK) which is frequently deregulated in GBM is considered as a promising target for GBM treatment. The c-MET plays a key role in cell proliferation, cell cycle progression, invasion, angiogenesis, and metastasis. Here, we investigated the anti-tumour activity of foretinib, a c-MET inhibitor, on three human GBM cells (T98G, U87MG and U251).

METHODS

Anti-proliferative effect of foretinib was determined using MTT, crystal violet staining, and clonogenic assays. PI and Annexin V/PI staining flow cytometry were used to evaluate the effects of foretinib on cell cycle and apoptosis, respectively. Scratch assay, qRT-PCR, western blot, and zymography analyses were applied to elucidate the molecular mechanisms underlying the anti-tumour activity of foretinib.

RESULTS

Foretinib treatment reduced phosphorylation of c-MET on T98G and U251 cells, but not in U87MG cells. The highest inhibitory effect was observed in T98G cells (IC₅₀ = 4.66 ± 0.29 µM) and the lowest one in U87MG cells (IC₅₀ = 29.99 ± 1.31 µM). The results showed that foretinib inhibited the proliferation of GBM cells through a G2/M cell cycle arrest and mitochondrial-mediated apoptosis in association with alternation in expression of the related genes and protein-regulated G2/M phase and apoptosis. Foretinib diminished GBM cell invasion through downregulation of the proteolytic cascade of MMP2, uPA and uPAR and epithelial-mesenchymal transition (EMT)-related genes. A different GBM cell sensitivity pattern was noticeable in all experiments which demonstrated T98G as a sensitive and U87MG as a resistant phenotype to foretinib treatment.

CONCLUSION

The results indicated that foretinib might have the therapeutic potential against human GBM which deserve further investigation.

Small-Molecule Drug Discovery in Triple Negative Breast Cancer: Current Situation and Future Directions

Triple negative breast cancer (TNBC) is the most aggressive subtype of breast cancer, but an effective targeted therapy has not been well-established so far. Considering the lack of effective targets, where do we go next in the current TNBC drug development? A promising intervention for TNBC might lie in de novo small-molecule drugs that precisely target different molecular characteristics of TNBC. However, an ideal single-target drug discovery still faces a huge challenge. Alternatively, other new emerging strategies, such as dual-target drug, drug repurposing, and combination strategies, may provide new insight into the improvement of TNBC therapeutics. In this review, we focus on summarizing the current situation of a series of candidate small-molecule drugs in TNBC therapy, including single-target drugs, dual-target drugs, as well as drug repurposing and combination strategies that will together shed new light on the future directions targeting TNBC vulnerabilities with small-molecule drugs for future therapeutic purposes.

Tweaking EMT and MDR dynamics to constrain triple-negative breast cancer invasiveness by EGFR and Wnt/β-catenin signaling regulation

PURPOSE

Due to a lack of effective targeted therapies, patients with metastatic triple-negative breast cancer (TNBC) have poor clinical outcomes. Epithelial to mesenchymal transition (EMT) is known to contribute to cancer progression, invasiveness and multidrug resistance (MDR). There is a strong correlation between various drug efflux mechanisms, cancer stem cells and tumor microenvironments, which in turn is synchronized by complex signaling crosstalk between EMT and MDR. We hypothesize that combining these regulatory connections with targeted combinatorial therapies may be an effective approach to annihilate the progression/metastasis of TNBC.

METHODS

AlamarBlue assays were used to depict TNBC cell viability, whereas flow cytometry was used to detect apoptotic cell populations, reactive-oxygen species (ROS) levels as well as mitochondrial depolarization. qRT-PCR, Western blotting and confocal microscopy were used to provide molecular-level information of the genes and proteins involved.

RESULTS

Our initial analyses showed that targeting EGFR by either erlotinib (EGFR inhibitor) or lapatinib (EGFR/HER-2 inhibitor) alone was ineffective against TNBC. Interestingly, we subsequently found that a low dose of lapatinib did act as a substrate rather than as an inhibitor facilitating EMT and MDR, leading to metastasis. Additional gene expression studies indicated that co-targeting the EGFR and Wnt/β-catenin pathways with lapatinib and XAV939 (a tankyrase inhibitor) promoted mesenchymal to epithelial transition (MET). Application of these inhibitors led to a 5.62-fold increase in the epithelial marker E-cadherin and a 3.33-fold decrease in the stemness marker EpCAM, with concomitant 1.5-fold and 3.22-fold reductions in the ABC transporters ABCB1 and ABCG2, respectively. These co-targeting effects resulted in overcoming EMT and MDR, which in turn was highlighted by reduced levels of pEGFR, pAKT, pMAPK, pSTAT-3, pGSK-3β and β-catenin.

CONCLUSIONS

Our data indicate that the synergistic action of targeting both the EGFR and Wnt/β-catenin signaling pathways in TNBC cells may open up new avenues for combatting this disease.

Dual inhibition of RNAi therapeutic miR-26a-5p targeting cMet and immunotherapy against EGFR in endometrial cancer treatment

Background

Precise prediction of drug combination targeting tumor cells effectively is a crucial challenge for tumor therapy, especially for endometrial cancer (EC). Considering the resistance, crosstalk that occurs between the receptor tyrosine kinase mesenchymal-epithelial transition factor (cMet) and epidermal growth factor receptor (EGFR), and their indispensable influence on the occurrence of EC, this study aimed to explore a novel therapeutic approach for EC treatment through blocking cMet and EGFR simultaneously.

Methods

In the present study, the expression of miR-26a-5p in EC cell lines was detected using quantitative real-time polymerase chain reaction assay. The potential role of miR-26a-5p in the development of EC was examined using cell counting kit assay, 5-ethynyl-2’- deoxyuridine staining, wound healing assay, and cell apoptosis staining assay. Subsequently, the effect of upregulated miR-26a-5p in vivo was confirmed on a xenograft model. Luciferase reporter assay and Western blot analysis were performed to verify the relation between miR-26a-5p and cMet. Furthermore, the dual therapeutic effect of miR-26a-5p and EGFR monoclonal antibody cetuximab was confirmed in vivo and in vitro.

Results

The results indicated that miR-26a-5p expression significantly reduced in EC cell lines compared with the normal endometrial cell line. Furthermore, the overexpression of miR-26a-5p inhibited the progression of EC, including cell migration, cell proliferation, and cell apoptosis in vivo and in vitro. Subsequently, mir-26a-5p regulated the expression of cMet and the downstream the hepatocyte growth factor (HGF)/cMet pathway, thus exerting an inhibitory effect on EC cells. In addition, the study also demonstrated that the upregulation of miR-26a-5p could significantly enhance the inhibitory effect of cetuximab compared with the use of cetuximab alone in vivo and in vitro.

Conclusions

RNAi therapeutic miR-26a-5p suppressed the progression of EC through regulating the cMet/HGF pathway. The dual therapy using RNA interference and neutralizing antibody simultaneously blocked tumor targets, including cMet and EGFR, thus providing a novel approach for overcoming the resistance to the inhibitors against a single target in EC treatment.

A Fluorescent Gelatin Degradation Assay to Study Melanoma Breakdown of Extracellular Matrix

In order to protrude within a dense tissue, tumor cells have to develop the ability to digest the extracellular matrix (ECM). Melanoma cells, similarly to other types of tumor cells, form invadopodia, membranous invaginations rich in filamentous actin and several other proteins including matrix metalloproteinases (MMPs). MMPs degrade ECM structural proteins such as collagens, fibronectin, or laminin. Here we describe an assay that allows the detection of gelatinase activity exhibited by tumor cells under 2D conditions and methods to present obtained data in both a quantitative and a qualitative manner.

MERTK in cancer therapy: Targeting the receptor tyrosine kinase in tumor cells and the immune system

The receptor tyrosine kinase MERTK is aberrantly expressed in numerous human malignancies, and is a novel target in cancer therapeutics. Physiologic roles of MERTK include regulation of tissue homeostasis and repair, innate immune control, and platelet aggregation. However, aberrant expression in a wide range of liquid and solid malignancies promotes neoplasia via growth factor independence, cell cycle progression, proliferation and tumor growth, resistance to apoptosis, and promotion of tumor metastases. Additionally, MERTK signaling contributes to an immunosuppressive tumor microenvironment via induction of an anti-inflammatory cytokine profile and regulation of the PD-1 axis, as well as regulation of macrophage, myeloid-derived suppressor cell, natural killer cell and T cell functions. Various MERTK-directed therapies are in preclinical development, and clinical trials are underway. In this review we discuss MERTK inhibition as an emerging strategy for cancer therapy, focusing on MERTK expression and function in neoplasia and its role in mediating resistance to cytotoxic and targeted therapies as well as in suppressing anti-tumor immunity. Additionally, we review preclinical and clinical pharmacological strategies to target MERTK.

MERTK in cancer therapy: Targeting the receptor tyrosine kinase in tumor cells and the immune system

The receptor tyrosine kinase MERTK is aberrantly expressed in numerous human malignancies, and is a novel target in cancer therapeutics. Physiologic roles of MERTK include regulation of tissue homeostasis and repair, innate immune control, and platelet aggregation. However, aberrant expression in a wide range of liquid and solid malignancies promotes neoplasia via growth factor independence, cell cycle progression, proliferation and tumor growth, resistance to apoptosis, and promotion of tumor metastases. Additionally, MERTK signaling contributes to an immunosuppressive tumor microenvironment via induction of an anti-inflammatory cytokine profile and regulation of the PD-1 axis, as well as regulation of macrophage, myeloid-derived suppressor cell, natural killer cell and T cell functions. Various MERTK-directed therapies are in preclinical development, and clinical trials are underway. In this review we discuss MERTK inhibition as an emerging strategy for cancer therapy, focusing on MERTK expression and function in neoplasia and its role in mediating resistance to cytotoxic and targeted therapies as well as in suppressing anti-tumor immunity. Additionally, we review preclinical and clinical pharmacological strategies to target MERTK.

Crizotinib induced antitumor activity and synergized with chemotherapy and hormonal drugs in breast cancer cells via downregulating MET and estrogen receptor levels

MET is a receptor tyrosine kinase known to drive neoplastic transformation and aggressive tumor phenotypes. Crizotinib is an oral multi-targeted tyrosine kinase inhibitor of MET, ALK, RON, and ROS1 kinases. In this study, the anticancer effects of crizotinib on breast cancer cells were investigated in vitro along with the molecular mechanisms associated with these effects. Besides, the antiproliferative effects of crizotinib in combination with chemotherapy, hormonal drugs, and targeted agents were examined. Results showed that crizotinib produced dose-dependent antiproliferative effects in BT-474 and SK-BR-3 breast cancer cells with IC₅₀ values of 1.7 μM and 5.2 μM, respectively. Crizotinib inhibited colony formation of BT-474 cells at low micromolar concentrations (1-5 μM). Immunofluorescence and Western blotting indicated that crizotinib reduced total levels of MET and estrogen receptor (ERα) in BT-474 cells. Also, crizotinib reduced the levels of phosphorylated (active) MET and HER2 in BT-474 cells. The combined treatment of crizotinib with doxorubicin and paclitaxel resulted in synergistic growth inhibition of BT-474 cells with combination index values of 0.46 and 0.35, respectively. Synergy was also observed with the combination of crizotinib with the hormonal drugs 4-hydroxytamoxifen and fulvestrant in BT-474 cells. Alternatively, the combination of crizotinib with lapatinib produced antagonistic antiproliferative effects in both BT-474 and SK-BR-3 cells. Collectively, these findings demonstrate the anticancer effects of crizotinib in breast cancer cells and reveal ERα as a potential therapeutic target of the drug apart from its classical kinase inhibitory activity. Crizotinib could be an appealing option in combination with chemotherapy or hormonal drugs for the management of breast cancer.

Targeting epidermal growth factor-overexpressing triple-negative breast cancer by natural killer cells expressing a specific chimeric antigen receptor

OBJECTIVES

Traditional cancer therapy and regular immunotherapy are ineffective for treating triple-negative breast cancer (TNBC) patients. Recently, chimeric antigen receptor-engineered natural killer cells (CAR NK) have been applied to target several hormone receptors on different cancer cells to improve the efficacy of immunotherapy. Furthermore, epidermal growth factor receptor (EGFR) is a potential therapeutic target for TNBC. Here, we demonstrated that EGFR-specific CAR NK cells (EGFR-CAR NK cells) could be potentially used to treat patients with TNBC exhibiting enhanced EGFR expression.

MATERIALS AND METHODS

We investigated the cytotoxic effects of EGFR-CAR NK cells against TNBC cells in vitro and in vivo. The two types of EGFR-CAR NK cells were generated by transducing lentiviral vectors containing DNA sequences encoding the single-chain variable fragment (scFv) regions of the two anti-EGFR antibodies. The cytotoxic and anti-tumor effects of the two cell types were examined by performing cytokine release and cytotoxicity assays in vitro, and tumor growth assays in breast cancer cell line-derived xenograft (CLDX) and patient-derived xenograft (PDX) mouse models.

RESULTS

Both EGFR-CAR NK cell types were activated by TNBC cells exhibiting upregulated EGFR expression and specifically triggered the lysis of the TNBC cells in vitro. Furthermore, the two EGFR-CAR NK cell types inhibited CLDX and PDX tumors in mice.

CONCLUSIONS

This study suggested that treatment with EGFR-CAR NK cells could be a promising strategy for TNBC patients.

Non-linear Deep Neural Network for Rapid and Accurate Prediction of Phenotypic Responses to Kinase Inhibitors

Protein kinase inhibitors are one of the most successful targeted therapies to date. Despite this progress, additional kinase inhibitors are needed to expand the target space as well as overcome drug resistance that has emerged in clinical setting. Here, we developed KiDNN (Kinase inhibitor prediction using Deep Neural Networks). KiDNN utilizes non-linear, multilayer feedforward network that mimics complex and dynamic kinase-driven signaling pathways. We used KiDNN to predict the effect of ∼200 kinase inhibitors on migration of breast and liver cancer cells. We show that the prediction accuracy of KiDNN outperformed other prediction tools based on linear models. We validated that an inhibitor of tyrosine kinase receptors, and an inhibitor of Src family kinases, decreased migration of triple-negative breast cancer cells, consistent with the role of these kinases in driving motility. Overall, we show that non-linear, DNN-based models provide a powerful approach to in silico screen hundreds of kinase inhibitors.

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Deep Neural Networks mimic non-linear, complex intracellular signaling pathways

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Multi-phase grid search identified best networks with less computation time

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Prediction accuracy of KiDNN outperformed linear models

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KiDNN can accelerate drug discovery and development efforts

Expression level of EGFR and MET receptors regulates invasiveness of melanoma cells

Epidermal and hepatocyte growth factors can stimulate invasive abilities of melanoma cells, while treatment with combination of their receptors' (EGFR and MET, respectively) inhibitors reduces viability of these cells, as we have previously shown. Proposed therapy has potential; however, used drugs block more than one goal effectively, what raises the question about the real target of analysed inhibitors. For this reason, we analysed direct involvement of these receptors in the invasion of melanoma cells inducing EGFR and MET up‐ and down‐regulations in examined cells. Results were acquired with assays evaluating cell migration and invasion (scratch wound assay, Transwell filter‐based method and single‐cell tracking). We revealed that cells' motile abilities are increased after EGFR overexpression and decreased following EGFR and MET silencing. This outcome correlates with elevated (EGFR up‐regulation) or reduced (EGFR/MET down‐regulation) number of formed invadopodia, visualized with immunofluorescence, and their rate of proteolytic abilities, evaluated by fluorescent gelatin degradation assay, and gelatin zymography, compared to control cells. Above‐mentioned data indicate that both—EGFR and MET signalling is directly connected with melanoma cells invasion, what establishes these receptors as promising targets for anti‐cancer treatment.

Antitumor Activity of DFX117 by Dual Inhibition of c-Met and PI3Kα in Non-Small Cell Lung Cancer

Aberrant activation of hepatocyte growth factor (HGF)/c-Met signaling pathway caused by gene amplification or mutation plays an important role in tumorigenesis. Therefore, c-Met is considered as an attractive target for cancer therapy and c-Met inhibitors have been developed with great interests. However, cancers treated with c-Met inhibitors inevitably develop resistance commonly caused by the activation of PI3K/Akt signal transduction pathway. Therefore, the combination of c-Met and PI3Kα inhibitors showed synergistic activities, especially, in c-Met hyperactivated and PIK3CA-mutated cells. In our previous study, we rationally designed and synthesized DFX117(6-(5-(2,4-difluorophenylsulfonamido)-6-methoxypyridin-3-yl)-N-(2-morpholinoethyl) imidazo[1,2-a]pyridine-3-carboxamide) as a novel PI3Kα selective inhibitor. Herein, the antitumor activity and underlying mechanisms of DFX117 against non-small cell lung cancer (NSCLC) cells were evaluated in both in vitro and in vivo animal models. Concurrent targeted c-Met and PI3Kα by DFX117 dose-dependent inhibited the cell growth of H1975 cells (PIK3CA mutation and c-Met amplification) and A549 cells (KRAS mutation). DFX117 subsequently induced G0/G1 cell cycle arrest and apoptosis. These data highlight the significant potential of DFX117 as a feasible and efficacious agent for the treatment of NSCLC patients.