Bone marrow X kinase-mediated signal transduction in irradiated vascular endothelium

Identification of an Innate Immune-Related Prognostic Signature in Early-Stage Lung Squamous Cell Carcinoma

Background

Early-stage lung squamous cell carcinoma (LUSC) progression is accompanied by changes in immune microenvironments and the expression of immune-related genes (IRGs). Identifying innate IRGs associated with prognosis may improve treatment and reveal new immunotherapeutic targets.

Methods

Gene expression profiles and clinical data of early-stage LUSC patients were obtained from the Gene Expression Omnibus and The Cancer Genome Atlas databases and IRGs from the InnateDB database. Univariate and multivariate Cox regression and LASSO regression analyses were performed to identify an innate IRG signature model prognostic in patients with early-stage LUSC. The predictive ability of this model was assessed by time-dependent receiver operator characteristic curve analysis, with the independence of the model-determined risk score assessed by univariate and multivariate Cox regression analyses. Overall survival (OS) in early-stage LUSC patients was assessed using a nomogram and decision curve analysis (DCA). Functional and biological pathways were determined by gene set enrichment analysis, and differences in biological functions and immune microenvironments between the high- and low-risk groups were assessed by ESTIMATE and the CIBERSORT algorithm.

Results

A signature involving six IRGs (SREBF2, GP2, BMX, NR1H4, DDX41, and GOPC) was prognostic of OS. Samples were divided into high- and low-risk groups based on median risk scores. OS was significantly shorter in the high-risk than in the low-risk group in the training (P < 0.001), GEO validation (P = 0.00021) and TCGA validation (P = 0.034) cohorts. Multivariate Cox regression analysis showed that risk score was an independent risk factor for OS, with the combination of risk score and T stage being optimally predictive of clinical benefit. GSEA, ESTIMATE, and the CIBERSORT algorithm showed that immune cell infiltration was higher and immune-related pathways were more strongly expressed in the low-risk group.

Conclusion

A signature that includes these six innate IRGs may predict prognosis in patients with early-stage LUSC.

Radiobiological Studies of Microvascular Damage through In Vitro Models: A Methodological Perspective

Ionizing radiation (IR) is used in radiotherapy as a treatment to destroy cancer. Such treatment also affects other tissues, resulting in the so-called normal tissue complications. Endothelial cells (ECs) composing the microvasculature have essential roles in the microenvironment's homeostasis (ME). Thus, detrimental effects induced by irradiation on ECs can influence both the tumor and healthy tissue. In-vitro models can be advantageous to study these phenomena. In this systematic review, we analyzed in-vitro models of ECs subjected to IR. We highlighted the critical issues involved in the production, irradiation, and analysis of such radiobiological in-vitro models to study microvascular endothelial cells damage. For each step, we analyzed common methodologies and critical points required to obtain a reliable model. We identified the generation of a 3D environment for model production and the inclusion of heterogeneous cell populations for a reliable ME recapitulation. Additionally, we highlighted how essential information on the irradiation scheme, crucial to correlate better observed in vitro effects to the clinical scenario, are often neglected in the analyzed studies, limiting the translation of achieved results.

BMX-Mediated Regulation of Multiple Tyrosine Kinases Contributes to Castration Resistance in Prostate Cancer

Prostate cancer responds to therapies that suppress androgen receptor (AR) activity (androgen deprivation therapy, ADT) but invariably progresses to castration-resistant prostate cancer (CRPC). The Tec family nonreceptor tyrosine kinase BMX is activated downstream of PI3K and has been implicated in regulation of multiple pathways and in the development of cancers including prostate cancer. However, its precise mechanisms of action, and particularly its endogenous substrates, remain to be established. Here, we demonstrate that BMX expression in prostate cancer is suppressed directly by AR via binding to the BMX gene and that BMX expression is subsequently rapidly increased in response to ADT. BMX contributed to CRPC development in cell line and xenograft models by positively regulating the activities of multiple receptor tyrosine kinases through phosphorylation of a phosphotyrosine-tyrosine (pYY) motif in their activation loop, generating pYpY that is required for full kinase activity. To assess BMX activity in vivo, we generated a BMX substrate-specific antibody (anti-pYpY) and found that its reactivity correlated with BMX expression in clinical samples, supporting pYY as an in vivo substrate. Inhibition of BMX with ibrutinib (developed as an inhibitor of the related Tec kinase BTK) or another BMX inhibitor BMX-IN-1 markedly enhanced the response to castration in a prostate cancer xenograft model. These data indicate that increased BMX in response to ADT contributes to enhanced tyrosine kinase signaling and the subsequent emergence of CRPC, and that combination therapies targeting AR and BMX may be effective in a subset of patients.Significance: The tyrosine kinase BMX is negatively regulated by androgen and contributes to castration-resistant prostate cancer by enhancing the phosphorylation and activation of multiple receptor tyrosine kinases following ADT. Cancer Res; 78(18); 5203-15. ©2018 AACR.

Kinomic profiling identifies focal adhesion kinase 1 as a therapeutic target in advanced clear cell renal cell carcinoma

The introduction of targeted therapies has caused a paradigm shift in the treatment of metastatic clear cell (cc)-renal cell carcinoma (RCC). We hypothesized that determining differential kinase activity between primary and metastatic tumor sites may identify critical drivers of progression and relevant therapeutic targets in metastatic disease. Kinomic profiling was performed on primary tumor and metastatic tumor deposits utilizing a peptide substrate microarray to detect relative tyrosine phosphorylation activity. Pharmacologic and genetic loss of function experiments were used to assess the biologic significance of the top scoring kinase on in vitro and in vivo tumor phenotypes. Kinomics identified 7 peptides with increased tyrosine phosphorylation in metastases that were significantly altered (p<0.005). Based on these peptides, bioinformatics analyses identified several candidate kinases activated in metastases compared to primary tumors. The highest ranked upstream kinase was Focal Adhesion Kinase 1 (FAK1). RCC lines demonstrate evidence of elevated FAK1 activation relative to non-transformed renal epithelial cells. Pharmacologic inhibition of FAK1 with GSK2256098 suppresses in vitro tumor phenotypes. In turn, FAK1 knockdown in RCC cells suppresses both in vitro phenotypes and in vivo tumor growth. Collectively, these data demonstrate functional activation of FAK1 in metastases and provide preclinical rationale for targeting this kinase in the setting of advanced ccRCC.

BMX/Etk promotes cell proliferation and tumorigenicity of cervical cancer cells through PI3K/AKT/mTOR and STAT3 pathways

Bone marrow X-linked kinase (BMX, also known as Etk) has been reported to be involved in cell proliferation, differentiation, apoptosis, migration and invasion in several types of tumors, but its role in cervical carcinoma remains poorly understood. In this study, we showed that BMX expression exhibits a gradually increasing trend from normal cervical tissue to cervical cancer in situ and then to invasive cervical cancer tissue. Through BMX-IN-1, a potent and irreversible BMX kinase inhibitor, inhibited the expression of BMX, the cell proliferation was significantly decreased. Knockdown of BMX in HeLa and SiHa cervical cancer cell lines using two different silencing technologies, TALEN and shRNA, inhibited cell growth in vitro and suppressed xenograft tumor formation in vivo, whereas overexpression of BMX in the cell line C-33A significantly increased cell proliferation. Furthermore, a mechanism study showed that silencing BMX blocked cell cycle transit from G0/G1 to S or G2/M phase, and knockdown of BMX inhibited the expression of p-AKT and p-STAT3. These results suggested that BMX can promote cell proliferation through PI3K/AKT/mTOR and STAT3 signaling pathways in cervical cancer cells.

Targeting the effector domain of the myristoylated alanine rich C-kinase substrate enhances lung cancer radiation sensitivity

Lung cancer is the leading cause of cancer related deaths. Common molecular drivers of lung cancer are mutations in receptor tyrosine kinases (RTKs) leading to activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pro-growth, pro-survival signaling pathways. Myristoylated alanine rich C-kinase substrate (MARCKS) is a protein that has the ability to mitigate this signaling cascade by sequestering the target of PI3K, phosphatidylinositol (4,5)-bisphosphate (PIP2). As such, MARCKS has been implicated as a tumor suppressor, though there is some evidence that MARCKS may be tumor promoting in certain cancer types. Since the MARCKS function depends on its phosphorylation status, which impacts its subcellular location, MARCKS role in cancer may depend highly on the signaling context. Currently, the importance of MARCKS in lung cancer biology is limited. Thus, we investigated MARCKS in both clinical specimens and cell culture models. Immunohistochemistry scoring of MARCKS protein expression in a diverse lung tumor tissue array revealed that the majority of squamous cell carcinomas stained positive for MARCKS while other histologies, such as adenocarcinomas, had lower levels. To study the importance of MARCKS in lung cancer biology, we used inducible overexpression of wild-type (WT) and non-phosphorylatable (NP)-MARCKS in A549 lung cancer cells that had a low level of endogenous MARCKS. We found that NP-MARCKS expression, but not WT-MARCKS, enhanced the radiosensitivity of A549 cells in part by inhibiting DNA repair as evidenced by prolonged radiation-induced DNA double strand breaks. We confirmed the importance of MARCKS phosphorylation status by treating several lung cancer cell lines with a peptide mimetic of the phosphorylation domain, the effector domain (ED), which effectively attenuated cell growth as measured by cell index. Thus, the MARCKS ED appears to be an important target for lung cancer therapeutic development.

Tyrosine kinase BMX phosphorylates phosphotyrosine-primed motif mediating the activation of multiple receptor tyrosine kinases

The nonreceptor tyrosine kinase BMX (bone marrow tyrosine kinase gene on chromosome X) is abundant in various cell types and activated downstream of phosphatidylinositol-3 kinase (PI3K) and the kinase Src, but its substrates are unknown. Positional scanning peptide library screening revealed a marked preference for a priming phosphorylated tyrosine (pY) in the -1 position, indicating that BMX substrates may include multiple tyrosine kinases that are fully activated by pYpY sites in the kinase domain. BMX phosphorylated focal adhesion kinase (FAK) at Tyr⁵⁷⁷ subsequent to its Src-mediated phosphorylation at Tyr⁵⁷⁶. Loss of BMX by RNA interference or by genetic deletion in mouse embryonic fibroblasts (MEFs) markedly impaired FAK activity. Phosphorylation of the insulin receptor in the kinase domain at Tyr¹¹⁸⁹ and Tyr¹¹⁹⁰, as well as Tyr¹¹⁸⁵, and downstream phosphorylation of the kinase AKT at Thr³⁰⁸ were similarly impaired by BMX deficiency. However, insulin-induced phosphorylation of AKT at Ser⁴⁷³ was not impaired in Bmx knockout MEFs or liver tissue from Bmx knockout mice, which also showed increased insulin-stimulated glucose uptake, possibly because of decreased abundance of the phosphatase PHLPP (PH domain leucine-rich repeat protein phosphatase). Thus, by identifying the pYpY motif as a substrate for BMX, our findings suggest that BMX functions as a central regulator among multiple signaling pathways mediated by tyrosine kinases.

Kinomic profiling approach identifies Trk as a novel radiation modulator

BACKGROUND

Ionizing radiation treatment is used in over half of all cancer patients, thus determining the mechanisms of response or resistance is critical for the development of novel treatment approaches.

MATERIALS AND METHODS

In this report, we utilize a high-content peptide array platform that performs multiplex kinase assays with real-time kinetic readout to investigate the mechanism of radiation response in vascular endothelial cells. We applied this technology to irradiated human umbilical vein endothelial cells (HUVEC).

RESULTS

We identified 49 specific tyrosine phosphopeptides that were differentially affected by irradiation over a time course of 1h. In one example, the Tropomyosin receptor kinase (Trk) family members, TrkA and TrkB, showed transient activation between 2 and 15 min following irradiation. When we targeted TrkA and TrkB using small molecule inhibitors, HUVEC were protected from radiation damage. Conversely, stimulation of TrkA using gambogic amide promoted radiation enhancement.

CONCLUSIONS

Thus, we show that our approach not only can identify rapid changes in kinase activity but also identify novel targets such as TrkA. TrkA inhibition resulted in radioprotection that correlated with enhanced repair of radiation-induced damage while TrkA stimulation by gambogic amide produced radiation sensitization.

Epigenetic regulation of CpG promoter methylation in invasive prostate cancer cells

BACKGROUND

Recently, much attention has been focused on gaining a better understanding of the different populations of cells within a tumor and their contribution to cancer progression. One of the most commonly used methods to isolate a more aggressive sub-population of cells utilizes cell sorting based on expression of certain cell adhesion molecules. A recently established method we developed is to isolate these more aggressive cells based on their properties of increased invasive ability. These more invasive cells have been previously characterized as tumor initiating cells (TICs) that have a stem-like genomic signature and express a number of stem cell genes including Oct3/4 and Nanog and are more tumorigenic compared to their 'non-invasive' counterpart. They also have a profile reminiscent of cells undergoing a classic pattern of epithelial to mesenchymal transition or EMT. Using this model of invasion, we sought to investigate which genes are under epigenetic control in this rare population of cells. Epigenetic modifications, specifically DNA methylation, are key events regulating the process of normal human development. To determine the specific methylation pattern in these invasive prostate cells, and if any developmental genes were being differentially regulated, we analyzed differences in global CpG promoter methylation.

RESULTS

Differentially methylated genes were determined and select genes were chosen for additional analyses. The non-receptor tyrosine kinase BMX and transcription factor SOX1 were found to play a significant role in invasion. Ingenuity pathway analysis revealed the methylated gene list frequently displayed genes from the IL-6/STAT3 pathway. Cells which have decreased levels of the targets BMX and SOX1 also display loss of STAT3 activity. Finally, using Oncomine, it was determined that more aggressive metastatic prostate cancers in humans also have higher levels of both Stat3 and Sox1.

CONCLUSIONS

Using this method we can begin to understand which genes are epigenetically regulated in the invasive population compared to the bulk tumor cells. These aggressive sub-populations of cells may be linked to the cancer stem cell hypothesis, making their patterns of epigenetic regulation very attractive for biomarker analysis.

Functional analyses of the bone marrow kinase in the X chromosome in vascular endothelial growth factor-induced lymphangiogenesis

OBJECTIVE

The goal of this study was to investigate the novel hypothesis that bone marrow kinase in the X chromosome (Bmx), an established inflammatory mediator of pathological angiogenesis, promotes lymphangiogenesis.

METHODS AND RESULTS

We have recently demonstrated a critical role for Bmx in inflammatory angiogenesis. However, the role of Bmx in lymphangiogenesis has not been investigated. Here, we show that in wild-type mice, Bmx is upregulated in lymphatic vessels in response to vascular endothelial growth factor (VEGF). In comparison with wild-type mice, Bmx-deficient mice mount weaker lymphangiogenic responses to VEGF-A and VEGF-C in 2 mouse models. In vitro, Bmx is expressed in cultured human dermal microvascular lymphatic endothelial cells. Furthermore, pharmacological inhibition and short interfering RNA mediated silencing of Bmx reduces VEGF-A and VEGF-C-induced signaling and lymphatic endothelial cell tube formation. Mechanistically, we demonstrated that Bmx differentially regulates VEGFR-2 and VEGFR-3 receptor signaling pathways: Bmx associates with and directly regulates VEGFR-2 activation, whereas Bmx associates with VEGFR-3 and regulates downstream signaling without an effect on the receptor autophosphorylation.

CONCLUSIONS

Our in vivo and in vitro results provide the first insight into the mechanism by which Bmx mediates VEGF-dependent lymphangiogenic signaling.

Metronomic small molecule inhibitor of Bcl-2 (TW-37) is antiangiogenic and potentiates the antitumor effect of ionizing radiation

PURPOSE

To investigate the effect of a metronomic (low-dose, high-frequency) small-molecule inhibitor of Bcl-2 (TW-37) in combination with radiotherapy on microvascular endothelial cells in vitro and in tumor angiogenesis in vivo.

METHODS AND MATERIALS

Primary human dermal microvascular endothelial cells were exposed to ionizing radiation and/or TW-37 and colony formation, as well as capillary sprouting in three-dimensional collagen matrices, was evaluated. Xenografts vascularized with human blood vessels were engineered by cotransplantation of human squamous cell carcinoma cells (OSCC3) and human dermal microvascular endothelial cells seeded in highly porous biodegradable scaffolds into the subcutaneous space of immunodeficient mice. Mice were treated with metronomic TW-37 and/or radiation, and tumor growth was evaluated.

RESULTS

Low-dose TW-37 sensitized primary endothelial cells to radiation-induced inhibition of colony formation. Low-dose TW-37 or radiation partially inhibited endothelial cell sprout formation, and in combination, these therapies abrogated new sprouting. Combination of metronomic TW-37 and low-dose radiation inhibited tumor growth and resulted in significant increase in time to failure compared with controls, whereas single agents did not. Notably, histopathologic analysis revealed that tumors treated with TW-37 (with or without radiation) are more differentiated and showed more cohesive invasive fronts, which is consistent with less aggressive phenotype.

CONCLUSIONS

These results demonstrate that metronomic TW-37 potentiates the antitumor effects of radiotherapy and suggest that patients with head and neck cancer might benefit from the combination of small molecule inhibitor of Bcl-2 and radiation therapy.