Inhibition of c-Src expression and activation in malignant pleural mesothelioma tissues leads to apoptosis, cell cycle arrest, and decreased migration and invasion

The overall process of metastasis: From initiation to a new tumor

Metastasis-a process that involves the migration of cells from the primary site to distant organs-is the leading cause of cancer-associated death. Improved technology and in-depth research on tumors have furthered our understanding of the various mechanisms involved in tumor metastasis. Metastasis is initiated by cancer cells of a specific phenotype, which migrate with the assistance of extracellular components and metastatic traits conferred via epigenetic regulation while modifying their behavior in response to the complex and dynamic human internal environment. In this review, we have summarized the general steps involved in tumor metastasis and their characteristics, incorporating recent studies and topical issues, including epithelial-mesenchymal transition, cancer stem cells, neutrophil extracellular traps, pre-metastatic niche, extracellular vesicles, and dormancy. Several feasible treatment directions have also been summarized. In addition, the correlation between cancer metastasis and lifestyle factors, such as obesity and circadian rhythm, has been illustrated.

Structure-Activity Relationship of Benzofuran Derivatives with Potential Anticancer Activity

Simple Summary

Cancer is the leading cause of death worldwide and responsible for killing approximately 10 million people per year. Fused heterocyclic ring systems such as benzofuran have emerged as important scaffolds with many biological properties. Furthermore, derivatives of benzofurans demonstrate a wide range of biological and pharmacological activities, including anticancer properties. The main aim of this review is to highlight and discuss the contribution of benzofuran derivatives as anticancer agents by considering and discussing the chemical structure of 20 different compounds. Evaluating the chemical structure of these compounds will guide future medicinal chemists in designing new drugs for cancer therapy that might give excellent results in in vivo/in vitro applications.

Abstract

Benzofuran is a heterocyclic compound found naturally in plants and it can also be obtained through synthetic reactions. Multiple physicochemical characteristics and versatile features distinguish benzofuran, and its chemical structure is composed of fused benzene and furan rings. Benzofuran derivatives are essential compounds that hold vital biological activities to design novel therapies with enhanced efficacy compared to conventional treatments. Therefore, medicinal chemists used its core to synthesize new derivatives that can be applied to a variety of disorders. Benzofuran exhibited potential effectiveness in chronic diseases such as hypertension, neurodegenerative and oxidative conditions, and dyslipidemia. In acute infections, benzofuran revealed anti-infective properties against microorganisms like viruses, bacteria, and parasites. In recent years, the complex nature and the number of acquired or resistant cancer cases have been largely increasing. Benzofuran derivatives revealed potential anticancer activity with lower incidence or severity of adverse events normally encountered during chemotherapeutic treatments. This review discusses the structure–activity relationship (SAR) of several benzofuran derivatives in order to elucidate the possible substitution alternatives and structural requirements for a highly potent and selective anticancer activity.

Nintedanib and Dasatinib Treatments Induce Protective Autophagy as a Potential Resistance Mechanism in MPM Cells

Malignant pleural mesothelioma (MPM) is a rare type of cancer with a grim prognosis. So far, no targetable oncogenic mutation was identified in MPM and biomarkers with predictive value toward drug sensitivity or resistance are also lacking. Nintedanib (BIBF1120) is a small-molecule tyrosine kinase inhibitor that showed promising efficacy preclinically and in phase II trial in MPM as an angiogenesis inhibitor combined with chemotherapy. However, the extended phase III trial failed. In this study, we investigated the effect of nintedanib on one of its targets, the SRC kinase, in two commercial and six novel MPM cell lines. Surprisingly, nintedanib treatment did not inhibit SRC activation in MPM cells and even increased phosphorylation of SRC in several cell lines. Combination treatment with the SRC inhibitor dasatinib could reverse this effect in all cell lines, however, the cellular response was dependent on the drug sensitivity of the cells. In 2 cell lines, with high sensitivity to both nintedanib and dasatinib, the drug combination had no synergistic effect but cell death was initiated. In 2 cell lines insensitive to nintedanib combination treatment reduced cell viability synergisticaly without cell death. In contrast, in these cells both treatments increased the autophagic flux assessed by degradation of the autophagy substrate p62 and increased presence of LC3B-II, increased number of GFP-LC3 puncta and decreased readings of the HiBiT-LC3 reporter. Additionaly, autophagy was synergistically promoted by the combined treatment. At the transcriptional level, analysis of lysosomal biogenesis regulator Transcription Factor EB (TFEB) showed that in all cell lines treated with nintedanib and to a lesser extent, with dasatinib, it became dephosphorylated and accumulated in the nucleus. Interestingly, the expression of certain known TFEB target genes implicated in autophagy or lysosomal biogenesis were significantly modified only in 1 cell line. Finally, we showed that autophagy induction in our MPM cell lines panel by nintedanib and dasatinib is independent of the AKT/mTOR and the ERK pathways. Our study reveals that autophagy can serve as a cytoprotective mechanism following nintedanib or dasatinib treatments in MPM cells.

Establishment and characterization of NCC‑DMM1‑C1, a novel patient‑derived cell line of desmoplastic malignant pleural mesothelioma

Desmoplastic malignant pleural mesothelioma (DMM) is a rare histological variant of malignant pleural mesothelioma, which is a highly aggressive neoplasm of the mesothelium. DMM is associated with distant metastases and short survival. Effective treatments for DMM are not established and the development of histotype-tailored treatments is difficult due to the rarity of the disease. Although patient-derived cancer models are crucial tools for the development of novel therapeutics, they are difficult to obtain for DMM; no DMM cell lines or xenografts are available from public biobanks and only two cell lines have been reported. Thus, the present study aimed to establish a novel cell line of DMM as a resource for drug screening. A cell line of DMM was established, designated as NCC-DMM1-C1, using surgically resected tumor tissues from a 73-year-old male patient with DMM. Characteristics of NCC-DMM1-C1 cells were examined, such as growth, spheroid formation and invasion capability. Drug targets and anti-cancer drugs with anti-proliferative efficacy were examined using a comprehensive kinase activity assay and drug screening of 213 anti-cancer agents, respectively. NCC-DMM1-C1 exhibited fast growth, spheroid formation and invasion capability, suggesting that the NCC-DMM1-C1 cells retained the aggressive features of DMM. NCC-DMM1-C1 cells and the tumor tissue shared common activity profiles of kinases, which included FES, Wee1, platelet-derived growth factor receptor-β and Src. The drug screening revealed that bortezomib, fostamatinib, gemcitabine, homoharringtonine and vinorelbine had anti-proliferative effects, which have not been previously reported for DMM. It was concluded that NCC-DMM1-C1 cells may be a useful tool for the study of DMM.

Anesthetic Propofol Promotes Tumor Metastasis in Lungs via GABAA R-Dependent TRIM21 Modulation of Src Expression

Generation of circulating tumor cells (CTCs), a key step in tumor metastasis, occurs during surgical tumor resection, often performed under general anesthesia. Propofol is the commonly used anesthetic, but its effects on CTCs and tumor metastasis remain largely unknown. Propofol effects are investigated in an experimental metastasis model by injecting tumor cells and, subsequently, low- or standard-dose propofol to nude mice through tail vein. Propofol- or vehicle-treated tumor cells are also injected to the mice. An in vitro tumor cell-vascular endothelial cell adhesion assay, immunofluorescence, and other methods are employed to assess how propofol affects tumor cell adhesion and extension. Propofol induces more lung tumor metastasis in mice than control. Mechanistically, propofol enhances tumor cell adhesion and extension through GABAA R to downregulate TRIM21 expression, leading to upregulation of Src, a protein associated with cell adhesion. These results demonstrate that propofol may promote tumor metastasis through GABAA R-TRIM21-Src mechanism.

c-Src promotes the growth and tumorigenesis of hepatocellular carcinoma via the Hippo signaling pathway

We investigated the association between c-Src and the progression of hepatocellular carcinoma (HCC) and its underlying mechanisms. The relationship between c-Src expression and the occurrence and development of HCC was explored using GEPIA and further confirmed by western blotting analysis and real-time quantitative PCR. CCK-8, flow cytometry, Transwell, and wound-healing assays were conducted to analyze the effects of c-Src on the growth, cell cycle, apoptosis, migration, and infiltration of HCC cells. Mouse models of transplanted xenogeneic human tumors were constructed to explore the effects of c-Src on HCC tumor growth. Compared with that in adjacent normal liver tissues, the expression level of c-Src in HCC tissues was significantly increased and was negatively correlated with patient survival. These findings are consistent with those in the GEPIA database. Downregulation of c-Src expression can inhibit the growth, infiltration, and migration of HCC cells. c-Src impeded the translocation of YAP from the nucleus to the cytoplasm and promoted Yes-associated protein transcriptional activity. In vivo experiments showed that c-Src inhibition suppressed tumor growth in mice. We found that c-Src can promote the growth and tumorigenesis of HCC cells by activating the Hippo signaling pathway.

Evolution of Genomic and T-cell Repertoire Heterogeneity of Malignant Pleural Mesothelioma Under Dasatinib Treatment

PURPOSE

Malignant pleural mesothelioma (MPM) is considered an orphan disease with few treatment options. Despite multimodality therapy, the majority of MPMs recur and eventually become refractory to any systemic treatment. One potential mechanism underlying therapeutic resistance may be intratumor heterogeneity (ITH), making MPM challenging to eradicate. However, the ITH architecture of MPM and its clinical impact have not been well studied.

EXPERIMENTAL DESIGN

We delineated the immunogenomic ITH by multiregion whole-exome sequencing and T-cell receptor (TCR) sequencing of 69 longitudinal MPM specimens from nine patients with resectable MPM, who were treated with dasatinib.

RESULTS

The median total mutation burden before dasatinib treatment was 0.65/Mb, similar with that of post-dasatinib treatment (0.62/Mb). The median proportion of mutations shared by any given pair of two tumor regions within the same tumors was 80% prior to and 83% post-dasatinib treatment indicating a relatively homogenous genomic landscape. T-cell clonality, a parameter indicating T-cell expansion and reactivity, was significantly increased in tumors after dasatinib treatment. Furthermore, on average, 82% of T-cell clones were restricted to individual tumor regions, with merely 6% of T-cell clones shared by all regions from the same tumors indicating profound TCR heterogeneity. Interestingly, patients with higher T-cell clonality and higher portion of T cells present across all tumor regions in post-dasatinib-treated tumors had significantly longer survival.

CONCLUSIONS

Despite the homogeneous genomic landscape, the TCR repertoire is extremely heterogeneous in MPM. Dasatinib may potentially induce T-cell response leading to improved survival.

Targeting SRC Family Kinases in Mesothelioma: Time to Upgrade

Malignant mesothelioma (MM) is a deadly tumor mainly caused by exposure to asbestos. Unfortunately, no current treatment is able to change significantly the natural history of the disease, which has a poor prognosis in the majority of patients. The non-receptor tyrosine kinase SRC and other SRC family kinase (SFK) members are frequently hyperactivated in many cancer types, including MM. Several works have indeed suggested that SFKs underlie MM cell proliferation, survival, motility, and invasion, overall affecting multiple oncogenic pathways. Consistently, SFK inhibitors effectively counteracted MM cancerous features at the preclinical level. Dasatinib, a multi-kinase inhibitor targeting SFKs, was also assessed in clinical trials either as second-line treatment for patients with unresectable MM or, more recently, as a neoadjuvant agent in patients with resectable MM. Here, we provide an overview of the molecular mechanisms implicating SFKs in MM progression and discuss possible strategies for a more successful clinical application of SFK inhibitors. Our aim is to stimulate discussion and further consideration of these agents in better designed preclinical and clinical studies to make the most of another class of powerful antitumoral drugs, which too often are lost in translation when applied to MM.

Scientific Advances and New Frontiers in Mesothelioma Therapeutics

Malignant pleural mesothelioma (MPM) is a rare and aggressive cancer that arises from the mesothelial surface of the pleural and peritoneal cavities, the pericardium, and rarely, the tunica vaginalis. The incidence of MPM is expected to increase worldwide in the next two decades. However, even with the use of multimodality treatment, MPM remains challenging to treat, with a 5-year survival rate of less than 5%. The International Association for the Study of Lung Cancer has gathered experts in different areas of mesothelioma research and management to summarize the most significant scientific advances and new frontiers related to mesothelioma therapeutics.

Targeting angiogenesis for patients with unresectable malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a global health issue, the principal cause of which is exposure to asbestos. The prevalence is anticipated to rise over the next 2 decades, particularly in developing countries, due to the 30-50-year latency period between exposure to asbestos and carcinogenic development. Unresectable MPM has a poor prognosis and limited treatment options and, as such, there is a broad range of therapeutic targets of interest, including angiogenesis, immune checkpoints, mesothelin, as well as chemotherapeutic agents. Recently, the results of several randomized trials in the first-line setting combining antiangiogenic agents with chemotherapy have been reported. This review examines the scientific rationale for targeting angiogenesis in the treatment of unresectable MPM and analyzes recent clinical results with antiangiogenic agents in development (bevacizumab, nintedanib, and cediranib) for the management of MPM.

Regulation of cisplatin-resistant head and neck squamous cell carcinoma by the SRC/ETS-1 signaling pathway

BACKGROUND

We investigated the role of the ETS-1 transcription factor in Head and Neck Squamous Cell Carcinoma (HNSCC) in multiple cisplatin-resistant HNSCC cell lines.

METHODS

We examined its molecular link with SRC and MEK/ERK pathways and determined the efficacy of either MEK/ERK inhibitor PD0325901 or SRC inhibitor Dasatinib on cisplatin-resistant HNSCC inhibition.

RESULTS

We found that ETS-1 protein expression levels in a majority of cisplatin-resistant HNSCC cell types were higher than those in their parental cisplatin sensitive partners. High ETS-1 expression was also found in patient-derived, cisplatin-resistant HNSCC cells. While ETS-1 knockdown inhibited cell proliferation, migration, and invasion, it could still re-sensitize cells to cisplatin treatment. Interestingly, previous studies have shown that MER/ERK pathways could regulate ETS-1 through its phosphorylation at threonine 38 (T38). Although almost all cisplatin-resistant HNSCC cells we tested showed higher ETS-1 phosphorylation levels at T38, we found that inhibition of MEK/ERK pathways with the MEK inhibitor PD0325901 did not block this phosphorylation. In addition, treatment of cisplatin-resistant HNSCC cells with the MEK inhibitor completely blocked ERK phosphorylation but did not re-sensitize cells to cisplatin treatment. Furthermore, we found that, consistent with ETS-1 increase, SRC phosphorylation dramatically increased in cisplatin-resistant HNSCC, and treatment of cells with the SRC inhibitor, Dasatinib, blocked SRC phosphorylation and decreased ETS-1 expression. Importantly, we showed that Dasatinib, as a single agent, significantly suppressed cell proliferation, migration, and invasion, in addition to survival.

CONCLUSIONS

Our results demonstrate that the SRC/ETS-1 pathway plays a crucial role and could be a key therapeutic target in cisplatin-resistant HNSCC treatment.

Mechanistic insights of epithelial protein lost in neoplasm in prostate cancer metastasis

EPLIN is frequently downregulated or lost in various cancers. The purpose of this study was to evaluate the importance of EPLIN in prostate cancer progression, with particular focus on the mechanistic implications to elucidate EPLIN's tumor suppressive function in cancer. EPLIN expression was evaluated in prostate cancer cell lines and tissues. PC-3 and LNCaP EPLINα overexpression models were generated through transfection with EPLINα sequence and EPLIN knockdown was achieved using shRNA in CA-HPV-10 cells. Functional assays were performed to evaluate cellular characteristics and potential mechanisms were evaluated using a protein microarray, and validated using western blot analysis. EPLIN expression was reduced in clinical prostate cancer sections, including hyperplasia (p ≤ 0.001) and adenocarcinoma (p = 0.005), when compared to normal prostate tissue. EPLINα overexpression reduced cell growth, migration and invasion, and influenced transcript, protein and phosphoprotein expression of paxillin, FAK and Src. EPLIN knockdown increased the invasive and migratory nature of CA-HPV-10 cells and also induced changes to FAK and Src total and/or phospho expression. Functional characterization of cellular migration and invasion in addition to FAK and Src inhibition demonstrated differential effects between control and EPLINα overexpression and EPLIN knockdown cell lines. This study highlights that EPLIN expression in prostate cancer is able to influence several aspects of cancer cell characteristics, including cell growth, migration and invasion. The mechanism of the tumor suppressive action of EPLIN remains to be fully elucidated; and this study proposes a role for EPLIN's ability to regulate the aggressive characteristics of prostate cancer cells partially through regulating FAK/Src signaling.

Targeting the Hippo Pathway Is a New Potential Therapeutic Modality for Malignant Mesothelioma

Malignant mesothelioma (MM) constitutes a very aggressive tumor that arises from the pleural or peritoneal cavities and is highly refractory to conventional therapies. Several key genetic alterations are associated with the development and progression of MM including mutations of the CDKN2A/ARF, NF2, and BAP1 tumor-suppressor genes. Notably, activating oncogene mutations are very rare; thus, it is difficult to develop effective inhibitors to treat MM. The NF2 gene encodes merlin, a protein that regulates multiple cell-signaling cascades including the Hippo pathway. MMs also exhibit inactivation of Hippo pathway components including LATS1/2, strongly suggesting that merlin-Hippo pathway dysregulation plays a key role in the development and progression of MM. Furthermore, Hippo pathway inactivation has been shown to result in constitutive activation of the YAP1/TAZ transcriptional coactivators, thereby conferring malignant phenotypes to mesothelial cells. Critical YAP1/TAZ target genes, including prooncogenic CCDN1 and CTGF, have also been shown to enhance the malignant phenotypes of MM cells. Together, these data indicate the Hippo pathway as a therapeutic target for the treatment of MM, and support the development of new strategies to effectively target the activation status of YAP1/TAZ as a promising therapeutic modality for this formidable disease.

Drug repurposing in malignant pleural mesothelioma: a breath of fresh air?

Drug repurposing is the use of known drugs for new indications. Malignant pleural mesothelioma (MPM) is a rare cancer with a poor prognosis. So far, few treatments have been approved in this disease. However, its incidence is expected to increase significantly, particularly in developing countries. Consequently, drug repurposing appears as an attractive strategy for drug development in MPM, since the known pharmacology and safety profile based on previous approvals of repurposed drugs allows for faster time-to-market for patients and lower treatment cost. This is critical in low- and middle-income countries where access to expensive drugs is limited. This review assesses the published preclinical and clinical data about drug repurposing in MPM.In this review, we identified 11 therapeutic classes that could be repositioned in mesothelioma. Most of these treatments have been evaluated in vitro, half have been evaluated in vivo in animal models of MPM and only three (i.e. valproate, thalidomide and zoledronic acid) have been investigated in clinical trials, with limited benefits so far. Efforts could be coordinated to pursue further investigations and test promising drugs identified in preclinical experiments in appropriately designed clinical trials.

Dasatinib modulates sensitivity to pemetrexed in malignant pleural mesothelioma cell lines

Background

Thymidylate synthase (TS), one of the key enzymes for thymidine synthesis, is a target of pemetrexed (PEM), a key agent for the systemic therapy of malignant pleural mesothelioma (MPM) and its overexpression has been correlated to PEM-resistance. In MPM, experimental data report activation of the c-SRC tyrosine kinase suggesting it as a potential target to be further investigated.

Results

MPM cell lines showed different sensitivity, being MSTO the most and REN the least sensitive to PEM. REN cells showed high levels of both TS and SRC: dasatinib inhibited SRC activation and suppressed TS protein expression, starting from 100 nM dose, blocking the PEM-induced up regulation of TS protein levels. Dasatinib treatment impaired cells migration, and both sequential and co-administration with PEM significantly increased apoptosis. Dasatinib pretreatment improved sensitivity to PEM, downregulated TS promoter activity and, in association with PEM, modulated the downstream PI3K-Akt-mTOR signaling.

Cell lines and Methods

In three MPM cell lines (MPP89, REN and MSTO), the effects of c-SRC inhibition, in correlation with TS expression and PEM sensitivity, were evaluated. PEM and dasatinib, a SRC inhibitor, were administered as single agents, in combination or sequentially. Cell viability, apoptosis and migration, as well as TS expression and SRC activation have been assessed.

Conclusions

These data indicate that dasatinib sensitizes mesothelioma cells to PEM through TS down-regulation.

Heterogeneous Contributing Factors in MPM Disease Development and Progression: Biological Advances and Clinical Implications

Malignant pleural mesothelioma (MPM) tumors are remarkably aggressive and most patients only survive for 5–12 months; irrespective of stage; after primary symptoms appear. Compounding matters is that MPM remains unresponsive to conventional standards of care; including radiation and chemotherapy. Currently; instead of relying on molecular signatures and histological typing; MPM treatment options are guided by clinical stage and patient characteristics because the mechanism of carcinogenesis has not been fully elucidated; although about 80% of cases can be linked to asbestos exposure. Several molecular pathways have been implicated in the MPM tumor microenvironment; such as angiogenesis; apoptosis; cell-cycle regulation and several growth factor-related pathways predicted to be amenable to therapeutic intervention. Furthermore, the availability of genomic data has improved our understanding of the pathobiology of MPM. The MPM genomic landscape is dominated by inactivating mutations in several tumor suppressor genes; such as CDKN2A; BAP1 and NF2. Given the complex heterogeneity of the tumor microenvironment in MPM; a better understanding of the interplay between stromal; endothelial and immune cells at the molecular level is required; to chaperone the development of improved personalized therapeutics. Many recent advances at the molecular level have been reported and several exciting new treatment options are under investigation. Here; we review the challenges and the most up-to-date biological advances in MPM pertaining to the molecular pathways implicated; progress at the genomic level; immunological progression of this fatal disease; and its link with developmental cell pathways; with an emphasis on prognostic and therapeutic treatment strategies.

c-Src activation promotes nasopharyngeal carcinoma metastasis by inducing the epithelial-mesenchymal transition via PI3K/Akt signaling pathway: a new and promising target for NPC

Aberrant activation of cellular Src (c-Src), a non-receptor tyrosine kinase, could promote cancer progression through activating its downstream signaling pathways. However, the roles of c-Src and phosphorylated-Src (p-Src) in nasopharyngeal carcinoma (NPC) progression are rarely investigated. Herein, we have identified high c-Src concentrations in the serum of NPC patients with distant metastasis using high-throughput protein microarrays. Levels of c-Src in serum and p-Src in human primary NPC samples were unfavorable independent prognostic factors for cancer-specific survival, disease-free survival, and distant metastasis-free survival. Depletion or inactivation of c-Src in NPC cells using sgRNA with CRISPR/Cas9 system or PP2 decreased cell viability, colony formation, migration and invasion in vitro and metastasis in vivo. In contrast, these malignancies could be up-regulated by overexpressed c-Src in a NPC cell line with low-metastasis potential. Furthermore, p-Src was involved in promoting NPC cell metastasis by inducing the epithelial-mesenchymal transition (EMT) process via activating the PI3K/Akt pathway and cytoskeleton remodeling. The p-Src-induced EMT process could be retarded by PP2, which mediated by down-regulating the PI3K/Akt pathway. In conclusion, elevated levels of c-Src in serum and p-Src in primary NPC tissue correlated with poor outcomes of NPC patients. And aberrant activation of c-Src facilitated NPC cells with malignant potential, especially metastasis ability, which mediated by the PI3K/Akt pathway activation and sequentially induced the EMT process. These findings unveiled a promising approach for targeted therapy of advanced NPC.

Biomarker-Integrated Neoadjuvant Dasatinib Trial in Resectable Malignant Pleural Mesothelioma

INTRODUCTION

Window of opportunity trials in malignant pleural mesothelioma (MPM) are challenging but can yield important translational information about a novel agent.

METHODS

We treated patients with MPM (N = 24) with 4 weeks of oral dasatinib followed by surgery with or without radiotherapy and then an optional 2 years of maintenance dasatinib. The primary end point was biomarker modulation of phosphorylated (p) Src^Tyr419.

RESULTS

For all patients, the median progression-free survival (PFS) was 7.5 months and the median overall survival was 19.1 months. No significant responses were seen after 4 weeks of dasatinib therapy; however, modulation of median p-Src^Tyr419 immunohistochemistry (IHC) scores was seen: the median pretreatment score was 70 (interquartile range 37.5-110), and the median posttreatment score was 41.9 (interquartile range 4.2-60) (p = 0.004). A decrease in p-Src^Tyr419 levels after dasatinib correlated with improved median PFS (6.9 months versus 0.94 months [p = 0.03]), suggesting that p-Src^Tyr419 is a viable pharmacodynamic biomarker for dasatinib in MPM. Platelet-derived growth factor receptor (PDGFR) pathway analysis correlated high PDGFR beta [PDGFRB) level (in the cytoplasm [hazard ratio] (HR) = 2.54, p = 0.05], stroma [HR = 2.79, p = 0.03], and nucleus [HR = 6.79, p = 0.023]) with a shorter PFS. Low (less than the median) cytoplasmic p-PDGFR alpha IHC levels were predictive of a decrease in positron emission tomography/computed tomography standard uptake values levels after dasatinib therapy (p = 0.04), whereas higher-than-median IHC scores of PDGFRB (cytoplasmic [HR = 2.8, p = 0.03] and nuclear [HR = 6.795, p = 0.02]) were correlated with rising standard uptake values levels.

CONCLUSIONS

In conclusion, there was no significant efficacy signal, and dasatinib monotherapy will not continue to be studied in MPM. However, our study demonstrated that PDGFR subtypes (platelet-derived growth factor receptor alpha and PDGFRB) may have differential roles in prognosis and resistance to antiangiogenic tyrosine kinase inhibitors and are important potential therapeutic targets that require further investigation.

Bosutinib versus Placebo for Autosomal Dominant Polycystic Kidney Disease

Overactivation of Src has been linked to the pathogenesis of autosomal dominant polycystic kidney disease (ADPKD). This phase 2, multisite study assessed the efficacy and safety of bosutinib, an oral dual Src/Bcr-Abl tyrosine kinase inhibitor, in patients with ADPKD. Patients with ADPKD, eGFR≥60 ml/min per 1.73 m2, and total kidney volume ≥750 ml were randomized 1:1:1 to bosutinib 200 mg/d, bosutinib 400 mg/d, or placebo for ≤24 months. The primary endpoint was annualized rate of kidney enlargement in patients treated for ≥2 weeks who had at least one postbaseline magnetic resonance imaging scan that was preceded by a 30-day washout (modified intent-to-treat population). Of 172 enrolled patients, 169 received at least one study dose. Per protocol amendment, doses for 24 patients who initially received bosutinib at 400 mg/d were later reduced to 200 mg/d. The annual rate of kidney enlargement was reduced by 66% for bosutinib 200 mg/d versus placebo (1.63% versus 4.74%, respectively; P=0.01) and by 82% for pooled bosutinib versus placebo (0.84% versus 4.74%, respectively; P<0.001). Over the treatment period, patients receiving placebo or bosutinib had similar annualized eGFR decline. Gastrointestinal and liver-related adverse events were the most frequent toxicities. In conclusion, compared with placebo, bosutinib at 200 mg/d reduced kidney growth in patients with ADPKD. The overall gastrointestinal and liver toxicity profile was consistent with the profile in prior studies of bosutinib; no new toxicities were identified. (ClinicalTrials.gov: NCT01233869).

Nintedanib Plus Pemetrexed/Cisplatin in Patients With Malignant Pleural Mesothelioma: Phase II Results From the Randomized, Placebo-Controlled LUME-Meso Trial

Purpose

LUME-Meso is a phase II/III randomized, double-blind trial designed to assess efficacy and safety of nintedanib plus chemotherapy as first-line treatment of malignant pleural mesothelioma (MPM). Phase II results are reported here.

Patients and Methods

Chemotherapy-naïve patients with unresectable, nonsarcomatoid MPM (Eastern Cooperative Oncology Group performance status 0 to 1), stratified by histology (epithelioid or biphasic), were randomly assigned in a 1:1 ratio to up to six cycles of pemetrexed and cisplatin plus nintedanib (200 mg twice daily) or placebo followed by nintedanib plus placebo monotherapy until progression. The primary end point was progression-free survival (PFS).

Results

Eighty-seven patients were randomly assigned. The median number of pemetrexed and cisplatin cycles was six; the median treatment duration for nintedanib was 7.8 months and 5.3 months for placebo. Primary PFS favored nintedanib (hazard ratio [HR], 0.56; 95% CI, 0.34 to 0.91; P = .017), which was confirmed in updated PFS analyses (HR, 0.54; 95% CI, 0.33 to 0.87; P = .010). A trend toward improved overall survival also favored nintedanib (HR, 0.77; 95% CI, 0.46 to 1.29; P = .319). Benefit was evident in epithelioid histology, with a median overall survival gain of 5.4 months (HR, 0.70; 95% CI, 0.40 to 1.21; P = .197; median [nintedanib v placebo], 20.6 months v 15.2 months) and median PFS gain of 4.0 months (HR, 0.49; 95% CI, 0.30 to 0.82; P = .006; median [nintedanib v placebo], 9.7 v 5.7 months). Neutropenia was the most frequent grade ≥ 3 adverse event (AE; nintedanib 43.2% v placebo 12.2%); rates of febrile neutropenia were low (4.5% in nintedanib group v 0% in placebo group). AEs leading to discontinuation were reported in 6.8% of those receiving nintedanib versus 17.1% of those in the placebo group.

Conclusion

Addition of nintedanib to pemetrexed plus cisplatin resulted in PFS improvement. AEs were manageable. The clinical benefit was evident in patients with epithelioid histology. The confirmatory phase III part of the study is ongoing.

Evaluation of the efficacy of dasatinib, a Src/Abl inhibitor, in colorectal cancer cell lines and explant mouse model

Background

Dysregulation of the Src pathway has been shown to be important at various stages of cancer. Dasatinib is a potent Src/Abl inhibitor and has demonstrated to have anti-proliferative and anti-invasive activity in many preclinical models. The objective of this study was to determine the anti-tumor activity of dasatinib using in vitro and in vivo preclinical colorectal (CRC) models.

Methods

CRC cell lines and patient-derived tumor explant (PDX) models were used to investigate the efficacy of dasatinib. We treated 50 CRC cell lines with dasatinib for 72 hours and proliferation was assayed by a sulforhodamine B (SRB) assay; an IC₅₀ ≤ 0.08 μmol/L was considered sensitive. We treated 17 patient-derived CRC explants with dasatinib (50 mg/kg/day, administered once-daily) for 28 days to determine in vivo efficacy. Tumor growth inhibition (TGI) ≥ 50% was considered sensitive.

Results

We found that 8 out of 50 CRC cell lines reached an IC₅₀ ≤ 0.08 μmol/L with dasatinib treatment. In addition, of 17 CRC explants grown in the xenograft mouse model, 2 showed sensitivity to dasatinib. The anti-tumor effects observed in this study were a result of G1 cell cycle arrest as the dasatinib sensitive CRC cell lines exhibited G1 inhibition. Moreover, those CRC cell lines that were responsive (0.08 μmol/L) to treatment demonstrated a significant baseline increase in Src and FAK gene expression.

Conclusion

Dasatinib demonstrated significant anti-proliferative activity in a subset of CRC cell lines in vitro, especially in those with increased Src expression at baseline, but only showed modest efficacy in CRC explants. Dasatinib is currently being studied in combination with chemotherapy in patients with advanced CRC, as its use as a single agent appears limited.

Efficacy in Treating Lung Metastasis of Invasive Breast Cancer with Functional Vincristine Plus Dasatinib Liposomes

Background: The metastasis of breast cancer is the leading cause of death, while lung metastasis is a major clinical phenomenon in patients with invasive breast cancer. The current treatment option comprising surgery, radiation, and standard chemotherapy cannot achieve a satisfactory effect on the treatment of lung metastasis of breast cancer. In this study, we report the potential of preventing lung metastasis of invasive breast cancer using the newly developed functional vincristine plus dasatinib liposomes. Methods: The investigations were performed on invasive breast cancer MDA-MB-231 cells in vitro and in lung metastatic model of invasive breast cancer MDA-MB-231 cells in nude mice. Results: The functional drug liposomes were able to induce cell cycle arrest at G2/M phase, induce apoptosis, inhibit adhesion, migration, and invasion of breast cancer cells in vitro, and prevent lung metastasis of breast cancer in nude mice. Conclusion: These findings indicate a potential clinical use of functional vincristine plus dasatinib liposomes for treating metastatic breast cancer.

LUME-Meso: Design and Rationale of the Phase III Part of a Placebo-Controlled Study of Nintedanib and Pemetrexed/Cisplatin Followed by Maintenance Nintedanib in Patients With Unresectable Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is a rare but aggressive disease: median survival is 6 to 9 months if untreated. Standard first-line treatment for patients with unresectable MPM is cisplatin/pemetrexed, with a median overall survival (OS) of approximately 1 year. Improvements in first-line treatment options are needed. With the benefit of combining bevacizumab with standard therapy shown in the Mesothelioma Avastin Cisplatin Pemetrexed Study (MAPS), vascular endothelial growth factor (VEGF) pathway inhibition has gained renewed interest as a treatment approach. Nintedanib is an oral angiokinase inhibitor targeting multiple signaling pathways implicated in the pathogenesis of MPM, including the VEGF receptor. The phase III part of the international, phase II/III LUME-Meso study is evaluating the efficacy and safety of nintedanib plus pemetrexed/cisplatin in patients with unresectable epithelioid MPM. Originally, this was a double-blind, randomized, phase II exploratory study and was amended to include a confirmatory phase III part following the recommendation of an internal Data Monitoring Committee and review of phase II data. The phase III part plans to enroll 450 chemotherapy-naive patients, who will be randomized to receive pemetrexed/cisplatin on day 1 and nintedanib or placebo on days 2 to 21, for a maximum of 6 cycles. Patients without disease progression who are eligible to continue study treatment will receive maintenance treatment with nintedanib or placebo until disease progression or undue toxicity. The primary end point is progression-free survival; OS is the key secondary end point. The study will use an adaptive design, including an interim analysis to reassess the number of OS events required to ensure sufficient power for OS analysis. The study is currently enrolling patients.

15α-methoxypuupehenol Induces Antitumor Effects In Vitro and In Vivo against Human Glioblastoma and Breast Cancer Models

Studies with 15α-methoxypuupehenol (15α-MP), obtained from the extracts of Hyrtios species, identified putative targets that are associated with its antitumor effects against human glioblastoma and breast cancer. In the human glioblastoma (U251MG) or breast cancer (MDA-MB-231) cells, treatment with 15α-MP repressed pY705Stat3, pErk1/2, pS147CyclinB1, pY507Alk (anaplastic lymphoma kinase), and pY478ezrin levels and induced pS10merlin, without inhibiting pJAK2 (Janus kinase) or pAkt induction. 15α-MP treatment induced loss of viability of breast cancer (MDA-MB-231, MDA-MB-468) and glioblastoma (U251MG) lines and glioblastoma patient-derived xenograft cells (G22) that harbor aberrantly active Stat3, with only moderate or little effect on the human breast cancer, MCF7, colorectal adenocarcinoma Caco-2, normal human lung fibroblast, WI-38, or normal mouse embryonic fibroblast (MEF Stat3^fl/fl) lines that do not harbor constitutively active Stat3 or the Stat3-null (Stat3^-/-) mouse astrocytes. 15α-MP-treated U251MG cells have severely impaired F-actin organization and altered morphology, including the cells rounding up, and undergo apoptosis, compared with a moderate, reversible morphology change observed for similarly treated mouse astrocytes. Treatment further inhibited U251MG or MDA-MB-231 cell proliferation, anchorage-independent growth, colony formation, and migration in vitro while only moderately or weakly affecting MCF7 cells or normal mouse astrocytes. Oral gavage delivery of 15α-MP inhibited the growth of U251MG subcutaneous tumor xenografts in mice, associated with apoptosis in the treated tumor tissues. Results together suggest that the modulation of Stat3, CyclinB1, Alk, ezrin, merlin, and Erk1/2 functions contributes to the antitumor effects of 15α-MP against glioblastoma and breast cancer progression. Mol Cancer Ther; 16(4); 601-13. ©2017 AACR.

An mRNA-specific tRNAi carrier eIF2A plays a pivotal role in cell proliferation under stress conditions: stress-resistant translation of c-Src mRNA is mediated by eIF2A

c-Src, a non-receptor protein tyrosine kinase, activates NF-κB and STAT3, which in turn triggers the transcription of anti-apoptosis- and cell cycle-related genes. c-Src protein regulates cell proliferation, cell motility and programmed cell death. And the elevated level of activated c-Src protein is related with solid tumor generation. Translation of c-Src mRNA is directed by an IRES element which mediates persistent translation under stress conditions when translation of most mRNAs is inhibited by a phosphorylation of the alpha subunit of eIF2 carrying the initiator tRNA (tRNA_i) to 40S ribosomal subunit under normal conditions. The molecular basis of the stress-resistant translation of c-Src mRNA remained to be elucidated. Here, we report that eIF2A, an alternative tRNA_i carrier, is responsible for the stress-resistant translation of c-Src mRNA. eIF2A facilitates tRNA_i loading onto the 40S ribosomal subunit in a c-Src mRNA-dependent manner. And a direct interaction between eIF2A and a stem-loop structure (SL I) in the c-Src IRES is required for the c-Src IRES-dependent translation under stress conditions but not under normal conditions. Finally, we showed that the eIF2A-dependent translation of c-Src mRNA plays a pivotal role in cell proliferation under stress conditions.

The resistance related to targeted therapy in malignant pleural mesothelioma: Why has not the target been hit yet?

Malignant pleural mesothelioma (MPM) is an aggressive tumor of the pleura with a poor prognosis. The most active first-line regimens are platinum compounds and pemetrexed. There is no standard second-line treatment in MPM. Advances in the understanding of tumor molecular biology have led to the development of several targeted treatments, which have been evaluated in clinical trials. Unfortunately none of the explored targeted treatments can currently be recommended as routine treatment in MPM. We reviewed the biological pathways involved in MPM, the clinical trials about targeted therapy, and possible related mechanisms of resistance. We suggest that specific genetic markers are needed as targets of selective therapy. By this way the selection of patients based on the molecular profile may facilitate a therapeutic strategy that allows the use of the most appropriate drug for each patient.

Induction Therapy for Mesothelioma

One particular approach of multimodality treatment for mesothelioma is induction therapy followed by surgery. Among its several advantages, the most important is downstaging of the tumor into a resectable stage, although morbidity and mortality might be increased. In this article we review the principles and outcome of different modalities for induction treatment of mesothelioma.

Design, synthesis, biological evaluation and molecular docking studies of novel benzofuran-pyrazole derivatives as anticancer agents

This study deals with design and synthesis of novel benzofuran-pyrazole hybrids as anticancer agents. Eight compounds were chosen by National Cancer Institute (NCI), USA to evaluate their in vitro antiproliferative activity at 10(-5)M in full NCI 60 cell panel. The preliminary screening of the tested compounds showed promising broad-spectrum anticancer activity. Compound 4c was further assayed for five dose molar ranges in full NCI 60 cell panel and exhibited remarkable growth inhibitory activity pattern against Leukemia CCRF-CEM, MOLT-4, Lung Cancer HOP-92, Colon Cancer HCC-2998, CNS Cancer SNB-75, Melanoma SK-MEL-2, Ovarian Cancer IGROV1, Renal Cancer 786-0, RXF 393, Breast Cancer HS 578T and T-47D (GI50: 1.00-2.71μM). Moreover, enzyme assays were carried out to investigate the possible antiproliferative mechanism of action of compound 4c. The results revealed that compound 4c has good c-Src inhibitory activity at 10μM. In addition, molecular docking studies showed that 4c could bind to the ATP Src pocket sites. Fulfilling the Lipinskiís rule of five in addition to its ADME profile and the biological results, all strongly suggest that 4c is a promising Src kinase inhibitor.

Local and systemic therapies for malignant pleural mesothelioma

OPINION STATEMENT

Malignant pleural mesothelioma (MPM) is a challenging disease to treat with median overall survival times ranging between 9-17 months for all stages of disease. Recent clinical trials have improved our understanding of the biology of MPM. However, survival results are still not ideal. For early-stage MPM, patients should be evaluated for trimodality therapy in an experienced cancer center. If treating off-protocol, MPM patients should receive a surgical staging evaluation. The decision to proceed with surgical resection also should be considered after an extensive and thorough pulmonary and cardiac evaluation. If deemed a good surgical candidate, patients should receive surgical resection (pleurectomy/decortication or extrapleural pneumonectomy), adjuvant radiation therapy (hemithoracic external beam or intensity modulated radiation therapy), and either neoadjuvant or adjuvant chemotherapy (cisplatin-pemetrexed for 4 cycles). The optimal precise sequence of the trimodality is unclear and should be decided upon by a multidisciplinary consensus for each individual patient. In general, clinical trial participation should be encouraged. Several trials are currently underway to examine intraoperative therapies, vaccines, immunotherapy additions, and novel radiation therapy techniques. Advances in the field of MPM are reliant on participation in clinical trials and identifying biomarkers that are predictive for response to systemic therapies and prognostic for survival benefit.

Dasatinib enhances antitumor activity of paclitaxel in ovarian cancer through Src signaling

Src family tyrosine kinase (SFK) activation is associated with ovarian cancer progression. Therefore, SFKs are targets for the development of potential treatments of ovarian cancer. Dasatinib is a tyrosine kinase inhibitor that targets SFK activity, and is used for the treatment of B cell and Abelson lymphomas. At the present time, the potential effect of dasatinib on ovarian cancer is not clear. The aim of the present study was to investigate the antitumor activity of dasatinib, alone and in combination with paclitaxel, in ovarian cancer in vitro and in vivo. In the present study, the expression of Src and phospho‑Src-Y416 (p‑Src) was measured in six ovarian cancer cell lines using western blotting and immunohistochemistry. In addition, cell viability and apoptosis were measured using an MTT assay and annexin V‑fluorescein isothiocyanate staining. An ovarian cancer murine xenograft model was established, in order to evaluate the antitumor effect of dasatinib alone and in combination with paclitaxel in ovarian cancer. High levels of p‑Src protein expression were observed in all cell lines, as compared with healthy cells, which indicated activation of the Src signaling pathway. p‑Src expression increased in ovarian cancer cells following paclitaxel treatment. Dasatinib treatment demonstrated anti‑ovarian cancer properties, by downregulating p‑Src expression and by inducing cancer cell apoptosis. Combined treatment with dasatinib and paclitaxel markedly inhibited proliferation and promoted apoptosis of ovarian cancer cells, compared with control cells. Combined dasatinib and paclitaxel treatment exhibited antitumor activities in vivo and in vitro (combination indices, 0.25‑0.93 and 0.31‑0.75; and tumor growth inhibitory rates, 76.7% and 58.5%, in A2780 and HO8910 cell lines, respectively), compared with paclitaxel treatment alone. Dasatinib monotherapy demonstrated anti‑ovarian cancer activities. The effects of dasatinib and paclitaxel treatments on ovarian cancer cells appeared to be mediated by the Src pathway.

Improved angiostatic activity of dasatinib by modulation with hydrophobic chains

Dasatinib is an orally active nonselective tyrosine kinase inhibitor used to treat certain types of adult leukemia. By inhibiting PDGFR-β and SFKs in both tumor cells and tumor-associated endothelial cells, dasatinib inhibits tumor growth and angiogenesis. Herein, dasatinib derivatives modified with hydrophobic chains were prepared and evaluated for their in vitro antiproliferative selectivity and their in vivo antiangiogenic activity. For one of the derivatives, modified with a long perfluorinated chain, a significant enhancement in antiangiogenic activity was observed. Combined, these results suggest a possible generic route to modulate the angiostatic activity of drugs.

The prognostic significance of Src and p-Src expression in patients with osteosarcoma

Background

The expression of Src and phospho-Src (p-Src) is closely related to tumor invasion and metastasis. The aim of the present study was to investigate the expression of these molecules in osteosarcoma and their relationship with each other, to provide a theoretical basis to understand the prognosis of osteosarcoma.

Material/Methods

We selected surgically resected osteosarcoma specimens from 116 patients of Zhongnan Hospital of Wuhan University and Hubei Cancer Hospital, Hubei, China, between January 2000 and January 2010 with detailed follow-up data. Twenty osteochondroma specimens from the corresponding period were used as controls. Expression of Src and p-Src was detected in osteosarcoma and osteochondroma by immunohistochemistry. We analyzed the relationship of the 2 proteins and osteosarcoma patient prognosis.

Results

The expression of Src and p-Src in osteosarcoma was significantly higher than the expression level in osteochondroma (P<0.05). The expression levels of the 2 proteins, clinical stage, and tumor metastasis were significantly associated with survival time (P<0.05), but there was no correlation between age or sex and survival time. The expression of Src and p-Src in osteosarcoma was positively correlated.

Conclusions

Src and p-Src can be used as an auxiliary indicator to determine a malignant phenotype of bone tumors, and the combined detection of Src and p-Src may indicate the prognosis of osteosarcoma.

Predictive biomarkers for dasatinib treatment in melanoma

Dasatinib has anti-proliferative and anti-invasive effects in melanoma cell lines. However clinical trials have shown modest activity for dasatinib in metastatic melanoma. Although dasatinib targets SRC kinase, neither expression nor phosphorylation of SRC appears to predict response to dasatinib. Identification of predictive biomarkers for dasatinib may facilitate selection of melanoma patients who are more likely to respond to dasatinib. We correlated the anti-proliferative effects of dasatinib in 8 melanoma cell lines with expression of a previously identified 6-gene biomarker panel. We examined the relationship between response to dasatinib and expression of each gene at both the mRNA and protein level. Dasatinib inhibited growth in 3 of the 8 cell lines tested. mRNA expression of the panel of 6 biomarkers did not correlate with response, whilst elevated protein expression of ANXA1, CAV-1 and EphA2 correlated significantly with response to dasatinib in the panel of cell lines. Expression of ANXA1, CAV-1 and EphA2 were analysed in 124 melanoma samples by immunohistochemistry. ANXA1 protein was detected in 81 % (97/120) of tumours, CAV-1 in 44 % (54/122) of tumours and EphA2 in 74 % (90/121) of tumours. Thirty one % (35/113) of tumours tested expressed all three markers and 19 % (21/112) had moderate or strong expression of ANXA1, CAV-1 and EphA2. Seventeen percent (19/112) of melanoma samples were positive for SRC kinase expression, combined with high expression of ANXA1, CAV-1 and EphA2. This subgroup may represent a population of melanoma patients who would be more likely to derive clinical benefit from dasatinib treatment.

Antitumor effects of immunotoxins are enhanced by lowering HCK or treatment with SRC kinase inhibitors

Recombinant immunotoxins (RIT) are agents being developed for cancer treatment. They are composed of an Fv that binds to a cancer cell, fused to a 38-kDa fragment of Pseudomonas exotoxin A. SS1P is a RIT that targets mesothelin, a protein expressed on mesothelioma as well as pancreatic, ovarian, lung, and other cancers. Because the protein tyrosine kinase family regulates a variety of cellular processes and pathways, we hypothesized that tyrosine kinases might regulate susceptibility to immunotoxin killing. To investigate their role, we used siRNAs to lower the level of expression of the 88 known tyrosine kinases. We identified five tyrosine kinases, INSR, HCK, SRC, PDGFRβ, and BMX that enhance the activity of SS1P when their level of expression is lowered by siRNAs. We further investigated the Src family member HCK in this study. Knocking down of SRC slightly increased SS1P killing in A431/H9 cells, but knocking down HCK substantially enhanced killing by SS1P. We investigated the mechanism of enhancement and found that HCK knockdown enhanced SS1P cleavage by furin and lowered levels of Mcl-1 and raised Bax. We then found that Src inhibitors mimic the stimulatory effect of HCK knockdown; both SU6656 and SKI-606 (bosutinib) enhanced immunotoxin killing of mesothelin-expressing cells by SS1P and CD22-expressing cells by HA22 (moxetumomab pasudotox). SU6656 also enhanced the antitumor effects of SS1P and HA22 in mouse xenograft tumor models. Our data suggest that the combination of immunotoxin with tyrosine kinase inhibitors may be an effective way to treat some cancers.

Simultaneous suppression of Src and signal transducer and activator of transcription 3 inhibits the growth of epithelial ovarian cancer cells

OBJECTIVE

The reciprocal regulation of c-Src and STAT3 activation seems to be associated with the poor response to c-Src inhibitors of ovarian cancer. This study aims to investigate inhibition of cell proliferation and enhancement of the cytotoxic effect of chemotherapeutic agents via simultaneous suppression of c-Src and STAT3 in ovarian cancer cell lines.

STUDY DESIGN

Specific siRNAs targeting c-Src and STAT3 were produced and transfected into an SKOV3 ovarian cancer cell line. We confirmed the downregulation of c-Src and STAT3 mRNAs by reverse transcriptase polymerase chain reaction. MTT assay was used to assess cytotoxicity following cisplatin administration. Protein expression level was evaluated by Western blot.

RESULTS

Cell growth was significantly inhibited by c-Src or STAT3 siRNA. Cytotoxicity was not increased in cisplatin-treated SKOV3 by c-Src siRNA only or STAT3 siRNA only, but cell viability was decreased significantly in cisplatin-treated cells after simultaneous transfection with c-Src and STAT3 siRNAs. Specifically, the viability was significantly decreased from 30% to 55% within the IC50 concentration following simultaneous transfection with c-Src and STAT3 siRNAs, particularly after 72 h. Src and survivin protein expression level was significantly decreased at 72 h after transfection of c-Src and STAT3 siRNAs.

CONCLUSIONS

This study has demonstrated the principle that the simultaneous suppression of c-Src and STAT3 inhibits the growth of epithelial ovarian cancer cells and seems to enhance the cytotoxicity of chemotherapeutic agents in ovarian cancer.

Yes is a central mediator of cell growth in malignant mesothelioma cells

The constitutive activation of the Src family kinases (SFKs) has been established as a poor prognostic factor in malignant mesothelioma (MM), however, the family member(s) which contribute to the malignancy have not been defined. This study aimed to identify the SFK member(s) contributing to cell growth using RNA interference in various MM cell lines. Silencing of Yes but not of c-Src or Fyn in MM cells leads to cell growth suppression. This suppressive effect caused by Yes silencing mainly depends on G1 cell cycle arrest and partly the induction of apoptosis. Also, the knockout of Yes induces the inactivation of β-catenin signaling and subsequently decreases the levels of cyclin D necessary for G1-S transition in the cell cycle. In addition, Yes knockout has less effect on cell growth suppression in β-catenin-deficient H28 MM cells compared to other MM cells which express the catenin. Overall, we conclude that Yes is a central mediator for MM cell growth that is not shared with other SFKs such as c-Src.

Targeted inhibition of Src kinase with dasatinib blocks thyroid cancer growth and metastasis

PURPOSE

There are no effective therapies for patients with poorly differentiated papillary thyroid cancer (PTC) or anaplastic thyroid cancer (ATC), and metastasis to the bone represents a significantly worse prognosis. Src family kinases (SFKs) are overexpressed and activated in numerous tumor types and have emerged as a promising therapeutic target, especially in relation to metastasis. We recently showed that Src is overexpressed and activated in thyroid cancer. We therefore tested whether inhibition of Src with dasatinib (BMS-354825) blocks thyroid cancer growth and metastasis.

EXPERIMENTAL DESIGN

The effects of dasatinib on thyroid cancer growth, signaling, cell cycle, and apoptosis were evaluated in vitro. The therapeutic efficacy of dasatinib was further tested in vivo using an orthotopic and a novel experimental metastasis model. Expression and activation of SFKs in thyroid cancer cells was characterized, and selectivity of dasatinib was determined using an Src gatekeeper mutant.

RESULTS

Dasatinib treatment inhibited Src signaling, decreased growth, and induced cell-cycle arrest and apoptosis in a subset of thyroid cancer cells. Immunoblotting showed that c-Src and Lyn are expressed in thyroid cancer cells and that c-Src is the predominant SFK activated. Treatment with dasatinib blocked PTC tumor growth in an orthotopic model by more than 90% (P = 0.0014). Adjuvant and posttreatment approaches with dasatinib significantly inhibited metastasis (P = 0.016 and P = 0.004, respectively).

CONCLUSION

These data provide the first evidence that Src is a central mediator of thyroid cancer growth and metastasis, indicating that Src inhibitors may have a higher therapeutic efficacy in thyroid cancer, as both antitumor and antimetastatic agents.

Preclinical studies identify novel targeted pharmacological strategies for treatment of human malignant pleural mesothelioma

The incidence of human malignant pleural mesothelioma (hMPM) is still increasing worldwide. hMPM prognosis is poor even if the median survival time has been slightly improved after the introduction of the up-to-date chemotherapy. Nevertheless, large phase II/III trials support the combination of platinum derivatives and pemetrexed or raltitrexed, as preferred first-line schedule. Better understanding of the molecular machinery of hMPM will lead to the design and synthesis of novel compounds targeted against pathways identified as crucial for hMPM cell proliferation and spreading. Among them, several receptors tyrosine kinase show altered activity in subsets of hMPM. This observation suggests that these kinases might represent novel therapeutic targets in this chemotherapy-resistant disease. Over these foundations, several promising studies are ongoing at preclinical level and novel molecules are currently under evaluation as well. Yet, established tumour cell lines, used for decades to investigate the efficacy of anticancer agents, although still the main source of drug efficacy studies, after long-term cultures tend to biologically diverge from the original tumour, limiting the predictive potential of in vivo efficacy. Cancer stem cells (CSCs), a subpopulation of malignant cells capable of self-renewal and multilineage differentiation, are believed to play an essential role in cancer initiation, growth, metastasization and relapse, being responsible of chemo- and radiotherapy refractoriness. According to the current carcinogenesis theory, CSCs represent the tumour-initiating cell (TIC) fraction, the only clonogenic subpopulation able to originate a tumour mass. Consequently, the recently described isolation of TICs from hMPM, the proposed main pharmacological target for novel antitumoural drugs, may contribute to better dissect the biology and multidrug resistance pathways controlling hMPM growth.

Furano-1,2-Naphthoquinone Inhibits Src and PI3K/Akt Signaling Pathways in Ca9-22 Human Oral Squamous Carcinoma Cells

Furano-1,2-naphthoquinone (FNQ), a biologically active component ofAvicennia marina, has been demonstrated to display anticancer activity. FNQ exerted cytotoxicity with the G2/M cell cycle arrest and apoptosis in Ca9-22 cells. FNQ-induced G2/M arrest was correlated with a marked decrease in the expression levels of cyclin A and cyclin B, and their activating partner cyclin-dependent kinases (CDK) 1 and 2 with concomitant induction of p27. FNQ-induced apoptosis was accompanied by Bax and Bad upregulation, and the downregulation of Bcl-2, Bcl-XL, Mcl-1, and X-linked inhibitor of apoptosis (XIAP), resulting in cytochrome C release and sequential activation of caspase-9 and caspase-3. Mechanistic studies showed that FNQ suppressed Src phosphorylation, PI3K, and Akt activation in Ca9-22 cells. Moreover, the Src inhibitor PP2 reduced the phosphorylation of Src and activation of PI3K/Akt, which was comparable with FNQ treatment. The combined treatment of FNQ with PP2 enhanced the cell cycle arrest and apoptosis and also led to the downregulation of Bcl-XL, Mcl-1, XIAP, cyclin A, cyclin B, CDK1, and CDK2 and upregulation of p27, Bax, and Bad. These findings suggest that FNQ-mediated cytotoxicity of Ca9-22 cells is related with the G2/M cell cycle arrest and apoptosis via inactivation of Src and PI3K/Akt-mediated signaling pathways.

Systemic treatment of malignant pleural mesothelioma

Malignant pleural mesothelioma is a rare malignancy with a dismal prognosis. The clinical management of most of the patients with this disease is quite challenging, and, overall, the therapeutic strategy has not yet benefited from the recent advances in molecular biology. Randomized evidence supports the use of cisplatin in combination with pemetrexed or raltitrexed as first-line treatments. In elderly patients with comorbidities cisplatin may be replaced by carboplatin because of a lesser burden of toxicities. The role of second-line chemotherapy is unproven, although pemetrexed can be regarded as the standard option in pemetrexed-naive patients and therapeutic rechallenge with pemetrexed may be considered in selected patients with prolonged disease control after first-line therapy. Targeted therapies failed to demonstrate any substantial activity; however, immunotherapies may complement other treatment strategies. In summary, there is an unmet clinical need and innovative approaches to select new potentially active drugs are highly warranted.

Deficiency of Fyn protein is prerequisite for apoptosis induced by Src family kinase inhibitors in human mesothelioma cells

Malignant mesothelioma is an aggressive tumor arising from mesothelial cells of serous membranes. Src family kinases (SFKs) have a pivotal role in cell adhesion, proliferation, survival and apoptosis. Here, we examined the effect of SFK inhibitors in NCI-H2052, ACC-MESO-4 and NCI-H28 cells, mesothelioma cell lines and Met5A, a human non-malignant mesothelial cell line. We found that PP2, a selective SFK inhibitor, inhibited SFK activity and induced apoptosis mediated by caspase-8 in NCI-H28 but not Met5A, NCI-H2052 and ACC-MESO-4 cells. Src, Yes, Fyn and Lyn protein, which are members of the SFK, were expressed in these cell lines, whereas NCI-H28 cells were deficient in Fyn protein. Small interfering RNA (siRNA) targeting Fyn facilitated PP2-induced apoptosis mediated by caspase-8 in NCI-H2052 and ACC-MESO-4 cells. PP2 reduced Lyn protein levels and suppressed SFK activity in all mesothelioma cell lines. Lyn siRNA induced caspase-8 activation and apoptosis in NCI-H28 cells but not in NCI-H2052 and ACC-MESO-4 cells. However, double RNA interference knockdown of Fyn and Lyn induced apoptosis accompanied by caspase-8 activation in NCI-H2052 and ACC-MESO-4 cells. Dasatinib, an inhibitor of multi-tyrosine kinases including SFK, also inhibited SFK activity and induced reduction of Lyn protein levels, caspase-8 activation and apoptosis in NCI-H28 cells but not in other cell lines. Present study suggests that SFK inhibitors induce caspase-8-dependent apoptosis caused by reduction of Lyn protein in Fyn-deficient mesothelioma cells.

STAT5A-mediated SOCS2 expression regulates Jak2 and STAT3 activity following c-Src inhibition in head and neck squamous carcinoma

PURPOSE

The inhibition of c-Src results in a striking reduction in cancer cell invasion, but the effect on cell survival is modest. Defining mechanisms that limit apoptosis following c-Src inhibition could result in an ideal therapeutic approach that both inhibits invasion and leads to apoptosis. In this regard, we discovered a novel feedback loop that results in STAT3 reactivation following sustained c-Src inhibition. Here we define the mechanism underlying this feedback loop and examine the effect of inhibiting it in vivo.

EXPERIMENTAL DESIGN

We measured levels and activity of pathway components using PCR, Western blotting, and kinase assays following their manipulation using both molecular and pharmacologic approaches. We used a heterotransplant animal model in which human oral squamous cancer is maintained exclusively in vivo.

RESULTS

Following c-Src inhibition, STAT5 is durably inhibited. The inhibition of STAT5A, but not STAT5B, subsequently reduces the expression of suppressors of cytokine signaling 2 (SOCS2). SOCS2 inhibits Janus kinase 2 (Jak2) activity and Jak2-STAT3 binding. SOCS2 expression is necessary for STAT3 inhibition by c-Src inhibitors. Overexpression of SOCS2 is adequate to prevent STAT3 reactivation and to enhance the cytotoxic effects of c-Src inhibition. Likewise, the combination of Jak and c-Src inhibitors led to significantly more apoptosis than either agent alone in vivo.

CONCLUSIONS

To our knowledge, ours is the first study that fully defines the mechanism underlying this feedback loop, in which sustained c-Src inhibition leads to diminished SOCS2 expression via sustained inhibition of STAT5A, allowing activation of Jak2 and STAT3, Jak2-STAT3 binding, and survival signals.