Association between Pak1 expression and subcellular localization and tamoxifen resistance in breast cancer patients

Spatio-temporal localization of P21-activated kinase in endometrial cancer

Endometrial cancer is the sixth most common gynecologic cancer, and has been reported as a malignancy arising due to the idiopathic effects of certain anticancer agents. Tamoxifen is the drug of choice in ER-positive breast cancer, and several studies have shown better disease-free survival in these patients. However, the long-term usage of tamoxifen has been associated with resistance and risk for endometrial malignancy. A direct mechanistic basis for tamoxifen-induced endometrial tumorigenesis is still unclear. Hyperactivation of PAK1 in endometrial cancer correlates with poor overall survival. The present study demonstrates that tamoxifen treatment induces nuclear localization of PAK1 in endometrial carcinoma cells. This nuclear transit is mediated through JAK2 phosphorylation of PAK1 and binding of β-PIX. In addition, a computational approach involving molecular modeling and simulation of phosphorylated and unphosphorylated forms of PAK1 was used to elucidate the dynamics of nuclear localization. Thus, PAK1 phosphorylation by JAK2 is a prerequisite for its nuclear localization and its tumorigenic effects on endometrial cancer cells.

Activation of oncogenic signaling kinase PAK1 by ionising radiation confers an aggressive phenotype in head and neck squamous cell carcinoma

Head and neck squamous cancers are very aggressive tumors often diagnosed in late stages with poor prognosis. HNSCCs are usually treated by a course of radiation (IR) therapy and followed by surgery. These treatment regimens fail to bring a complete response. Molecular signatures in tumors are attributed to this response and an improved understanding of the signaling events could offer new avenues for therapy. Here, we show that P21 activated kinase-1 (PAK1) - an oncogenic signaling serine/threonine kinase, is activated upon exposure to IR and this leads to an accelerated tumorigenic character in HNSCC cells. Our results show that PAK1 is highly expressed in HNSCC cell lines, as compared to normal buccal mucosa cells and when HNSCC cells were exposed to IR, they show activated PAK1 and an aggressive phenotype as determined by in vitro functional assays. PAK1 levels were elevated in HNSCC as compared to adjacent normal oral tissues and our results also show convincing evidence of activated PAK1 in patient tumor samples of post- IR treatment as compared to pre-IR treatment and is associated with poor survival. Pak1 Knockout (KO) clones in HNSCC cells showed that they were more sensitive to IR as compared to wild type (wt) cells. This altered sensitivity to IR was attributed to enhanced DNA damage response modulated by PAK1 in cells. Overall, our results suggest that PAK1 expression in HNSCC could be a critical determinant in IR therapy response and silencing PAK1 is likely to be a treatment modality to improve clinical outcomes.

Scoparone induces autophagic cell death via the PAK1/AKT axis in colorectal cancer

Colorectal cancer (CRC) is one of most common malignancies worldwide, yet curative therapy remains a clinical challenge. Here, we demonstrate that scoparone (Scop), a traditional Chinese medicine monomer, inhibits the growth of CRC cells both in vitro and in vivo. Further studies found that Scop treatment induces complete autophagic flux in CRC cells, while inhibition of autophagy markedly represses the antiproliferative activities of Scop, suggesting an antitumour property of Scop-induced autophagy in CRC. Mechanistically, Scop induced autophagy initiation by reducing P21-activated kinase 1 (PAK1) expression and subsequently repressing the AKT/mTOR signaling pathway. Collectively, our study suggests that Scop is a potential anti-CRC therapeutic option and provides an underlying molecular mechanism for its antitumour effect in CRC.

PAK1 copy number in breast cancer-Associations with proliferation and molecular subtypes

INTRODUCTION

P21-activated kinase 1 (PAK1) is known to be overexpressed in several human tumour types, including breast cancer (BC). It is located on chromosome 11 (11q13.5-q14.1) and plays a significant role in proliferation in BC. In this study we aimed to assess PAK1 gene copy number (CN) in primary breast tumours and their corresponding lymph node metastases, and associations between PAK1 CN and proliferation status, molecular subtype, and prognosis. In addition, we aimed to study associations between CNs of PAK1 and CCND1. Both genes are located on the long arm of chromosome 11 (11q13).

METHODS

Fluorescence in situ hybridization for PAK1 and Chromosome enumeration probe (CEP)11 were used on tissue microarray sections from a series of 512 BC cases. Copy numbers were estimated by counting the number of fluorescent signals for PAK1 and CEP11 in 20 tumour cell nuclei. Pearson's x2 test was performed to assess associations between PAK1 CN and tumour features, and between PAK1 and CCND1 CNs. Cumulative risk of death from BC and hazard ratios were estimated in analysis of prognosis.

RESULTS

We found mean PAK1 CN ≥4<6 in 26 (5.1%) tumours, and CN ≥ 6 in 22 (4.3%) tumours. The proportion of cases with copy number increase (mean CN ≥4) was highest among HER2 type and Luminal B (HER2-) tumours. We found an association between PAK1 CN increase, and high proliferation, and high histological grade, but not prognosis. Of cases with PAK1 CN ≥ 6, 30% also had CCND1 CN ≥ 6.

CONCLUSIONS

PAK1 copy number increase is associated with high proliferation and high histological grade, but not with prognosis. PAK1 CN increase was most frequent in the HER2 type and Luminal B (HER2-) subtype. PAK1 CN increase is associated with CN increase of CCND1.

Differentially Expressed Genes Induced by Erythropoietin Receptor Overexpression in Rat Mammary Adenocarcinoma RAMA 37-28 Cells

The erythropoietin receptor (EPOR) is a transmembrane type I receptor with an essential role in the proliferation and differentiation of erythroid progenitors. Besides its function during erythropoiesis, EPOR is expressed and has protective effect in various non-hematopoietic tissues, including tumors. Currently, the advantageous aspect of EPOR related to different cellular events is still under scientific investigation. Besides its well-known effect on cell proliferation, apoptosis and differentiation, our integrative functional study revealed its possible associations with metabolic processes, transport of small molecules, signal transduction and tumorigenesis. Comparative transcriptome analysis (RNA-seq) identified 233 differentially expressed genes (DEGs) in EPOR overexpressed RAMA 37-28 cells compared to parental RAMA 37 cells, whereas 145 genes were downregulated and 88 upregulated. Of these, for example, GPC4, RAP2C, STK26, ZFP955A, KIT, GAS6, PTPRF and CXCR4 were downregulated and CDH13, NR0B1, OCM2, GPM6B, TM7SF3, PARVB, VEGFD and STAT5A were upregulated. Surprisingly, two ephrin receptors, EPHA4 and EPHB3, and EFNB1 ligand were found to be upregulated as well. Our study is the first demonstrating robust differentially expressed genes evoked by simple EPOR overexpression without the addition of erythropoietin ligand in a manner which remains to be elucidated.

Correlations between serum lipid and Ki-67 levels in different breast cancer molecular subcategories

Breast cancer has the highest incidence rate among all cancer types worldwide, seriously threatening women's health. The present retrospective study explored differences in serum lipid contents in different breast cancer (BC) subcategories and their correlation with Ki-67 expression levels in patients with invasive BC with the aim of identifying novel diagnostic and prognostic indicators for personalized BC treatment. The study included 170 patients diagnosed with BC who were diagnosed with invasive BC by postoperative pathological examination. Data on patient age, body mass index and menopausal status were collected, in addition to estrogen receptor, progesterone receptor, human epidermal growth factor receptor 2 (HER2) and antigen Ki-67 expression levels and pathological tumor type. Preoperative circulating lipid levels, specifically the levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglycerides (TG) and apolipoproteins A1 (ApoA1) and B (ApoB) were also obtained. Molecular subcategories of BC were grouped based on their immunohistochemistry. Differences in serum lipid levels between the groups were assessed, and correlations between serum lipid and Ki-67 expression levels were explored. While TC, LDL-C, HDL-C and ApoA1 levels differed significantly among molecular subcategories. TG and ApoB levels did not. Circulating TC and LDL-C levels were considerably higher in patients with triple-negative BC (TNBC) and HER2-positive [hormone receptor (HR)-negative] BC than in those with luminal A and B (HER2-negative) BC. Serum HDL-C levels were significantly diminished in the TNBC and HER2-positive (HR-negative) groups compared with the luminal A and B (HER2-negative) groups. ApoA1 levels were significantly reduced in cases of TNBC and HER2-positive (HR-negative) BC compared with luminal A and B BC. Ki-67 expression levels were positively correlated with circulating TC and LDL-C levels and inversely correlated with circulating HDL-C and ApoA1 levels but exhibited no correlation with serum ApoB and TG levels. The results indicate that elevated TC and LDL-C levels and diminished HDL-C and ApoA1 levels were high-risk factors in patients with TNBC and HER2-positive (HR-negative) BC, but not patients with luminal subcategories of BC. Abnormal serum lipid levels were correlated with Ki-67 expression levels, with elevated circulating TC and LDL-C levels and reduced circulating HDL-C and ApoA1 levels indicating a poor prognosis in patients with BC.

p21-Activated Kinase 1 Promotes Breast Tumorigenesis via Phosphorylation and Activation of the Calcium/Calmodulin-Dependent Protein Kinase II

p21-Activated kinase-1 (Pak1) is frequently overexpressed and/or amplified in human breast cancer and is necessary for transformation of mammary epithelial cells. Here, we show that Pak1 interacts with and phosphorylates the Calcium/Calmodulin-dependent Protein Kinase II (CaMKII), and that pharmacological inhibition or depletion of Pak1 leads to diminished activity of CaMKII. We found a strong correlation between Pak1 and CaMKII expression in human breast cancer samples, and combined inhibition of Pak1 and CaMKII with small-molecule inhibitors was synergistic and induced apoptosis more potently in Her2 positive and triple negative breast cancer (TNBC) cells. Co-adminstration of Pak and CaMKII small-molecule inhibitors resulted in a dramatic reduction of proliferation and an increase in apoptosis in a 3D cell culture setting, as well as an impairment in migration and invasion of TNBC cells. Finally, mice bearing xenografts of TNBC cells showed a significant delay in tumor growth when treated with small-molecule inhibitors of Pak and CaMKII. These data delineate a signaling pathway from Pak1 to CaMKII that is required for efficient proliferation, migration and invasion of mammary epithelial cells, and suggest new therapeutic strategies in breast cancer.

p21 activated kinase-1 and tamoxifen - A deadly nexus impacting breast cancer outcomes

Tamoxifen is a commonly used drug in the treatment of ER + ve breast cancers since 1970. However, development of resistance towards tamoxifen limits its remarkable clinical success. In this review, we have attempted to provide a brief overview of multiple mechanism that may lead to tamoxifen resistance, with a special emphasis on the roles played by the oncogenic kinase- PAK1. Analysing the genomic data sets available in the cBioPortal, we found that PAK1 gene amplification significantly affects the Relapse Free Survival of the ER + ve breast cancer patients. While PAK1 is known to promote tamoxifen resistance by phosphorylating ERα at Ser305, existing literature suggests that PAK1 can fuel up tamoxifen resistance obliquely by phosphorylating other substrates. We have summarised some of the approaches in the mass spectrometry based proteomics, which would enable us to study the tamoxifen resistance specific phosphoproteomic landscape of PAK1. We also propose that elucidating the multiple mechanisms by which PAK1 promotes tamoxifen resistance might help us discover druggable targets and biomarkers.

Tumor co-expression of progranulin and sortilin as a prognostic biomarker in breast cancer

Background

The growth factor progranulin has been implicated in numerous biological processes such as wound healing, inflammation and progressive tumorigenesis. Both progranulin and its receptor sortilin are known to be highly expressed in subgroups of breast cancer and have been associated with various clinical properties including tamoxifen resistance. Recent data further suggest that progranulin, via its receptor sortilin, drives breast cancer stem cell propagation in vitro and increases metastasis formation in an in vivo breast cancer xenograft model. In this retrospective biomarker analysis, we aimed to determine whether tumor co-expression of progranulin and sortilin has prognostic and treatment predictive values for breast cancer patients.

Methods

We explored how co-expression of progranulin and sortilin was associated with established clinical markers by analyzing a tissue microarray including 560 randomized premenopausal breast cancer patients receiving either 2 years of tamoxifen treatment or no adjuvant treatment, with a median follow-up time of 28 years. Breast cancer-specific survival was analyzed using Kaplan-Meier and Cox Proportional Hazards regression models to assess the prognostic and predictive value of progranulin and sortilin in relation to known clinical markers.

Results

Co-expression of progranulin and sortilin was observed in 20% of the breast cancer samples. In untreated patients, prognostic considerations could be detailed separately from treatment prediction and the high progranulin and sortilin expressing subgroup was significantly associated with breast cancer-specific death in multivariable analyses (HR=2.188, CI: 1.317–3.637, p=0.003) along with tumor size, high tumor grade and lymph node positivity. When comparing the untreated patients with tamoxifen treated patients in the ERα positive subgroup, co-expression of progranulin and sortilin was not linked to tamoxifen resistance.

Conclusion

Data suggest that co-expression of progranulin and its receptor sortilin is a novel prognostic biomarker combination identifying a highly malignant subgroup of breast cancer. Importantly, this subpopulation could potentially be targeted with anti-sortilin based therapies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-07854-0.

Novel biomarkers and prediction model for the pathological complete response to neoadjuvant treatment of triple-negative breast cancer

Objective: To develop and validate a prediction model for the pathological complete response (pCR) to neoadjuvant chemotherapy (NCT) of triple-negative breast cancer (TNBC). Methods: We systematically searched Gene Expression Omnibus, ArrayExpress, and PubMed for the gene expression profiles of operable TNBC accessible to NCT. Molecular heterogeneity was detected with hierarchical clustering method, and the biological profiles of differentially expressed genes were investigated by Gene Ontology, Kyoto Encyclopedia of Genes and Genomes analyses, and Gene Set Enrichment Analysis (GSEA). Next, machine-learning algorithms including random-forest analysis and least absolute shrinkage and selection operator (LASSO) analysis were synchronously performed and, then, the intersected proportion of significant genes was undergone binary logistic regression to fulfill variables selection. The predictive response score (pRS) system was built as the product of the gene expression and coefficient obtained from the logistic analysis. Last, the cohorts were randomly divided in a 7:3 ratio into training cohort and validation cohort for the introduction of a robust model, and a nomogram was constructed with the independent predictors for pCR rate. Results: A total of 217 individuals from four cohort datasets (GSE32646, GSE25065, GSE25055, GSE21974) with complete clinicopathological information were included. Based on the microarray data, a six-gene panel (ATP4B, FBXO22, FCN2, RRP8, SMERK2, TET3) was identified. A robust nomogram, adopting pRS and clinical tumor size stage, was established and the performance was successively validated by calibration curves and receiver operating characteristic curves with the area under curve 0.704 and 0.756, respectively. Results of GSEA revealed that the biological processes including apoptosis, hypoxia, mTORC1 signaling and myogenesis, and oncogenic features of EGFR and RAF were in proactivity to attribute to an inferior response. Conclusions: This study provided a robust prediction model for pCR rate and revealed potential mechanisms of distinct response to NCT in TNBC, which were promising and warranted to further validate in the perspective.

Chemical carcinogen-induced rat mammary carcinogenesis is a potential model of p21-activated kinase positive female breast cancer

The p21-activated kinase 1 (PAK1) gene encodes a serine/threonine kinase that is overexpressed in a subset of human breast carcinomas with poor prognosis. The laboratory rat (Rattus norvegicus) orthologous gene is located at Mammary carcinoma susceptibility 3 (Mcs3) QTL on rat chromosome 1. We used quantitative PCR to determine effects of Mcs3 genotype and 7,12-dimethylbenz(a)anthracene (DMBA) exposure on Pak1 expression. There was no effect of Mcs3 genotype; however, there was a 3.5-fold higher Pak1 level in DMBA-exposed mammary glands (MGs) than in unexposed glands (P < 0.05). Sequence variants in Pak1 exons did not alter amino acid sequence between Mcs3-susceptible and -resistant strains. Protein expression of PAK1/Pak1 in human breast carcinomas and DMBA-exposed rat mammary glands was detected using immunohistochemistry (IHC). Rat mammary glands from 12-wk-old females unexposed to DMBA were negative for Pak1, whereas 24% of carcinogen-exposed mammary glands from age-matched females stained positive for Pak1. The positive mammary glands exposed to carcinogen had no pathological signs of disease. Human breast carcinomas, used as comparative controls, had a 22% positivity rats. This was consistent with other human breast cancer studies of PAK1 expression. Similar frequencies of human/rat PAK1/Pak1 expression in female breast carcinomas and carcinogen-induced rat mammary glands, showing no visible pathogenesis of disease, suggests aberrant PAK1 expression is an early event in development of some breast cancers. Laboratory rats will be a useful experimental organism for comparative studies of Pak1-mediated mechanisms of breast carcinogenesis. Future studies of PAK1 as a diagnostic marker of early breast disease are warranted.

Liposomes Targeting P21 Activated Kinase-1 (PAK-1) and Selective for Secretory Phospholipase A2 (sPLA2) Decrease Cell Viability and Induce Apoptosis in Metastatic Triple-Negative Breast Cancer Cells

P21 activated kinases (or group I PAKs) are serine/threonine kinases whose expression is altered in prostate and breast cancers. PAK-1 activity is inhibited by the small molecule "Inhibitor targeting PAK-1 activation-3" (IPA-3), which has selectivity for PAK-1 but is metabolically unstable. Secretory Group IIA phospholipase A₂ (sPLA₂) expression correlates to increased metastasis and decreased survival in many cancers. We previously designed novel liposomal formulations targeting both PAK-1 and sPLA_2, called Secretory Phospholipase Responsive liposomes or SPRL-IPA-3, and demonstrated their ability to alter prostate cancer growth. The efficacy of SPRL against other types of cancers is not well understood. We addressed this limitation by determining the ability of SPRL to induce cell death in a diverse panel of cells representing different stages of breast cancer, including the invasive but non-metastatic MCF-7 cells, and metastatic triple-negative breast cancer (TNBC) cells such as MDA-MB-231, MDA-MB-468, and MDA-MB-435. We investigated the role of sPLA₂ in the disposition of these liposomes by comparing the efficacy of SPRL-IPA-3 to IPA-3 encapsulated in sterically stabilized liposomes (SSL-IPA-3), a formulation shown to be less sensitive to sPLA₂. Both SSL-IPA-3 and SPRL-IPA-3 induced time- and dose-dependent decreases in MTT staining in all cell lines tested, but SPRL-IPA-3-induced effects in metastatic TNBC cell lines were superior over SSL-IPA-3. The reduction in MTT staining induced by SPRL-IPA-3 correlated to the expression of Group IIA sPLA₂. sPLA₂ expression also correlated to increased induction of apoptosis in TNBC cell lines by SPRL-IPA-3. These data suggest that SPRL-IPA-3 is selective for metastatic TNBC cells and that the efficacy of SPRL-IPA-3 is mediated, in part, by the expression of Group IIA sPLA₂.

Combined LIM kinase 1 and p21-Activated kinase 4 inhibitor treatment exhibits potent preclinical antitumor efficacy in breast cancer

LIM kinase 1 (LIMK1) and p21-activated kinase 4 (PAK4) are often over-expressed in breast tumors, which causes aggressive cancer phenotypes and unfavorable clinical outcomes. In addition to the well-defined role in regulating cell division, proliferation and invasion, the two kinases promote activation of the MAPK pathway and cause endocrine resistance through phosphorylating estrogen receptor alpha (ERα). PAK4 specifically phosphorylates LIMK1 and its functional partners, indicating possible value of suppressing both kinases in cancers that over-express PAK4 and/or LIMK1. Here, for the first time, we assessed the impact of combining LIMK1 inhibitor LIMKi 3 and PAK4 inhibitor PF-3758309 in preclinical breast cancer models. LIMK1 and PAK4 pharmacological inhibition synergistically reduced the survival of various cancer cell lines, exhibiting specific efficacy in luminal and HER2-enriched models, and suppressed development and ERα-driven signals in a BT474 xenograft model. In silico analysis demonstrated the cell lines with reliance on LIMK1 were the most prone to be susceptible to PAK4 inhibition. Double LIMK1 and PAK4 targeting therapy can be a successful therapeutic strategy for breast cancer, with a unique efficiency in the subtypes of luminal and HER2-enriched tumors.

Coordinated dysregulation of cancer progression by the HER family and p21-activated kinases

Most epithelial cancer types are polygenic in nature and are driven by coordinated dysregulation of multiple regulatory pathways, genes, and protein modifications. The process of coordinated regulation of cancer promoting pathways in response to extrinsic and intrinsic signals facilitates the dysregulation of several pathways with complementary functions, contributing to the hallmarks of cancer. Dysregulation and hyperactivation of cell surface human epidermal growth factor receptors (HERs) and cytoskeleton remodeling by p21-activated kinases (PAKs) are two prominent interconnected aspects of oncogenesis. We briefly discuss the discoveries and significant advances in the area of coordinated regulation of HERs and PAKs in the development and progression of breast and other epithelial cancers. We also discuss how initial studies involving heregulin signaling via HER3-HER2 axis and HER2-overexpressing breast cancer cells not only discovered a mechanistic role of PAK1 in breast cancer pathobiology but also acted as a bridge in generating a broader cancer research interest in other PAK family members and cancer types and catalyzed establishing the role of PAKs in human cancer, at-large. In addition, growth factor stimulation of the PAK pathway also helped to recognize new facets of PAKs, connecting the PAK pathway to oncogenesis, nuclear signaling, gene expression, mitotic progression, DNA damage response, among other phenotypic responses, and shaped the field of PAK cancer research. Finally, we recount some of the current limitations of HER- and PAK-directed therapeutics in counteracting acquired therapeutic resistance and discuss how cancer's as a polygenic disease may be best targeted with a polygenic approach.

Antitumor effects of ivermectin at clinically feasible concentrations support its clinical development as a repositioned cancer drug

PURPOSE

Ivermectin is an antiparasitic drug that exhibits antitumor effects in preclinical studies, and as such is currently being repositioned for cancer treatment. However, divergences exist regarding its employed doses in preclinical works. Therefore, the aim of this study was to determine whether the antitumor effects of ivermectin are observable at clinically feasible drug concentrations.

METHODS

Twenty-eight malignant cell lines were treated with 5 μM ivermectin. Cell viability, clonogenicity, cell cycle, cell death and pharmacological interaction with common cytotoxic drugs were assessed, as well as the consequences of its use on stem cell-enriched populations. The antitumor in vivo effects of ivermectin were also evaluated.

RESULTS

The breast MDA-MB-231, MDA-MB-468, and MCF-7, and the ovarian SKOV-3, were the most sensitive cancer cell lines to ivermectin. Conversely, the prostate cancer cell line DU145 was the most resistant to its use. In the most sensitive cells, ivermectin induced cell cycle arrest at G₀-G₁ phase, with modulation of proteins associated with cell cycle control. Furthermore, ivermectin was synergistic with docetaxel, cyclophosphamide and tamoxifen. Ivermectin reduced both cell viability and colony formation capacity in the stem cell-enriched population as compared with the parental one. Finally, in tumor-bearing mice ivermectin successfully reduced both tumor size and weight.

CONCLUSION

Our results on the antitumor effects of ivermectin support its clinical testing.

Targeting signaling pathways of VEGFR1 and VEGFR2 as a potential target in the treatment of breast cancer

Tumor angiogenesis allows tumor cells to grow and migrate toward the bloodstream and initiate metastasis. The interactions of vascular endothelial growth factors (VEGF) A and B, as the important regulating factors for blood vessel growth, with VEGFR1 and VEGFR2 trigger angiogenesis process. Thus, preventing these interactions led to the effective blockade of VEGF/VEGFRs signaling pathways. In this study, the inhibitory effect of a 23-mer linear peptide (VGB4), which binds to both VEGFR1 and VEGFR2, on VEGF-stimulated Human Umbilical Vein Endothelial Cells (HUVECs) and highly metastatic human breast cancer cell MDA-MB-231 proliferation was examined using MTT assay. To assess the anti-migratory potential of VGB4, HUVECs and also MDA-MB-231 cells wound healing assay was carried out at 48 and 72 h. In addition, downstream signaling pathways of VEGF associated with cell migration and invasion were investigated by quantification of mRNA and protein expression using real-time quantitative PCR and western blot in 4T1 tumor tissues and MDA-MB-231 cells. The results revealed that VGB4 significantly impeded proliferation of HUVECs and MDA-MB-231 cells, in a dose- and time-dependent manner, and migration of HUVECs and MDA-MB-231 cells for a prolonged time. We also observed statistically significant reduction of the transcripts and protein levels of focal adhesion kinase (FAK), Paxillin, matrix metalloproteinase-2 (MMP-2), RAS-related C3 botulinum substrate 1 (Rac1), P21-activated kinase-2 (PAK-2) and Cofilin-1 in VGB4-treated 4T1 tumor tissues compared to controls. The protein levels of phospho-VEGFR1, phospho-VEGFR2, Vimentin, β-catenin and Snail were markedly decreased in both VGB4-treated MDA-MB-231 cells and VGB4-treated 4T1 tumor tissues compared to controls as evidenced by western blotting. These results, in addition to our previous studies, confirm that dual blockage of VEGFR1 and VEGFR2, due to the inactivation of diverse signaling mediators, effectively suppresses tumor growth and metastasis.

A novel PAK1 variant causative of neurodevelopmental disorder with postnatal macrocephaly

p21-activated kinases (PAKs) are protein serine/threonine kinases stimulated by Rho-family p21 GTPases such as CDC42 and RAC. PAKs have been implicated in several human disorders, with pathogenic variants in PAK3 associated with intellectual disability and several PAK members, especially PAK1 and PAK4, overexpressed in human cancer. Recently, de novo PAK1 variants were reported to be causative of neurodevelopmental disorder (ND) with secondary macrocephaly in three patients. We herein report a fourth patient with ND, epilepsy, and macrocephaly caused by a de novo PAK1 missense variant. Two previously reported missense PAK1 variants functioned as activating alleles by reducing PAK1 homodimerization. To examine the pathogenicity of the identified novel p.Ser110Thr variant, we carried out in silico structural analysis. Our findings suggest that this variant also prevents PAK1 homodimerization, leading to constitutive PAK1 activation.

Effect of PAK Inhibition on Cell Mechanics Depends on Rac1

Besides biochemical and molecular regulation, the migration and invasion of cells is controlled by the environmental mechanics and cellular mechanics. Hence, the mechanical phenotype of cells, such as fibroblasts, seems to be crucial for the migratory capacity in confined 3D extracellular matrices. Recently, we have shown that the migratory and invasive capacity of mouse embryonic fibroblasts depends on the expression of the Rho-GTPase Rac1, similarly it has been demonstrated that the Rho-GTPase Cdc42 affects cell motility. The p21-activated kinase (PAK) is an effector down-stream target of both Rho-GTPases Rac1 and Cdc42, and it can activate via the LIM kinase-1 its down-stream target cofilin and subsequently support the cell migration and invasion through the polymerization of actin filaments. Since Rac1 deficient cells become mechanically softer than controls, we investigated the effect of group I PAKs and PAK1 inhibition on cell mechanics in the presence and absence of Rac1. Therefore, we determined whether mouse embryonic fibroblasts, in which Rac1 was knocked-out, and control cells, displayed cell mechanical alterations after treatment with group I PAKs or PAK1 inhibitors using a magnetic tweezer (adhesive cell state) and an optical cell stretcher (non-adhesive cell state). In fact, we found that group I PAKs and Pak1 inhibition decreased the stiffness and the Young’s modulus of fibroblasts in the presence of Rac1 independent of their adhesive state. However, in the absence of Rac1 the effect was abolished in the adhesive cell state for both inhibitors and in their non-adhesive state, the effect was abolished for the FRAX597 inhibitor, but not for the IPA3 inhibitor. The migration and invasion were additionally reduced by both PAK inhibitors in the presence of Rac1. In the absence of Rac1, only FRAX597 inhibitor reduced their invasiveness, whereas IPA3 had no effect. These findings indicate that group I PAKs and PAK1 inhibition is solely possible in the presence of Rac1 highlighting Rac1/PAK I (PAK1, 2, and 3) as major players in cell mechanics.

The molecular genetic make-up of male breast cancer

Male breast cancer (MBC) is extremely rare and accounts for less than 1% of all breast malignancies. Therefore, clinical management of MBC is currently guided by research on the disease in females. In this study, DNA obtained from 45 formalin-fixed paraffin-embedded (FFPE) MBCs with and 90 MBCs (52 FFPE and 38 fresh-frozen) without matched normal tissues was subjected to massively parallel sequencing targeting all exons of 1943 cancer-related genes. The landscape of mutations and copy number alterations was compared to that of publicly available estrogen receptor (ER)-positive female breast cancers (smFBCs) and correlated to prognosis. From the 135 MBCs, 90% showed ductal histology, 96% were ER-positive, 66% were progesterone receptor (PR)-positive, and 2% HER2-positive, resulting in 50, 46 and 4% luminal A-like, luminal B-like and basal-like cases, respectively. Five patients had Klinefelter syndrome (4%) and 11% of patients harbored pathogenic BRCA2 germline mutations. The genomic landscape of MBC to some extent recapitulated that of smFBC, with recurrent PIK3CA (36%) and GATA3 (15%) somatic mutations, and with 40% of the most frequently amplified genes overlapping between both sexes. TP53 (3%) somatic mutations were significantly less frequent in MBC compared to smFBC, whereas somatic mutations in genes regulating chromatin function and homologous recombination deficiency-related signatures were more prevalent. MDM2 amplifications were frequent (13%), correlated with protein overexpression (P = 0.001) and predicted poor outcome (P = 0.007). In conclusion, despite similarities in the genomic landscape between MBC and smFBC, MBC is a molecularly unique and heterogeneous disease requiring its own clinical trials and treatment guidelines.

Effect of P21-activated kinase 1 (PAK-1) inhibition on cancer cell growth, migration, and invasion

P21-activated kinase-1 (PAK-1) is a serine/threonine kinase involved in multiple signaling pathways that mediate cellular functions such as cytoskeletal motility, cell proliferation, and survival. PAK-1 expression is altered in various cancers, including prostate and breast. Our recent studies showed that prostate cancer cells expressing higher levels of PAK-1 were resistant to the cytotoxic effects of the PAK-1 inhibitor, inhibitor targeting PAK-1 activation-3 (IPA-3), compared to those with lower expression. This study expanded these findings to other cancers (breast and melanoma) by testing the hypothesis that genetic and pharmacological inhibition of PAK-1 alters cell growth, migration, and invasion in prostate, breast, and skin cancer cell lines. We also tested the specificity of IPA-3 for PAK-1 and the hypothesis that gene silencing of PAK-1 altered the efficacy of sterically stabilized liposomes (SSL) containing IPA-3 (SSL-IPA-3). PAK-1 expression was identified in four different breast cancer cell lines, and in a melanoma cell line. The expression of PAK-1 correlated to the IC50 of IPA-3 as measured by MTT staining. PAK-1 inhibition using shRNA correlated with decreased cell migration and invasion in prostate cancer DU-145 and breast cancer MCF-7 cells. Decreased migration and invasion also correlated to decreased expression of E-cadherin and alterations in C-X-C Chemokine Receptor type 4 and Homing Cell Adhesion Molecule expression. PAK-1 inhibition increased the cytotoxicity of IPA-3, and the cytotoxicity of SSL-IPA-3 to levels comparable to that of free drug. These data demonstrate that both pharmacological and molecular inhibition of PAK-1 decreased growth in prostate, breast, and melanoma cancer cell lines, and increased the toxicity of IPA-3 and its liposomal formulation. These data also show the specificity of IPA-3 for PAK-1, are some of the first data suggesting that IPA-3 is a therapeutic treatment for breast cancer and melanoma, and demonstrate the efficacy of liposome-encapsulated IPA-3 in breast cancer cells.

Dynamic interactions between the extracellular matrix and estrogen activity in progression of ER+ breast cancer

Metastatic, anti-estrogen resistant estrogen receptor α positive (ER+) breast cancer is the leading cause of breast cancer deaths in U.S. women. While studies have demonstrated the importance of the stromal tumor microenvironment in cancer progression and therapeutic responses, effects on the responses of ER+ cancers to estrogen and anti-estrogens are poorly understood, particularly in the complex in vivo environment. In this study, we used an estrogen responsive syngeneic mouse model to interrogate how a COL1A1-enriched fibrotic ECM modulates integrated hormonal responses in cancer progression. We orthotopically transplanted the ER+ TC11 cell line into wild-type (WT) or collagen-dense (Col1a1^tm1Jae/+, mCol1a1) syngeneic FVB/N female mice. Once tumors were established, recipients were supplemented with 17β-estradiol (E2), tamoxifen, or left untreated. Although the dense/stiff environment in mCol1a1 recipients did not alter the rate of E2-induced proliferation of the primary tumor, it fostered the agonist activity of tamoxifen to increase proliferation and AP-1 activity. Manipulation of estrogen activity did not alter the incidence of lung lesions in either WT or mCol1a1 hosts. However, the mCol1a1 environment enabled tamoxifen-stimulated growth of pulmonary metastases and further fueled estrogen-driven growth. Moreover, E2 remodeled peritumoral ECM architecture in WT animals, modifying alignment of collagen fibers and altering synthesis of ECM components associated with increased alignment and stiffness, and increasing FN1 and POSTN expression in the pulmonary metastatic niche. These studies demonstrate dynamic interactions between ECM properties and estrogen activity in progression of ER+ breast cancer, and support the need for therapeutics that target both ER and the tumor microenvironment.

Naringenin ameliorates progression of endometriosis by modulating Nrf2/Keap1/HO1 axis and inducing apoptosis in rats

Endometriosis is mainly characterized by the presence of endometrial tissue exterior to the uterus, however, the exact pathophysiology of this disease still remains uncertain. Moreover, the incidence significantly contributes to infertility among women and hence, a novel treatment for endometriosis is widely investigated. Naringenin is a plant-derived flavonoid having anti-proliferative, anti-inflammatory, and anti-angiogenic properties in chronic and metabolic diseases. The current study was planned with an objective to demonstrate the anti-endometriotic therapeutic potential of naringenin in rats and to examine its impact on various cellular aspects with a view to define the mechanism involved. The endometrial lesion volumes, weight, serum TNF-α level and the histopathologic scores were significantly reduced in the naringenin- treated group as compared to the endometriotic control group. Naringenin ameliorated the expression of prognostic markers (TAK1, PAK1, VEGF and PCNA) involved in development and progression of endometriotic cells. Naringenin caused dose-dependent loss of mitochondrial membrane potential, induced apoptosis and inhibited proliferation in these cells. Further, a significant increase in level of Nrf2 and its downstream molecules (NQO1, HO-1) was found in endometriotic lesion, with a subsequent decrease in its repressor molecule Keap-1. Naringenin significantly modulated the expression of Nrf2 and its effector molecules downstream. It also inhibited the invasion of endometrial cells by reducing the expression of MMP-2 and MMP-9 in in-vitro primary culture. We conclude that naringenin may have a therapeutic potential in the treatment of endometriosis via induction of ROS-mediated apoptosis and its anti-invasive effects.

Mixed lineage kinase 3 promotes breast tumorigenesis via phosphorylation and activation of p21-activated kinase 1

Mixed lineage kinase 3 (MLK3), a MAP3K member has been envisioned as a viable drug target in cancer, yet its detailed function and signaling is not fully elucidated. We identified that MLK3 tightly associates with an oncogene, PAK1. Mammalian PAK1 being a Ste20 (MAP4K) member, we tested whether it is an upstream regulator of MLK3. In contrast to our hypothesis, MLK3 activated PAK1 kinase activity directly, as well as in the cells. Although, MLK3 can phosphorylate PAK1 on Ser133 and Ser204 sites, PAK1S133A mutant is constitutively active, whereas, PAK1S204A is not activated by MLK3. Stable overexpression of PAK1S204A in breast cancer cells, impedes migration, invasion, and NFĸB activity. In vivo breast cancer cell tumorigenesis is significantly reduced in tumors expressing PAK1S204A mutant. These results suggest that mammalian PAK1 does not act as a MAP4K and MLK3-induced direct activation of PAK1 plays a key role in breast cancer tumorigenesis.

Nudt21 regulates the alternative polyadenylation of Pak1 and is predictive in the prognosis of glioblastoma patients

Alternative polyadenylation (APA) has emerged as a prevalent feature associated with cancer development and progression. The advantage of APA to tumor progression is to induce oncogenes through 3'-UTR shortening, and to inactivate tumor suppressor genes via the re-routing of microRNA competition. We previously identified the Mammalian Cleavage Factor I-25 (CFIm25) (encoded by Nudt21 gene) as a master APA regulator whose expression levels directly impact the tumorigenicity of glioblastoma (GBM) in vitro and in vivo. Despite its importance, the role of Nudt21 in GBM development is not known and the genes subject to Nudt21 APA regulation that contribute to GBM progression have not been identified. Here, we find that Nudt21 is reduced in low grade glioma (LGG) and all four subtypes of high grade glioma (GBM). Reduced expression of Nudt21 associates with worse survival in TCGA LGG cohorts and two TCGA GBM cohorts. Moreover, although CFIm25 was initially identified as biochemically associated with both CFIm59 and CFIm68, we observed three CFIm distinct subcomplexes exist and CFIm59 protein level is dependent on Nudt21 expression in GBM cells, but CFIm68 is not, and that only CFIm59 predicts prognosis of GBM patients similar to Nudt21. Through the use of Poly(A)-Click-Seq to characterize APA, we define the mRNAs subject to 3'-UTR shortening upon Nudt21 depletion in GBM cells and observed enrichment in genes important in the Ras signaling pathway, including Pak1. Remarkably, we find that Pak1 expression is regulated by Nudt21 through its 3'-UTR APA, and the combination of Pak1 and Nudt21 expression generates an even stronger prognostic indicator of GBM survival versus either value used alone. Collectively, our data uncover Nudt21 and its downstream target Pak1 as a potential "combination biomarker" for predicting prognosis of GBM patients.

PAK1 Expression in Pancreatic Cancer: Clinicopathological Characteristics and Prognostic Significance

Background:

Improvement of the management of pancreatic cancer requires a better understanding of the genetic and molecular changes responsible for the development of the disease. The family of p21-activated kinases (PAKs) and especially PAK1 appears to mediate many cellular processes that contribute to the development and progression of pancreatic cancer, but the clinical relevance of PAK1 expression with the disease still remains unclear. Aim of the study was to assess the clinical value and the potential prognostic significance of PAK1 in pancreatic adenocarcinoma.

Methods:

We investigated the relationship between the PAK1 expression and the clinical and histopathologic characteristics of pancreatic cancer patients and the potential significance of PAK1 on survival. We examined tissue samples from 51 patients operated for pancreatic cancer. PAK1 expression was investigated with immunohistochemistry and correlated to clinicopathological parameters.

Results:

PAK1 was detected in all tumor samples and high expression was found in most patients. High PAK1 expression was also associated with younger age and well-differentiated tumors, but no association was found between PAK1 expression and Tumor-Node-Metastasis stage as well as deceased or alive status on follow-up. Moderate to high PAK1 expression favored higher 6-month and 1-year survival and low PAK1 expression 2-year survival but without statistical significance.

Conclusions

Our results indicate that PAK1 could potentially be used as a prognostic marker in pancreatic cancer. Further studies could clarify whether utilization of PAK1 in therapeutic protocols for the treatment of pancreatic cancer will render them more effective.

Relevance of small GTPase Rac1 pathway in drug and radio-resistance mechanisms: Opportunities in cancer therapeutics

Rac1 GTPase signaling pathway has a critical role in the regulation of a plethora of cellular functions governing cancer cell behavior. Recently, it has been shown a critical role of Rac1 in the emergence of resistance mechanisms to cancer therapy. This review describes the current knowledge regarding Rac1 pathway deregulation and its association with chemoresistance, radioresistance, resistance to targeted therapies and immune evasion. This supports the idea that interfering Rac1 signaling pathway could be an interesting approach to tackle cancer resistance.

Reactivation of cAMP Pathway by PDE4D Inhibition Represents a Novel Druggable Axis for Overcoming Tamoxifen Resistance in ER-positive Breast Cancer

Purpose: Tamoxifen remains an important hormonal therapy for ER-positive breast cancer; however, development of resistance is a major obstacle in clinics. Here, we aimed to identify novel mechanisms of tamoxifen resistance and provide actionable drug targets overcoming resistance.Experimental Design: Whole-transcriptome sequencing, downstream pathway analysis, and drug repositioning approaches were used to identify novel modulators [here: phosphodiesterase 4D (PDE4D)] of tamoxifen resistance. Clinical data involving tamoxifen-treated patients with ER-positive breast cancer were used to assess the impact of PDE4D in tamoxifen resistance. Tamoxifen sensitization role of PDE4D was tested in vitro and in vivo Cytobiology, biochemistry, and functional genomics tools were used to elucidate the mechanisms of PDE4D-mediated tamoxifen resistance.Results: PDE4D, which hydrolyzes cyclic AMP (cAMP), was significantly overexpressed in both MCF-7 and T47D tamoxifen-resistant (TamR) cells. Higher PDE4D expression predicted worse survival in tamoxifen-treated patients with breast cancer (n = 469, P = 0.0036 for DMFS; n = 561, P = 0.0229 for RFS) and remained an independent prognostic factor for RFS in multivariate analysis (n = 132, P = 0.049). Inhibition of PDE4D by either siRNAs or pharmacologic inhibitors (dipyridamole and Gebr-7b) restored tamoxifen sensitivity. Sensitization to tamoxifen is achieved via cAMP-mediated induction of unfolded protein response/ER stress pathway leading to activation of p38/JNK signaling and apoptosis. Remarkably, acetylsalicylic acid (aspirin) was predicted to be a tamoxifen sensitizer using a drug repositioning approach and was shown to reverse resistance by targeting PDE4D/cAMP/ER stress axis. Finally, combining PDE4D inhibitors and tamoxifen suppressed tumor growth better than individual groups in vivoConclusions: PDE4D plays a pivotal role in acquired tamoxifen resistance via blocking cAMP/ER stress/p38-JNK signaling and apoptosis. Clin Cancer Res; 24(8); 1987-2001. ©2018 AACR.

IGF1R signaling drives antiestrogen resistance through PAK2/PIX activation in luminal breast cancer

Antiestrogen resistance in estrogen receptor positive (ER⁺) breast cancer is associated with increased expression and activity of insulin-like growth factor 1 receptor (IGF1R). Here, a kinome siRNA screen has identified 10 regulators of IGF1R-mediated antiestrogen with clinical significance. These include the tamoxifen resistance suppressors BMPR1B, CDK10, CDK5, EIF2AK1, and MAP2K5, and the tamoxifen resistance inducers CHEK1, PAK2, RPS6KC1, TTK, and TXK. The p21-activated kinase 2, PAK2, is the strongest resistance inducer. Silencing of the tamoxifen resistance inducing genes, particularly PAK2, attenuates IGF1R-mediated resistance to tamoxifen and fulvestrant. High expression of PAK2 in ER⁺ metastatic breast cancer patients is correlated with unfavorable outcome after first-line tamoxifen monotherapy. Phospho-proteomics has defined PAK2 and the PAK-interacting exchange factors PIXα/β as downstream targets of IGF1R signaling, which are independent from PI3K/ATK and MAPK/ERK pathways. PAK2 and PIXα/β modulate IGF1R signaling-driven cell scattering. Targeting PIXα/β entirely mimics the effect of PAK2 silencing on antiestrogen re-sensitization. These data indicate PAK2/PIX as an effector pathway in IGF1R-mediated antiestrogen resistance.

HDAC2 and HDAC5 Up-Regulations Modulate Survivin and miR-125a-5p Expressions and Promote Hormone Therapy Resistance in Estrogen Receptor Positive Breast Cancer Cells

Intrinsic or acquired resistance to hormone therapy is frequently reported in estrogen receptor positive (ER⁺) breast cancer patients. Even though dysregulations of histone deacetylases (HDACs) are known to promote cancer cells survival, the role of different HDACs in the induction of hormone therapy resistance in ER⁺ breast cancer remains unclear. Survivin is a well-known pro-tumor survival molecule and miR-125a-5p is a recently discovered tumor suppressor. In this study, we found that ER⁺, hormone-independent, tamoxifen-resistant MCF7-TamC3 cells exhibit increased expression of HDAC2, HDAC5, and survivin, but show decreased expression of miR-125a-5p, as compared to the parental tamoxifen-sensitive MCF7 breast cancer cells. Molecular down-regulations of HDAC2, HDAC5, and survivin, and ectopic over-expression of miR-125a-5p, increased the sensitivity of MCF7-TamC3 cells to estrogen deprivation and restored the sensitivity to tamoxifen. The same treatments also further increased the sensitivity to estrogen-deprivation in the ER⁺ hormone-dependent ZR-75-1 breast cancer cells in vitro. Kaplan-Meier analysis and receiver operating characteristic curve analysis of expression cohorts of breast tumor showed that high HDAC2 and survivin, and low miR-125a-5p, expression levels correlate with poor relapse-free survival in endocrine therapy and tamoxifen-treated ER⁺ breast cancer patients. Further molecular analysis revealed that HDAC2 and HDAC5 positively modulates the expression of survivin, and negatively regulates the expression miR-125a-5p, in ER⁺ MCF7, MCF7-TamC3, and ZR-75-1 breast cancer cells. These findings indicate that dysregulations of HDAC2 and HDAC5 promote the development of hormone independency and tamoxifen resistance in ERC breast cancer cells in part through expression regulation of survivin and miR-125a-5p.

p21-activated kinase 1 (PAK1) expression correlates with prognosis in solid tumors: A systematic review and meta-analysis

p21 protein (Cdc42/Rac)-activated kinase 1 (PAK1) expression appears to be predictive of prognosis in various solid tumors, though the evidence is not yet conclusive. We therefore performed a meta-analysis to explore the relationship between PAK1 and prognosis in patients with solid tumors. Relevant publications were searched in several widely used databases, and 15 studies (3068 patients) were included in the meta-analysis. Pooled hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated to evaluate the strength of the association between PAK1 and prognosis. Associations between PAK1 expression and prognosis were observed for overall survival (HR = 2.81, 95% CI = 1.07-7.39) and disease-specific survival (HR = 2.15, 95% CI = 1.47-3.16). No such association was detected for time to tumor progression (HR = 1.78, 95% CI = 0.99-3.21).Our meta-analysis thus indicates that PAK1 expression may be a predictive marker of overall survival and disease-specific survival in patients with solid tumors.

ndmaSNF: cancer subtype discovery based on integrative framework assisted by network diffusion model

Recently, with the rapid progress of high-throughput sequencing technology, diverse genomic data are easy to be obtained. To effectively exploit the value of those data, integrative methods are urgently needed. In this paper, based on SNF (Similarity Network Diffusion) [1], we proposed a new integrative method named ndmaSNF (network diffusion model assisted SNF), which can be used for cancer subtype discovery with the advantage of making use of somatic mutation data and other discrete data. Firstly, we incorporate network diffusion model on mutation data to make it smoothed and adaptive. Then, the mutation data along with other data types are utilized in the SNF framework by constructing patient-by-patient similarity networks for each data type. Finally, a fused patient network containing all the information from different input data types is obtained by using a nonlinear iterative method. The fused network can be used for cancer subtype discovery through the clustering algorithm. Experimental results on four cancer datasets showed that our ndmaSNF method can find subtypes with significant differences in the survival profile and other clinical features.

Targeting PAK1

p21-Activated kinase 1 (PAK1) has attracted much attention as a potential therapeutic target due to its central role in many oncogenic signaling pathways, its frequent dysregulation in cancers and neurological disorders, and its tractability as a target for small-molecule inhibition. To date, several PAK1-targeting compounds have been developed as preclinical agents, including one that has been evaluated in a clinical trial. A series of ATP-competitive inhibitors, allosteric inhibitors and peptide inhibitors with distinct biochemical and pharmacokinetic properties represent useful laboratory tools for studies on the role of PAK1 in biology and in disease contexts, and could lead to promising therapeutic agents. Given the central role of PAK1 in vital signaling pathways, future clinical development of PAK1 inhibitors will require careful investigation of their safety and efficacy.

Overexpression of PAK1 Correlates with Aberrant Expression of EMT Markers and Poor Prognosis in Non-Small Cell Lung Cancer

Objective: p21-activated kinases (PAKs) are serine/threonine protein kinases. PAK1 and epithelial-mesenchymal transition (EMT) are key therapeutic targets in cancer. The clinical significance of PAK1 and its potential association with EMT phenotype in non-small cell lung cancer (NSCLC) was investigated. Methods: Immunohistochemistry was used to detect the expression of PAK1, and mesenchymal and epithelial markers (vimentin, N-cadherin, and E-cadherin) in 186 cases of NSCLC tissues and 50 cases of tumor-adjacent normal tissues. The correlation of PAK1 with the clinicopathological characteristics, prognosis, and mesenchymal and epithelial markers in NSCLC were analyzed. Results: Compared with the non-tumor tissues, PAK1, vimentin, and N-cadherin levels were markedly elevated in NSCLC tissues, whereas the E-cadherin levels were significantly decreased (P<0.05). The aberrant expression of PAK1 was significantly associated with TNM stage and metastasis (P<0.001). Patients who displayed high expression of PAK1 may achieve a poorer progression-free survival (PFS) and overall survival (OS), compared to those with low expression of PAK1 (P=0.001 and P<0.001). Univariate and multivariate analysis showed that high expression of PAK1 was an independent predictor of poor prognosis [hazard ratio (HR) =2.121, P<0.001, HR=1.928, P=0.001, respectively]. In addition, significant correlations were observed between the EMT markers and OS or PFS (P<0.01). Interestingly, PAK1 expression was positively correlated with vimentin and N-cadherin levels (r=0.473, P<0.001; r=0.526, P<0.001, respectively) and negatively correlated with E-cadherin levels (r=-0.463, P<0.001) in NSCLC tissues. Conclusion: PAK1 may promote NSCLC progression and metastasis through EMT, thereby exhibiting the potential of an efficient prognostic predictor in NSCLC patients.

Structure, biochemistry, and biology of PAK kinases

PAKs, p21-activated kinases, play central roles and act as converging junctions for discrete signals elicited on the cell surface and for a number of intracellular signaling cascades. PAKs phosphorylate a vast number of substrates and act by remodeling cytoskeleton, employing scaffolding, and relocating to distinct subcellular compartments. PAKs affect wide range of processes that are crucial to the cell from regulation of cell motility, survival, redox, metabolism, cell cycle, proliferation, transformation, stress, inflammation, to gene expression. Understandably, their dysregulation disrupts cellular homeostasis and severely impacts key cell functions, and many of those are implicated in a number of human diseases including cancers, neurological disorders, and cardiac disorders. Here we provide an overview of the members of the PAK family and their current status. We give special emphasis to PAK1 and PAK4, the prototypes of groups I and II, for their profound roles in cancer, the nervous system, and the heart. We also highlight other family members. We provide our perspective on the current advancements, their growing importance as strategic therapeutic targets, and our vision on the future of PAKs.

p21-activated kinase group II small compound inhibitor GNE-2861 perturbs estrogen receptor alpha signaling and restores tamoxifen-sensitivity in breast cancer cells

Estrogen receptor alpha (ERα) is highly expressed in most breast cancers. Consequently, ERα modulators, such as tamoxifen, are successful in breast cancer treatment, although tamoxifen resistance is commonly observed. While tamoxifen resistance may be caused by altered ERα signaling, the molecular mechanisms regulating ERα signaling and tamoxifen resistance are not entirely clear. Here, we found that PAK4 expression was consistently correlated to poor patient outcome in endocrine treated and tamoxifen-only treated breast cancer patients. Importantly, while PAK4 overexpression promoted tamoxifen resistance in MCF-7 human breast cancer cells, pharmacological treatment with a group II PAK (PAK4, 5, 6) inhibitor, GNE-2861, sensitized tamoxifen resistant MCF-7/LCC2 breast cancer cells to tamoxifen. Mechanistically, we identified a regulatory positive feedback loop, where ERα bound to the PAK4 gene, thereby promoting PAK4 expression, while PAK4 in turn stabilized the ERα protein, activated ERα transcriptional activity and ERα target gene expression. Further, PAK4 phosphorylated ERα-Ser305, a phosphorylation event needed for the PAK4 activation of ERα-dependent transcription. In conclusion, PAK4 may be a suitable target for perturbing ERα signaling and tamoxifen resistance in breast cancer patients.

PAK1 confers chemoresistance and poor outcome in non-small cell lung cancer via β-catenin-mediated stemness

PAK1 confers resistance to the estrogen antagonist tamoxifen in breast cancer. However, a role for PAK1 remains to be elucidated for chemoresistance and prognosis in non-small cell lung cancer (NSCLC). We provide evidence that PAK1 confers cisplatin resistance by increasing β-catenin expression through ERK/GSK3β signaling. The increased β-catenin expression promotes sphere cell formation and expression of stemness markers and this β-catenin-induced stemness is responsible for PAK1-mediated cisplatin resistance. We enrolled 87 NSCLC patients who had received cisplatin-based chemotherapy to confirm the association between PAK1 expression and response to chemotherapy and outcomes. PAK1 expression, evaluated by immunohistochemistry, was positively correlated with pERK and β-catenin expression in lung tumors. Patients with high-PAK1, high-pERK, and high-nuclear β-catenin tumors more frequently showed an unfavorable response to cisplatin-based chemotherapy when compared to their counterparts. Kaplan-Meier and Cox regression analysis also indicated a poorer overall survival (OS) and relapse free survival (RFS) in patients with high-PAK1, high-pERK, and high-nuclear β-catenin tumors. In conclusion, PAK1 confers cisplatin resistance in NSCLC via β-catenin-mediated stemness. Therefore, we suggest that clinical use of a combination of the MEK/ERK inhibitor AZD6244 and cisplatin might improve sensitivity to cisplatin-based chemotherapy and outcomes in NSCLC patients who harbor high-PAK1-expressing tumors.

Prolactin-induced PAK1 tyrosyl phosphorylation promotes FAK dephosphorylation, breast cancer cell motility, invasion and metastasis

BACKGROUND

The serine/threonine kinase PAK1 is an important regulator of cell motility. Both PAK1 and the hormone/cytokine prolactin (PRL) have been implicated in breast cancer cell motility, however, the exact mechanisms guiding PRL/PAK1 signaling in breast cancer cells have not been fully elucidated. Our lab has previously demonstrated that PRL-activated tyrosine kinase JAK2 phosphorylates PAK1 on tyrosines 153, 201, and 285, and that tyrosyl phosphorylated PAK1 (pTyr-PAK1) augments migration and invasion of breast cancer cells.

RESULTS

Here we further investigate the mechanisms by which pTyr-PAK1 enhances breast cancer cell motility in response to PRL. We demonstrate a distinct reduction in PRL-induced FAK auto-phosphorylation in T47D and TMX2-28 breast cancer cells overexpressing wild-type PAK1 (PAK1 WT) when compared to cells overexpressing either GFP or phospho-tyrosine-deficient mutant PAK1 (PAK1 Y3F). Furthermore, pTyr-PAK1 phosphorylates MEK1 on Ser298 resulting in subsequent ERK1/2 activation. PRL-induced FAK auto-phosphorylation is rescued in PAK1 WT cells by inhibiting tyrosine phosphatases and tyrosine phosphatase inhibition abrogates cell motility and invasion in response to PRL. siRNA-mediated knockdown of the tyrosine phosphatase PTP-PEST rescues FAK auto-phosphorylation in PAK1 WT cells and reduces both cell motility and invasion. Finally, we provide evidence that PRL-induced pTyr-PAK1 stimulates tumor cell metastasis in vivo.

CONCLUSION

These data provide insight into the mechanisms guiding PRL-mediated breast cancer cell motility and invasion and highlight a significant role for pTyr-PAK1 in breast cancer metastasis.

Potential biomarker panels in overall breast cancer management: advancements by multilevel diagnostics

Breast cancer (BC) prevalence has reached an epidemic scale with half a million deaths annually. Current deficits in BC management include predictive and preventive approaches, optimized screening programs, individualized patient profiling, highly sensitive detection technologies for more precise diagnostics and therapy monitoring, individualized prediction and effective treatment of BC metastatic disease. To advance BC management, paradigm shift from delayed to predictive, preventive and personalized medical services is essential. Corresponding step forwards requires innovative multilevel diagnostics procuring specific panels of validated biomarkers. Here, we discuss current instrumental advancements including genomics, proteomics, epigenetics, miRNA, metabolomics, circulating tumor cells and cancer stem cells with a focus on biomarker discovery and multilevel diagnostic panels. A list of the recommended biomarker candidates is provided.

The Group I Pak inhibitor Frax-1036 sensitizes 11q13-amplified ovarian cancer cells to the cytotoxic effects of Rottlerin

The p21-activated kinases (PAKs) are Cdc42/Rac-activated serine-threonine protein kinases that regulate several key cancer-relevant signaling pathways, such as the Mek/Erk, PI3K/Akt, and Wnt/β-catenin cascades. Pak1 is frequently overexpressed and/or hyperactivated in different human cancers, including breast, ovary, prostate, and brain cancer. PAK1 genomic amplification at 11q13 is the most common mechanism of Pak1 hyperactivation, though Pak1 mRNA and/or protein may be overexpressed in the absence of gene amplification. In previous in vitro and in vivo studies we have shown that ovarian cancer cells with amplified/overexpressed Pak1 were significantly more sensitive to pharmacologic inhibition of Pak1 compared to cells without 11q13 amplification. In the present study we examined if additional signaling pathways might be targeted in tandem with the Group I Pak inhibitor Frax-1036 in ovarian cancer cells. Using the ICCB Known Bioactives Library, we found that the cytotoxic effect of Frax-1036 was significantly higher in combination with the PKCδ inhibitor, Rottlerin, suggesting that Pak inhibitors might be combined with other agents to treat 11q13-amplified ovarian cancer.

Systematic drug screening reveals specific vulnerabilities and co-resistance patterns in endocrine-resistant breast cancer

Background

The estrogen receptor (ER) inhibitor tamoxifen reduces breast cancer mortality by 31 % and has served as the standard treatment for ER-positive breast cancers for decades. However, 50 % of advanced ER-positive cancers display de novo resistance to tamoxifen, and acquired resistance evolves in 40 % of patients who initially respond. Mechanisms underlying resistance development remain poorly understood and new therapeutic opportunities are urgently needed. Here, we report the generation and characterization of seven tamoxifen-resistant breast cancer cell lines from four parental strains.

Methods

Using high throughput drug sensitivity and resistance testing (DSRT) with 279 approved and investigational oncology drugs, exome-sequencing and network analysis, we for the first time, systematically determine the drug response profiles specific to tamoxifen resistance.

Results

We discovered emerging vulnerabilities towards specific drugs, such as ERK1/2-, proteasome- and BCL-family inhibitors as the cells became tamoxifen-resistant. Co-resistance to other drugs such as the survivin inhibitor YM155 and the chemotherapeutic agent paclitaxel also occurred.

Conclusion

This study indicates that multiple molecular mechanisms dictate endocrine resistance, resulting in unexpected vulnerabilities to initially ineffective drugs, as well as in emerging co-resistances. Thus, combatting drug-resistant tumors will require patient-tailored strategies in order to identify new drug vulnerabilities, and to understand the associated co-resistance patterns.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2452-5) contains supplementary material, which is available to authorized users.

LSD1 engages a corepressor complex for the activation of the estrogen receptor α by estrogen and cAMP

The estrogen receptor α (ERα) is a transcription factor that can be directly activated by estrogen or indirectly by other signaling pathways. We previously reported that activation of the unliganded ERα by cAMP is mediated by phosphorylation of the transcriptional coactivator CARM1 by protein kinase A (PKA), allowing CARM1 to bind ERα directly. This being insufficient by itself to activate ERα, we looked for additional factors and identified the histone H3 demethylase LSD1 as a substrate of PKA and an important mediator of this signaling crosstalk as well as of the response to estrogen. Surprisingly, ERα engages not only LSD1, but its partners of the CoREST corepressor complex and the molecular chaperone Hsp90. The recruitment of Hsp90 to promote ERα transcriptional activity runs against the steroid receptor paradigm and suggests that it might be involved as an assembly factor or scaffold. In a breast cancer cell line, which is resistant to the anti-estrogen tamoxifen because of constitutively activated PKA, some interactions are constitutive and drug combinations partially rescue tamoxifen sensitivity. In ERα-positive breast cancer patients, high expression of the genes encoding some of these factors correlates with poor prognosis. Thus, these mechanisms might contribute to ERα-driven breast cancer.

Pak1, adjuvant tamoxifen therapy, and breast cancer recurrence risk in a Danish population-based study

Background Adjuvant tamoxifen therapy approximately halves the risk of estrogen receptor-positive (ER+) breast cancer recurrence, but many women do not respond to therapy. Observational studies nested in clinical trial populations suggest that overexpression or nuclear localization of p21-activated kinase 1 (Pak1) in primary tumors predicts tamoxifen failure. Material and methods We measured the association between Pak1 expression and breast cancer recurrence in a Danish population-based case-control study. Pak1 cytoplasmic expression level and nuclear positivity were determined by immunohistochemical staining of primary breast tumors from recurrence cases and matched controls from two breast cancer populations; women diagnosed with ER-positive tumors who received at least one year of tamoxifen therapy (ER+/TAM+), and women diagnosed with ER-negative tumors who survived for at least one year (ER-/TAM-). Pak1 staining was assessed by a single, blinded pathologist, and associations were estimated with conditional logistic regression models. Results We included 541 recurrence cases and 1:1 matched controls from the ER+/TAM + group and 300 recurrence cases and 1:1 matched controls from the ER-/TAM - group. Pak1 cytoplasmic intensity was not associated with breast cancer recurrence in either group (ER+/TAM + ORadj for strong vs. no cytoplasmic staining = 0.91, 95% CI 0.57, 1.5; ER-/TAM - ORadj for strong vs. no cytoplasmic staining = 0.74, 95% CI 0.39, 1.4). Associations between Pak1 nuclear positivity and breast cancer recurrence were similarly near null in both groups. Conclusion Pak1 positivity in primary breast tumors was neither predictive nor prognostic in this prospective, population-based study.

Potential role of p21 Activated Kinase 1 (PAK1) in the invasion and motility of oral cancer cells

BACKGROUND

Oral cancer malignancy consists of uncontrolled division of cells primarily in and around the floor of the oral cavity, gingiva, oropharynx, lower lip and base of the tongue. According to GLOBOCAN 2012 report, oral cancer is one of the most common cancers among males and females in India. Even though significant advancements have been made in the field of oral cancer treatment modalities, the overall prognosis for the patients has not improved in the past few decades and hence, this demands a new thrust for the identification of novel therapeutic targets in oral cancer. p21 Activated Kinases (PAKs) are potential therapeutic targets that are involved in numerous physiological functions. PAKs are serine-threonine kinases and they serve as important regulators of cytoskeletal dynamics and cell motility, transcription through MAP kinase cascades, death and survival signalling, and cell-cycle progression. Although PAKs are known to play crucial roles in cancer progression, the role and clinical significance of PAKs in oral cancer remains poorly understood.

RESULTS

Our results suggest that PAK1 is over-expressed in oral cancer cell lines. Stimulation of Oral Squamous Cell Carcinoma (OSCC) cells with serum growth factors leads to PAK1 re-localization and might cause a profound cytoskeletal remodelling. PAK1 was also found to be involved in the invasion, migration and cytoskeletal remodelling of OSCC cells.

CONCLUSIONS

Our study revealed that PAK1 may play a crucial role in the progression of OSCC. Studying the role of PAK1 and its substrates is likely to enhance our understanding of oral carcinogenesis and potential therapeutic value of PAKs in oral cancer.

PAK1 Is a Novel Therapeutic Target in Tyrosine Kinase Inhibitor-Resistant Lung Adenocarcinoma Activated by the PI3K/AKT Signaling Regardless of EGFR Mutation

PURPOSE

EGFR mutation as a biomarker has documented that EGFR-mutant patients will derive clinical benefit from tyrosine kinase inhibitor (TKI) treatment. Unfortunately, most patients show TKI resistance and tumor recurrence after therapy. Therefore, we expected that an adjuvant biomarker other than EGFR mutation is needed for predicting TKI resistance.

EXPERIMENTAL DESIGN

Molecular manipulations were performed to verify whether TKI resistance mediated by p21-activated kinase (PAK1) could be through increasing Mcl-1 protein stability via the PI3K/AKT/C/EBP-β/miR-145 cascade. Xenograft mouse models were used to confirm the mechanistic action of PAK1 on TKI resistance. Forty-six tumor tissues from patients with lung adenocarcinoma who received TKI therapy were collected to evaluate PAK1 and E-cadherin mRNA expressions by real-time PCR. The association of PAK1 and E-cadherin mRNA expressions with tumor response to TKI treatment and outcomes was evaluated.

RESULTS

We demonstrate that PAK1 confers TKI resistance in EGFR-mutant cells as well as in EGFR-wild-type cells. Mechanistically, the positive feedback loop of PAK1/PI3K/AKT/C/EBP-β/miR-145 cascades persistently activates the PI3K/AKT signaling pathway to protect Mcl-1 degradation by Fbw7, which results, in turn, in TKI resistance and cell invasion via epithelial-to-mesenchymal transition due to a decrease in E-cadherin expression. The mechanism underlying the cell model is further confirmed in xenograft tumors. Among patients, high-PAK1 or low-E-cadherin tumors more commonly exhibited an unfavorable response to TKI and poorer outcome compared with low-PAK1 or low-E-cadherin tumors.

CONCLUSIONS

The combination of TKI with AKT inhibitor might confer TKI sensitivity and in turn improve outcomes in patients with lung adenocarcinoma who harbored high PAK1 mRNA-expressing tumors. Clin Cancer Res; 22(21); 5370-82. ©2016 AACR.

Myricetin suppresses p21-activated kinase 1 in human breast cancer MCF-7 cells through downstream signaling of the β-catenin pathway

As a main active compound in the bark of waxberry (Myrica rubra), myricetin is a macrocyclic diarylheptanoid, and can trigger the apoptosis of HeLa and PC3 cells. The aim of the present study was to elucidate the anticancer effect of myricetin on human breast cancer MCF-7 cells and to explore the possible mechanisms of action. MCF-7 cells were treated with different concentrations of myricetin (0-80 µM) for 12, 24 and 48 h. In the present study, we found that myricetin suppressed the cell viability of the MCF-7 cells at least partly through the induction of apoptosis as determined by MTT assay and flow cytometry. Western blot analysis revealed that myricetin effectively suppressed the protein expression of p21-activated kinase 1 (PAK1), MEK and phosphorylated extracellular mitogen-activated protein kinase (ERK1/2). In addition, treatment of myricetin activated glycogen synthase kinase-3β (GSK3β) and Bax protein expression, and inhibited β-catenin/cyclin D1/proliferating cell nuclear antigen (PCNA)/survivin and promoted caspase-3 activity in the MCF-7 cells. These results demonstrated that myricetin suppressed the cell viability of human breast cancer MCF-7 cells through PAK1/MEK/ERK/GSK3β/β-catenin/cyclin D1/PCNA/survivin/Bax-caspase-3 signaling.