Combined targeting of Raf and Mek synergistically inhibits tumorigenesis in triple negative breast cancer model systems

A potent formula against triple-negative breast cancer-sorafenib-carbon nanotubes-folic acid: Targeting, apoptosis triggering, and bioavailability enhancing

Triple-negative breast cancer (TNBC) has short survival rates. This study aimed to prepare a novel formula of sorafenib, carbon nanotubes (CNTs), and folic acid to be tested as a drug delivery system targeting versus TNBC compared with free sorafenib and to evaluate the formula stability, in vitro pharmacodynamic, and in vivo pharmacokinetic properties. The formula preparation was done by the synthesis of polyethylene glycol bis amine linker, CNT PEGylation, folic acid attachment, and sorafenib loading. The prepared formula has been characterized using X-ray diffraction, Flourier-transform infrared, 1HNMR, UV, high resolution-transmission electron microscope, field emission scanning electron microscopy, and Zeta potential. In vitro studies included drug release determination, MTT assay, flow cytometry to determine the apoptotic stage with percent, cell cycle analysis, and apoptotic marker assays for caspase-3, 8, 9, cytochrome c, and BCL-2. The in vivo study was performed to determine bioavailability and half-life in rats. The in vitro MTT antiproliferative assay revealed that the formula was threefold more cytotoxic toward TNBC cells than free sorafenib, and the flow cytometry showed a significant increase in apoptosis and necrosis. The formula has a greater inhibitory effect on BCL-2 and a lessening effect on cytochrome c and caspases 3, 8, and 9 than free sorafenib. In vivo experiments proved that our novel formula was superior to free sorafenib by increasing bioavailability by eight times and prolonging the half-life by three times. These results confirmed the successful preparation of the desired formula with better pharmacodynamic and pharmacokinetic properties. These promising results may show a novel therapeutic strategy for TNBC patients.

Triazole-Estradiol Analogs Induce Apoptosis and Inhibit EGFR and Its Downstream Pathways in Triple Negative Breast Cancer

Triple negative breast cancer, TNBC, is a difficult disease to treat due to relapse and resistance to known therapies. Epidermal growth factor receptor (EGFR), a tyrosine kinase responsible for downstream signaling leading to cell growth and survival, is typically overexpressed in TNBC. Our previous work has detailed the synthesis of triazole-estradiol derivatives as inhibitors of EGFR and downstream receptors, and this work continues that discussion by evaluating them in EGFR-dependent TNBC cell models MDA-MB-231 and MDA-MB-468. Compound Fz25 was cytotoxic against both MDA-MB-231 and MDA-MB-468 cell lines, yielding IC50 values of 8.12 ± 0.85 and 25.43 ± 3.68 µM, respectively. However, compounds Fz57 and Fz200 were potent against only MDA-MB-231 cells, generating IC50 values of 21.18 ± 0.23 and 10.86 ± 0.69 µM, respectively. Pathway analyses revealed that Fz25, Fz57 and Fz200 arrested the G0/G1 phase of the cell cycle and concomitantly suppressed cell cycle regulators, cyclin D1, cyclin E and Dyrk1B in MDA-MB-231 cells. Additionally, all compounds inhibited EGFR and its downstream signaling pathways-extracellular receptor kinase (ERK) and the mammalian target of rapamycin (mTOR)-in a dose-dependent manner. Furthermore, Fz25, Fz57 and Fz200 induced apoptosis in MDA-MB-231 cells by modulating morphological changes, including chromatin condensation, and attenuating the levels of cytochrome c, APAF1, caspases-3 and -9 as well as cleaved PARP. Of these compounds, only Fz25 showed overall satisfactory ADMET properties in silico. Similarly, Fz25 showed suitable binding parameters explored using molecular dynamic simulations in silico. These findings suggest that Fz25 warrants further preclinical and clinical investigations as a new generation of triazole congeners with significant potency in EFGR-dependent TNBC.

Antiproliferation and apoptosis studies of estrone pharmacophores in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer that shows high metastatic capability and poor prognosis. The aggressive behavior of TNBC may involve amplified EGFR expression. Currently, no targeted therapy has been approved for treating TNBC, which urgently needs novel treatment options. In this study, we report that estrone analogs with novel pharmacophores exhibited high potency toward TNBC cells through multiple mechanisms, inhibition of cell proliferation via EGFR receptor, and induction of mitochondrial apoptosis. Molecular docking studies revealed that hit analogs MMA307 and MMA321 were potent against the EGFR receptor (pdb code: 1M17) in silico and were over 10-fold more potent than sorafenib (positive control) when dosed against MDA-MB-468 cells in vitro. MMA307 and MMA321 induced mitochondrial apoptosis as characterized by condensed nuclei with fragmented chromatin, phosphatidylserine flip and modulated expressions of Apaf1, cytochrome c, and caspases 3 and 9. MMA307 and MMA321 inhibited TNBC proliferation through suppression of EGFR and activated EGFR (Y1068) expressions. Similarly, EGFR signaling pathways, RAF/ERK and AKT/mTOR, were inhibited as pARaf, pERK1/2 (characterizes RAF/ERK pathway) and pAKT, pmTOR, p70S6Kα (characterizes AKT/mTOR pathway) were all suppressed. Moreover, MMA307 and MMA321 inhibited TNBC cell growth through downregulation of cyclin D1 expression and arresting TNBC cells in the G1 phase of cell cycle. This study reports for the first time that estrone congeners with novel pharmacophores may be an effective therapy for TNBC. Findings from this research provide a solid foundation for further preclinical and clinical studies in developing estrone derivatives as novel TNBC therapeutics.

Identification of Lethal Inhibitors and Inhibitor Combinations for Mono-Driver versus Multi-Driver Triple-Negative Breast Cancer Cells

There are no signaling-based targeted therapies for triple-negative breast cancer. The development of targeted cancer therapy relies on identifying oncogenic signaling drivers, understanding their contributions to oncogenesis and developing inhibitors to block such drivers. In this study, we determine that DU-4475 is a mono-driver cancer cell line relying on BRAF and the mitogen-activated protein kinase pathway for viability and proliferation. It is fully and lethally inhibited by BRAF or Mek inhibitors at low nM concentrations, but it is resistant to inhibitors targeting other signaling pathways. The inhibitory lethality caused by blocking Mek or BRAF is through apoptosis. In contrast, MDA-MB-231 is a multi-driver triple-negative breast cancer cell line dependent on both Src and the KRAS-activated mitogen-activated kinase pathway for proliferation and viability. Blocking each pathway alone only partially inhibits cell proliferation without killing them, but the combination of dasatinib, an Src inhibitor, and trametinib, a Mek inhibitor, achieves synthetic lethality. The combination is highly potent, with an IC50 of 8.2 nM each, and strikingly synergistic, with a combination index of less than 0.003 for 70% inhibition. The synthetic lethality of the drug combination is achieved by apoptosis. These results reveal a crucial difference between mono-driver and multi-driver cancer cells and suggest that pharmacological synthetic lethality may provide a basis for effectively inhibiting multi-driver cancers.

Signaling Pathways and Natural Compounds in Triple-Negative Breast Cancer Cell Line

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer, having a poor prognosis and rapid metastases. TNBC is characterized by the absence of estrogen, progesterone, and human epidermal growth receptor-2 (HER2) expressions and has a five-year survival rate. Compared to other breast cancer subtypes, TNBC patients only respond to conventional chemotherapies, and even then, with limited success. Shortages of chemotherapeutic medication can lead to resistance, pressured index therapy, non-selectivity, and severe adverse effects. Finding targeted treatments for TNBC is difficult owing to the various features of cancer. Hence, identifying the most effective molecular targets in TNBC pathogenesis is essential for predicting response to targeted therapies and preventing TNBC cell metastases. Nowadays, natural compounds have gained attention as TNBC treatments, and have offered new strategies for solving drug resistance. Here, we report a systematic review using the database from Pubmed, Science Direct, MDPI, BioScince, Springer, and Nature for articles screening from 2003 to 2022. This review analyzes relevant signaling pathways and the prospect of utilizing natural compounds as a therapeutic agent to improve TNBC treatments in the future.

Chemotherapy Resistance: Role of Mitochondrial and Autophagic Components

Simple Summary

Chemotherapy resistance is a common occurrence during cancer treatment that cancer researchers are attempting to understand and overcome. Mitochondria are a crucial intracellular signaling core that are becoming important determinants of numerous aspects of cancer genesis and progression, such as metabolic reprogramming, metastatic capability, and chemotherapeutic resistance. Mitophagy, or selective autophagy of mitochondria, can influence both the efficacy of tumor chemotherapy and the degree of drug resistance. Regardless of the fact that mitochondria are well-known for coordinating ATP synthesis from cellular respiration in cellular bioenergetics, little is known its mitophagy regulation in chemoresistance. Recent advancements in mitochondrial research, mitophagy regulatory mechanisms, and their implications for our understanding of chemotherapy resistance are discussed in this review.

Abstract

Cancer chemotherapy resistance is one of the most critical obstacles in cancer therapy. One of the well-known mechanisms of chemotherapy resistance is the change in the mitochondrial death pathways which occur when cells are under stressful situations, such as chemotherapy. Mitophagy, or mitochondrial selective autophagy, is critical for cell quality control because it can efficiently break down, remove, and recycle defective or damaged mitochondria. As cancer cells use mitophagy to rapidly sweep away damaged mitochondria in order to mediate their own drug resistance, it influences the efficacy of tumor chemotherapy as well as the degree of drug resistance. Yet despite the importance of mitochondria and mitophagy in chemotherapy resistance, little is known about the precise mechanisms involved. As a consequence, identifying potential therapeutic targets by analyzing the signal pathways that govern mitophagy has become a vital research goal. In this paper, we review recent advances in mitochondrial research, mitophagy control mechanisms, and their implications for our understanding of chemotherapy resistance.

Inhibitors of PD-1/PD-L1 and ERK1/2 impede the proliferation of receptor positive and triple-negative breast cancer cell lines

PURPOSE

Triple-negative breast cancer (TNBC) is characterized by an unfavorable prognosis and missing systemic therapeutic approaches beside chemotherapy. Targeting the immune checkpoint PD-1/PD-L1 showed promising results in breast cancer and especially in TNBC. The extracellular signal-regulated kinase 1/2 (ERK1/2) is an important driver of carcinogenesis. Here, the effect of combined PD-1/PD-L1 and ERK1/2 inhibitor treatment is investigated of cell growth and intracellular impact of breast cancer cell lines.

METHODS

The IC50 values of each inhibitor and the effect of combined treatment were determined in three TNBC cell lines of different subtypes and one non-TNBC cell line. Phospho-specific antibodies were used in western blot analyses to investigate an effect on ERK1/2 activation. Expressions of immune modulatory and cell cycle-associated genes were examined by quantitative reverse transcription PCR.

RESULTS

Both inhibitors PD-1/PD-L1 and ERK1/2 impeded the proliferation of TNBC to a higher extent than of non-TNBC. By combined treatment, cell lines were inhibited either synergistically or additively. ERK1/2 and S6 phosphorylation were reduced and expressions of c-Fos and FosL were diminished after ERK1/2 inhibitor as single and combined treatment. Between genes involved in immune modulation, IL-8 was upregulated in TNBC cells after combined treatment.

CONCLUSION

In conclusion, combination of PD-1/PD-L1 and ERK1/2 inhibitors showed favorable effects for a new therapy strategy, with better results in TNBC cell lines than in non-TNBC cells. The effects have to be validated in models that can reflect the interaction between immune and tumor cells like the situation in the tumor micro-environment.

Therapeutically Targeting Cancers That Overexpress FOXC1: A Transcriptional Driver of Cell Plasticity, Partial EMT, and Cancer Metastasis

Metastasis accounts for more than 90% of cancer related mortality, thus the most pressing need in the field of oncology today is the ability to accurately predict future onset of metastatic disease, ideally at the time of initial diagnosis. As opposed to current practice, what would be desirable is that prognostic, biomarker-based detection of metastatic propensity and heightened risk of cancer recurrence be performed long before overt metastasis has set in. Without such timely information it will be impossible to formulate a rational therapeutic treatment plan to favorably alter the trajectory of disease progression. In order to help inform rational selection of targeted therapeutics, any recurrence/metastasis risk prediction strategy must occur with the paired identification of novel prognostic biomarkers and their underlying molecular regulatory mechanisms that help drive cancer recurrence/metastasis (i.e. recurrence biomarkers). Traditional clinical factors alone (such as TNM staging criteria) are no longer adequately prognostic for this purpose in the current molecular era. FOXC1 is a pivotal transcription factor that has been functionally implicated to drive cancer metastasis and has been demonstrated to be an independent predictor of heightened metastatic risk, at the time of initial diagnosis. In this review, we present our viewpoints on the master regulatory role that FOXC1 plays in mediating cancer stem cell traits that include cellular plasticity, partial EMT, treatment resistance, cancer invasion and cancer migration during cancer progression and metastasis. We also highlight potential therapeutic strategies to target cancers that are, or have evolved to become, “transcriptionally addicted” to FOXC1. The potential role of FOXC1 expression status in predicting the efficacy of these identified therapeutic approaches merits evaluation in clinical trials.

Genetic differences between benign phyllodes tumors and fibroadenomas revealed through targeted next generation sequencing

Breast fibroepithelial lesions are biphasic tumors which comprise the common benign fibroadenomas (FAs) and the rarer phyllodes tumors (PTs). This study analyzed 262 (42%) conventional FAs, 45 (7%) cellular FAs, and 321 (51%) benign PTs contributed by the International Fibroepithelial Consortium, using a previously curated 16 gene panel. Benign PTs were found to possess a higher number of mutations, and higher rates of cancer driver gene alterations than both groups of FAs, in particular MED12, TERT promoter, RARA, FLNA, SETD2, RB1, and EGFR. Cases with MED12 mutations were also more likely to have TERT promoter, RARA, SETD2, and EGFR. There were no significant differences detected between conventional FAs and cellular FAs, except for PIK3CA and MAP3K1. TERT promoter alterations were most optimal in discriminating between FAs and benign PTs. Our study affirms the role of sequencing and key mutations that may assist in refining diagnoses of these lesions.

Combination of Fish Oil and Selenium Enhances Anticancer Efficacy and Targets Multiple Signaling Pathways in Anti-VEGF Agent Treated-TNBC Tumor-Bearing Mice

Fish oil (FO) and selenium (Se) possess antiangiogenic potential in malignant tumors. This study aimed to determine whether combination of FO and Se enhanced treatment efficacy of low-dose antiangiogenic agent Avastin (bevacizumab) in a dose-dependent manner and targeted multiple signaling pathways in triple-negative breast cancer (TNBC)-bearing mice. Randomized into five groups, mice received treatment with either physiological saline (control), Avastin alone, or Avastin in combination with low, medium, and high doses of FO/Se. The target signaling molecules for anticancer were determined either by measuring protein or mRNA expression. Avastin-treated mice receiving FO/Se showed lower tumor growth and metastasis than did mice treated with Avastin alone. Combination-treated mice exhibited lower expressions in multiple proangiogenic (growth) factors and their membrane receptors, and altered cytoplasmic signaling molecules (PI3K-PTEN-AKT-TSC-mTOR-p70S6K-4EBP1, Ras-Raf-MEK-ERK, c-Src-JAK2-STAT3-TMEPAI-Smad, LKB1-AMPK, and GSK3β/β-catenin). Dose-dependent inhibition of down-stream targets including epithelial-to-mesenchymal transition transcription factors, nuclear cyclin and cyclin-dependent kinases, cancer stem cell markers, heat shock protein (HSP-90), hypoxia-inducible factors (HIF-1α/-2α), matrix metalloprotease (MMP-9), and increased apoptosis were observed. These results suggest that combination treatment with FO and Se increases the therapeutic efficacy of Avastin against TNBC in a dose-dependent manner through multiple signaling pathways in membrane, cytoplasmic, and nucleic targets.

Yap1 Mediates Trametinib Resistance in Head and Neck Squamous Cell Carcinomas

PURPOSE

In a head and neck squamous cell carcinoma (HNSCC) "window of opportunity" clinical trial, we reported that trametinib reduced MEK-Erk1/2 activation and resulted in tumor responses in a subset of patients. Here, we investigated resistance to trametinib and molecular correlates in HNSCC cell lines and patient samples.

EXPERIMENTAL DESIGN

HNSCC cell lines were treated with trametinib to generate resistant lines. Candidate bypass pathways were assessed using immunoblotting, CRISPR knockout, and survival assays. Effectiveness of combined trametinib and verteporfin targeting was evaluated. Patient-derived xenografts (PDXs) from responder patients were treated with trametinib and resistant tumors were analyzed. Window trial clinical samples were subjected to whole-exome and RNA sequencing.

RESULTS

HNSCC cell lines developed resistance (CAL27-TR and HSC3-TR) after prolonged trametinib exposure. Downstream effectors of the Hippo pathway were activated in CAL27-TR and HSC3-TR, and combined trametinib and verteporfin treatment resulted in synergistic treatment response. We defined the Hippo pathway effector Yap1 as an induced survival pathway promoting resistance to trametinib in HSC3-TR. Yap1 was necessary for HSC3-TR trametinib resistance, and constitutively active Yap1 was sufficient to confer resistance in parental HSC3. Analysis of trametinib neoadjuvant trial patient tumors indicated canonical MEK-Erk1/2 pathway activating mutations were infrequent, and Yap1 activity increased following trametinib treatment. Trametinib treatment of a PDX from a responder patient resulted in evolution of resistance with increased Yap1 expression and activity.

CONCLUSIONS

These studies identify a Yap1-dependent resistance to trametinib therapy in HNSCCs. Combined Yap1 and MEK targeting may represent a strategy to enhance HNSCC response.

New Entrants into Clinical Trials for Targeted Therapy of Breast Cancer: An Insight

Breast cancer is too complex with various different molecular alterations involved in its pathogenesis and progression. Over the decade, we have seen a surge in the development of drugs for bimolecular targets and for the signal transduction pathways involved in the treatment line of breast cancer. These drugs, either alone or in combination with conventional treatments like chemotherapy, hormone therapy and radiotherapy, will help oncologists to get a better insight and do the needful treatment. These novel therapies bring various challenges along with them, which include the dosage selection, patient selection, schedule of treatment and weighing of clinical benefits over side effects. In this review, we highlight the recently studied target molecules that have received indications in breast carcinoma, both in the localized and in an advanced state and about their inhibitors which are in clinical development which can give the immense potential to clinical care in the near future.

Simultaneous targeting of HER family pro-survival signaling with Pan-HER antibody mixture is highly effective in TNBC: a preclinical trial with PDXs

BACKGROUND

The human epidermal growth factor receptor (HER) family, notably EGFR, is overexpressed in most triple-negative breast cancer (TNBC) cases and provides cancer cells with compensatory signals that greatly contribute to the survival and development of resistance in response to therapy. This study investigated the effects of Pan-HER (Symphogen, Ballerup, Denmark), a novel mixture of six monoclonal antibodies directed against members of the HER family EGFR, HER2, and HER3, in a preclinical trial of TNBC patient-derived xenografts (PDXs).

METHODS

Fifteen low passage TNBC PDX tumor samples were transferred into the right mammary fat pad of mice for engraftment. When tumors reached an average size of 100-200 mm3, mice were randomized (n ≥ 6 per group) and treated following three 1-week cycles consisting of three times/week intraperitoneal (IP) injection of either formulation buffer (vehicle control) or Pan-HER (50 mg/kg). At the end of treatment, tumors were collected for Western blot, RNA, and immunohistochemistry analyses.

RESULTS

All 15 TNBC PDXs were responsive to Pan-HER treatment, showing significant reductions in tumor growth consistent with Pan-HER-mediated tumor downmodulation of EGFR and HER3 protein levels and significantly decreased activation of associated HER family signaling pathways AKT and ERK. Tumor regression was observed in five of the models, which corresponded to those PDX tumor models with the highest level of HER family activation.

CONCLUSIONS

The marked effect of Pan-HER in numerous HER family-dependent TNBC PDX models justifies further studies of Pan-HER in TNBC clinical trials as a potential therapeutic option.

Protein phosphatase 2A activation as a therapeutic strategy for managing MYC-driven cancers

The tumor suppressor protein phosphatase 2A (PP2A) is a serine/threonine phosphatase whose activity is inhibited in most human cancers. One of the best-characterized PP2A substrates is MYC proto-oncogene basic helix-loop-helix transcription factor (MYC), whose overexpression is commonly associated with aggressive forms of this disease. PP2A directly dephosphorylates MYC, resulting in its degradation. To explore the therapeutic potential of direct PP2A activation in a diverse set of MYC-driven cancers, here we used biochemical assays, recombinant cell lines, gene expression analyses, and immunohistochemistry to evaluate a series of first-in-class small-molecule activators of PP2A (SMAPs) in Burkitt lymphoma, KRAS-driven non-small cell lung cancer, and triple-negative breast cancer. In all tested models of MYC-driven cancer, the SMAP treatment rapidly and persistently inhibited MYC expression through proteasome-mediated degradation, inhibition of MYC transcriptional activity, decreased cancer cell proliferation, and tumor growth inhibition. Importantly, we generated a series of cell lines expressing PP2A-dependent phosphodegron variants of MYC and demonstrated that the antitumorigenic activity of SMAPs depends on MYC degradation. Collectively, the findings presented here indicate a pharmacologically tractable approach to drive MYC degradation by using SMAPs for the management of a broad range of MYC-driven cancers.

Molecular Mechanisms Underlying Autophagy-Mediated Treatment Resistance in Cancer

Despite advances in diagnostic tools and therapeutic options, treatment resistance remains a challenge for many cancer patients. Recent studies have found evidence that autophagy, a cellular pathway that delivers cytoplasmic components to lysosomes for degradation and recycling, contributes to treatment resistance in different cancer types. A role for autophagy in resistance to chemotherapies and targeted therapies has been described based largely on associations with various signaling pathways, including MAPK and PI3K/AKT signaling. However, our current understanding of the molecular mechanisms underlying the role of autophagy in facilitating treatment resistance remains limited. Here we provide a comprehensive summary of the evidence linking autophagy to major signaling pathways in the context of treatment resistance and tumor progression, and then highlight recently emerged molecular mechanisms underlying autophagy and the p62/KEAP1/NRF2 and FOXO3A/PUMA axes in chemoresistance.

Targeting Autophagy for Overcoming Resistance to Anti-EGFR Treatments

Epidermal growth factor receptor (EGFR) plays critical roles in cell proliferation, tumorigenesis, and anti-cancer drug resistance. Overexpression and somatic mutations of EGFR result in enhanced cancer cell survival. Therefore, EGFR can be a target for the development of anti-cancer therapy. Patients with cancers, including non-small cell lung cancers (NSCLC), have been shown to response to EGFR-tyrosine kinase inhibitors (EGFR-TKIs) and anti-EGFR antibodies. However, resistance to these anti-EGFR treatments has developed. Autophagy has emerged as a potential mechanism involved in the acquired resistance to anti-EGFR treatments. Anti-EGFR treatments can induce autophagy and result in resistance to anti-EGFR treatments. Autophagy is a programmed catabolic process stimulated by various stimuli. It promotes cellular survival under these stress conditions. Under normal conditions, EGFR-activated phosphoinositide 3-kinase (PI3K)/AKT serine/threonine kinase (AKT)/mammalian target of rapamycin (mTOR) signaling inhibits autophagy while EGFR/rat sarcoma viral oncogene homolog (RAS)/mitogen-activated protein kinase kinase (MEK)/mitogen-activated protein kinase (MAPK) signaling promotes autophagy. Thus, targeting autophagy may overcome resistance to anti-EGFR treatments. Inhibitors targeting autophagy and EGFR signaling have been under development. In this review, we discuss crosstalk between EGFR signaling and autophagy. We also assess whether autophagy inhibition, along with anti-EGFR treatments, might represent a promising approach to overcome resistance to anti-EGFR treatments in various cancers. In addition, we discuss new developments concerning anti-autophagy therapeutics for overcoming resistance to anti-EGFR treatments in various cancers.

Anti-tumor and anti-metastasis efficacy of E6201, a MEK1 inhibitor, in preclinical models of triple-negative breast cancer

PURPOSE

Triple-negative breast cancer (TNBC) lacks the receptor targets estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2, and thus, it does not respond to receptor-targeted treatments. TNBC has higher recurrence, metastasis, and mortality rates than other subtypes of breast cancer. Mounting data suggest that the MAPK (also known as RAS-RAF-MEK-ERK) pathway is an important therapeutic target in TNBC.

METHODS

To evaluate anti-tumor and anti-metastasis efficacy of E6201, we used cell proliferation assay, soft agar assay, cell cycle assay, Annexin V staining assay, immunoblotting analysis, immunohistochemistry, migration assay, invasion assay, mammary fat pad xenograft, and experimental and spontaneous metastasis xenograft models. We also evaluated the anti-tumor efficacy of E6201 plus CDK4/6 inhibitor, mTOR inhibitor, or ATR inhibitor.

RESULTS

E6201 inhibited TNBC cell colony formation, migration, and invasion in a dose-dependent manner. E6201 induced G1 cell cycle arrest and apoptosis. E6201 inhibited TNBC xenograft growth and inhibited TNBC lung metastasis and improved mouse survival in experimental metastasis and spontaneous metastasis assays. Immunohistochemical staining demonstrated that E6201 decreased the metastatic burden in the lung and decreased phosphorylated ERK expression in a dose-dependent manner. Combination of E6201 with CDK4/6 inhibitor or mTOR inhibitor enhanced E6201's in vitro anti-tumor efficacy.

CONCLUSION

These results indicate that E6201 exhibits anti-tumor efficacy against TNBC in vitro and anti-metastasis efficacy against TNBC in vivo. These results provide a rationale for further clinical development of E6201 as a MAPK-pathway-targeted therapy for TNBC.

Insights into Molecular Classifications of Triple-Negative Breast Cancer: Improving Patient Selection for Treatment

Triple-negative breast cancer (TNBC) remains the most challenging breast cancer subtype to treat. To date, therapies directed to specific molecular targets have rarely achieved clinically meaningful improvements in outcomes of patients with TNBC, and chemotherapy remains the standard of care. Here, we seek to review the most recent efforts to classify TNBC based on the comprehensive profiling of tumors for cellular composition and molecular features. Technologic advances allow for tumor characterization at ever-increasing depth, generating data that, if integrated with clinical-pathologic features, may help improve risk stratification of patients, guide treatment decisions and surveillance, and help identify new targets for drug development. SIGNIFICANCE: TNBC is characterized by higher rates of relapse, greater metastatic potential, and shorter overall survival compared with other major breast cancer subtypes. The identification of biomarkers that can help guide treatment decisions in TNBC remains a clinically unmet need. Understanding the mechanisms that drive resistance is key to the design of novel therapeutic strategies to help prevent the development of metastatic disease and, ultimately, to improve survival in this patient population.

Combination of MEK Inhibitor and the JAK2-STAT3 Pathway Inhibition for the Therapy of Colon Cancer

The study aimed to investigate the reason of HCT116 cell resistance to MEK inhibitor, and the combination treatment effects of MEK inhibitor AZD6244 and JAK2/STAT3 inhibitor AG490 on colon cancer in vitro and in vivo, including cell viability, apoptosis, and explore the partial mechanisms focused on AZD6244 promoted the activation of JAK2-STAT3 pathways. In vitro, we examined the HCT116 cell viability by CCK8, cell apoptosis by flow cytometry; Western blot measured p-ERK, p-JAK2, p-STAT3 and STAT3 expression. In vivo, nude mice were subcutaneously injected by HCT116 cells. The tumor volume and weight were detected. HCT116 cell resistance to MEK inhibitor AZD6244, which inhibited the activation of ERK and promoted the activation of JAK2-STAT3 signaling. The combination treatment of AZD6244 and AG490 significantly inhibited cell viability and induced cell apoptosis, and completely inhibited the activation of ERK and JAK2-STAT3 signaling. Combination treatment of AZD6244 and AG490 had a stronger effect than that of AZD6244 as a monotherapy in vitro and in vivo. The treatment of AZD6244 on K-Ras mutations HCT116 cells promoted the activation of JAK2/STAT3 signaling. JAK2/STAT3 inhibitor AG490 synergistically increases effects of AZD6244 on colon cancer in vitro and in vivo. Collectively, these results provide a rationale for combining inhibitors of the JAK/STAT pathway and MEK inhibitors to reduce the potential impact of drug resistance.

Pan-RAF and MEK vertical inhibition enhances therapeutic response in non-V600 BRAF mutant cells

BACKGROUND

Currently, there are no available targeted therapy options for non-V600 BRAF mutated tumors. The aim of this study was to investigate the effects of RAF and MEK concurrent inhibition on tumor growth, migration, signaling and apoptosis induction in preclinical models of non-V600 BRAF mutant tumor cell lines.

METHODS

Six BRAF mutated human tumor cell lines CRL5885 (G466 V), WM3629 (D594G), WM3670 (G469E), MDAMB231 (G464 V), CRL5922 (L597 V) and A375 (V600E as control) were investigated. Pan-RAF inhibitor (sorafenib or AZ628) and MEK inhibitor (selumetinib) or their combination were used in in vitro viability, video microscopy, immunoblot, cell cycle and TUNEL assays. The in vivo effects of the drugs were assessed in an orthotopic NSG mouse breast cancer model.

RESULTS

All cell lines showed a significant growth inhibition with synergism in the sorafenib/AZ628 and selumetinib combination. Combination treatment resulted in higher Erk1/2 inhibition and in increased induction of apoptosis when compared to single agent treatments. However, single selumetinib treatment could cause adverse therapeutic effects, like increased cell migration in certain cells, selumetinib and sorafenib combination treatment lowered migratory capacity in all the cell lines. Importantly, combination resulted in significantly increased tumor growth inhibition in orthotropic xenografts of MDAMB231 cells when compared to sorafenib - but not to selumetinib - treatment.

CONCLUSIONS

Our data suggests that combined blocking of RAF and MEK may achieve increased therapeutic response in non-V600 BRAF mutant tumors.