FAK inhibition alone or in combination with adjuvant therapies reduces cancer stem cell activity

Prospects of focal adhesion kinase inhibitors as a cancer therapy in preclinical and early phase study

INTRODUCTION

FAK, a nonreceptor cytoplasmic tyrosine kinase, plays a crucial role in tumor metastasis, drug resistance, tumor stem cell maintenance, and regulation of the tumor microenvironment. FAK has emerged as a promising target for tumor therapy based on both preclinical and clinical data.

AREAS COVERED

This paper aims to summarize the molecular mechanisms underlying FAK's involvement in tumorigenesis and progression. Encouraging results have emerged from ongoing clinical trials of FAK inhibitors. Additionally, we present an overview of clinical trials for FAK inhibitors, examining their potential as promising treatments. The pertinent studies gathered from databases including PubMed, ClinicalTrials.gov.

EXPERT OPINION

Since the first finding in 1990s, targeting FAK has became the focus of interests in many pharmaceutical companies. Through 30 years' discovery, the industry and academy gradually realized the features of FAK target which may not be a driver gene but a solid defense system for the cancer initiation and development. Currently, the ongoing clinical regimens involving FAK inhibition are all the combination strategies in which FAK inhibitors can further strengthen the cancer cell killing effects of other testing agents. The emerging positive signal in clinical trials foresee targeting FAK as class will be an effective mean to fight against cancers.

Targeting of focal adhesion kinase enhances the immunogenic cell death of PEGylated liposome doxorubicin to optimize therapeutic responses of immune checkpoint blockade

BACKGROUNDS

Immune checkpoint blockade (ICB) is widely considered to exert long-term treatment benefits by activating antitumor immunity. However, many cancer patients show poor clinical responses to ICB due in part to the lack of an immunogenic niche. Focal adhesion kinase (FAK) is frequently amplified and acts as an immune modulator across cancer types. However, evidence illustrates that targeting FAK is most effective in combination therapy rather than in monotherapy.

METHODS

Here, we used drug screening, in vitro and in vivo assays to filter out that doxorubicin and its liposomal form pegylated liposome doxorubicin (PLD) showed synergistic anti-tumor effects in combination with FAK inhibitor IN10018. We hypothesized that anti-tumor immunity and immunogenic cell death (ICD) may be involved in the treatment outcomes through the data analysis of our clinical trial testing the combination of IN10018 and PLD. We then performed cell-based assays and animal studies to detect whether FAK inhibition by IN10018 can boost the ICD of PLD/doxorubicin and further established syngeneic models to test the antitumor effect of triplet combination of PLD, IN10018, and ICB.

RESULTS

We demonstrated that the combination of FAK inhibitor IN10018, and PLD/doxorubicin exerted effective antitumor activity. Notably, the doublet combination regimen exhibited response latency and long-lasting treatment effects clinically, outcomes frequently observed in immunotherapy. Our preclinical study confirmed that the 2-drug combination can maximize the ICD of cancer cells. This approach primed the tumor microenvironment, supplementing it with sufficient tumor-infiltrating lymphocytes (TILs) to activate antitumor immunity. Finally, different animal studies confirmed that the antitumor effects of ICB can be significantly enhanced by this doublet regimen.

CONCLUSIONS

We confirmed that targeting FAK by IN10018 can enhance the ICD of PLD/doxorubicin, further benefiting the anti-tumor effect of ICB. The animal tests of the triplet regimen warrant further discovery in the real world.

The Anticancer Effects of Marine Carotenoid Fucoxanthin through Phosphatidylinositol 3-Kinase (PI3K)-AKT Signaling on Triple-Negative Breast Cancer Cells

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer that lacks specific targets such as estrogen, progesterone, and HER2 receptors. TNBC affects one in eight women in the United States, making up 15-20% of breast cancer cases. Patients with TNBC can develop resistance to chemotherapy over time, leading to treatment failure. Therefore, finding other options like natural products is necessary for treatment. The advantages of using natural products sourced from plants as anticancer agents are that they are less toxic, more affordable, and have fewer side effects. These products can modulate several cellular processes of the tumor microenvironment, such as proliferation, migration, angiogenesis, cell cycle arrest, and apoptosis. The phosphatidyl inositol 3-kinase (PI3K)-AKT signaling pathway is an important pathway that contributes to the survival and growth of the tumor microenvironment and is associated with these cellular processes. This current study examined the anticancer effects of fucoxanthin, a marine carotenoid isolated from brown seaweed, in the MDA-MB-231 and MDA-MB-468 TNBC cell lines. The methods used in this study include a cytotoxic assay, PI3K-AKT signaling pathway PCR arrays, and Wes analysis. Fucoxanthin (6.25 µM) + TNF-α (50 ng/mL) and TNF-α (50 ng/mL) showed no significant effect on cell viability compared to the control in both MDA-MB-231 and MDA-MB-468 cells after a 24 h treatment period. PI3K-AKT signaling pathway PCR array studies showed that in TNF-α-stimulated (50 ng/mL) MDA-MB-231 and MDA-MB-468 cells, fucoxanthin (6.25 µM) modulated the mRNA expression of 12 genes, including FOXO1, RASA1, HRAS, MAPK3, PDK2, IRS1, EIF4EBP1, EIF4B, PTK2, TIRAP, RHOA, and ELK1. Additionally, fucoxanthin significantly downregulated the protein expression of IRS1, EIF4B, and ELK1 in MDA-MB-231 cells, and no change in the protein expression of EIF4B and ELK1 was shown in MDA-MB-468 cells. Fucoxanthin upregulated the protein expression of RHOA in both cell lines. The modulation of the expression of genes and proteins of the PI3K-AKT signaling pathway may elucidate fucoxanthin's effects in cell cycle progression, apoptotic processes, migration, and proliferation, which shows that PI3K-AKT may be the possible molecular mechanism for fucoxanthin's effects. In conclusion, the results obtained in this study elucidate fucoxanthin's molecular mechanisms and indicate that fucoxanthin may be considered a promising candidate for breast cancer-targeted therapy.

ID1 expressing macrophages support cancer cell stemness and limit CD8+ T cell infiltration in colorectal cancer

Elimination of cancer stem cells (CSCs) and reinvigoration of antitumor immunity remain unmet challenges for cancer therapy. Tumor-associated macrophages (TAMs) constitute the prominant population of immune cells in tumor tissues, contributing to the formation of CSC niches and a suppressive immune microenvironment. Here, we report that high expression of inhibitor of differentiation 1 (ID1) in TAMs correlates with poor outcome in patients with colorectal cancer (CRC). ID1 expressing macrophages maintain cancer stemness and impede CD8+ T cell infiltration. Mechanistically, ID1 interacts with STAT1 to induce its cytoplasmic distribution and inhibits STAT1-mediated SerpinB2 and CCL4 transcription, two secretory factors responsible for cancer stemness inhibition and CD8+ T cell recruitment. Reducing ID1 expression ameliorates CRC progression and enhances tumor sensitivity to immunotherapy and chemotherapy. Collectively, our study highlights the pivotal role of ID1 in controlling the protumor phenotype of TAMs and paves the way for therapeutic targeting of ID1 in CRC.

An ULK1/2-PXN mechanotransduction pathway suppresses breast cancer cell migration

The remodeling and stiffening of the extracellular matrix (ECM) is a well-recognized modulator of breast cancer progression. How changes in the mechanical properties of the ECM are converted into biochemical signals that direct tumor cell migration and metastasis remain poorly characterized. Here, we describe a new role for the autophagy-inducing serine/threonine kinases ULK1 and ULK2 in mechanotransduction. We show that ULK1/2 activity inhibits the assembly of actin stress fibers and focal adhesions (FAs) and as a consequence impedes cell contraction and migration, independent of its role in autophagy. Mechanistically, we identify PXN/paxillin, a key component of the mechanotransducing machinery, as a direct binding partner and substrate of ULK1/2. ULK-mediated phosphorylation of PXN at S32 and S119 weakens homotypic interactions and liquid-liquid phase separation of PXN, impairing FA assembly, which in turn alters the mechanical properties of breast cancer cells and their response to mechanical stimuli. ULK1/2 and the well-characterized PXN regulator, FAK/Src, have opposing functions on mechanotransduction and compete for phosphorylation of adjacent serine and tyrosine residues. Taken together, our study reveals ULK1/2 as important regulator of PXN-dependent mechanotransduction.

Focal adhesion kinase: from biological functions to therapeutic strategies

Focal adhesion kinase (FAK), a nonreceptor cytoplasmic tyrosine kinase, is a vital participant in primary cellular functions, such as proliferation, survival, migration, and invasion. In addition, FAK regulates cancer stem cell activities and contributes to the formation of the tumor microenvironment (TME). Importantly, increased FAK expression and activity are strongly associated with unfavorable clinical outcomes and metastatic characteristics in numerous tumors. In vitro and in vivo studies have demonstrated that modulating FAK activity by application of FAK inhibitors alone or in combination treatment regimens could be effective for cancer therapy. Based on these findings, several agents targeting FAK have been exploited in diverse preclinical tumor models. This article briefly describes the structure and function of FAK, as well as research progress on FAK inhibitors in combination therapies. We also discuss the challenges and future directions regarding anti-FAK combination therapies.

Breast stiffness, a risk factor for cancer and the role of radiology for diagnosis

Over the last five decades, breast density has been associated with increased risk of developing breast cancer. Mammographically dense breasts are considered those belonging to the heterogeneously dense breasts, and extremely dense breasts subgroups according to the American College of Radiology's Breast Imaging Reporting and Data System (BI-RADS). There is a statistically significant correlation between the increased mammographic density and the presence of more glandular tissue alone. However, the strength of this correlation is weak. Although the mechanisms driving breast density-related tumor initiation and progression are still unknown, there is evidence suggesting that certain molecular pathways participating in epithelial-stromal interactions may play a pivotal role in the deposition of fibrillar collagen, increased matrix stiffness, and cell migration that favor breast density and carcinogenesis. This article describes these molecular mechanisms as potential "landscapers" for breast density-related cancer. We also introduce the term "Breast Compactness" to reflect collagen density of breast tissue on chest CT scan and the use of breast stiffness measurements as imaging biomarkers for breast cancer screening and risk stratification.

Ebastine impairs metastatic spread in triple-negative breast cancer by targeting focal adhesion kinase

We sought to investigate the utility of ebastine (EBA), a second-generation antihistamine with potent anti-metastatic properties, in the context of breast cancer stem cell (BCSC)-suppression in triple-negative breast cancer (TNBC). EBA binds to the tyrosine kinase domain of focal adhesion kinase (FAK), blocking phosphorylation at the Y397 and Y576/577 residues. FAK-mediated JAK2/STAT3 and MEK/ERK signaling was attenuated after EBA challenge in vitro and in vivo. EBA treatment induced apoptosis and a sharp decline in the expression of the BCSC markers ALDH1, CD44 and CD49f, suggesting that EBA targets BCSC-like cell populations while reducing tumor bulk. EBA administration significantly impeded BCSC-enriched tumor burden, angiogenesis and distant metastasis while reducing MMP-2/-9 levels in circulating blood in vivo. Our findings suggest that EBA may represent an effective therapeutic for the simultaneous targeting of JAK2/STAT3 and MEK/ERK for the treatment of molecularly heterogeneous TNBC with divergent profiles. Further investigation of EBA as an anti-metastatic agent for the treatment of TNBC is warranted.

MSC-1186, a Highly Selective Pan-SRPK Inhibitor Based on an Exceptionally Decorated Benzimidazole-Pyrimidine Core

The highly conserved catalytic sites in protein kinases make it difficult to identify ATP competitive inhibitors with kinome-wide selectivity. Serendipitously, during a dedicated fragment campaign for the focal adhesion kinase (FAK), a scaffold that had lost its initial FAK affinity showed remarkable potency and selectivity for serine-arginine-protein kinases 1-3 (SRPK1-3). Non-conserved interactions with the uniquely structured hinge region of the SRPK family were the key drivers of the exclusive selectivity of the discovered fragment hit. Structure-guided medicinal chemistry efforts led to the SRPK inhibitor MSC-1186, which fulfills all hallmarks of a reversible chemical probe, including nanomolar cellular potency and excellent kinome-wide selectivity. The combination of MSC-1186 with CDC2-like kinase (CLK) inhibitors showed additive attenuation of SR-protein phosphorylation compared to the single agents. MSC-1186 and negative control (MSC-5360) are chemical probes available via the Structural Genomics Consortium chemical probe program (https://www.sgc-ffm.uni-frankfurt.de/).

FAK downregulation suppresses stem-like properties and migration of human colorectal cancer cells

Focal adhesion kinase (FAK) is a cytoplasmic protein tyrosine kinase, which is overexpressed in colorectal cancer cells. FAK could be activated by phosphorylation to participate in the transduction of multiple signaling pathways and self-renewal of cancer stem cells. Whether the downregulation of FAK inhibits the metastasis in colorectal cancer through the weakening of stem cell-like properties and its mechanisms has yet to be established. CD44, CD133, c-Myc, Nanog, and OCT4 were known to mark colorectal cancer stem cell properties. In this study, AKT inhibitor (MK-2206 2HCl) or FAK inhibitor (PF-562271) decreased the expression of stem cell markers (Nanog, OCT4, CD133, CD44, c-Myc) and spheroid formation in colorectal cancer. Moreover, FAK and AKT protein was shown to interact verified by co-immunoprecipitation. Furthermore, downregulation of FAK, transfected Lenti-FAK-EGFP-miR to colorectal cancer cells, reduced p-AKT but not AKT and decreased the expression of stem cell markers and spheroid formation in colorectal cancer. In conclusion, we demonstrated that downregulation of FAK inhibited stem cell-like properties and migration of colorectal cancer cells partly due to altered modulation of AKT phosphorylation by FAK.

LINC00589-dominated ceRNA networks regulate multiple chemoresistance and cancer stem cell-like properties in HER2+ breast cancer

Resistance to human epidermal growth factor receptor 2 (HER2)-targeted therapy (trastuzumab), cancer stem cell (CSC)-like properties and multiple chemoresistance often concur and intersect in breast cancer, but molecular links that may serve as effective therapeutic targets remain largely unknown. Here, we identified the long noncoding RNA, LINC00589 as a key regulatory node for concurrent intervention of these processes in breast cancer cells in vitro and in vivo. We demonstrated that the expression of LINC00589 is clinically valuable as an independent prognostic factor for discriminating trastuzumab responders. Mechanistically, LINC00589 serves as a ceRNA platform that simultaneously sponges miR-100 and miR-452 and relieves their repression of tumor suppressors, including discs large homolog 5 (DLG5) and PR/SET domain 16 (PRDM16, a transcription suppressor of mucin4), thereby exerting multiple cancer inhibitory functions and counteracting drug resistance. Collectively, our results disclose two LINC00589-initiated ceRNA networks, the LINC00589-miR-100-DLG5 and LINC00589-miR-452-PRDM16- mucin4 axes, which regulate trastuzumab resistance, CSC-like properties and multiple chemoresistance of breast cancer, thus providing potential diagnostic and prognostic markers and therapeutic targets for HER2-positive breast cancer.

Focal adhesion kinase priming in pancreatic cancer, altering biomechanics to improve chemotherapy

The dense desmoplastic and fibrotic stroma is a characteristic feature of pancreatic ductal adenocarcinoma (PDAC), regulating disease progression, metastasis and response to treatment. Reciprocal interactions between the tumour and stroma are mediated by bidirectional integrin-mediated signalling, in particular by Focal Adhesion Kinase (FAK). FAK is often hyperactivated and overexpressed in aggressive cancers, promoting stromal remodelling and inducing tissue stiffness which can accelerate cancer cell proliferation, survival and chemoresistance. Therapeutic targeting of the PDAC stroma is an evolving area of interest for pre-clinical and clinical research, where a subtle reshaping of the stromal architecture prior to chemotherapy may prove promising in the clinical management of disease and overall patient survival. Here, we describe how transient stromal manipulation (or ‘priming’) via short-term FAK inhibition, rather than chronic treatment, can render PDAC cells exquisitely vulnerable to subsequent standard-of-care chemotherapy. We assess how our priming publication fits with the recent literature and describe in this perspective how this could impact future cancer treatment. This highlights the significance of treatment timing and warrants further consideration of anti-fibrotic therapies in the clinical management of PDAC and other fibrotic diseases.

Ras-Related Protein Rab-32 and Thrombospondin 1 Confer Resistance to the EGFR Tyrosine Kinase Inhibitor Osimertinib by Activating Focal Adhesion Kinase in Non-Small Cell Lung Cancer

Simple Summary

Osimertinib is a third-generation EGFR tyrosine kinase inhibitor and the standard of care therapy for non-small cell lung cancer patients harboring EGFR-activating mutations. However, even for patients treated with osimertinib, resistance inevitably occurs leading to disease progression. Here, we utilized two osimertinib-resistant cell lines and investigated their RNA profiles. We found that Ras-related protein Rab-32 (RAB32) and thrombospondin 1 (THBS1) were upregulated and associated with resistance in osimertinib-resistant cells as well as in liquid biopsies from patients with disease progression following osimertinib treatment. Moreover, we found RAB32 and THBS1 to be mechanistically linked to activation of the focal adhesion pathway where combination of osimertinib with a FAK inhibitor resulted in a synergistic suppression of viability of osimertinib-resistant cells. Our findings propose a potential therapeutic strategy for overcoming acquired resistance to osimertinib in non-small cell lung cancer.

Abstract

Treatment with the tyrosine kinase inhibitor (TKI) osimertinib is the standard of care for non-small cell lung cancer (NSCLC) patients with activating mutations in the epidermal growth factor receptor (EGFR). Osimertinib is also used in T790M-positive NSCLC that may occur de novo or be acquired following first-line treatment with other EGFR TKIs (i.e., gefitinib, erlotinib, afatinib, or dacomitinib). However, patients treated with osimertinib have a high risk of developing resistance to the treatment. A substantial fraction of the mechanisms for resistance is unknown and may involve RNA and/or protein alterations. In this study, we investigated the full transcriptome of parental and osimertinib-resistant cell lines, revealing 131 differentially expressed genes. Knockdown screening of the genes upregulated in resistant cell lines uncovered eight genes to partly confer resistance to osimertinib. Among them, we detected the expression of Ras-related protein Rab-32 (RAB32) and thrombospondin 1 (THBS1) in plasmas sampled at baseline and at disease progression from EGFR-positive NSCLC patients treated with osimertinib. Both genes were upregulated in progression samples. Moreover, we found that knockdown of RAB32 and THBS1 reduced the expression of phosphorylated focal adhesion kinase (FAK). Combination of osimertinib with a FAK inhibitor resulted in synergistic toxicity in osimertinib-resistant cells, suggesting a potential therapeutic drug combination for overcoming resistance to osimertinib in NSCLC patients.

FAK PROTAC Inhibits Ovarian Tumor Growth and Metastasis by Disrupting Kinase Dependent and Independent Pathways

Focal adhesion kinase (FAK) is highly expressed in a variety of human cancers and is a target for cancer therapy. Since FAK kinase inhibitors only block the kinase activity of FAK, they are not highly effective in clinical trials. FAK also functions as a scaffold protein in a kinase-independent pathway. To effectively target FAK, it is required to block both FAK kinase-dependent and FAK-independent pathways. Thus, we tested a new generation drug FAK PROTAC for ovarian cancer therapy, which blocks both kinase and scaffold activity. We tested the efficacy of FAK PROTAC and its parent kinase inhibitor (VS-6063) in ovarian cancer cell lines in vitro by performing cell functional assays including cell proliferation, migration, invasion. We also tested in vivo activity in orthotopic ovarian cancer mouse models. In addition, we assessed whether FAK PROTAC disrupts kinase-dependent and kinase-independent pathways. We demonstrated that FAK PROTAC is highly effective as compared to its parent FAK kinase inhibitor VS-6063 in inhibiting cell proliferation, survival, migration, and invasion. FAK PROTAC not only inhibits the FAK kinase activity but also FAK scaffold function by disrupting the interaction between FAK and its interaction protein ASAP1. We further showed that FAK PROTAC effectively inhibits ovarian tumor growth and metastasis. Taken together, FAK PROTAC inhibits both FAK kinase activity and its scaffold protein activity by disrupting the interaction between FAK and ASAP1 and is highly effective in inhibiting ovarian tumor growth and metastasis.

Invasive phenotype in triple negative breast cancer is inhibited by blocking SIN3A-PF1 interaction through KLF9 mediated repression of ITGA6 and ITGB1

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We show that the PAH2 domain of SIN3A is a target when it is inhibited from binding to PF1 results in inhibition of invasive phenotype in TNBC.

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Epigenetic repression of integrins expression and downstream pathways results from enhanced binding of KLF9 /SIN3A repressor complex to their promoters.

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Genome wide transcriptomic analysis showed downregulation of multiple invasion related genes. Tumor growth and lung metastasis were markedly decreased in vivo.

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Our studies highlight that PF1 might serve as a gatekeeper for trafficking SID protein binding to PAH2 of SIN3A and has functional role in presentation of different regulatory complexes.

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Blocking the function of PAH2 offers a promising targeted therapy approach for inhibiting the invasive phenotype in TNBC.

SIN3A, a scaffold protein has regulatory functions in tumor biology. Through its Paired amphipathic helix (PAH2) domain, SIN3A interacts with PHF12 (PF1), a protein with SIN3 interaction domain (SID) that forms a complex with MRG15 and KDM5A/B. These components are often overexpressed in cancer. In the present study, we evaluated the role of SIN3A and its interacting partner PF1 in mediating inhibition of tumor growth and invasion in triple negative breast cancer (TNBC). We found profound inhibition of invasion, migration, and induction of cellular senescence by specific disruption of the PF1/SIN3A PAH2 domain interaction in TNBC cells expressing PF1-SID transcript or peptide treatment. Genome-wide transcriptomic analysis by RNA-seq revealed that PF1-SID downregulates several gene sets and pathways linked to invasion and migration. Integrin α6 (ITGA6) and integrin ß1 (ITGB1) and their downstream target proteins were downregulated in PF1-SID cells. We further determined increased presence of SIN3A and transcriptional repressor, KLF9, on promoters of ITGA6 and ITGB1 in PF1-SID cells. Knockdown of KLF9 leads to re-expression of ITGA6 and ITGB1 and restoration of the invasive phenotype, functionally linking KLF9 to this process. Overall, these data demonstrate that specific disruption of PF1/SIN3A, inhibits tumor growth, migration, and invasion. Also, PF1-SID not only inhibits tumor growth by senescence induction and reduced proliferation, but it also targets cancer stem cell gene expression and blocks mammosphere formation. Overall, these data demonstrate a mechanism whereby invasion and metastasis of TNBC can be suppressed by inhibiting SIN3A-PF1 interaction and enhancing KLF9 mediated suppression of ITGA6 and ITGB1.