HIF-1α-independent hypoxia-induced rapid PTK6 stabilization is associated with increased motility and invasion

Identification of immune-associated biomarker for predicting lung adenocarcinoma: bioinformatics analysis and experiment verification of PTK6

BACKGROUND

Abnormal expression of protein tyrosine kinase 6 (PTK6) has been proven to be involved in the development of gynecological tumors. However, its immune-related carcinogenic mechanism in other tumors remains unclear.

OBJECTIVE

The aim of this study was to identify PTK6 as a novel prognostic biomarker in pan-cancer, especially in lung adenocarcinoma (LUAD), which is correlated with immune infiltration, and to clarify its clinicopathological and prognostic significance.

METHODS

The prognostic value and immune relevance of PTK6 were investigated by using bio-informatics in this study. PTK6 expression was validated in vitro experiments (lung cancer cell lines PC9, NCI-H1975, and HCC827; human normal lung epithelial cells BEAS-2B). Western blot (WB) revealed the PTK6 protein expression in lung cancer cell lines. PTK6 expression was inhibited by Tilfrinib. Colony formation and the Cell Counting Kit-8 (CCK-8) assay were used to detect cell proliferation. The wound healing and trans-well were performed to analyze the cell migration capacity. Then flow cytometry was conducted to evaluate the cell apoptosis. Eventually, the relationship between PTK6 and immune checkpoints was examined. WB was used to estimate the PD-L1 expression at different Tilfrinib doses.

RESULTS

PTK6 was an independent predictive factor for LUAD and was substantially expressed in LUAD. Pathological stage was significantly correlated with increased PTK6 expression. In accordance with survival analysis, poor survival rate in LUAD was associated with a high expression level of PTK6. Functional enrichment of the cell cycle and TGF-β signaling pathway was demonstrated by KEGG and GSEA analysis. Moreover, PTK6 expression considerably associated with immune infiltration in LUAD, as determined by immune analysis. Thus, the result of vitro experiments indicated that cell proliferation and migration were inhibited by the elimination of PTK6. Additionally, PTK6 suppression induced cell apoptosis. Obviously, PD-L1 protein expression level up-regulated while PTK6 was suppressed.

CONCLUSION

PTK6 has predictive value for LUAD prognosis, and could up regulated PD-L1.

Prognostic impact of PTK6 expression in triple negative breast cancer

BACKGROUND

The aim of this study was to investigate the expression of PTK6 in different groups of triple negative breast cancer and its impact on prognosis.

METHODS

Retrospective study of a total of 209 surgical specimens of breast cancer were identified by IHC or FISH methods as triple negative,and divided into a lymph node metastasis positive (LNM +)group (n = 102) and a lymph node metastasis negative(LNM-) group (n = 107) according to the lymph node status of the surgical specimen. PTK6 expression was detected by IHC technique in all surgical specimens. PTK6 expression and clinicopathological features was explored by Chi-square test. The prognosis of different groups of patients was analyzed by Kaplan-Meier survival analysis and COX analysis.

RESULTS

The incidence of PTK6 expression in the LNM + group (78.4%) was significantly higher than in the LNM- group (28%). Clinicopathological analysis showed that PTK6 expression in the LNM + group was negatively correlated with the 5-year survival of patients. Kaplan-Meier analysis showed that only PTK6 expression in the LNM + group was negatively correlated with OS and DFS. COX analysis also showed that PTK6 expression and N stage were independent prognostic factors for DFS in the LNM + group. No correlation was observed between HER2 and PTK6 expression in any of the groups.

CONCLUSIONS

This study suggests that PTK6 promotes tumor development and was associated with poor prognosis in the LNM + group of triple negative breast cancer. Inhibition of PTK6 may be a new approach for the treatment of triple negative breast cancer patients, especially those with metastasis.

Large-scale genome sequencing redefines the genetic footprints of high-altitude adaptation in Tibetans

BACKGROUND

Tibetans are genetically adapted to high-altitude environments. Though many studies have been conducted, the genetic basis of the adaptation remains elusive due to the poor reproducibility for detecting selective signatures in the Tibetan genomes.

RESULTS

Here, we present whole-genome sequencing (WGS) data of 1001 indigenous Tibetans, covering the major populated areas of the Qinghai-Tibetan Plateau in China. We identify 35 million variants, and more than one-third of them are novel variants. Utilizing the large-scale WGS data, we construct a comprehensive map of allele frequency and linkage disequilibrium and provide a population-specific genome reference panel, referred to as 1KTGP. Moreover, with the use of a combined approach, we redefine the signatures of Darwinian-positive selection in the Tibetan genomes, and we characterize a high-confidence list of 4320 variants and 192 genes that have undergone selection in Tibetans. In particular, we discover four new genes, TMEM132C, ATP13A3, SANBR, and KHDRBS2, with strong signals of selection, and they may account for the adaptation of cardio-pulmonary functions in Tibetans. Functional annotation and enrichment analysis indicate that the 192 genes with selective signatures are likely involved in multiple organs and physiological systems, suggesting polygenic and pleiotropic effects.

CONCLUSIONS

Overall, the large-scale Tibetan WGS data and the identified adaptive variants/genes can serve as a valuable resource for future genetic and medical studies of high-altitude populations.

Breast Tumour Kinase (Brk/PTK6) Contributes to Breast Tumour Xenograft Growth and Modulates Chemotherapeutic Responses In Vitro

Breast tumour kinase (Brk/PTK6) is overexpressed in up to 86% of breast cancers and is associated with poorer patient outcomes. It is considered a potential therapeutic target in breast cancer, even though the full spectrum of its kinase activity is not known. This study investigated the role of the kinase domain in promoting tumour growth and its potential in sensitising triple negative breast cancer cells to standard of care chemotherapy. Triple negative human xenograft models revealed that both kinase-inactive and wild-type Brk promoted xenograft growth. Suppression of Brk activity in cells subsequently co-treated with the chemotherapy agents doxorubicin or paclitaxel resulted in an increased cell sensitivity to these agents. In triple negative breast cancer cell lines, the inhibition of Brk kinase activity augmented the effects of doxorubicin or paclitaxel. High expression of the alternatively spliced isoform, ALT-PTK6, resulted in improved patient outcomes. Our study is the first to show a role for kinase-inactive Brk in human breast tumour xenograft growth; therefore, it is unlikely that kinase inhibition of Brk, in isolation, would halt tumour growth in vivo. Breast cancer cell responses to chemotherapy in vitro were kinase-dependent, indicating that treatment with kinase inhibitors could be a fruitful avenue for combinatorial treatment. Of particular prognostic value is the ratio of ALT-PTK6:Brk expression in predicating patient outcomes.

Potential Biological Targets Prediction, ADME Profiling, & Molecular Docking studies of Novel Steroidal Products from Cunninghamella Blakesleana

BACKGROUND

New potential biological targets prediction through inverse molecular docking technique is an another smart strategy to forecast the possibility of compounds being biologically active against various target receptors.

OBJECTIVES

In this case of designed study, we screened our recently obtained novel acetylinic steroidal biotransformed products [(1) 8-β-methyl-14-α-hydroxy∆4tibolone (2) 9-α-Hydroxy∆4 tibolone (3) 8-β-methyl-11-β-hydroxy∆4tibolone (4) 6-β-hydroxy∆4tibolone, (5) 6-β-9-α-dihydroxy∆4tibolone (6) 7-β-hydroxy∆4tibolone) ] from fungi Cunninghemella Blakesleana to predict their possible biological targets and profiling of ADME properties.

METHOD

The prediction of pharmacokinetics properties membrane permeability as well as bioavailability radar properties were carried out by using Swiss target prediction, and Swiss ADME tools, respectively these metabolites were also subjected to predict the possible mechanism of action along with associated biological network pathways by using Reactome data-base.

RESULTS

All the six screened compounds possess excellent drug ability criteria, and exhibited exceptionally excellent non inhibitory potential against all five isozymes of CYP450 enzyme complex, including (CYP1A2, CYP2C19, CYP2C9, CYP2D6, and CYP3A4) respectively. All the screened compounds are lying within the acceptable pink zone of bioavailability radar and showing excellent descriptive properties. Compounds [1-4 & 6] are showing high BBB (Blood Brain Barrier) permeation, while compound 5 is exhibiting high HIA (Human Intestinal Absorption) property of (Egan Egg).

CONCLUSION

In conclusion, the results of this study smartly reveals that in-silico based studies are considered to provide robustness towards a rational drug designing and development approach, therefore in this way it helps to avoid the possibility of failure of drug candidates in the later experimental stages of drug development phases.

Putting the BRK on breast cancer: From molecular target to therapeutics

BReast tumor Kinase (BRK, also known as PTK6) is a non-receptor tyrosine kinase that is highly expressed in breast carcinomas while having low expression in the normal mammary gland, which hints at the oncogenic nature of this kinase in breast cancer. In the past twenty-six years since the discovery of BRK, an increasing number of studies have strived to understand the cellular roles of BRK in breast cancer. Since then, BRK has been found both in vitro and in vivo to activate a multitude of oncoproteins to promote cell proliferation, metastasis, and cancer development. The compelling evidence concerning the oncogenic roles of BRK has also led, since then, to the rapid and exponential development of inhibitors against BRK. This review highlights recent advances in BRK biology in contributing to the “hallmarks of cancer”, as well as BRK's therapeutic significance. Importantly, this review consolidates all known inhibitors of BRK activity and highlights the connection between drug action and BRK-mediated effects. Despite the volume of inhibitors designed against BRK, none have progressed into clinical phase. Understanding the successes and challenges of these inhibitor developments are crucial for the future improvements of new inhibitors that can be clinically relevant.

Targeting protein tyrosine kinase 6 in cancer

Protein tyrosine kinase 6 (PTK6) is the most well studied member of the PTK6 family of intracellular tyrosine kinases. While it is expressed at highest levels in differentiated cells in the regenerating epithelial linings of the gastrointestinal tract and skin, induction and activation of PTK6 is detected in several cancers, including breast and prostate cancer where high PTK6 expression correlates with worse outcome. PTK6 expression is regulated by hypoxia and cell stress, and its kinase activity is induced by several growth factor receptors implicated in cancer including members of the ERBB family, IGFR1 and MET. Activation of PTK6 at the plasma membrane has been associated with the epithelial mesenchymal transition and tumor metastasis. Several lines of evidence indicate that PTK6 has context dependent functions that depend on cell type, intracellular localization and kinase activation. Systemic disruption of PTK6 has been shown to reduce tumorigenesis in mouse models of breast and prostate cancer, and more recently small molecule inhibitors of PTK6 have exhibited efficacy in inhibiting tumor growth in animal models. Here we review data that suggest targeting PTK6 may have beneficial therapeutic outcomes in some cancers.

Taxol Induces Brk-dependent Prosurvival Phenotypes in TNBC Cells through an AhR/GR/HIF-driven Signaling Axis

The metastatic cascade is a complex process that requires cancer cells to survive despite conditions of high physiologic stress. Previously, cooperation between the glucocorticoid receptor (GR) and hypoxia-inducible factors (HIF) was reported as a point of convergence for host and cellular stress signaling. These studies indicated p38 MAPK-dependent phosphorylation of GR on Ser134 and subsequent p-GR/HIF-dependent induction of breast tumor kinase (PTK6/Brk), as a mediator of aggressive cancer phenotypes. Herein, p-Ser134 GR was quantified in human primary breast tumors (n = 281) and the levels of p-GR were increased in triple-negative breast cancer (TNBC) relative to luminal breast cancer. Brk was robustly induced following exposure of TNBC model systems to chemotherapeutic agents (Taxol or 5-fluorouracil) and growth in suspension [ultra-low attachment (ULA)]. Notably, both Taxol and ULA resulted in upregulation of the Aryl hydrocarbon receptor (AhR), a known mediator of cancer prosurvival phenotypes. Mechanistically, AhR and GR copurified and following chemotherapy and ULA, these factors assembled at the Brk promoter and induced Brk expression in an HIF-dependent manner. Furthermore, Brk expression was upregulated in Taxol-resistant breast cancer (MCF-7) models. Ultimately, Brk was critical for TNBC cell proliferation and survival during Taxol treatment and in the context of ULA as well as for basal cancer cell migration, acquired biological phenotypes that enable cancer cells to successfully complete the metastatic cascade. These studies nominate AhR as a p-GR binding partner and reveal ways to target epigenetic events such as adaptive and stress-induced acquisition of cancer skill sets required for metastatic cancer spread.Implication: Breast cancer cells enlist intracellular stress response pathways that evade chemotherapy by increasing cancer cell survival and promoting migratory phenotypes. Mol Cancer Res; 16(11); 1761-72. ©2018 AACR.

WSB-1 regulates the metastatic potential of hormone receptor negative breast cancer

BACKGROUND

Metastatic spread is responsible for the majority of cancer-associated deaths. The tumour microenvironment, including hypoxia, is a major driver of metastasis. The aim of this study was to investigate the role of the E3 ligase WSB-1 in breast cancer biology in the context of the hypoxic tumour microenvironment, particularly regarding metastatic spread.

METHODS

In this study, WSB-1 expression was evaluated in breast cancer cell lines and patient samples. In silico analyses were used to determine the impact of WSB-1 expression on distant metastasis-free survival (DMFS) in patients, and correlation between WSB1 expression and hypoxia gene expression signatures. The role of WSB-1 on metastasis promotion was evaluated in vitro and in vivo.

RESULTS

High WSB1 expression was associated with decreased DMFS in ER-breast cancer and PR-breast cancer patients. Surprisingly, WSB1 expression was not positively correlated with known hypoxic gene expression signatures in patient samples. Our study is the first to show that WSB-1 knockdown led to decreased metastatic potential in breast cancer hormone receptor-negative models in vitro and in vivo. WSB-1 knockdown was associated with decreased metalloproteinase (MMP) activity, vascular endothelial growth factor (VEGF) secretion, and angiogenic potential.

CONCLUSIONS

Our data suggests that WSB-1 may be an important regulator of aggressive metastatic disease in hormone receptor-negative breast cancer. WSB-1 could therefore represent a novel regulator and therapeutic target for secondary breast cancer in these patients.

PTK6 regulates growth and survival of endocrine therapy-resistant ER+ breast cancer cells

The non-receptor tyrosine kinase, PTK6/BRK, is highly expressed in multiple tumor types, including prostate, ovarian, and breast cancers, and regulates oncogenic phenotypes such as proliferation, migration, and survival. PTK6 inhibition also overcomes targeted therapy resistance of HER2+ breast cancer. Although PTK6 is highly expressed in ER+ Luminal breast cancers, the role of PTK6 in this subtype has not been elucidated. In this study, we investigated the functions of PTK6 in ER+ Luminal breast cancer cells, including those that are relatively resistant to estrogen deprivation or targeted endocrine therapies used in the treatment of ER+ cancers. Enhanced expression of PTK6 in ER+ breast cancer cells enhances growth of ER+ breast cancer cells, including tamoxifen-treated cells. Downregulation of PTK6 in ER+ breast cancer cells, including those resistant to tamoxifen, fulvestrant, and estrogen deprivation, induces apoptosis, as evidenced by increased levels of cleaved PARP, and an increase in the AnnexinV+ population. PTK6 downregulation impairs growth of these cells in 3D Matrigel^TM cultures, and virtually abrogates primary tumor growth of both tamoxifen-sensitive and resistant MCF-7 xenografts. Finally, we show that p38 MAPK activation is critical for PTK6 downregulation-induced apoptosis, a mechanism that we previously reported for survival of HER2+ breast cancer cells, highlighting conserved mechanisms of survival regulation by PTK6 across breast cancer subtypes. In conclusion, our studies elucidate critical functions of PTK6 in ER+ Luminal breast cancers and support PTK6 as an attractive therapeutic target for ER+ breast cancers.

Drugs that target a tumor-promoting enzyme called protein tyrosine kinase 6 (PTK6) could help treat hormone-receptor positive breast cancer. A team led by Hanna Irie from the Icahn School of Medicine at Mount Sinai in New York, NY, USA, investigated the role of PTK6, also known as breast tumor kinase, in breast cancer cells that grow in response to the hormone estrogen. They boosted the enzyme’s expression in estrogen receptor-expressing breast cancer cells and saw enhanced growth. Conversely, downregulating PTK6 levels led to cell death, including in tumor cells that were resistant to tamoxifen
 and other therapies commonly used to treat estrogen-receptor positive breast cancer. The researchers showed that this effect was dependent on the activation of a signaling pathway previously found to be important in another subtype of breast cancer, highlighting a conserved mechanism of cell survival regulation by PTK6.

Targeting the hypoxic fraction of tumours using hypoxia-activated prodrugs

The presence of a microenvironment within most tumours containing regions of low oxygen tension or hypoxia has profound biological and therapeutic implications. Tumour hypoxia is known to promote the development of an aggressive phenotype, resistance to both chemotherapy and radiotherapy and is strongly associated with poor clinical outcome. Paradoxically, it is recognised as a high-priority target and one of the therapeutic strategies designed to eradicate hypoxic cells in tumours is a group of compounds known collectively as hypoxia-activated prodrugs (HAPs) or bioreductive drugs. These drugs are inactive prodrugs that require enzymatic activation (typically by 1 or 2 electron oxidoreductases) to generate cytotoxic species with selectivity for hypoxic cells being determined by (1) the ability of oxygen to either reverse or inhibit the activation process and (2) the presence of elevated expression of oxidoreductases in tumours. The concepts underpinning HAP development were established over 40 years ago and have been refined over the years to produce a new generation of HAPs that are under preclinical and clinical development. The purpose of this article is to describe current progress in the development of HAPs focusing on the mechanisms of action, preclinical properties and clinical progress of leading examples.

Targeting the hypoxic fraction of tumours using hypoxia-activated prodrugs

The presence of a microenvironment within most tumours containing regions of low oxygen tension or hypoxia has profound biological and therapeutic implications. Tumour hypoxia is known to promote the development of an aggressive phenotype, resistance to both chemotherapy and radiotherapy and is strongly associated with poor clinical outcome. Paradoxically, it is recognised as a high-priority target and one of the therapeutic strategies designed to eradicate hypoxic cells in tumours is a group of compounds known collectively as hypoxia-activated prodrugs (HAPs) or bioreductive drugs. These drugs are inactive prodrugs that require enzymatic activation (typically by 1 or 2 electron oxidoreductases) to generate cytotoxic species with selectivity for hypoxic cells being determined by (1) the ability of oxygen to either reverse or inhibit the activation process and (2) the presence of elevated expression of oxidoreductases in tumours. The concepts underpinning HAP development were established over 40 years ago and have been refined over the years to produce a new generation of HAPs that are under preclinical and clinical development. The purpose of this article is to describe current progress in the development of HAPs focusing on the mechanisms of action, preclinical properties and clinical progress of leading examples.

Transarterial oily chemoembolization with lidamycin shows potent therapeutic efficacy in VX2 rabbit liver tumor

Transarterial oily chemoembolization (TOCE) is one of the most effective approaches for the treatment of patients with hepatocellular carcinoma (HCC), who are not suitable for surgical therapy. Lidamycin (LDM), a potent antitumor antibiotic, demonstrates good antitumor efficacy in various tumor types, both in vitro and in vivo. In this study, the antitumor efficacy of LDM combined with TOCE against the rabbit VX2 tumor was assessed. A toxicity assay with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) demonstrated that a combination of LDM with lipiodol did not impair the cytotoxicity of LDM against HepG2 cells in vitro. Using TOCE in rabbit VX2 tumor models, LDM showed a more powerful inhibitory effect against the tumor and lowered the expression levels of proliferating cell nuclear antigen (PCNA), cluster of differentiation 31 (CD31), and vascular endothelial growth factor (VEGF) compared to Adriamycin (ADM); moreover, this improvement was not accompanied by an increase of hepatotoxicity as shown by alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels. These results suggested that LDM combined with TOCE may be a feasible strategy in HCC therapy in the future.

Protein tyrosine kinase 6 promotes ERBB2-induced mammary gland tumorigenesis in the mouse

Protein tyrosine kinase 6 (PTK6) expression, activation, and amplification of the PTK6 gene have been reported in ERBB2/HER2-positive mammary gland cancers. To explore contributions of PTK6 to mammary gland tumorigenesis promoted by activated ERBB2, we crossed Ptk6^−/− mice with the mouse mammary tumor virus-ERBB2 transgenic mouse line expressing activated ERBB2 and characterized tumor development and progression. ERBB2-induced tumorigenesis was significantly delayed and diminished in mice lacking PTK6. PTK6 expression was induced in the mammary glands of ERBB2 transgenic mice before tumor development and correlated with activation of signal transducer and activator of transcription 3 (STAT3) and increased proliferation. Disruption of PTK6 impaired STAT3 activation and proliferation. Phosphorylation of the PTK6 substrates focal adhesion kinase (FAK) and breast cancer anti-estrogen resistance 1 (BCAR1; p130CAS) was decreased in Ptk6^−/− mammary gland tumors. Reduced numbers of metastases were detected in the lungs of Ptk6^−/− mice expressing activated ERBB2, compared with wild-type ERBB2 transgenic mice. PTK6 activation was detected at the edges of ERBB2-positive tumors. These data support roles for PTK6 in both ERBB2-induced mammary gland tumor initiation and metastasis, and identify STAT3, FAK, and BCAR1 as physiologically relevant PTK6 substrates in breast cancer. Including PTK6 inhibitors as part of a treatment regimen could have distinct benefits in ERBB2/HER2-positive breast cancers.

Tracing the footprints of the breast cancer oncogene BRK - Past till present

Twenty years have passed since the non-receptor tyrosine kinase, Breast tumor kinase (BRK) was cloned. While BRK is evolutionarily related to the Src family kinases it forms its own distinct sub-family referred here to as the BRK family kinases. The detection of BRK in over 60% of breast carcinomas two decades ago and more remarkably, its absence in the normal mammary gland attributed to its recognition as a mammary gland-specific potent oncogene and led BRK researchers on a wild chase to characterize the role of the enzyme in breast cancer. Where has this chase led us? An increasing number of studies have been focused on understanding the cellular roles of BRK in breast carcinoma and normal tissues. A majority of such studies have proposed an oncogenic function of BRK in breast cancers. Thus far, the vast evidence gathered highlights a regulatory role of BRK in critical cellular processes driving tumor formation such as cell proliferation, migration and metastasis. Functional characterization of BRK has identified several signaling proteins that work in concert with the enzyme to sustain such a malignant phenotype. As such targeting the non-receptor tyrosine kinase has been proposed as an attractive approach towards therapeutic intervention. Yet much remains to be explored about (a) the discrepant expression levels of BRK in cancer versus normal conditions, (b) the dependence on the enzymatic activity of BRK to promote oncogenesis and (c) an understanding of the normal physiological roles of the enzyme. This review outlines the advances made towards understanding the cellular and physiological roles of BRK, the mechanisms of action of the protein and its therapeutic significance, in the context of breast cancer.