An aberrant spliced transcript of focal adhesion kinase is exclusively expressed in human breast cancer

Design, synthesis, and biological evaluation of diaminopyrimidine derivatives as novel focal adhesion kinase inhibitors

Focal adhesion kinase (FAK) is a cytoplasmic non-receptor protein tyrosine kinase that belongs to the family of focal adhesion complexes and is responsible for the development of various tumors. Herein, 24 diaminopyrimidine derivatives were designed and synthesized based on TAE-226. Several compounds with good activity were further evaluated regarding their antiproliferative activities against two cancer cells with high FAK expression. Compound A12 showed potent anticancer activity against A549 and MDA-MB-231 cell lines with IC50 values of 130 nM and 94 nM, respectively. In vitro metabolic stability and cytochrome P450 (CYP) inhibition assays showed that A12 exhibited favorable stability and weak inhibitory activity on CYP isoforms. Preliminary evaluation of kinase selectivity showed that A12 was a multi-kinase inhibitor. The acute toxicity in vivo indicated that A12 possessed acceptable safety. Compound A12 was also selected for molecular docking studies and the prediction of molecular properties and drug-like properties. These results indicated that compound A12 could be used as a potential lead compound targeting FAK for further development.

Functional and clinical characteristics of focal adhesion kinases in cancer progression

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase and an adaptor protein that primarily regulates adhesion signaling and cell migration. FAK promotes cell survival in response to stress. Increasing evidence has shown that at the pathological level, FAK is highly expressed in multiple tumors in several systems (including lung, liver, gastric, and colorectal cancers) and correlates with tumor aggressiveness and patient prognosis. At the molecular level, FAK promotes tumor progression mainly by altering survival signals, invasive capacity, epithelial-mesenchymal transition, the tumor microenvironment, the Warburg effect, and stemness of tumor cells. Many effective drugs have been developed based on the comprehensive role of FAK in tumor cells. In addition, its potential as a tumor marker cannot be ignored. Here, we discuss the pathological and pre-clinical evidence of the role of FAK in cancer development; we hope that these findings will assist in FAK-based clinical studies.

FAK in Cancer: From Mechanisms to Therapeutic Strategies

Focal adhesion kinase (FAK), a non-receptor tyrosine kinase, is overexpressed and activated in many cancer types. FAK regulates diverse cellular processes, including growth factor signaling, cell cycle progression, cell survival, cell motility, angiogenesis, and the establishment of immunosuppressive tumor microenvironments through kinase-dependent and kinase-independent scaffolding functions in the cytoplasm and nucleus. Mounting evidence has indicated that targeting FAK, either alone or in combination with other agents, may represent a promising therapeutic strategy for various cancers. In this review, we summarize the mechanisms underlying FAK-mediated signaling networks during tumor development. We also summarize the recent progress of FAK-targeted small-molecule compounds for anticancer activity from preclinical and clinical evidence.

Focal adhesion kinase splicing and protein activation in papillary thyroid carcinoma progression

Papillary thyroid carcinoma (PTC), a common endocrine malignancy, presents a challenge from a prognostic standpoint. Molecular alterations underlying PTC progression include deregulation of focal adhesion kinase (FAK) at post-transcriptional and post-translational levels. Searching for candidate markers of PTC progression, we investigated the prognostic significance of FAK alterations on mRNA/protein level. The expression levels and subcellular localisation of auto-phosphorylated FAK (pY397-FAK) were determined by western blot (WB) and immunohistochemistry. The quantity of total FAK mRNA, alternatively spliced FAK-Del26 and FAK-Del33 variants were analysed by RT-qPCR and related to pY397-FAK expression and subcellular distribution. The results were correlated with clinicopathological parameters of the patients. The expression of pY397-FAK was significantly elevated in malignant samples. Active FAK showed predominant cytoplasmic distribution with co-occurrence along the membrane, while nuclear staining was found less frequently. Expression of pY397-FAK in separate cellular compartments correlated with adverse clinicopathological parameters, but the strongest association was found when their mean scores were calculated. Alternatively spliced FAK-Del33 and total FAK transcripts positively correlated to pY397-FAK protein levels as well as to characteristics of PTC advancement. Over-expression of FAK on mRNA (total and Del-33) and activated protein (pY397-FAK) levels is a feature of PTC advanced stages. Of the analysed alterations, the mean pY397-FAK IHC score showed the best predictive performance. Correlation between mRNA FAK-Del33 and pY397-FAK expression implies a regulatory role of alternative splicing in PTC patients.

Focal Adhesion Kinase Fine Tunes Multifaced Signals toward Breast Cancer Progression

Breast cancer represents the most common diagnosed malignancy and the main leading cause of tumor-related death among women worldwide. Therefore, several efforts have been made in order to identify valuable molecular biomarkers for the prognosis and prediction of therapeutic responses in breast tumor patients. In this context, emerging discoveries have indicated that focal adhesion kinase (FAK), a non-receptor tyrosine kinase, might represent a promising target involved in breast tumorigenesis. Of note, high FAK expression and activity have been tightly correlated with a poor clinical outcome and metastatic features in several tumors, including breast cancer. Recently, a role for the integrin-FAK signaling in mechanotransduction has been suggested and the function of FAK within the breast tumor microenvironment has been ascertained toward tumor angiogenesis and vascular permeability. FAK has been also involved in cancer stem cells (CSCs)-mediated initiation, maintenance and therapeutic responses of breast tumors. In addition, the potential of FAK to elicit breast tumor-promoting effects has been even associated with the capability to modulate immune responses. On the basis of these findings, several agents targeting FAK have been exploited in diverse preclinical tumor models. Here, we recapitulate the multifaceted action exerted by FAK and its prognostic significance in breast cancer. Moreover, we highlight the recent clinical evidence regarding the usefulness of FAK inhibitors in the treatment of breast tumors.

Alternative Splicing: Expanding the Landscape of Cancer Biomarkers and Therapeutics

Alternative splicing (AS) is a critical post-transcriptional regulatory mechanism used by more than 95% of transcribed human genes and responsible for structural transcript variation and proteome diversity. In the past decade, genome-wide transcriptome sequencing has revealed that AS is tightly regulated in a tissue- and developmental stage-specific manner, and also frequently dysregulated in multiple human cancer types. It is currently recognized that splicing defects, including genetic alterations in the spliced gene, altered expression of both core components or regulators of the precursor messenger RNA (pre-mRNA) splicing machinery, or both, are major drivers of tumorigenesis. Hence, in this review we provide an overview of our current understanding of splicing alterations in cancer, and emphasize the need to further explore the cancer-specific splicing programs in order to obtain new insights in oncology. Furthermore, we also discuss the recent advances in the identification of dysregulated splicing signatures on a genome-wide scale and their potential use as biomarkers. Finally, we highlight the therapeutic opportunities arising from dysregulated splicing and summarize the current approaches to therapeutically target AS in cancer.

Design, synthesis, biological evaluation and molecular docking study of novel thieno[3,2-d]pyrimidine derivatives as potent FAK inhibitors

A series of 2,7-disubstituted-thieno[3,2-d]pyrimidine derivatives were designed, synthesized and evaluated as novel focal adhesion kinase (FAK) inhibitors. The novel 2,7-disubstituted-thieno[3,2-d]pyrimidine scaffold has been designed as a new kinase inhibitor platform that mimics the bioactive conformation of the well-known diaminopyrimidine motif. Most of the compounds potently suppressed the enzymatic activities of FAK and potently inhibited the proliferation of U-87MG, A-549 and MDA-MB-231 cancer cell lines. Among these derivatives, the optimized compound 26f potently inhibited the enzyme (IC₅₀ = 28.2 nM) and displayed stronger potency than TAE-226 in U-87MG, A-549 and MDA-MB-231 cells, with IC₅₀ values of 0.16, 0.27, and 0.19 μM, respectively. Compound 26f also exhibited relatively less cytotoxicity (IC₅₀ = 3.32 μM) toward a normal human cell line, HK2. According to the flow cytometry results, compound 26f induced the apoptosis of MDA-MB-231 cells in a dose-dependent manner and effectively arrested MDA-MB-231 cells in G0/G1 phase. Further investigations revealed that compound 26f potently suppressed the migration of MDA-MB-231 cells. Collectively, these data support the further development of compound 26f as a lead compound for FAK-targeted anticancer drug discovery.

UCP2 promotes proliferation and chemoresistance through regulating the NF-κB/β-catenin axis and mitochondrial ROS in gallbladder cancer

Uncoupling protein 2 (UCP2) is a mitochondrial anion carrier which plays a key role in energy homeostasis. UCP2 is deregulated in several human cancers and has been suggested to regulate cancer metabolism. However, the role of UCP2 in gallbladder cancer has not been defined. Using clinical samples, we found highly expressed UCP2 in gallbladder cancer tissues, and higher expression levels of UCP2 correlated with worse clinical characteristics. To study whether UCP2 promotes gallbladder cancer growth, UCP2 stable knockdown cells were generated, and cell proliferation was suppressed in these knockdown cells. Further studies demonstrated that glycolysis was inhibited and IKKβ, as well as the downstream signaling molecules NF-κB/FAK/β-catenin, were downregulated in UCP2 knockdown cells. More importantly, gallbladder cancer cells became sensitive to gemcitabine treatments when UCP2 was inhibited. UCP2 knockdown suppressed the activation of the NF-κB/β-catenin axis and promoted the increases in mitochondrial ROS in gallbladder cancer cells exposed to gemcitabine treatments. The UCP2 inhibitor genipin suppressed xenograft tumor growth and sensitized grafted tumors to gemcitabine treatments. These results suggest targeting UCP2 as a novel therapeutic strategy for the treatment of gallbladder cancer.

Genome-wide profiling of prognosis-related alternative splicing signatures in sarcoma

BACKGROUND

Sarcomas (SARCs) are rare malignant tumors with poor prognosis. Increasing evidence has suggested that aberrant alternative splicing (AS) is strongly associated with tumor initiation and progression. We considered whether survival-related AS events might serve as prognosis predictors and underlying targeted molecules in SARC treatment.

METHODS

RNA-Seq data of the SARC cohort were downloaded from The Cancer Genome Atlas (TCGA) database. Survival-related AS events were selected by univariate and multivariate Cox regression analyses. Metascape was used for constructing a gene interaction network and performing functional enrichment analysis. Then, prognosis predictors were established based on statistically significant survival-related AS events and evaluated by receiver operator characteristic (ROC) curve analysis. Finally, the potential regulatory network was analyzed via Pearson's correlation between survival-related AS events and splicing factors (SFs).

RESULTS

A total of 3,610 AS events and 2,291 genes were found to be prognosis-related in 261 SARC samples. The focal adhesion pathway was identified as the most critical molecular mechanism corresponding to poor prognosis. Notably, several prognosis predictors based on survival-related AS events showed excellent performance in prognosis prediction. The area under the curve of the ROC of the risk score was 0.85 in the integrated predictor. The splicing network proved complicated regulation between prognosis-related SFs and AS events. Also, driver gene mutations were significantly associated with AS in SARC patients.

CONCLUSIONS

Survival-related AS events may become ideal indictors for the prognosis prediction of SARCs. Corresponding splicing regulatory mechanisms are worth further exploration.

Design, synthesis and biological evaluation of novel 7H-pyrrolo[2,3-d]pyrimidine derivatives as potential FAK inhibitors and anticancer agents

A series of 7H-pyrrolo[2,3-d]pyrimidine derivatives possessing a dimethylphosphine oxide moiety were designed, synthesized and evaluated as novel Focal adhesion kinase (FAK) inhibitors. Most compounds potently suppressed the enzymatic activities of FAK, with IC₅₀ values in the 10^-8-10^-9 M range, and potently inhibited the proliferation of breast (MDA-MB-231) and lung (A549) cancer cell lines. The representative compound 25b exhibited potent enzyme inhibition (IC₅₀ = 5.4 nM) and good selectivity when tested on a panel of 26 kinases. 25b exhibited antiproliferative activity against A549 cells (IC₅₀ = 3.2 μM) and relatively less cytotoxicity to a normal human cell line HK2. Compound 25b also induced apoptosis and suppressed the migration of A549 cells in a concentration-dependent manner. Further profiling of compound 25b revealed it had good metabolic stability in mouse, rat and human liver microsomes in vitro and showed weak inhibitory activity against various subtypes of human cytochrome P450. The docking study of compound 25b was performed to elucidate its possible binding modes and to provide a structural basis for further structure-guided design of FAK inhibitors.

WT1 associated protein promotes metastasis and chemo-resistance to gemcitabine by stabilizing Fak mRNA in pancreatic cancer

WT1 associated protein (WTAP), playing an important role in several malignancies owing to its complex function in transcriptional and post-transcriptional regulation, is an independent prognostic indicator for pancreatic cancer (PC). However, its specific role and underlying mechanism in PC remain unclear. In the present study, we found that WTAP could promote migration/invasion and suppress chemo-sensitivity to gemcitabine in PC. Further mechanical investigation revealed that WTAP could bind to and stabilize Fak mRNA which in turn activated the Fak-PI3K-AKT and Fak-Src-GRB2-Erk1/2 signaling pathways. In addition, GSK2256098, a specific Fak inhibitor, could reverse WTAP-mediated chemo-resistance to gemcitabine and metastasis in PC. Taken together, Fak inhibitor might be a promising therapeutic option for PC patients with WTAP overexpression.

Influence of transcriptional variants on metastasis

Cancer metastasis is defined as the dissemination of malignant cells from the primary tumor site, leading to colonization of distant organs and the establishment of a secondary tumor. Metastasis is frequently associated with chemoresistance and is the major cause of cancer-related mortality. Metastatic cells need to acquire the ability to resist to stresses provided by different environments, such as reactive oxygen species, shear stress, hemodynamic forces, stromal composition, and immune responses, to colonize other tissues. Hence, only a small population of cells has a metastasis-initiating potential. Several studies have revealed the misregulation of transcriptional variants during cancer progression, and many splice events can be used to distinguish between normal and tumoral tissue. These variants, which are abnormally expressed in malignant cells, contribute to an adaptive response of tumor cells and the success of the metastatic cascade, promoting an anomalous cell cycle, cellular adhesion, resistance to death, cell survival, migration and invasion. Understanding the different aspects of splicing regulation and the influence of transcriptional variants that control metastatic cells is critical for the development of therapeutic strategies. In this review, we describe how transcriptional variants contribute to metastatic competence and discuss how targeting specific isoforms may be a promising therapeutic strategy.

Disialoganglioside GD2 as a therapeutic target for human diseases

INTRODUCTION

Ganglioside GD2 is found in vertebrates and invertebrates, overexpressed among pediatric and adult solid tumors, including neuroblastoma, glioma, retinoblastoma, Ewing's family of tumors, rhabdomyosarcoma, osteosarcoma, leiomyosarcoma, liposarcoma, fibrosarcoma, small cell lung cancer and melanoma. It is also found on stem cells, neurons, some nerve fibers and basal layer of the skin.

AREAS COVERED

GD2 provides a promising clinical target for radiolabeled antibodies, bispecific antibodies, chimeric antigen receptor (CAR)-modified T cells, drug conjugates, nanoparticles and vaccines. Here, we review its biochemistry, normal physiology, role in tumorigenesis, important characteristics as a target, as well as anti-GD2-targeted strategies.

EXPERT OPINION

Bridging the knowledge gaps in understanding the interactions of GD2 with signaling molecules within the glycosynapses, and the regulation of its cellular expression should improve therapeutic strategies targeting this ganglioside. In addition to anti-GD2 IgG mAbs, their drug conjugates, radiolabeled forms especially when genetically engineered to improve therapeutic index and novel bispecific forms or CARs to retarget T-cells are promising candidates for treating metastatic cancers.

FAK signaling in human cancer as a target for therapeutics

Focal adhesion kinase (FAK) is a key regulator of growth factor receptor- and integrin-mediated signals, governing fundamental processes in normal and cancer cells through its kinase activity and scaffolding function. Increased FAK expression and activity occurs in primary and metastatic cancers of many tissue origins, and is often associated with poor clinical outcome, highlighting FAK as a potential determinant of tumor development and metastasis. Indeed, data from cell culture and animal models of cancer provide strong lines of evidence that FAK promotes malignancy by regulating tumorigenic and metastatic potential through highly-coordinated signaling networks that orchestrate a diverse range of cellular processes, such as cell survival, proliferation, migration, invasion, epithelial-mesenchymal transition, angiogenesis and regulation of cancer stem cell activities. Such an integral role in governing malignant characteristics indicates that FAK represents a potential target for cancer therapeutics. While pharmacologic targeting of FAK scaffold function is still at an early stage of development, a number of small molecule-based FAK tyrosine kinase inhibitors are currently undergoing pre-clinical and clinical testing. In particular, PF-00562271, VS-4718 and VS-6063 show promising clinical activities in patients with selected solid cancers. Clinical testing of rationally designed FAK-targeting agents with implementation of predictive response biomarkers, such as merlin deficiency for VS-4718 in mesothelioma, may help improve clinical outcome for cancer patients. In this article, we have reviewed the current knowledge regarding FAK signaling in human cancer, and recent developments in the generation and clinical application of FAK-targeting pharmacologic agents.

FAK in cancer: mechanistic findings and clinical applications

Focal adhesion kinase (FAK) is a cytoplasmic protein tyrosine kinase that is overexpressed and activated in several advanced-stage solid cancers. FAK promotes tumour progression and metastasis through effects on cancer cells, as well as stromal cells of the tumour microenvironment. The kinase-dependent and kinase-independent functions of FAK control cell movement, invasion, survival, gene expression and cancer stem cell self-renewal. Small molecule FAK inhibitors decrease tumour growth and metastasis in several preclinical models and have initial clinical activity in patients with limited adverse events. In this Review, we discuss FAK signalling effects on both tumour and stromal cell biology that provide rationale and support for future therapeutic opportunities.