Gene array and fluorescence in situ hybridization biomarkers of activity of saracatinib (AZD0530), a Src inhibitor, in a preclinical model of colorectal cancer

Dual Drug Repurposing: The Example of Saracatinib

Saracatinib (AZD0530) is a dual Src/Abl inhibitor initially developed by AstraZeneca for cancer treatment; however, data from 2006 to 2024 reveal that this drug has been tested not only for cancer treatment, but also for the treatment of other diseases. Despite the promising pre-clinical results and the tolerability shown in phase I trials, where a maximum tolerated dose of 175 mg was defined, phase II clinical data demonstrated a low therapeutic action against several cancers and an elevated rate of adverse effects. Recently, pre-clinical research aimed at reducing the toxic effects and enhancing the therapeutic performance of saracatinib using nanoparticles and different pharmacological combinations has shown promising results. Concomitantly, saracatinib was repurposed to treat Alzheimer's disease, targeting Fyn. It showed great clinical results and required a lower daily dose than that defined for cancer treatment, 125 mg and 175 mg, respectively. In addition to Alzheimer's disease, this Src inhibitor has also been studied in relation to other health conditions such as pulmonary and liver fibrosis and even for analgesic and anti-allergic functions. Although saracatinib is still not approved by the Food and Drug Administration (FDA), the large number of alternative uses for saracatinib and the elevated number of pre-clinical and clinical trials performed suggest the huge potential of this drug for the treatment of different kinds of diseases.

Functional roles of SRC signaling in pancreatic cancer: Recent insights provide novel therapeutic opportunities

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignant disease with a 5-year survival rate of <10%. Aberrant activation or elevated expression of the tyrosine kinase c-SRC (SRC) is frequently observed in PDAC and is associated with a poor prognosis. Preclinical studies have revealed a multifaceted role for SRC activation in PDAC, including promoting chronic inflammation, tumor cell proliferation and survival, cancer cell stemness, desmoplasia, hypoxia, angiogenesis, invasion, metastasis, and drug resistance. Strategies to inhibit SRC signaling include suppressing its catalytic activity, inhibiting protein stability, or by interfering with signaling components of the SRC signaling pathway including suppressing protein interactions of SRC. In this review, we discuss the molecular and immunological mechanisms by which aberrant SRC activity promotes PDAC tumorigenesis. We also provide a comprehensive update of SRC inhibitors in the clinic, and discuss the clinical challenges associated with targeting SRC in pancreatic cancer.

Integrative and Comprehensive Pan-Cancer Analysis of Lymphocyte-Specific Protein Tyrosine Kinase in Human Tumors

Lymphocyte-specific protein tyrosine kinase (LCK) is common in a variety of hematologic malignancies but comparatively less common in solid tumors. This study aimed to explore the potential diagnostic and prognostic value of LCK across tumors through integrative and comprehensive pan-cancer analysis, as well as experimental validation. Multiple databases were used to explore the expression, alteration, prognostic value, association with immune infiltration, and potential functional pathways of LCK in pan-cancers. The results were further validated by western blotting and qPCR of patient samples as well as tumor cell lines. High LCK expression typically represents a better prognosis. Notably, drug sensitivity prediction of LCK identified P-529 as a candidate for drug development. Gene Annotations (GO) and KEGG analyses showed significant enrichment of PD-L1 and the T-cell receptor pathway. The results from patient samples and tumor cell lines confirmed these conclusions in LIHC. In conclusion, LCK is differentially expressed in multiple tumors and normal tissues. Further analysis highlighted its association with prognostic implications, pan-cancer genetic alterations, and immune signatures. Our data provide evidence for a diagnostic marker of LCK and the possible use of LCK as a target for the treatment of tumors.

YES1: a novel therapeutic target and biomarker in cancer

YES1 is a non-receptor tyrosine kinase that belongs to the SRC family of kinases (SFKs) and controls multiple cancer signaling pathways. YES1 is amplified and overexpressed in many tumor types, where it promotes cell proliferation, survival and invasiveness. Therefore, YES1 has been proposed as an emerging target in solid tumors. In addition, studies have shown that YES1 is a prognostic biomarker and a predictor of dasatinib activity. Several SFKs-targeting drugs have been developed and some of them have reached clinical trials. However, these drugs have encountered challenges to their utilization in the clinical practice in unselected patients due to toxicity and lack of efficacy. In the case of YES1, novel specific inhibitors have been developed and tested in preclinical models, with impressive antitumor effects. In this review, we summarize the structure and activation of YES1 and describe its role in cancer as a target and prognostic and companion biomarker. We also address the efficacy of SFKs inhibitors that are currently in clinical trials, highlighting the main hindrances for their clinical use. Current available information strongly suggests that inhibiting YES1 in tumors with high expression of this protein is a promising strategy against cancer.

An integrative gene expression signature analysis identifies CMS4 KRAS-mutated colorectal cancers sensitive to combined MEK and SRC targeted therapy

BACKGROUND

Over half of colorectal cancers (CRCs) are hard-wired to RAS/RAF/MEK/ERK pathway oncogenic signaling. However, the promise of targeted therapeutic inhibitors, has been tempered by disappointing clinical activity, likely due to complex resistance mechanisms that are not well understood. This study aims to investigate MEK inhibitor-associated resistance signaling and identify subpopulation(s) of CRC patients who may be sensitive to biomarker-driven drug combination(s).

METHODS

We classified 2250 primary and metastatic human CRC tumors by consensus molecular subtypes (CMS). For each tumor, we generated multiple gene expression signature scores measuring MEK pathway activation, MEKi "bypass" resistance, SRC activation, dasatinib sensitivity, EMT, PC1, Hu-Lgr5-ISC, Hu-EphB2-ISC, Hu-Late TA, Hu-Proliferation, and WNT activity. We carried out correlation, survival and other bioinformatic analyses. Validation analyses were performed in two independent publicly available CRC tumor datasets (n = 585 and n = 677) and a CRC cell line dataset (n = 154).

RESULTS

Here we report a central role of SRC in mediating "bypass"-resistance to MEK inhibition (MEKi), primarily in cancer stem cells (CSCs). Our integrated and comprehensive gene expression signature analyses in 2250 CRC tumors reveal that MEKi-resistance is strikingly-correlated with SRC activation (Spearman P < 10-320), which is similarly associated with EMT (epithelial to mesenchymal transition), regional metastasis and disease recurrence with poor prognosis. Deeper analysis shows that both MEKi-resistance and SRC activation are preferentially associated with a mesenchymal CSC phenotype. This association is validated in additional independent CRC tumor and cell lines datasets. The CMS classification analysis demonstrates the strikingly-distinct associations of CMS1-4 subtypes with the MEKi-resistance and SRC activation. Importantly, MEKi + SRCi sensitivities are predicted to occur predominantly in the KRAS mutant, mesenchymal CSC-like CMS4 CRCs.

CONCLUSIONS

Large human tumor gene expression datasets representing CRC heterogeneity can provide deep biological insights heretofore not possible with cell line models, suggesting novel repurposed drug combinations. We identified SRC as a common targetable node--an Achilles' heel--in MEKi-targeted therapy-associated resistance in mesenchymal stem-like CRCs, which may help development of a biomarker-driven drug combination (MEKi + SRCi) to treat problematic subpopulations of CRC.

Identification of Biomarkers Related to Regulatory T Cell Infiltration in Oral Squamous Cell Carcinoma Based on Integrated Bioinformatics Analysis

Background

Oral squamous cell carcinoma (OSCC) is one of the most prevalent malignancies worldwide. More recently, the administration of immune checkpoint inhibitors has opened up more possibilities for cancer treatment.

Methods

We utilized a weighted gene co-expression network and the single sample gene set enrichment analysis (ssGSEA) algorithm in the TCGA database and identified a module highly correlated with regulatory T cell (Treg) abundance in OSCC. Subsequently, we verified the results by tissue microarrays and utilized immunohistochemical staining (IHC) to test the relationship between the expression level and clinicopathological staging. CCK-8, transwell, and wound healing assays were utilized to detect the functions of OSCC cells.

Results

LCK, IL10RA, and TNFRSF1B were selected as biomarkers related to regulatory T cell infiltration. IHC staining showed significantly increased expression of LCK, IL10RA or TNFRSF1B in OSCC patients, and the expression levels were associated with tumor stage, lymph node metastasis, pathological stage, clinical status and the overall survival. In vitro experiments showed that LCK, IL10RA or TNFRSF1B knockdown efficiently impaired the proliferative, migrative, and invasive capacity in OSCC cell lines.

Conclusion

We performed a series of bioinformatics analyses in OSCC and identified three oncogenic indicators: LCK, IL10RA, TNFRSF1B. These findings uncovered the potential prognostic values of hub genes, thus laying foundations for in-depth research in OSCC.

Predicting the Survival and Immune Landscape of Colorectal Cancer Patients Using an Immune-Related lncRNA Pair Model

Background

Accumulating evidence has demonstrated that immune-related long non-coding ribonucleic acids (irlncRNAs) can be used as prognostic indicators of overall survival (OS) in patients with colorectal cancer (CRC). Our aim in this research, therefore, was to construct a risk model using irlncRNA pairs with no requirement for a specific expression level, in hope of reliably predicting the prognosis and immune landscape of CRC patients.

Methods

Clinical and transcriptome profiling data of CRC patients downloaded from the Cancer Genome Atlas (TCGA) database were analyzed to identify differentially expressed (DE) irlncRNAs. The irlncRNA pairs significantly correlated with the prognosis of patients were screened out by univariable Cox regression analysis and a prognostic model was constructed by Lasso and multivariate Cox regression analyses. A receiver operating characteristic (ROC) curve was then plotted, with the area under the curve calculated to confirm the reliability of the model. Based on the optimal cutoff value, CRC patients in the high- or low-risk groups were distinguished, laying the ground for evaluating the risk model from the following perspectives: survival, clinicopathological traits, tumor-infiltrating immune cells (TIICs), antitumor drug efficacy, kinase inhibitor efficacy, and molecules related to immune checkpoints.

Results

A prognostic model consisting of 15 irlncRNA pairs was constructed, which was found to have a high correlation with patient prognosis in a cohort from the TCGA (p < 0.001, HR = 1.089, 95% CI [1.067-1.112]). According to both univariate and multivariate Cox analyses, this model could be used as an independent prognostic indicator in the TCGA cohort (p < 0.001). Effective differentiation between high- and low-risk patients was also accomplished, on the basis of aggressive clinicopathological characteristics, sensitivity to antitumor drugs, and kinase inhibitors, the tumor immune infiltration status, and the expression levels of specific molecules related to immune checkpoints.

Conclusion

The prognostic model established with irlncRNA pairs is a promising indicator for prognosis prediction in CRC patients.

Identifying Biomarkers from Transcriptomic Signatures in Renal Allograft Biopsies Using Deceased and Living Donors

The survival of transplant kidneys using deceased donors (DD) is inferior to living donors (LD). In this study, we conducted a whole-transcriptome expression analysis of 24 human kidney biopsies paired at 30 minutes and 3 months post-transplantation using DD and LD. The transcriptome profile was found significantly different between two time points regardless of donor types. There were 446 differentially expressed genes (DEGs) between DD and LD at 30 minutes and 146 DEGs at 3 months, with 25 genes common to both time points. These DEGs reflected donor injury and acute immune responses associated with inflammation and cell death as early as at 30 minutes, which could be a precious window of potential intervention. DEGs at 3 months mainly represented the changes of adaptive immunity, immunosuppressive treatment, remodeling or fibrosis via different networks and signaling pathways. The expression levels of 20 highly DEGs involved in kidney diseases and 10 genes dysregulated at 30 minutes were found correlated with renal function and histology at 12 months, suggesting they could be potential biomarkers. These genes were further validated by quantitative polymerase chain reaction (qPCR) in 24 samples analysed by microarray, as well as in a validation cohort of 33 time point unpaired allograft biopsies. This analysis revealed that SERPINA3, SLPI and CBF were up-regulated at 30 minutes in DD compared to LD, while FTCD and TASPN7 were up-regulated at both time points. At 3 months, SERPINA3 was up-regulated in LD, but down-regulated in DD, with increased VCAN and TIMP1, and decreased FOS, in both donors. Taken together, divergent transcriptomic signatures between DD and LD, and changed by the time post-transplantation, might contribute to different allograft survival of two type kidney donors. Some DEGs including FTCD and TASPN7 could be novel biomarkers not only for timely diagnosis, but also for early precise genetic intervention at donor preservation, implantation and post-transplantation, in particular to effectively improve the quality and survival of DD.

Src family kinases, adaptor proteins and the actin cytoskeleton in epithelial-to-mesenchymal transition

Over a century of scientific inquiry since the discovery of v-SRC but still no final judgement on SRC function. However, a significant body of work has defined Src family kinases as key players in tumor progression, invasion and metastasis in human cancer. With the ever-growing evidence supporting the role of epithelial-mesenchymal transition (EMT) in invasion and metastasis, so does our understanding of the role SFKs play in mediating these processes. Here we describe some key mechanisms through which Src family kinases play critical role in epithelial homeostasis and how their function is essential for the propagation of invasive signals. Video abstract.

HCK maintains the self-renewal of leukaemia stem cells via CDK6 in AML

Background:

Leukaemia stem cells (LSCs) are responsible for the initiation, maintenance, and recurrence of acute myeloid leukaemia (AML), an aggressive haematological malignancy associated with drug resistance and relapse. Identifying therapeutic LSC targets is critical to curing AML.

Methods

Bioinformatics databases were used to identify therapeutic LSC targets. The conditional knockout mice were used to analyse the role of HCK in leukaemogenesis or normal haematopoiesis. Colony-forming assays, cell counting, and flow cytometry were used to detect the viability and function of leukaemia cells. RT-PCR, western blotting, and RNA sequencing were used to detect mRNA and protein expression.

Result

HCK is expressed at higher levels in LSCs than in haematopoietic stem cells (HSCs), and high HCK levels are correlated with reduced survival time in AML patients. Knockdown of HCK leads to cell cycle arrest, which results in a dramatic decrease in the proliferation and colony formation in human AML cell lines. Moreover, HCK is required for leukemogenesis and leukaemia maintenance in vivo and in vitro. HCK is necessary for the self-renewal of LSCs during serial transplantation and limiting dilution assay. The phenotypes resulting from HCK deficiency can be rescued by CDK6 overexpression in the human cell line. RNA sequencing and gene expression have demonstrated that HCK may sustain cell cycle entry and maintain the self-renewal ability of LSCs through activating the ERK1/2-c-Myc-CDK6 signalling axis. In contrast, HCK deletion does not affect normal haematopoiesis or haematopoietic reconstruction in mice.

Conclusions

HCK maintains the self-renewal of leukaemia stem cells via CDK6 in AML and may be an ideal therapeutic target for eradicating LSCs without influencing normal haematopoiesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02007-4.

Identification of lymphocyte cell-specific protein-tyrosine kinase (LCK) as a driver for invasion and migration of oral cancer by tumor heterogeneity exploitation

BACKGROUND

Cancer metastases are the main cause of lethality. The five-year survival rate for patients diagnosed with advanced stage oral cancer is 30%. Hence, the identification of novel therapeutic targets is an urgent need. However, tumors are comprised of a heterogeneous collection of cells with distinct genetic and molecular profiles that can differentially promote metastasis making therapy development a challenging task. Here, we leveraged intratumoral heterogeneity in order to identify drivers of cancer cell motility that might be druggable targets for anti-metastasis therapy.

METHODS

We used 2D migration and 3D matrigel-based invasion assays to characterize the invasive heterogeneity among and within four human oral cancer cell lines in vitro. Subsequently, we applied mRNA-sequencing to map the transcriptomes of poorly and strongly invasive subclones as well as primary tumors and matched metastasis.

RESULTS

We identified SAS cells as a highly invasive oral cancer cell line. Clonal analysis of SAS yielded a panel of 20 subclones with different invasive capacities. Integrative gene expression analysis identified the Lymphocyte cell-specific protein-tyrosine kinase (LCK) as a druggable target gene associated with cancer cell invasion and metastasis. Inhibition of LCK using A-770041 or dasatinib blocked invasion of highly aggressive SAS cells. Interestingly, reduction of LCK activity increased the formation of adherens junctions and induced cell differentiation.

CONCLUSION

Analysis of invasive heterogeneity led to the discovery of LCK as an important regulator of motility in oral cancer cells. Hence, small molecule mediated inhibition of LCK could be a promising anti-metastasis therapy option for oral cancer patients.

Anti-GPR56 monoclonal antibody potentiates GPR56-mediated Src-Fak signaling to modulate cell adhesion

GPR56 is a member of the adhesion G-protein-coupled receptor family shown to play important roles in cell adhesion, brain development, immune function, and tumorigenesis. GPR56 is highly upregulated in colorectal cancer and correlates with poor prognosis. Several studies have shown GPR56 couples to the Gα_12/13 class of heterotrimeric G-proteins to promote RhoA activation. However, due to its structural complexity and lack of a high-affinity receptor-specific ligand, the complete GPR56 signaling mechanism remains largely unknown. To delineate the activation mechanism and intracellular signaling functions of GPR56, we generated a monoclonal antibody (mAb) that binds with high affinity and specificity to the extracellular domain (ECD). Using deletion mutants, we mapped the mAb binding site to the GAIN domain, which mediates membrane-proximal autoproteolytic cleavage of the ECD. We showed that GPR56 overexpression in 293T cells leads to increased phosphorylation of Src, Fak, and paxillin adhesion proteins and activation of the Gα_12/13-RhoA-mediated serum response factor (SRF) pathway. Treatment with the mAb potentiated Src-Fak phosphorylation, RhoA–SRF signaling, and cell adhesion. Consistently, GPR56 knockdown in colorectal cancer cells decreased Src–Fak pathway phosphorylation and cell adhesion. Interestingly, GPR56-mediated activation of Src–Fak phosphorylation occurred independent of RhoA, yet mAb-induced potentiation of RhoA–SRF signaling was Src-dependent. Furthermore, we show that the C-terminal portion of the Serine–Threonine–Proline-rich (STP) region, adjacent to the GAIN domain, was required for Src–Fak activation. However, autoproteolytic cleavage of the ECD was dispensable. These data support a new ECD-dependent mechanism by which GPR56 functions to regulate adhesion through activation of Src–Fak signaling.

Targeting the Extra-Cellular Matrix-Tumor Cell Crosstalk for Anti-Cancer Therapy: Emerging Alternatives to Integrin Inhibitors

The extracellular matrix (ECM) is a complex network composed of a multitude of different macromolecules. ECM components typically provide a supportive structure to the tissue and engender positional information and crosstalk with neighboring cells in a dynamic reciprocal manner, thereby regulating tissue development and homeostasis. During tumor progression, tumor cells commonly modify and hijack the surrounding ECM to sustain anchorage-dependent growth and survival, guide migration, store pro-tumorigenic cell-derived molecules and present them to enhance receptor activation. Thereby, ECM potentially supports tumor progression at various steps from initiation, to local growth, invasion, and systemic dissemination and ECM-tumor cells interactions have long been considered promising targets for cancer therapy. Integrins represent key surface receptors for the tumor cell to sense and interact with the ECM. Yet, attempts to therapeutically impinge on these interactions using integrin inhibitors have failed to deliver anticipated results, and integrin inhibitors are still missing in the emerging arsenal of drugs for targeted therapies. This paradox situation should urge the field to reconsider the role of integrins in cancer and their targeting, but also to envisage alternative strategies. Here, we review the therapeutic targets implicated in tumor cell adhesion to the ECM, whose inhibitors are currently in clinical trials and may offer alternatives to integrin inhibition.

HCK can serve as novel prognostic biomarker and therapeutic target for Breast Cancer patients

The role of HCK expression in the prognosis of breast cancer patients is unclear. Thus, this study aimed to explore the clinical implications of HCK expression in breast cancer. We assessed HCK expression and genetic variations in breast cancer using Oncomine, GEPIA, UALCAN, and cBioPortal databases. Then, immunochemistry was used to analyze HCK expression in breast cancer specimens, non-cancer tissues and metastatic cancer tissues. Consequently, we evaluated the effect of HCK expression on survival outcomes set as disease-free survival (DFS) and overall survival (OS). Finally, STRING, Coexpedia, and TISIDB database were explored to identify the molecular functions and regulation pathways of HCK. We found that breast cancer tissues have more HCK mRNA transcripts than non-cancer tissues. Patients with HCK expression had significantly shorter DFS and OS. The ratio of HCK expression was higher in cancer tissues than in non-cancer tissues. These results from STRING database, FunRich software, and TISIDB database showed that HCK was involved in mediating multiple biological processes including immune response-regulating signaling pathway, cell growth and maintenance through multiple signaling pathways including epithelial to mesenchymal transition, PI3K/AKT signaling pathway, and focal adhesion. Overall, HCK may be an oncogene in the development of breast cancer and thus may as a novel biomarker and therapeutic target for breast cancer.

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.

Tyrosyl phosphorylation of KRAS stalls GTPase cycle via alteration of switch I and II conformation

Deregulation of the RAS GTPase cycle due to mutations in the three RAS genes is commonly associated with cancer development. Protein tyrosine phosphatase SHP2 promotes RAF-to-MAPK signaling pathway and is an essential factor in RAS-driven oncogenesis. Despite the emergence of SHP2 inhibitors for the treatment of cancers harbouring mutant KRAS, the mechanism underlying SHP2 activation of KRAS signaling remains unclear. Here we report tyrosyl-phosphorylation of endogenous RAS and demonstrate that KRAS phosphorylation via Src on Tyr32 and Tyr64 alters the conformation of switch I and II regions, which stalls multiple steps of the GTPase cycle and impairs binding to effectors. In contrast, SHP2 dephosphorylates KRAS, a process that is required to maintain dynamic canonical KRAS GTPase cycle. Notably, Src- and SHP2-mediated regulation of KRAS activity extends to oncogenic KRAS and the inhibition of SHP2 disrupts the phosphorylation cycle, shifting the equilibrium of the GTPase cycle towards the stalled ‘dark state’.

Deregulation of the RAS GTPase cycle due to mutations in RAS genes is commonly associated with cancer development. Here authors use NMR and mass spectrometry to shows that KRAS phosphorylation via Src alters the conformation of switch I and II regions and thereby impacts the GTPase cycle.

MicroRNA-137-mediated Src oncogenic signaling promotes cancer progression

The tyrosine kinase c-Src is frequently overexpressed and activated in a wide variety of human cancers. However, the molecular mechanisms responsible for the upregulation of c-Src remain elusive. To examine whether microRNA-mediated c-Src upregulation promotes cancer progression, we screened miRNAs with complementarity to the 3'-UTR of c-Src mRNA. Among these miRNAs, down-regulation of miR-137 was tightly associated with c-Src-mediated tumor progression of human colon cancer cells/tissues. Re-expression of miR-137 in human colon cancer cells suppressed tumor growth and caused the disruption of focal contacts, suppression of cell adhesion, and invasion, although restoration of c-Src in miR-137-treated cells could not fully rescue the tumor-suppressive effect of miR-137. We found that miR-137 targets AKT2 and paxillin also and miR-137-mediated regulation of c-Src /AKT2 is crucial for controlling tumor growth, whereas that of c-Src/paxillin contributes to malignancy. miR-137 suppressed Src-related oncogenic signaling and changed the expression of miRNAs that are regulated by Src activation. miR-137 controls the expression of c-Src/AKT2/paxillin and synergistically suppresses Src oncogenic signaling evoked from focal adhesions. In various human cancers that harbor c-Src upregulation, the dysfunction of this novel mechanism would serve as a critical trigger for tumor progression.

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.

Development and Maintenance of a Preclinical Patient Derived Tumor Xenograft Model for the Investigation of Novel Anti-Cancer Therapies

Patient derived tumor xenograft (PDTX) models provide a necessary platform in facilitating anti-cancer drug development prior to human trials. Human tumor pieces are injected subcutaneously into athymic nude mice (immunocompromised, T cell deficient) to create a bank of tumors and subsequently are passaged into different generations of mice in order to maintain these tumors from patients. Importantly, cellular heterogeneity of the original tumor is closely emulated in this model, which provides a more clinically relevant model for evaluation of drug efficacy studies (single agent and combination), biomarker analysis, resistant pathways and cancer stem cell biology. Some limitations of the PDTX model include the replacement of the human stroma with mouse stroma after the first generation in mice, inability to investigate treatment effects on metastasis due to the subcutaneous injections of the tumors, and the lack of evaluation of immunotherapies due to the use of immunocompromised mice. However, even with these limitations, the PDTX model provides a powerful preclinical platform in the drug discovery process.

Plasticity of Cancer Cell Invasion-Mechanisms and Implications for Therapy

Cancer cell migration is a plastic and adaptive process integrating cytoskeletal dynamics, cell-extracellular matrix and cell-cell adhesion, as well as tissue remodeling. In response to molecular and physical microenvironmental cues during metastatic dissemination, cancer cells exploit a versatile repertoire of invasion and dissemination strategies, including collective and single-cell migration programs. This diversity generates molecular and physical heterogeneity of migration mechanisms and metastatic routes, and provides a basis for adaptation in response to microenvironmental and therapeutic challenge. We here summarize how cytoskeletal dynamics, protease systems, cell-matrix and cell-cell adhesion pathways control cancer cell invasion programs, and how reciprocal interaction of tumor cells with the microenvironment contributes to plasticity of invasion and dissemination strategies. We discuss the potential and future implications of predicted "antimigration" therapies that target cytoskeletal dynamics, adhesion, and protease systems to interfere with metastatic dissemination, and the options for integrating antimigration therapy into the spectrum of targeted molecular therapies.

Targeting metastasis

Tumour metastasis, the movement of tumour cells from a primary site to progressively colonize distant organs, is a major contributor to the deaths of cancer patients. Therapeutic goals are the prevention of an initial metastasis in high-risk patients, shrinkage of established lesions and prevention of additional metastases in patients with limited disease. Instead of being autonomous, tumour cells engage in bidirectional interactions with metastatic microenvironments to alter antitumour immunity, the extracellular milieu, genomic stability, survival signalling, chemotherapeutic resistance and proliferative cycles. Can targeting of these interactions significantly improve patient outcomes? In this Review preclinical research, combination therapies and clinical trial designs are re-examined.

A NOTCH1 gene copy number gain is a prognostic indicator of worse survival and a predictive biomarker to a Notch1 targeting antibody in colorectal cancer

Dysregulation of the Notch1 receptor has been shown to facilitate the development and progression of colorectal cancer (CRC) and has been identified as an independent predictor of disease progression and worse survival. Although mutations in the NOTCH1 receptor have not been described in CRC, we have previously discovered a NOTCH1 gene copy number gain in a portion of CRC tumor samples. Here, we demonstrated that a NOTCH1 gene copy number gain is significantly associated with worse survival and a high percentage of gene duplication in a cohort of patients with advanced CRC. In our CRC patient-derived tumor xenograft (PDTX) model, tumors harboring a NOTCH1 gain exhibited significant elevation of the Notch1 receptor, JAG1 ligand and cleaved Notch1 activity. In addition, a significant association was identified between a gain in NOTCH1 gene copy number and sensitivity to a Notch1-targeting antibody. These findings suggest that patients with metastatic CRC that harbor a gain in NOTCH1 gene copy number have worse survival and that targeting this patient population with a Notch1 antibody may yield improved outcomes.

Hematopoietic cell kinase (HCK) as a therapeutic target in immune and cancer cells

The hematopoietic cell kinase (HCK) is a member of the SRC family of cytoplasmic tyrosine kinases (SFKs), and is expressed in cells of the myeloid and B-lymphocyte cell lineages. Excessive HCK activation is associated with several types of leukemia and enhances cell proliferation and survival by physical association with oncogenic fusion proteins, and with functional interactions with receptor tyrosine kinases. Elevated HCK activity is also observed in many solid malignancies, including breast and colon cancer, and correlates with decreased patient survival rates. HCK enhances the secretion of growth factors and pro-inflammatory cytokines from myeloid cells, and promotes macrophage polarization towards a wound healing and tumor-promoting alternatively activated phenotype. Within tumor associated macrophages, HCK stimulates the formation of podosomes that facilitate extracellular matrix degradation, which enhance immune and epithelial cell invasion. By virtue of functional cooperation between HCK and bona fide oncogenic tyrosine kinases, excessive HCK activation can also reduce drug efficacy and contribute to chemo-resistance, while genetic ablation of HCK results in minimal physiological consequences in healthy mice. Given its known crystal structure, HCK therefore provides an attractive therapeutic target to both, directly inhibit the growth of cancer cells, and indirectly curb the source of tumor-promoting changes in the tumor microenvironment.

MicroRNAs as the fine-tuners of Src oncogenic signalling

The cellular Src (c-Src) tyrosine kinase is upregulated and believed to play a pivotal role in various human cancers. However, the molecular mechanism underlying c-Src-mediated tumour progression remains elusive. Recent studies have revealed that several microRNAs (miRNAs) function as tumour suppressors by regulating the malignant expression of signalling molecules. Aberrant expression of miRNAs is frequently observed in human cancers and should be exploited to seek related molecular targets. In this review, we focus on miRNAs found to be involved in Src signalling in various cancers. We summarize recent findings on Src-related miRNAs, their target genes, mechanisms behind their interplay and their implications for cancer therapeutics.

Src mutation induces acquired lapatinib resistance in ERBB2-amplified human gastroesophageal adenocarcinoma models

ERBB2-directed therapy is now a routine component of therapy for ERBB2-amplified metastatic gastroesophageal adenocarcinomas. However, there is little knowledge of the mechanisms by which these tumors develop acquired resistance to ERBB2 inhibition. To investigate this question we sought to characterize cell line models of ERBB2-amplified gastroesophageal adenocarcinoma with acquired resistance to ERBB2 inhibition. We generated lapatinib-resistant (LR) subclones from an initially lapatinib-sensitive ERBB2-amplified esophageal adenocarcinoma cell line, OE19. We subsequently performed genomic characterization and functional analyses of resistant subclones with acquired lapatinib resistance. We identified a novel, acquired SrcE527K mutation in a subset of LR OE19 subclones. Cells with this mutant allele harbour increased Src phosphorylation. Genetic and pharmacologic inhibition of Src resensitized these subclones to lapatinib. Biochemically, Src mutations could activate both the phosphatidylinositol 3-kinase and mitogen activated protein kinase pathways in the lapatinib-treated LR OE19 cells. Ectopic expression of SrcE527K mutation also was sufficient to induce lapatinib resistance in drug-naïve cells. These results indicate that pathologic activation of Src is a potential mechanism of acquired resistance to ERBB2 inhibition in ERBB2-amplified gastroesophageal cancer. Although Src mutation has not been described in primary tumor samples, we propose that the Src hyperactivation should be investigated in the settings of acquired resistance to ERBB2 inhibition in esophageal and gastric adenocarcinoma.

An ovarian cancer model with positive ER: Reversion of ER antagonist resistance by Src blockade

Approximately 60% of ovarian cancers are positive for the estrogen receptor (ER); however, ER-targeted treatment is disappointing due to drug resistance as compared with breast cancer. In estrogen-sensitive cancers, estrogen activates Src to phosphorylate p27 promoting its degradation and increasing cell cycle progression. Since Src is frequently activated in ovarian cancers, we investigated whether combined Src and ER blockade by saracatinib and fulvestrant would circumvent anti-estrogen resistance. In 20 out of 40 enrolled patients with immunohistochemically ER-positive ovarian cancer, phosphorylated Src (p-Src) at the site of 416 tyrosine was expressed with a propensity for metastasis and a poorer disease-free survival (DFS) at 3 years following ER antagonist treatment. The effects of ER and Src blockade on cell cycle were assayed in estrogen receptor α (ERα)-positive ovarian cancer. We observed that Src activity was fairly greater in anti-estrogen-resistant ovarian cancer cells than that in the anti-estrogen-sensitive cell line. Estrogen activated Src via ER-Src binding and ER translocation from cytoplasm to nucleus. Mitogenesis was mediated via ERα, not ERβ. Combined saracatinib and fulvestrant increased p27 and inhibited cell cycle progression. Furthermore, dual therapy induced autophagy and inhibited ovarian cancer xenograft growth more effectively than monotherapy. Saracatinib facilitated the therapeutic effects of fulvestrant by antagonizing the estrogen-mediated Src activation. These are supportive of further preclinical assessment of combined fulvestrant and saracatinib in patients with ovarian cancer.

SRC family kinases as novel therapeutic targets to treat breast cancer brain metastases

Despite better control of early-stage disease and improved overall survival of patients with breast cancer, the incidence of life-threatening brain metastases continues to increase in some of these patients. Unfortunately, other than palliative treatments there is no effective therapy for this condition. In this study, we reveal a critical role for Src activation in promoting brain metastasis in a preclinical model of breast cancer and we show how Src-targeting combinatorial regimens can treat HER2(+) brain metastases in this model. We found that Src was hyperactivated in brain-seeking breast cancer cells derived from human cell lines or from patients' brain metastases. Mechanistically, Src activation promoted tumor cell extravasation into the brain parenchyma via permeabilization of the blood-brain barrier. When combined with the EGFR/HER2 dual-targeting drug lapatinib, an Src-targeting combinatorial regimen prevented outgrowth of disseminated breast cancer cells through the induction of cell-cycle arrest. More importantly, this combinatorial regimen inhibited the outgrowth of established experimental brain metastases, prolonging the survival of metastases-bearing mice. Our results provide a rationale for clinical evaluation of Src-targeting regimens to treat patients with breast cancer suffering from brain metastasis.

Antitumor activity of saracatinib (AZD0530), a c-Src/Abl kinase inhibitor, alone or in combination with chemotherapeutic agents in gastric cancer

Src is a nonreceptor tyrosine kinase involved in the cross-talk and mediation of many signaling pathways that promote cell proliferation, adhesion, invasion, migration, and tumorigenesis. Increased Src activity has been reported in many types of human cancer, including gastric cancer. Therefore, this factor has been identified as a promising therapeutic target for cancer treatments, and targeting Src in gastric cancer is predicted to have potent effects. We evaluated the antitumor effect of a c-Src/Abl kinase inhibitor, saracatinib (AZD0530), alone or combined with chemotherapeutic agents in gastric cancer cell lines and a NCI-N87 xenograft model. Among 10 gastric cancer cell lines, saracatinib specifically inhibited the growth and migration/invasion of SNU216 and NCI-N87 cells. Saracatinib blocked the Src/FAK, HER family, and oncogenic signaling pathways, and it induced G(1) arrest and apoptosis in SNU216 and NCI-N87 cells. Apoptosis required induction of the proapoptotic BCL2 family member Bim. Knockdown of Bim using siRNA decreased apoptosis induced by treatment with saracatinib, suggesting that Bim has an important role in saracatinib-induced apoptosis. Saracatinib enhanced the effects of lapatinib, an EGFR/HER2 dual inhibitor, in SNU216 and NCI-N87 cells. Furthermore, combined treatment with saracatinib and 5-fluorouracil (5-FU) or cisplatin exerted synergistic effects in both saracatinib-sensitive and saracatinib-resistant cells. Consistent with our in vitro findings, cotreatment with saracatinib and 5-FU resulted in enhanced antitumor activity in the NCI-N87 xenografts. These data indicate that the inhibition of Src kinase activity by saracatinib alone or in combination with other agents can be a strategy to target gastric cancer.

Common PIK3CA mutants and a novel 3' UTR mutation are associated with increased sensitivity to saracatinib

PURPOSE

Dysregulation of the phosphoinositide 3-kinase (PI3K) and Src signaling pathways commonly occur in colorectal cancer. Mutations in the PIK3CA gene are associated with an increase in severity of disease and worse clinical outcomes. Elevated levels of Src have been identified in premalignant lesions and are suggested to play a central role in tumor progression. Because these pathways appear to enhance tumor growth and metastasis, molecularly targeted agents for both pathways are currently being evaluated in early-phase clinical trials.

EXPERIMENTAL DESIGN

We used colorectal cancer cell lines and a patient-derived explant model to investigate the efficacy of saracatinib. Mutations in the PIK3CA were evaluated to examine the association between mutations in the PIK3CA gene and sensitivity to saracatinib.

RESULTS

We have identified a subset of patients with a PIK3CA (exon 9 and 20) mutation with increased sensitivity to saracatinib. A novel 3' untranslated region (UTR) mutation was also shown to be associated with increased sensitivity to saracatinib and have a reduced affinity for miR-520a and miR-525a. Importantly, we show that Src inhibition reduces the interaction between Src and p85, subsequently decreasing Akt-dependent signaling.

CONCLUSION

These results indicate that a personalized approach in targeting Src in PIK3CA-mutant patients with colorectal cancers may prove effective in a subset of patients with this genetic alteration.

Oncogenic signaling by tyrosine kinases of the SRC family in advanced colorectal cancer

The non-receptor tyrosine kinases of the SRC family (SFK) play important roles in signal transduction induced by a large variety of extracellular stimuli, including growth factors and Integrins. When deregulated, SFKs show oncogenic activity, as originally reported for v-Src, the transforming product of the avian retrovirus RSV, and then, in many human cancers, particularly colorectal cancer (CRC). In CRC, SFK deregulation largely occurs in the absence of mutations of the corresponding genes, but the underlying molecular mechanisms involved are still unclear. In addition to a role in early tumor progression, SFK deregulation may also be important in advanced CRC, as suggested by the association between increased SFK activity and poor clinical outcome. However, SFK contribution to CRC metastasis formation is still poorly documented. Here, we will review recent findings that broaden our understanding of the mechanisms underlying SFK deregulation and signaling in advanced CRC. We will also discuss the implication of these observations for SFK-based therapy in metastatic CRC.

Histological and molecular evaluation of patient-derived colorectal cancer explants

Mouse models have been developed to investigate colorectal cancer etiology and evaluate new anti-cancer therapies. While genetically engineered and carcinogen-induced mouse models have provided important information with regard to the mechanisms underlying the oncogenic process, tumor xenograft models remain the standard for the evaluation of new chemotherapy and targeted drug treatments for clinical use. However, it remains unclear to what extent explanted colorectal tumor tissues retain inherent pathological features over time. In this study, we have generated a panel of 27 patient-derived colorectal cancer explants (PDCCEs) by direct transplantation of human colorectal cancer tissues into NOD-SCID mice. Using this panel, we performed a comparison of histology, gene expression and mutation status between PDCCEs and the original human tissues from which they were derived. Our findings demonstrate that PDCCEs maintain key histological features, basic gene expression patterns and KRAS/BRAF mutation status through multiple passages. Altogether, these findings suggest that PDCCEs maintain similarity to the patient tumor from which they are derived and may have the potential to serve as a reliable preclinical model that can be incorporated into future strategies to optimize individual therapy for patients with colorectal cancer.

Patient-derived tumour xenografts as models for oncology drug development

Progress in oncology drug development has been hampered by a lack of preclinical models that reliably predict clinical activity of novel compounds in cancer patients. In an effort to address these shortcomings, there has been a recent increase in the use of patient-derived tumour xenografts (PDTX) engrafted into immune-compromised rodents such as athymic nude or NOD/SCID mice for preclinical modelling. Numerous tumour-specific PDTX models have been established and, importantly, they are biologically stable when passaged in mice in terms of global gene-expression patterns, mutational status, metastatic potential, drug responsiveness and tumour architecture. These characteristics might provide significant improvements over standard cell-line xenograft models. This Review will discuss specific PDTX disease examples illustrating an overview of the opportunities and limitations of these models in cancer drug development, and describe concepts regarding predictive biomarker development and future applications.

Antitumor activity of Src inhibitor saracatinib (AZD-0530) in preclinical models of biliary tract carcinomas

Biliary tract carcinoma (BTC) has a poor prognosis due to limited treatment options. There is, therefore, an urgent need to identify new targets and to design innovative therapeutic approaches. Among potential candidate molecules, we evaluated the nonreceptor tyrosine kinase Src, observing promising antitumor effects of its small-molecule inhibitor saracatinib in BTC preclinical models. The presence of an active Src protein was investigated by immunohistochemistry in 19 surgical samples from patients with BTC. Upon saracatinib treatment, the phosphorylation of Src and of its downstream transducers was evaluated in the BTC cell lines TFK-1, EGI-1, HuH28, and TGBC1-TKB. The effect of saracatinib on proliferation and migration was analyzed in these same cell lines, and its antitumor activity was essayed in EGI-1 mouse xenografts. Saracatinib-modulated transcriptome was profiled in EGI-1 cells and in tumor samples of the xenograft model. Src was activated in about 80% of the human BTC samples. In cultured BTC cell lines, low-dose saracatinib counteracted the activation of Src and of its downstream effectors, increased the fraction of cells in G(0)-G(1) phase, and inhibited cell migration. At high concentrations (median dose from 2.26-6.99 μmol/L), saracatinib was also capable of inhibiting BTC cell proliferation. In vivo, saracatinib treatment resulted in delayed tumor growth, associated with an impaired vascular network. Here, we provide a demonstration that the targeted inhibition of Src kinase by saracatinib is of therapeutic benefit in preclinical models of BTC. We propose our results as a basis for the design of saracatinib-based clinical applications.

Distinct effects of saracatinib on memory CD8+ T cell differentiation

Immunologic memory involving CD8(+) T cells is a hallmark of an adaptive Ag-specific immune response and constitutes a critical component of protective immunity. Designing approaches that enhance long-term T cell memory would, for the most part, fortify vaccines and enhance host protection against infectious diseases and, perhaps, cancer immunotherapy. A better understanding of the cellular programs involved in the Ag-specific T cell response has led to new approaches that target the magnitude and quality of the memory T cell response. In this article, we show that T cells from TCR transgenic mice for the nucleoprotein of influenza virus NP68 exhibit the distinct phases--priming, expansion, contraction, and memory--of an Ag-specific T cell response when exposed in vitro to the cognate peptide. Saracatinib, a specific inhibitor of Src family kinases, administered at low doses during the expansion or contraction phases, increased CD62L(high)/CD44(high) central memory CD8(+) T cells and IFN-γ production but suppressed immunity when added during the priming phase. These effects by saracatinib were not accompanied by the expected decline of Src family kinases but were accompanied by Akt-mammalian target of rapamycin suppression and/or mediated via another pathway. Increased central memory cells by saracatinib were recapitulated in mice using a poxvirus-based influenza vaccine, thus underscoring the importance of dose and timing of the inhibitor in the context of memory T cell differentiation. Finally, vaccine plus saracatinib treatment showed better protection against tumor challenge. The immune-potentiating effects on CD8(+) T cells by a low dose of saracatinib might afford better protection from pathogens or cancer when combined with vaccine.

CD31, EDNRB and TSPAN7 are promising prognostic markers in clear-cell renal cell carcinoma revealed by genome-wide expression analyses of primary tumors and metastases

Currently used clinicopathological parameters are insufficient for a reliable prediction of metastatic risk and disease-free survival (DFS) of patients with clear-cell renal cell carcinoma (ccRCC). To identify prognostic genes, the expression profiles of primary ccRCC obtained from patients with different DFS--eight synchronously, nine metachronously and seven not metastasized tumors--were determined by genome-wide expression analyses. Synchronously and metachronously metastasized primary ccRCC differed in the expression of 167 genes. Thirty-six of these genes were also differentially expressed in synchronously vs. metachronously developed pulmonary metastases analyzed in a previous study. Because of their DFS-associated deregulation that is concordant in metastases and primary ccRCC, these genes are potentially functionally involved in metastatic tumor growth and are also prognostically useful. A prognostic impact was confirmed for the genes CD31, EDNRB and TSPAN7 at the mRNA level (n=86), and for TSPAN7 at the protein level (n=106). Patients with a higher gene expression of EDNRB or TSPAN7, or with TSPAN7-positive vessels in both cores investigated on tissue microarrays had a significantly longer DFS and tumor-specific survival (TSS). Patients with a higher CD31 gene expression showed a significantly longer TSS. EDNRB was an independent prognostic marker for the DFS. CD31, EDNRB and TSPAN7 had an independent impact on the TSS. In summary, comparative analysis of primary tumors and metastases is appropriate to identify independent prognostic markers in ccRCC. Gene expression of CD31 and EDNRB, and endothelial TSPAN7 protein level are potentially useful to improve outcome prediction because of their independent prognostic impact.

Targeting Src family kinases in anti-cancer therapies: turning promise into triumph

Src is a non-receptor tyrosine kinase that is deregulated in many types of cancer. Decades of research have revealed the crucial role of Src in many aspects of tumor development, including proliferation, survival, adhesion, migration, invasion and, most importantly, metastasis, in multiple tumor types. Despite extensive preclinical evidence that warrants targeting Src as a promising therapeutic approach for cancer, Src inhibitor(s) showed only minimal therapeutic activity in various types of solid tumors when used as a single agent in recent early-phase clinical trials. In this review, we highlight the most recent advances from preclinical studies and clinical trials that shed light on potential clinical use of Src inhibitor-containing combinatorial regimens in overcoming resistance to current anticancer therapies and in preventing metastatic recurrence.

Targeting Src family kinases in anti-cancer therapies: turning promise into triumph

Src is a non-receptor tyrosine kinase that is deregulated in many types of cancer. Decades of research have revealed the crucial role of Src in many aspects of tumor development, including proliferation, survival, adhesion, migration, invasion and, most importantly, metastasis, in multiple tumor types. Despite extensive preclinical evidence that warrants targeting Src as a promising therapeutic approach for cancer, Src inhibitor(s) showed only minimal therapeutic activity in various types of solid tumors when used as a single agent in recent early-phase clinical trials. In this review, we highlight the most recent advances from preclinical studies and clinical trials that shed light on potential clinical use of Src inhibitor-containing combinatorial regimens in overcoming resistance to current anticancer therapies and in preventing metastatic recurrence.

Current status of SRC inhibitors in solid tumor malignancies

SUMMARY

Src is believed to play an important role in cancer, and several agents targeting Src are in clinical development.

DESIGN

We reviewed Src structure and function and preclinical data supporting its role in the development of cancer via a PubMed search. We conducted an extensive review of Src inhibitors by searching abstracts from major oncology meeting databases in the last 3 years and by comprehensively reviewing ongoing clinical trials on ClinicalTrials.gov.

RESULTS

In this manuscript, we briefly review Src structure and function, mechanisms involving Src that lead to the development of cancer, and Src inhibitors and key preclinical data establishing a rationale for clinical application. We then focus on clinical data supporting their use in solid tumor malignancies, a newer arena than their more well-established hematologic applications. Particularly highlighted are clinical trials investigating new biomarkers as well as ongoing studies assessing Src inhibitor activity in biomarker-selected patient populations. We also review newer investigational Src-targeting agents.

CONCLUSIONS

Src inhibitors have shown little activity in monotherapy trials in unselected solid tumor patient populations. Combination studies and biomarker-driven clinical trials are under way.