A renaissance for SRC

Src Kinase Is Biphosphorylated at Y416/Y527 and Activates the CUB-Domain Containing Protein 1/Protein Kinase C δ Pathway in a Subset of Triple-Negative Breast Cancers

Targeted therapeutics are needed for triple-negative breast cancer (TNBC). In this study, we investigated the activation of Src family of cytoplasmic tyrosine kinases (SFKs) and two SFK substrates-CUB-domain containing protein 1 (CDCP1) and protein kinase C δ (PKCδ)-in 56 formalin-fixed, paraffin-embedded (FFPE) TNBCs. Expression of SFK phosphorylated at Y416 (SFK_pY416⁺) in tumor cells was strongly associated with phosphorylation of CDCP1 and PKCδ (CDCP1_ pY743⁺ and PKCδ_pY311⁺), as assessed by immunohistochemistry, indicating increased SFK activity in situ. To enable biochemical analysis, protein extraction from FFPE tissue was optimized. Cleaved CDCP1 isoform (70 kDa) was expressed to a varying degree in all samples but only phosphorylated in TNBC tumor cells that expressed SFK_pY416. Interestingly, active SFK was found to be biphosphorylated (SFK_pY416⁺/pY527⁺). Biphosphorylated active SFK was observed more frequently in forkhead box protein A1 (FOXA1)^- TNBCs. In addition, in SFK_pY416^- samples, FOXA1⁺ TNBC tended to be SFK_pY527⁺ (classic inactive SFK), and FOXA1^- TNBC tended to be SFK_pY527^- (SFK poised for activation). Strong SFK_pY416 staining was also observed in tumor-infiltrating lymphocytes in a subset of TNBCs with high tumor-infiltrating lymphocyte content. This report will facilitate protein biochemical analysis of FFPE tumor samples and justifies the development of therapies targeting the SFK/CDCP1/PKCδ pathway for TNBC treatment.

Proliferative signaling by ERBB proteins and RAF/MEK/ERK effectors in polycystic kidney disease

A primary pathological feature of polycystic kidney disease (PKD) is the hyperproliferation of epithelial cells in renal tubules, resulting in formation of fluid-filled cysts. The proliferative aspects of the two major forms of PKD-autosomal dominant PKD (ADPKD), which arises from mutations in the polycystins PKD1 and PKD2, and autosomal recessive PKD (ARPKD), which arises from mutations in PKHD1-has encouraged investigation into protein components of the core cell proliferative machinery as potential drivers of PKD pathogenesis. In this review, we examine the role of signaling by ERBB proteins and their effectors, with a primary focus on ADPKD. The ERBB family of receptor tyrosine kinases (EGFR/ERBB1, HER2/ERBB2, ERBB3, and ERBB4) are activated by extracellular ligands, inducing multiple pro-growth signaling cascades; among these, activation of signaling through the RAS GTPase, and the RAF, MEK1/2, and ERK1/2 kinases enhance cell proliferation and restrict apoptosis during renal tubuloepithelial cyst formation. Characteristics of PKD include overexpression and mislocalization of the ERBB receptors and ligands, leading to enhanced activation and increased activity of downstream signaling proteins. The altered regulation of ERBBs and their effectors in PKD is influenced by enhanced activity of SRC kinase, which is promoted by the loss of cytoplasmic Ca²⁺ and an increase in cAMP-dependent PKA kinase activity that stimulates CFTR, driving the secretory phenotype of ADPKD. We discuss the interplay between ERBB/SRC signaling, and polycystins and their depending signaling, with emphasis on thes changes that affect cell proliferation in cyst expansion, as well as the inflammation-associated fibrogenesis, which characterizes progressive disease. We summarize the current progress of preclinical and clinical trials directed at inhibiting this signaling axis, and discuss potential future strategies that may be productive for controlling PKD.

Intramitochondrial Src kinase links mitochondrial dysfunctions and aggressiveness of breast cancer cells

High levels and activity of Src kinase are common among breast cancer subtypes, and several inhibitors of the kinase are currently tested in clinical trials. Alterations in mitochondrial activity is also observed among the different types of breast cancer. Src kinase is localized in several subcellular compartments, including mitochondria where it targets several proteins to modulate the activity of the organelle. Although the subcellular localization of other oncogenes modulates the potency of known treatments, nothing is known about the specific role of intra-mitochondrial Src (mtSrc) in breast cancer. The aim of this work was to determine whether mtSrc kinase has specific impact on breast cancer cells. We first observed that activity of mtSrc is higher in breast cancer cells of the triple negative subtype. Over-expression of Src specifically targeted to mitochondria reduced mtDNA levels, mitochondrial membrane potential and cellular respiration. These alterations of mitochondrial functions led to lower cellular viability, shorter cell cycle and increased invasive capacity. Proteomic analyses revealed that mtSrc targets the mitochondrial single-stranded DNA-binding protein, a regulator of mtDNA replication. Our findings suggest that mtSrc promotes aggressiveness of breast cancer cells via phosphorylation of mitochondrial single-stranded DNA-binding protein leading to reduced mtDNA levels and mitochondrial activity. This study highlights the importance of considering the subcellular localization of Src kinase in the development of potent therapy for breast cancer.

XIAP Interaction with E2F1 and Sp1 via its BIR2 and BIR3 domains specific activated MMP2 to promote bladder cancer invasion

XIAP has generally been thought to function in bladder cancer. However, the potential function of structure-based function of XIAP in human BC invasion has not been well explored before. We show here that ectopic expression of the BIR domains of XIAP specifically resulted in MMP2 activation and cell invasion in XIAP-deleted BC cells, while Src was further defined as an XIAP downstream negative regulator for MMP2 activation and BC cell invasion. The inhibition of Src expression by the BIR domains was caused by attenuation of Src protein translation upon miR-203 upregulation; which was resulted from direct interaction of BIR2 and BIR3 with E2F1 and Sp1, respectively. The interaction of BIR2/BIR3 with E2F1/Sp1 unexpectedly occurred, which could be blocked by serum-induced XIAP translocation. Taken together, our studies, for the first time revealed that: (1) BIR2 and BIR3 domains of XIAP play their role in cancer cell invasion without affecting cell migration by specific activation of MMP2 in human BC cells; (2) by BIR2 interacting with E2F1 and BIR3 interacting with Sp1, XIAP initiates E2F1/Sp1 positive feedback loop-dependent transcription of miR-203, which in turn inhibits Src protein translation, further leading to MMP2-cleaved activation; (3) XIAP interaction with E2F1 and Sp1 is observed in the nucleus. Our findings provide novel insights into understanding the specific function of BIR2 and BIR3 of XIAP in BC invasion, which will be highly significant for the design/synthesis of new BIR2/BIR3-based compounds for invasive BC treatment.

PTPRS drives adaptive resistance to MEK/ERK inhibitors through SRC

PTPRS is the most commonly mutated receptor tyrosine phosphatase in colorectal cancer (CRC). PTPRS has been shown to directly affect ERK and regulate its activation and nuclear localization. Here we identify that PTPRS may play a significant role in developing adaptive resistance to MEK/ERK inhibitors (MEKi/ERKi) through SRC activation. Moreover, we demonstrate a new clinical approach to averting adaptive resistance through the use of the SRC inhibitor, dasatinib. Our data suggest the potential for dasatinib to enhance the efficacy of MEKi and ERKi by preventing adaptive resistance pathways operating through SRC.

Luteolin attenuates migration and invasion of lung cancer cells via suppressing focal adhesion kinase and non-receptor tyrosine kinase signaling pathway

BACKGROUND/OBJECTIVES

Non-small cell lung cancer is mostly recognized among other types of lung cancer with a poor prognosis by cause of chemotherapeutic resistance and increased metastasis. Luteolin has been found to decrease cell metastasis. However, its underlying mechanisms remain unresolved. The objective of this study was to examine the effect (and its mechanism) of luteolin on the migration and invasion of human non-small cell lung cancer A549 cells.

MATERIALS/METHODS

Cell viability was investigated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Wound healing and transwell assays were evaluated to assess migration and invasion, respectively. Western blot analysis and immunofluorescence were further performed to investigate the role of luteolin and its mechanisms of action.

RESULTS

Administration with up to 40 µM luteolin showed no cytotoxic activity on lung cancer A549 cells or non-cancer MRC-5 cells. Additionally, luteolin at 20-40 µM significantly suppressed A549 cells' migration, invasion, and the formation of filopodia in a concentration-dependent manner at 24 h. This is similar with western blot analysis, which revealed diminished the phosphorylated focal adhesion kinase (pFAK), phosphorylated non-receptor tyrosine kinase (pSrc), Ras-related C3 botulinum toxin substrate 1 (Rac1), cell division control protein 42 (Cdc42), and Ras homolog gene family member A (RhoA) expression levels.

CONCLUSIONS

Overall, our data indicate that luteolin plays a role in controlling lung cancer cells' migration and invasion via Src/FAK and its downstream Rac1, Cdc42, and RhoA pathways. Luteolin might be considered a promising candidate for suppressing invasion and metastasis of lung cancer cells.

The Differential Impact of SRC Expression on the Prognosis of Patients with Head and Neck Squamous Cell Carcinoma

Aberrant SRC expression and activation is frequently detected in multiple cancers, and hence, targeting SRC has emerged as a promising therapeutic strategy. Different SRC inhibitors have demonstrated potent anti-tumor activity in preclinical models, although they largely lack clinical efficacy as monotherapy in late-stage solid tumors, including head and neck squamous cell carcinomas (HNSCC). Adequate selection and stratification of patients who may respond to and benefit from anti-SRC therapies is therefore needed to guide clinical trials and treatment efficacy. This study investigates the prognostic significance of active SRC expression in a homogeneous cohort of 122 human papillomavirus (HPV)-negative, surgically treated HNSCC patients. Immunohistochemical evaluation of the active form of SRC by means of anti-SRC Clone 28 monoclonal antibody was specifically performed and subsequently correlated with clinical data. The expression of p-SRC (Tyr419), total SRC, and downstream SRC effectors was also analyzed. Our results uncovered striking differences in the prognostic relevance of SRC expression in HNSCC patients depending on the tumor site. Active SRC expression was found to significantly associate with advanced disease stages, presence of lymph node metastasis, and tumor recurrences in patients with laryngeal tumors, but not in the pharyngeal subgroup. Multivariate Cox analysis further revealed active SRC expression as an independent predictor of cancer-specific mortality in patients with laryngeal carcinomas. Concordantly, expression of p-SRC (Tyr419) and the SRC substrates focal adhesion kinase (FAK) and the Arf GTPase-activating protein ASAP1 also showed specific associations with poor prognosis in the larynx. These findings could have important implications in ongoing Src family kinase (SFK)-based clinical trials, as these new criteria could help to improve patient selection and develop biomarker-stratified trials.

Small molecule FAK activator promotes human intestinal epithelial monolayer wound closure and mouse ulcer healing

GI mucosal healing requires epithelial sheet migration. The non-receptor tyrosine kinase focal adhesion kinase (FAK) stimulates epithelial motility. A virtual screen identified the small drug-like FAK mimic ZINC40099027, which activates FAK. We assessed whether ZINC40099027 promotes FAK-Tyr-397 phosphorylation and wound healing in Caco-2 monolayers and two mouse intestinal injury models. Murine small bowel ulcers were generated by topical serosal acetic acid or subcutaneous indomethacin in C57BL/6J mice. One day later, we began treatment with ZINC40099027 or DMSO, staining the mucosa for phosphorylated FAK and Ki-67 and measuring mucosal ulcer area, serum creatinine, ALT, and body weight at day 4. ZINC40099027 (10–1000 nM) dose-dependently activated FAK phosphorylation, without activating Pyk2-Tyr-402 or Src-Tyr-419. ZINC40099027 did not stimulate proliferation, and stimulated wound closure independently of proliferation. The FAK inhibitor PF-573228 prevented ZINC40099027-stimulated wound closure. In both mouse ulcer models, ZINC40099027accelerated mucosal wound healing. FAK phosphorylation was increased in jejunal epithelium at the ulcer edge, and Ki-67 staining was unchanged in jejunal mucosa. ZINC40099027 serum concentration at sacrifice resembled the effective concentration in vitro. Weight, creatinine and ALT did not differ between groups. Small molecule FAK activators can specifically promote epithelial restitution and mucosal healing and may be useful to treat gut mucosal injury.

The Leptin induced Hic-5 expression and actin puncta formation by the FAK/Src-dependent pathway in MCF10A mammary epithelial cells

Introduction: Leptin is a hormone secreted by adipocytes that has been associated with the epithelial-mesenchymal transition (EMT). Additionally, leptin promotes the migration and invasion of mammary epithelial cells through the activation of FAK and Src kinases, which are part of a regulatory complex of signaling pathways that promotes the expression of proteins related to the formation of proteolytic structures involved in the invasion and progression of cancer. Recently, overexpression and activation of Hic-5 during the EMT have been shown to induce the formation of actin puncta; these structures are indicative of the formation and functionality of invadopodia, which promote the local degradation of extracellular matrix components and cancer metastasis. Objective: To evaluate the role of FAK and Src kinases in the expression of Hic-5 during the epithelial-mesenchymal transition induced by leptin in MCF10A cells. Materials and methods: We used specific inhibitors of FAK (PF-573228) and Src (PP2) to evaluate Hic-5 expression and subcellular localization by Western blot and immunofluorescence assays and to investigate the formation of actin puncta by epifluorescence in MCF10A cells stimulated with leptin. Results: Leptin induced an increase in Hic-5 expression and the formation of actin puncta. Pretreatment with inhibitors of FAK (PF-573228) and Src (PP2) promoted a decrease in Hic-5 expression and actin puncta formation in the non-tumorigenic mammary epithelial cell line MCF10A. Conclusion: In MCF10A cells, leptin-induced Hic-5 expression and perinuclear localization, as well as the formation of actin puncta through a mechanism dependent on the kinase activity of FAK and Src.

Targeting the complexity of Src signalling in the tumour microenvironment of pancreatic cancer: from mechanism to therapy

Pancreatic cancer, a disease with extremely poor prognosis, has been notoriously resistant to virtually all forms of treatment. The dynamic crosstalk that occurs between tumour cells and the surrounding stroma, frequently mediated by intricate Src/FAK signalling, is increasingly recognised as a key player in pancreatic tumourigenesis, disease progression and therapeutic resistance. These important cues are fundamental for defining the invasive potential of pancreatic tumours, and several components of the Src and downstream effector signalling have been proposed as potent anticancer therapeutic targets. Consequently, numerous agents that block this complex network are being extensively investigated as potential antiinvasive and antimetastatic therapeutic agents for this disease. In this review, we will discuss the latest evidence of Src signalling in PDAC progression, fibrotic response and resistance to therapy. We will examine future opportunities for the development and implementation of more effective combination regimens, targeting key components of the oncogenic Src signalling axis, and in the context of a precision medicine-guided approach.

SRC fine-tunes ADAM10 shedding activity to promote pituitary adenoma cell progression

A disintegrin and metalloproteinase domain-containing protein 10 (ADAM10) is a metalloproteinase known to modulate the progression of several types of tumor. However, the role played by ADAM10 in pituitary adenomas is currently unknown, and what factors orchestrate the activation of ADAM10 in this kind of tumor is also unclear. Here, we found that SRC kinase is an ADAM10-interacting partner and that SRC kinase activity is required for this interaction. As a new positive regulator promoting the shedding activity of ADAM10, SRC could compete with calmodulin 1 (CALM1) for ADAM10 binding in a mutually exclusive manner. Strikingly, the interaction between ADAM10 and CALM1 is regulated by SRC activity. Furthermore, we proved that the cytoplasmic region of ADAM10 is required for the shedding activity of ADAM10 upon SRC activation. As a proof-of-concept, we discovered that the combination of ADAM10 and SRC inhibitors can inhibit cell proliferation and migration to a great extent. Thus, our findings shed light on a novel therapeutic strategy to block the tumorigenesis and migration of pituitary adenoma.

A Tyrosine Kinase Expression Signature Predicts the Post-Operative Clinical Outcome in Triple Negative Breast Cancers

Triple negative breast cancer (TNBC) represent 15% of breast cancers. Histoclinical features and marketed prognostic gene expression signatures (GES) failed to identify good- and poor-prognosis patients. Tyrosine kinases (TK) represent potential prognostic and/or therapeutic targets for TNBC. We sought to define a prognostic TK GES in a large series of TNBC. mRNA expression and histoclinical data of 6379 early BCs were collected from 16 datasets. We searched for a TK-based GES associated with disease-free survival (DFS) and tested its robustness in an independent validation set. A total of 1226 samples were TNBC. In the learning set of samples (N = 825), we identified a 13-TK GES associated with DFS. This GES was associated with cell proliferation and immune response. In multivariate analysis, it outperformed the previously published GESs and classical prognostic factors in the validation set (N = 401), in which the patients classified as "low-risk" had a 73% 5-year DFS versus 53% for "high-risk" patients (p = 1.85 × 10-3). The generation of 100,000 random 13-gene signatures by a resampling scheme showed the non-random nature of our classifier, which was also prognostic for overall survival in multivariate analysis. We identified a robust and non-random 13-TK GES that separated TNBC into subgroups of different prognosis. Clinical and functional validations are warranted.

The SRC Inhibitor Dasatinib Induces Stem Cell-Like Properties in Head and Neck Cancer Cells that are Effectively Counteracted by the Mithralog EC-8042

The frequent dysregulation of SRC family kinases (SFK) in multiple cancers prompted various inhibitors to be actively tested in preclinical and clinical trials. Disappointingly, dasatinib and saracatinib failed to demonstrate monotherapeutic efficacy in patients with head and neck squamous cell carcinomas (HNSCC). Deeper functional and mechanistic knowledge of the actions of these drugs is therefore needed to improve clinical outcome and to develop more efficient combinational strategies. Even though the SFK inhibitors dasatinib and saracatinib robustly blocked cell migration and invasion in HNSCC cell lines, this study unveils undesirable stem cell-promoting functions that could explain the lack of clinical efficacy in HNSCC patients. These deleterious effects were targeted by the mithramycin analog EC-8042 that efficiently eliminated cancer stem cells (CSC)-enriched tumorsphere cultures as well as tumor bulk cells and demonstrated potent antitumor activity in vivo. Furthermore, combination treatment of dasatinib with EC-8042 provided favorable complementary anti-proliferative, anti-invasive, and anti-CSC functions without any noticeable adverse interactions of both agents. These findings strongly support combinational strategies with EC-8042 for clinical testing in HNSCC patients. These data may have implications on ongoing dasatinib-based trials.

An effective cell-penetrating antibody delivery platform

Despite their well-recognized success in the clinic, antibodies generally do not penetrate cellular membranes to target intracellular molecules, many of which underlie incurable diseases. Here we show that covalently conjugating phosphorothioated DNA oligonucleotides to antibodies enabled their efficient cellular internalization. Antibody cell penetration was partially mediated by membrane potential alteration. Moreover, without an antigen to bind, intracellular levels of the modified antibodies underwent cellular clearance, which involved efflux and lysosomal degradation, enabling detection of intended intracellular molecules as tested in fibroblasts, tumor cells, and T cells. This target-dependent cellular retention of modified antibodies extended to in vivo studies. Both local and systemic administrations of low doses of modified antibodies effectively inhibited intracellular targets, such as transcription factors Myc, interferon regulatory factor 4, and tyrosine-protein kinase SRC, and expression of their downstream genes in tumors, resulting in tumor cell apoptosis and tumor growth inhibition. This simple modification enables the use of antibodies to detect and modulate intracellular molecules in both cultured living cells and in whole animals, forming the foundation for a new paradigm for antibody-based research, diagnostics, and therapeutics.

A phase 1 and randomized, placebo-controlled phase 2 trial of bevacizumab plus dasatinib in patients with recurrent glioblastoma: Alliance/North Central Cancer Treatment Group N0872

BACKGROUND

Src signaling is markedly upregulated in patients with invasive glioblastoma (GBM) after the administration of bevacizumab. The Src family kinase inhibitor dasatinib has been found to effectively block bevacizumab-induced glioma invasion in preclinical models, which led to the hypothesis that combining bevacizumab with dasatinib could increase bevacizumab efficacy in patients with recurrent GBM.

METHODS

After the completion of the phase 1 component, the phase 2 trial (ClinicalTrials.gov identifier NCT00892177) randomized patients with recurrent GBM 2:1 to receive 100 mg of oral dasatinib twice daily (arm A) or placebo (arm B) on days 1 to 14 of each 14-day cycle combined with 10 mg/kg of intravenous bevacizumab on day 1 of each 14-day cycle. The primary endpoint was 6-month progression-free survival (PFS6).

RESULTS

In the 121 evaluable patients, the PFS6 rate was numerically, but not statistically, higher in arm A versus arm B (28.9% [95% CI, 19.5%-40.0%] vs 18.4% [95% CI, 7.7%-34.4%]; P = .22). Similarly, there was no significant difference in the median overall survival noted between the treatment arms (7.3 months and 7.7 months, respectively; P = .93). The objective response rate was 15.7% in arm A and 26.3% in arm B (P = .52), but with a significantly longer duration in patients treated on arm A (16.3 months vs 2 months). The incidence of grade ≥3 toxicity was comparable between treatment arms, with hematologic toxicities occurring more frequently in arm A versus arm B (15.7% vs 7.9%) (adverse events were assessed as per the National Cancer Institute Common Terminology Criteria for Adverse Events [version 4.0]). Correlative tissue analysis demonstrated an association between pSRC/LYN signaling in patient tumors and outcome.

CONCLUSIONS

Despite upregulation of Src signaling in patients with GBM, the combination of bevacizumab with dasatinib did not appear to significantly improve the outcomes of patients with recurrent GBM compared with bevacizumab alone.

SNX10 (sorting nexin 10) inhibits colorectal cancer initiation and progression by controlling autophagic degradation of SRC

The non-receptor tyrosine kinase SRC is a key mediator of cellular protumorigenic signals. SRC is aberrantly over-expressed and activated in more than 80% of colorectal cancer (CRC) patients, therefore regulation of its stability and activity is essential. Here, we report a significant down regulation of SNX10 (sorting nexin 10) in human CRC tissues, which is closely related to tumor differentiation, TNM stage, lymph node metastasis and survival period. SNX10 deficiency in normal and neoplastic colorectal epithelial cells promotes initiation and progression of CRC in mice. SNX10 controls SRC levels by mediating autophagosome-lysosome fusion and SRC recruitment for autophagic degradation. These mechanisms ensure proper controlling of the activities of SRC-STAT3 and SRC-CTNNB1 signaling pathways by up-regulating SNX10 expression under stress conditions. These findings suggest that SNX10 acts as a tumor suppressor in CRC and it could be a potential therapeutic target for future development.Abbreviations: ACTB: actin beta; ATG5: autophagy related 5; ATG12: autophagy related 12; CQ: chloroquine; CRC: colorectal cancer; CTNNB1: catenin beta 1; EBSS: Earle's balanced salt solution; KO: knockout; LAMP1: lysosomal associated membrane protein 1; LAMP2: lysosomal associated membrane protein 2; MAP1LC3: microtubule associated protein 1 light chain 3; MKI67: marker of proliferation Ki-67; mRNA: messenger RNA; PX: phox homology; RT-qPCR: real time quantitative polymerase chain reaction; siRNA: small interfering RNA; SNX10: sorting nexin 10; SQSTM1: sequestosome 1; SRC: SRC proto-oncogene, non-receptor tyrosine kinase; STAT3: signal transducer and activator of transcription 3; WT: wild type.

TNFα promotes mucosal wound repair through enhanced platelet activating factor receptor signaling in the epithelium

Pathobiology of several chronic inflammatory disorders, including ulcerative colitis and Crohn's disease is related to intermittent, spontaneous injury/ulceration of mucosal surfaces. Disease morbidity has been associated with pathologic release of the pro-inflammatory cytokine tumor necrosis factor alpha (TNFα). In this report, we show that TNFα promotes intestinal mucosal repair through upregulation of the GPCR platelet activating factor receptor (PAFR) in the intestinal epithelium. Platelet activating factor (PAF) was increased in healing mucosal wounds and its engagement with epithelial PAFR leads to activation of epidermal growth factor receptor, Src and Rac1 signaling to promote wound closure. Consistent with these findings, delayed colonic mucosal repair was observed after administration of a neutralizing TNFα antibody and in mice lacking PAFR. These findings suggest that in the injured mucosa, the pro-inflammatory milieu containing TNFα and PAF sets the stage for reparative events mediated by PAFR signaling.

A New Strategy for Glioblastoma Treatment: In Vitro and In Vivo Preclinical Characterization of Si306, a Pyrazolo[3,4-d]Pyrimidine Dual Src/P-Glycoprotein Inhibitor

Overexpression of P-glycoprotein (P-gp) and other ATP-binding cassette (ABC) transporters in multidrug resistant (MDR) cancer cells is responsible for the reduction of intracellular drug accumulation, thus decreasing the efficacy of chemotherapeutics. P-gp is also found at endothelial cells' membrane of the blood-brain barrier, where it limits drug delivery to central nervous system (CNS) tumors. We have previously developed a set of pyrazolo[3,4-d]pyrimidines and their prodrugs as novel Src tyrosine kinase inhibitors (TKIs), showing a significant activity against CNS tumors in in vivo. Here we investigated the interaction of the most promising pair of drug/prodrug with P-gp at the cellular level. The tested compounds were found to increase the intracellular accumulation of Rho 123, and to enhance the efficacy of paclitaxel in P-gp overexpressing cells. Encouraging pharmacokinetics properties and tolerability in vivo were also observed. Our findings revealed a novel role of pyrazolo[3,4-d]pyrimidines which may be useful for developing a new effective therapy in MDR cancer treatment, particularly against glioblastoma.

c-Src is required for hypoxia-induced metastasis-associated functions in prostate cancer cells

Background: Metastasis is the major cause of therapeutic failure in prostate cancer patients, and hypoxia has been shown to promote metastatic functions. However, whether Src family kinases (SFKs) can be upregulated under hypoxia is unclear.

Materials and methods: In the current study, we evaluated the effects of hypoxia on cellular functions and activities of different SFK members (c-Src, Lyn, Fyn) in prostate cancer cells. Prostate cancer cell functions were determined in vitro including migration (wound-healing assay), invasion (Matrigel-based transwell assay) and clonogenic cell survival (colony formation assay). Protein expression was detected by Western blotting and gene knockdown was accomplished by siRNA transfection.

Results:SRC, but not LYN and FYN, is associated with overall survival in prostate cancer patients, while all three phosphorylated proteins are highly expressed in tumors compared to normal tissues. Short-term hypoxic exposure significantly enhances cell migration, invasion, clonogenic survival, and consistently, c-Src phosphorylation in both PC-3ML and C4-2B cells. Knockdown of SRC, but not LYN or FYN, abolished hypoxia-induced functions. Finally, small molecule Src inhibitors strongly inhibited cell behaviors and c-Src activation under hypoxic conditions.

Conclusion: Our data show that hypoxia is able to enhance metastatic-associated cell functions by activating c-Src in prostate cancer cells. Importantly, SFK inhibition by small molecule inhibitors was able to impair hypoxia-induced metastasis associated cell functions, suggesting a possible role of SFK inhibitors for prostate cancer treatment.

Structure and mechanisms of ROS generation by NADPH oxidases

NADPH oxidases (NOXs) are integral membrane enzymes that produce reactive oxygen species. Humans have seven NOX enzymes that feature a very similar catalytic core but distinct regulatory mechanisms. The recent structural elucidation of the NOX catalytic domains has been a step forward in the field. NADPH, FAD, and two hemes form a linear array of redox cofactors that transfer electrons across to the two sides of the membrane. Oxygen is reduced through an unusual outer sphere mechanism that does not involve any covalent intermediate with the heme iron. Several recent studies have expanded the roles of NOXs in cell signaling, innate immune response, and cell proliferation including oncogenic transformation. This work reinforces NOX-generated ROS as powerful signaling molecules. A challenging question is to understand the specific mechanisms of enzyme regulation and to harness the growing insight on NOXs' structure and biochemistry to generate more powerful small-molecule modulators of NOX activities.

Actomyosin contraction during cellularization is regulated in part by Src64 control of Actin 5C protein levels

Src64 is required for actomyosin contraction during cellularization of the Drosophila embryonic blastoderm. The mechanism of actomyosin ring constriction is poorly understood even though a number of cytoskeletal regulators have been implicated in the assembly, organization, and contraction of these microfilament rings. How these cytoskeletal processes are regulated during development is even less well understood. To investigate the role of Src64 as an upstream regulator of actomyosin contraction, we conducted a proteomics screen to identify proteins whose expression levels are controlled by src64. Global levels of actin are reduced in src64 mutant embryos. Furthermore, we show that reduction of the actin isoform Actin 5C causes defects in actomyosin contraction during cellularization similar to those caused by src64 mutation, indicating that a relatively high level of Actin 5C is required for normal actomyosin contraction and furrow canal structure. However, reduction of Actin 5C levels only slows down actomyosin ring constriction rather than preventing it, suggesting that src64 acts not only to modulate actin levels, but also to regulate the actomyosin cytoskeleton by other means.

Src Family Kinase Inhibitors Block Translation of Alphavirus Subgenomic mRNAs

Alphaviruses are arthropod-transmitted RNA viruses that can cause arthralgia, myalgia, and encephalitis in humans. Since the role of cellular kinases in alphavirus replication is unknown, we profiled kinetic changes in host kinase abundance and phosphorylation following chikungunya virus (CHIKV) infection of fibroblasts.

Alphaviruses are arthropod-transmitted RNA viruses that can cause arthralgia, myalgia, and encephalitis in humans. Since the role of cellular kinases in alphavirus replication is unknown, we profiled kinetic changes in host kinase abundance and phosphorylation following chikungunya virus (CHIKV) infection of fibroblasts. Based upon the results of this study, we treated CHIKV-infected cells with kinase inhibitors targeting the Src family kinase (SFK)–phosphatidylinositol 3-kinase (PI3K)–AKT–mTORC signaling pathways. Treatment of cells with SFK inhibitors blocked the replication of CHIKV as well as multiple other alphaviruses, including Mayaro virus, O’nyong-nyong virus, Ross River virus, and Venezuelan equine encephalitis virus. Dissecting the effect of SFK inhibition on alphavirus replication, we found that viral structural protein levels were significantly reduced, but synthesis of viral genomic and subgenomic RNAs was unaffected. By measuring the association of viral RNA with polyribosomes, we found that the SFK inhibitor dasatinib blocks alphavirus subgenomic RNA translation. Our results demonstrate a role for SFK signaling in alphavirus subgenomic RNA translation and replication. Targeting host factors involved in alphavirus replication represents an innovative, perhaps paradigm-shifting, strategy for exploring the replication of CHIKV and other alphaviruses while promoting antiviral therapeutic development.

A novel ex vivo tumor system identifies Src-mediated invasion and metastasis in mesenchymal tumor cells in non-small cell lung cancer

Lung cancer is the foremost cause of cancer related deaths in the U.S. It is a heterogeneous disease composed of genetically and phenotypically distinct tumor cells surrounded by heterotypic cells and extracellular matrix dynamically interacting with the tumor cells. Research in lung cancer is often restricted to patient-derived tumor specimens, in vitro cell cultures and limited animal models, which fail to capture the cellular or microenvironment heterogeneity of the tumor. Therefore, our knowledge is primarily focused on cancer-cell autonomous aberrations. For a fundamental understanding of lung cancer progression and an exploration of therapeutic options, we focused our efforts to develop an Ex Vivo Tumor platform to culture tumors in 3D matrices, which retains tumor cell heterogeneity arising due to in vivo selection pressure and environmental influences and recapitulate responses of tumor cells to external manipulations. To establish this model, implanted syngeneic murine tumors from a mutant KRAS/p53 model were harvested to yield multicellular tumor aggregates followed by culture in 3D extracellular matrices. Using this system, we identified Src signaling as an important driver of invasion and metastasis in lung cancer and demonstrate that EVTs are a robust experimental tool bridging the gap between conventional in vitro and in vivo models.

Mbt/PAK4 together with SRC modulates N-Cadherin adherens junctions in the developing Drosophila eye

Tissue morphogenesis is accompanied by changes of adherens junctions (AJ). During Drosophila eye development, AJ reorganization includes the formation of isolated N-Cadherin AJ between photoreceptors R3/R4. Little is known about how these N-Cadherin AJ are established and maintained. This study focuses on the kinases Mbt/PAK4 and SRC, both known to alter E-Cadherin AJ across phyla. Drosophila p21-activated kinase Mbt and the non-receptor tyrosine kinases Src64 and Src42 regulate proper N-Cadherin AJ. N-Cadherin AJ elongation depends on SRC kinase activity. Cell culture experiments demonstrate binding of both Drosophila SRC isoforms to N-Cadherin and its subsequent tyrosine phosphorylation. In contrast, Mbt stabilizes but does not bind N-Cadherin in vitro. Mbt is required in R3/R4 for zipping the N-Cadherin AJ between these cells, independent of its kinase activity and Cdc42-binding. The mbt phenotype can be reverted by mutations in Src64 and Src42. Because Mbt neither directly binds to SRC proteins nor has a reproducible influence on their kinase activity, the conclusion is that Mbt and SRC signaling converge on N-Cadherin. N-Cadherin AJ formation during eye development requires a proper balance between the promoting effects of Mbt and the inhibiting influences of SRC kinases.

Summary: N-Cadherin adherens junction formation in the Drosophila larval eye imaginal disc is controlled by the combined functions of the p21-activated kinase Mbt/PAK4 and the kinases Src64 and Src42.

Src in endosomal membranes promotes exosome secretion and tumor progression

c-Src is a membrane-associated tyrosine kinase that has key roles in the signaling transduction that controls cell growth, adhesion, and migration. In the early stage of carcinogenesis, c-Src is activated under the plasma membrane and transduces oncogenic signals. Here we show that c-Src localized to the endosomal membrane has unique functions in c-Src-transformed cells. Our results indicate that activated c-Src in the endosomal membrane promoted the secretion of exosomes, in which c-Src was encapsulated. In addition, the ESCRT-interacting molecule, Alix was identified as a c-Src-interacting protein in exosomes. We revealed that the interaction between the SH3 domain of c-Src and the proline-rich region of Alix activates ESCRT-mediated intra-luminal vesicle (ILV) formation, resulting in the upregulation of exosome secretion in c-Src-transformed cells. We observed also a correlation between malignant phenotypes and Alix-dependent aberrant exosome secretion in Src-upregulated cancer cells. Collectively, our findings provide a unique mechanism for the upregulation of exosomes in cancer cells, as well as new insights into the significance of exosome secretion in cancer progression.

Drosophila melanogaster: A Model Organism to Study Cancer

Cancer is a multistep disease driven by the activation of specific oncogenic pathways concomitantly with the loss of function of tumor suppressor genes that act as sentinels to control physiological growth. The conservation of most of these signaling pathways in Drosophila, and the ability to easily manipulate them genetically, has made the fruit fly a useful model organism to study cancer biology. In this review we outline the basic mechanisms and signaling pathways conserved between humans and flies responsible of inducing uncontrolled growth and cancer development. Second, we describe classic and novel Drosophila models used to study different cancers, with the objective to discuss their strengths and limitations on their use to identify signals driving growth cell autonomously and within organs, drug discovery and for therapeutic approaches.

BRAF V600E and SRC mutations as molecular markers for predicting prognosis and conversion surgery in Stage IV colorectal cancer

Comprehensive genomic sequencing (CGS) enables us to detect numerous genetic alterations in a single assay. We aimed to identify molecular markers for predicting prognosis and conversion surgery in Stage IV colorectal cancer (CRC) using CGS. One-hundred eleven patients with Stage IV CRC who underwent primary tumor resection were analyzed. We retrospectively investigated genetic alterations using CGS of a 415-gene panel. Clinicopathological variables and genetic alterations were analyzed to identify independent prognostic factors of overall survival (OS). Forty-five of 111 patients had R0 resection; of these, 11 patients underwent conversion surgery. Univariate and multivariate analyses identified histopathological grade 3, R0 resection, BRAF V600E mutation, and SRC mutation as independent prognostic factors for OS (P = 0.041, P = 0.013, P = 0.005, and P = 0.023, respectively). BRAF V600E and SRC mutations were mutually exclusive, and SRC mutation was significantly associated with left-sided tumor and liver metastasis compared to BRAF V600E mutation (P = 0.016 and P = 0.025, respectively). Eleven of the 74 initially unresectable patients underwent conversion surgery for R0 resection, yet none harbored BRAF V600E or SRC mutations. BRAF V600E and SRC mutations are important molecular markers which can predict prognosis and conversion surgery in Stage IV CRC.

Src kinase inhibition restores E-cadherin expression in dasatinib-sensitive pancreatic cancer cells

The Src family of non-receptor tyrosine kinases are frequently activated in pancreatic ductal adenocarcinoma (PDAC), contributing to disease progression through downregulation of E-cadherin and induction of epithelial-to-mesenchymal transition (EMT). The purpose of this study was to examine the efficacy of Src kinase inhibition in restoring E-cadherin levels in PDAC. Immunohistochemical analysis of human PDAC samples showed Src activation is inversely correlated with E-cadherin levels. Protein and mRNA levels of E-cadherin, the gene expression of its various transcriptional repressors (Zeb1, Snail, Slug, LEF-1, TWIST), and changes in sub-cellular localization of E-cadherin/β-catenin in PDAC cells were characterized in response to treatment with the Src inhibitor, dasatinib (DST). DST repressed Slug mRNA expression, promoted E-cadherin transcription, and increased total and membranous E-cadherin/β-catenin levels in drug-sensitive PDAC cells (BxPC3 and SW1990), however no change was observed in drug-resistant PANC1 cells. BxPC3, PANC1, and MiaPaCa-2 flank tumor xenografts were treated with DST to examine changes in E-cadherin levels in vivo. Although DST inhibited Src phosphorylation in all xenograft models, E-cadherin levels were only restored in BxPC3 xenograft tumors. These results suggest that Src kinase inhibition reverses EMT in drug-sensitive PDAC cells through Slug-mediated repression of E-cadherin and identifies E-cadherin as potential biomarker for determining response to DST treatment.

A Myristoyl-Binding Site in the SH3 Domain Modulates c-Src Membrane Anchoring

The c-Src oncogene is anchored to the cytoplasmic membrane through its N-terminal myristoylated SH4 domain. This domain is part of an intramolecular fuzzy complex with the SH3 and Unique domains. Here we show that the N-terminal myristoyl group binds to the SH3 domain in the proximity of the RT loop, when Src is not anchored to a lipid membrane. Residues in the so-called Unique Lipid Binding Region modulate this interaction. In the presence of lipids, the myristoyl group is released from the SH3 domain and inserts into the lipid membrane. The fuzzy complex with the SH4 and Unique domains is retained in the membrane-bound form, placing the SH3 domain close to the membrane surface and restricting its orientation. The apparent affinity of myristoylated proteins containing the SH4, Unique, and SH3 domains is modulated by these intramolecular interactions, suggesting a mechanism linking c-Src activation and membrane anchoring.

GPR35 promotes glycolysis, proliferation, and oncogenic signaling by engaging with the sodium potassium pump

The sodium potassium pump (Na/K-ATPase) ensures the electrochemical gradient of a cell through an energy-dependent process that consumes about one-third of regenerated ATP. We report that the G protein-coupled receptor GPR35 interacted with the α chain of Na/K-ATPase and promotes its ion transport and Src signaling activity in a ligand-independent manner. Deletion of Gpr35 increased baseline Ca²⁺ to maximal levels and reduced Src activation and overall metabolic activity in macrophages and intestinal epithelial cells (IECs). In contrast, a common T108M polymorphism in GPR35 was hypermorphic and had the opposite effects to Gpr35 deletion on Src activation and metabolic activity. The T108M polymorphism is associated with ulcerative colitis and primary sclerosing cholangitis, inflammatory diseases with a high cancer risk. GPR35 promoted homeostatic IEC turnover, whereas Gpr35 deletion or inhibition by a selective pepducin prevented inflammation-associated and spontaneous intestinal tumorigenesis in mice. Thus, GPR35 acts as a central signaling and metabolic pacesetter, which reveals an unexpected role of Na/K-ATPase in macrophage and IEC biology.

Dasatinib sensitises triple negative breast cancer cells to chemotherapy by targeting breast cancer stem cells

BACKGROUND

Patients with triple negative breast cancer (TNBC) exhibit poor prognosis and are at high risk of tumour relapse, due to the resistance to chemotherapy. These aggressive phenotypes are in part attributed to the presence of breast cancer stem cells (BCSCs). Therefore, targeting BCSCs is a priority to overcoming chemotherapy failure in TNBCs.

METHODS

We generated paclitaxel (pac)-resistant TNBC cells which displayed higher sphere forming potential and percentage of BCSC subpopulations compared to the parental cells. A screen with various kinase inhibitors revealed dasatinib, a Src kinase family inhibitor, as a potent suppressor of BCSC expansion/sphere formation in pac-resistant TNBC cells.

RESULTS

We found dasatinib to block pac-induced BCSC enrichment and Src activation in both parental and pac-resistant TNBC cells. Interestingly, dasatinib induced an epithelial differentiation of the pac-resistant mesenchymal cells, resulting in their enhanced sensitivity to paclitaxel. The combination treatment of dasatinib and paclitaxel not only decreased the BCSCs numbers and their sphere forming capacity but also synergistically reduced cell viability of pac-resistant cells. Preclinical models of breast cancer further demonstrated the efficiency of the dasatinib/paclitaxel combination treatment in inhibiting tumour growth.

CONCLUSIONS

Dasatinib is a promising anti-BCSC drug that could be used in combination with paclitaxel to overcome chemoresistance in TNBC.

SRC inhibition prevents P-cadherin mediated signaling and function in basal-like breast cancer cells

BACKGROUND

Basal-like breast cancer (BLBC) is a poor prognosis subgroup of triple-negative carcinomas that still lack specific target therapies and accurate biomarkers for treatment selection. P-cadherin is frequently overexpressed in these tumors, promoting cell invasion, stem cell activity and tumorigenesis by the activation of Src-Family kinase (SRC) signaling. Therefore, our aim was to evaluate if the treatment of BLBC cells with dasatinib, the FDA approved SRC inhibitor, would impact on P-cadherin induced tumor aggressive behavior.

METHODS

P-cadherin and SRC expression was evaluated in a series of invasive Breast Cancer and contingency tables and chi-square tests were performed. Cell-cell adhesion measurements were performed by Atomic Force Microscopy, where frequency histograms and Gaussian curves were applied. 2D and 3D cell migration and invasion, proteases secretion and self-renew potential were evaluated in vitro. Student's t-tests were used to determine statistically significant differences. The cadherin/catenin complex interactions were evaluated by in situ proximity-ligation assay, and statistically significant results were determined by using Mann-Whitney test with a Bonferroni correction. In vivo xenograft mouse models were used to evaluate the impact of dasatinib on tumor growth and survival. ANOVA test was used to evaluate the differences in tumor size, considering a confidence interval of 95%. Survival curves were estimated by the Kaplan-Meier's method, using the log-rank test to assess significant differences for mice overall survival.

RESULTS

Our data demonstrated that P-cadherin overexpression is significantly associated with SRC activation in breast cancer cells, which was also validated in a large series of primary tumor samples. SRC activity suppression with dasatinib significantly prevented the in vitro functional effects of P-cadherin overexpressing cells, as well as their in vivo tumorigenic and metastatic ability, by increasing mice overall survival. Mechanistically, SRC inhibition affects P-cadherin downstream signaling, rescues the E-cadherin/p120-catenin complex to the cell membrane, recovering cell-cell adhesion function.

CONCLUSIONS

In conclusion our findings show that targeting P-cadherin/SRC signaling and functional activity may open novel therapeutic opportunities for highly aggressive and poor prognostic basal-like breast cancer.

Long non-coding RNA DLEU1 exerts an oncogenic function in non-small cell lung cancer

OBJECTIVE

To explore the role of long non-coding RNA DLEU1 in the tumorigenesis and progression of non-small cell lung cancer (NSCLC) and the underlying mechanisms.

METHODS

The expression of DLEU1 in NSCLC tumor tissues and adjacent normal tissues was evaluated using bioinformatics analysis and qPCR. The effects of DLEU1 overexpression or deficiency on cell proliferation, apoptosis, migration and invasion were explored experimentally. Additionally, the impact of DLEU1 up-regulation on tumourigenesis was also assessed in vivo.

RESULTS

The expression of DLEU1 was up-regulated in NSCLC tumor tissues. DLEU1 overexpression promoted the proliferation, migration, and invasion, but inhibited the apoptosis of NSCLC cells by upregulating CDK1 expression, binding with SRC and altering the expression of P70(S6K), MMP2 and E-cadherin. Besides, xenograft tumors in nude mice demonstrated that DLEU1 overexpression accelerated tumor growth.

CONCLUSIONS

DLEU1 promoted tumorigenesis and progression of NSCLC, and might be a promising therapeutic target for NSCLC.

Direct cysteine sulfenylation drives activation of the Src kinase

The Src kinase controls aspects of cell biology and its activity is regulated by intramolecular structural changes induced by protein interactions and tyrosine phosphorylation. Recent studies indicate that Src is additionally regulated by redox-dependent mechanisms, involving oxidative modification(s) of cysteines within the Src protein, although the nature and molecular-level impact of Src cysteine oxidation are unknown. Using a combination of biochemical and cell-based studies, we establish the critical importance of two Src cysteine residues, Cys-185 and Cys-277, as targets for H2O2-mediated sulfenylation (Cys-SOH) in redox-dependent kinase activation in response to NADPH oxidase-dependent signaling. Molecular dynamics and metadynamics simulations reveal the structural impact of sulfenylation of these cysteines, indicating that Cys-277-SOH enables solvent exposure of Tyr-416 to promote its (auto)phosphorylation, and that Cys-185-SOH destabilizes pTyr-527 binding to the SH2 domain. These redox-dependent Src activation mechanisms offer opportunities for development of Src-selective inhibitors in treatment of diseases where Src is aberrantly activated.

Anoikis‑resistant human osteosarcoma cells display significant angiogenesis by activating the Src kinase‑mediated MAPK pathway

Tumor cells must resist anoikis to metastasize. There is a key role of angiogenesis in the growth and metastasis of tumors. However, the relationship between anoikis resistance and angiogenesis has not been well explored in human osteosarcoma. In the present study, we reported the higher expression of vascular endothelial growth factor-A (VEGF-A) in osteosarcoma cells that were resistant to anoikis than in parental osteosarcoma cells, promoting the proliferation, tube formation, and migration of human umbilical vein endothelial cells (HUVECs). Src, JNK (Jun amino-terminal kinase) and ERK (extracellular signal-regulated kinase) signaling pathway phosphorylation was activated in anoikis-resistant cells; Src inhibitor reduced the expression of VEGF-A and angiogenesis and inhibited JNK and ERK pathway activity. Overexpression of phosphorylated (p)-Src and VEGF-A was positively correlated to the metastatic potential in human osteosarcoma tissues, as quantified by immunohistochemistry. In addition, p-Src expression was directly correlated with VEGF-A expression and microvessel density in vivo. Our findings revealed that anoikis resistance in osteosarcoma cells increased the expression of VEGF-A and angiogenesis through the Src/JNK/ERK signaling pathways. Thus, Src may be a potential therapeutic alternative in osteosarcoma angiogenesis and metastasis.

The Src family kinase Fgr is a transforming oncoprotein that functions independently of SH3-SH2 domain regulation

Fgr is a member of the Src family of nonreceptor tyrosine kinases, which are overexpressed and constitutively active in many human cancers. Fgr expression is restricted to myeloid hematopoietic cells and is markedly increased in a subset of bone marrow samples from patients with acute myeloid leukemia (AML). Here, we investigated the oncogenic potential of Fgr using Rat-2 fibroblasts that do not express the kinase. Expression of either wild-type or regulatory tail-mutant constructs of Fgr promoted cellular transformation (inferred from colony formation in soft agar), which was accompanied by phosphorylation of the Fgr activation loop, suggesting that the kinase domain of Fgr functions independently of regulation by its noncatalytic SH3-SH2 region. Unlike other family members, recombinant Fgr was not activated by SH3-SH2 domain ligands. However, hydrogen-deuterium exchange mass spectrometry data suggested that the regulatory SH3 and SH2 domains packed against the back of the kinase domain in a Src-like manner. Sequence alignment showed that the activation loop of Fgr was distinct from that of all other Src family members, with proline rather than alanine at the +2 position relative to the activation loop tyrosine. Substitution of the activation loop of Fgr with the sequence from Src partially inhibited kinase activity and suppressed colony formation. Last, Fgr expression enhanced the sensitivity of human myeloid progenitor cells to the cytokine GM-CSF. Because its kinase domain is not sensitive to SH3-SH2–mediated control, simple overexpression of Fgr without mutation may contribute to oncogenic transformation in AML and other blood cancers.

The Two Isoforms of Lyn Display Different Intramolecular Fuzzy Complexes with the SH3 Domain

The function of the intrinsically disordered Unique domain of the Src family of tyrosine kinases (SFK), where the largest differences between family members are concentrated, remains poorly understood. Recent studies in c-Src have demonstrated that the Unique region forms transient interactions, described as an intramolecular fuzzy complex, with the SH3 domain and suggested that similar complexes could be formed by other SFKs. Src and Lyn are members of a distinct subfamily of SFKs. Lyn is a key player in the immunologic response and exists in two isoforms originating from alternative splicing in the Unique domain. We have used NMR to compare the intramolecular interactions in the two isoforms and found that the alternatively spliced segment interacts specifically with the so-called RT-loop in the SH3 domain and that this interaction is abolished when a polyproline ligand binds to the SH3 domain. These results support the generality of the fuzzy complex formation in distinct subfamilies of SFKs and its physiological role, as the naturally occurring alternative splicing modulates the interactions in this complex.

Inhibition of SRC/FAK cue: A novel pathway for the synergistic effect of rosuvastatin on the anti-cancer effect of dasatinib in hepatocellular carcinoma

PURPOSE

Statins extended their hypocholestremic effect to show a promising anticancer activity. Hepatocellular carcinoma (HCC), the third common cause of cancer-related death, responded positively to statins. Some in-vitro studies reveal the rosuvastatin antitumor effect, but barely in-vivo studies. Hence, we evaluated the antitumor potential of rosuvastatin in a HCC model, the possible signaling cues involved, and whether it augments the dasatinib anticancer effect.

METHOD

For the in-vitro study, the IC₅₀ and the combination (CI)/dose reduction (DRI) indices were determined for HCC cell line (HepG2) treated with dasatinib and/or rosuvastatin. For the in-vivo study, mice with diethylnitrosamine-induced HCC were treated for 21 days with dasatinib and/or rosuvastatin (10 and 20 mg/kg, respectively). The p-focal adhesion kinase/p-rous sarcoma oncogene cellular homolog (p-FAK/p-Src) cascade and its downstream molecules were assessed.

RESULTS

The in-vitro study confirmed the synergistic effect of rosuvastatin with dasatinib, which entailed the in-vivo results. The two drugs decreased the p-FAK/p-Src cue along with p-Ras/c-Raf, p-STAT-3, and p-Akt levels to enhance apoptosis by an increase in caspase-3 level and a decline in survivin level. Additionally, they inhibited HGF, VEGF, and the MMP-9. Moreover, the different treatments downregulated the expression of proliferative cell nuclear antigen (PCNA) and Ki-67. The best effect was mediated by the combination regimen that surpassed the effect of either drug alone.

CONCLUSION

Our results highlighted some of the signals involved in rosuvastatin antitumor effect and nominate it as an adds-on therapy with dasatinib to yield a better effect in HCC through inhibiting the FAK/Src cascade.

Suppression of lung cancer progression by isoliquiritigenin through its metabolite 2, 4, 2', 4'-Tetrahydroxychalcone

Background

Licorice is an herb extensively used for both culinary and medicinal purposes. Various constituents of licorice have been shown to exhibit anti-tumorigenic effect in diverse cancer types. However, majority of these studies focus on the aspect of their growth-suppressive role. In this study, we systematically analyzed known licorice’s constituents on the goal of identifying component(s) that can effectively suppress both cell migration and growth.

Methods

Effect of licorice’s constituents on cell growth was evaluated by MTT assay while cell migration was assessed by both wound-healing and Transwell assays. Cytoskeleton reorganization and focal adhesion assembly were visualized by immunofluorescence staining with labeled phalloidin and anti-paxillin antibody. Activity of Src in cells was judged by western blot using phosphor-Src416 antibody while Src kinase activity was measured using Promega Src kinase assay system. Anti-tumorigenic capabilities of isoliquiritigenin (ISL) and 2, 4, 2′, 4’-Tetrahydroxychalcone (THC) were investigated using lung cancer xenograft model.

Results

Using a panel of lung cancer cell lines, ISL was identified as the only licorice’s constituent capable of inhibiting both cell migration and growth. ISL-led inhibition in cell migration resulted from impaired cytoskeleton reorganization and focal adhesion assembly. Assessing the phosphorylation of 141 cytoskeleton dynamics-associated proteins revealed that ISL reduced the abundance of Tyr421-phosphorylation of cortactin, Tyr925- and Tyr861-phosphorylation of FAK, indicating the involvement of Src because these sites are known to be phosphorylated by Src. Enigmatically, ISL inhibited Src in cells while displayed no effect on Src activity in cell-free system. The discrepancy was explained by the observation that THC, one of the major ISL metabolite identified in lung cancer cells abrogated Src activity both in cells and cell-free system. Similar to ISL, THC deterred cell migration and abolished cytoskeleton reorganization/focal adhesion assembly. Furthermore, we showed both ISL and THC suppressed in vitro lung cancer cell invasion and in vivo tumor progression.

Conclusion

Our study suggests that ISL inhibits lung cancer cell migration and tumorigenesis by interfering with Src through its metabolite THC. As licorice is safely used for culinary purposes, our study suggests that ISL or THC may be safely used as a Src inhibitor.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0902-4) contains supplementary material, which is available to authorized users.

Visualizing Spatiotemporal Dynamics of Intercellular Mechanotransmission upon Wounding

During cell-to-cell communications, the interplay between physical and biochemical cues is essential for informational exchange and functional coordination, especially in multicellular organisms. However, it remains a challenge to visualize intercellular signaling dynamics in single live cells. Here, we report a photonic approach, based on laser microscissors and Förster resonance energy transfer (FRET) microscopy, to study intercellular signaling transmission. First, using our high-throughput screening platform, we developed a highly sensitive FRET-based biosensor (SCAGE) for Src kinase, a key regulator of intercellular interactions and signaling cascades. Notably, SCAGE showed a more than 40-fold sensitivity enhancement than the original biosensor in live mammalian cells. Next, upon local severance of physical intercellular connections by femtosecond laser pulses, SCAGE enabled the visualization of a transient Src activation across neighboring cells. Lastly, we found that this observed transient Src activation following the loss of cell-cell contacts depends on the passive structural support of cytoskeleton but not on the active actomyosin contractility. Hence, by precisely introducing local physical perturbations and directly visualizing spatiotemporal transmission of ensuing signaling events, our integrated approach could be broadly applied to mimic and investigate the wounding process at single-cell resolutions. This integrated approach with highly sensitive FRET-based biosensors provides a unique system to advance our in-depth understanding of molecular mechanisms underlying the physical-biochemical basis of intercellular coupling and wounding processes.

Targeting Anaplastic Lymphoma Kinase (ALK) in Rhabdomyosarcoma (RMS) with the Second-Generation ALK Inhibitor Ceritinib

Background

The receptor tyrosine kinase (RTK) anaplastic lymphoma kinase (ALK) has been implicated in the tumorigenesis of rhabdomyosarcoma (RMS). However, the exact role of ALK in RMS is debatable and remains to be elucidated.

Objective

To determine the in vitro and in vivo effects and mechanism of action of the second-generation ALK inhibitor ceritinib on RMS cell growth.

Methods

Effects of ceritinib on cell proliferation, wound healing, cell cycle, and RTK signaling were determined in alveolar and embryonal rhabdomyosarcoma (ARMS, ERMS). In addition, possible synergistic effects of combined treatment with ceritinib and the Abl/Src family kinase inhibitor dasatinib were determined.

Results

Ceritinib treatment led to decreased cell proliferation, cell cycle arrest, apoptosis, and decreased in vivo tumor growth for the ARMS subtype. ERMS cell lines were less affected and showed no cell cycle arrest or apoptosis. Both subtypes lacked intrinsic ALK phosphorylation, and ceritinib was shown to affect the IGF1R signaling pathway. High levels of phosphorylated Src (Tyr416) were present following ceritinib treatment, making combined treatment with a Src inhibitor a potential treatment option. Combined treatment of ceritinib and dasatinib showed synergistic effects in both ERMS and ARMS cell lines.

Conclusion

This study shows that monotherapy with an ALK inhibitor, such as ceritinib, in RMS, has no effect on ALK signaling. However, the synergistic effects of ceritinib and dasatinib are promising, most probably due to targeting of IGF1R and Src.

Electronic supplementary material

The online version of this article (10.1007/s11523-017-0528-z) contains supplementary material, which is available to authorized users.

Introducing novel potent anticancer agents of 1H-benzo[f]chromene scaffolds, targeting c-Src kinase enzyme with MDA-MB-231 cell line anti-invasion effect

In our effort to develop novel and powerful agents with anti-proliferative activity, two new series of 1H-benzo[f]chromene derivatives, 4a–h and 6a–h, were synthesised using heterocyclocondensation methodologies under microwave irradiation condition. The structures of the target compounds were established on the basis of their spectral data, IR, ¹H NMR, ¹³ C NMR, ¹³ C NMR-DEPT/APT, and MS data. The new compounds have been examined for their anti-proliferative activity against three cancer cell lines, MCF-7, HCT-116, and HepG-2. Vinblastine and Doxorubicin have been used as positive controls in the viability assay. The obtained results confirmed that most of the tested molecules revealed strong and selective cytotoxic activity against the three cancer cell lines. Moreover, these molecules exhibited weak cytotoxicity on the HFL-1 line, which suggested that they might be ideal anticancer candidates. The SAR study of the new benzochromene compounds verified that the substituents on the phenyl ring of 1H-benzo[f]chromene nucleus, accompanied with the presence of bromine atom or methoxy group at the 8-position, increases the ability of these molecules against the different cell lines. Due to their high anti-proliferative activity, compounds 4c and 6e were selected to be examined their proficiency to inhibit the invasiveness of the highly sensitive and invasive breast cancer cell line, MDA-MB-231. The anti-invasion behaviour of these molecules against the highly sensitive, non-oestrogen, and progesterone MDA-MB-231 cell line gave rise to their decreasing metastatic effect compared to the reference drug. Furthermore, this report explores the apoptotic mechanistic pathway of the cytotoxicity of the target compounds and reveals that most of these compounds enhance the Caspase 3/7 activity that could be considered as potential anticancer agents.