Dysregulation of PAK1 Is Associated with DNA Damage and Is of Prognostic Importance in Primary Esophageal Small Cell Carcinoma

Circ_0023990 Promotes the Proliferation, Invasion, and Glycolysis of Esophageal Squamous Cell Carcinoma Cells Via Targeting miR-6884-5p/PAK1 Axis

Circular RNAs are emerging players in human cancers, including esophageal squamous cell carcinoma (ESCC). Herein, we assessed the expression level of circ_0023990 and explored the molecular mechanisms of circ_0023990 in ESCC. circ_0023990, miR-6884-5p, and PAK1 expressions in ESCC tissues and cells were detected by quantitative real-time polymerase chain reaction and western blot. ESCC cells were transfected with different constructs to alter the expression of circ_0023990, miR-6884-5p, and PAK1. The effect of circ_0023990 on the proliferation, invasion, and glycolysis of ESCC cells was observed. The interaction between circ_0023990 and miR-6884-5p and between miR-6884-5p and PAK1 were explored. A mouse model of ESCC was established to study the in vivo effect of circ_0023990 knockdown on tumor formation.The expression levels of circ_0023990 was upregulated in ESCC tissues and cells. Inhibiting circ_0023990 suppressed the proliferation, invasion, and glycolysis of ESCC cells. circ_0023990 might target miR-6884-5p and consequently modulate the expression and activity of PAK1. Knockdown of circ_0023990 led to significantly reduced tumor volume and weight in mice with ESCC.These findings overall suggest an oncogenic role of circ_0023990 in ESCC. Future research is warranted to confirm the expression pattern and clinical significance of circ_0023990 in ESCC.

GTPases, genome, actin: A hidden story in DNA damage response and repair mechanisms

The classical small Rho GTPase (Rho, Rac, and Cdc42) protein family is mainly responsible for regulating cell motility and polarity, membrane trafficking, cell cycle control, and gene transcription. Cumulative recent evidence supports important roles for these proteins in the maintenance of genomic stability. Indeed, DNA damage response (DDR) and repair mechanisms are some of the prime biological processes that underlie several disease phenotypes, including genetic disorders, cancer, senescence, and premature aging. Many reports guided by different experimental approaches and molecular hypotheses have demonstrated that, to some extent, direct modulation of Rho GTPase activity, their downstream effectors, or actin cytoskeleton regulation contribute to these cellular events. Although much attention has been paid to this family in the context of canonical actin cytoskeleton remodeling, here we provide a contextualized review of the interplay between Rho GTPase signaling pathways and the DDR and DNA repair signaling components. Interesting questions yet to be addressed relate to the spatiotemporal dynamics of this collective response and whether it correlates with different subcellular pools of Rho GTPases. We highlight the direct and indirect targets, some of which still lack experimental validation data, likely associated with Rho GTPase activation that provides compelling evidence for further investigation in DNA damage-associated events and with potential therapeutic applications in translational medicine.

Blockage of PAK1 alleviates the proliferation and invasion of NSCLC cells via inhibiting ERK and AKT signaling activity

PURPOSE

P21-activated kinase 1 (PAK1), a serine/threonine protein kinase which functions downstream of RAC and CDC42 GTPase, is activated by a variety of stimuli, including RAS and other growth signaling factors. The extracellular signal kinase (ERK) and protein kinase B (AKT) signal pathways have been implicated in the pathogenesis of cancers. Whether PAK1 is sensitive to KRAS mutation signals and plays a role through ERK and AKT signaling pathways in NSCLC needs to be studied.

METHODS

The expression of PAK1, ERK and AKT was detected in both lung cancer cell lines and clinical samples. PAK1 RNA interference and specific inhibitor of PAK1(IPA-3) were applied to lung cancer cell lines and mouse xenograft tumors. Cell growth was measured by MTT and colony formation assays. Cell migration and invasion were detected by wound healing and transwell assays. RAS mutation was detected by Taqman probe method. Correlation between KRAS, PAK1, ERK and AKT activities was analyzed in lung cancer patients.

RESULTS

PAK1 was highly expressed not only in RAS mutant but also in RAS wild-type lung cancer cells. Using specific inhibitor of PAK1, IPA-3 and PAK1 RNA interference, cell proliferation, migration and invasion of lung cancer cells were reduced significantly, accompanied by decreased activities of ERK and AKT. Dual inhibition of ERK and AKT suppressed these cellular processes to levels comparable to those achieved by reduction in PAK1 expression. In NSCLC patients, PAK1 was not correlated with KRAS mutation but was significantly positively correlated with pERK and pAKT.

CONCLUSION

PAK1 played roles in NSCLC proliferation and invasion via ERK and AKT signaling and suggested a therapeutic target for NSCLC.

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.

Epigenetic Alterations in Oesophageal Cancer: Expression and Role of the Involved Enzymes

Oesophageal cancer is a life-threatening disease, accounting for high mortality rates. The poor prognosis of this malignancy is mostly due to late diagnosis and lack of effective therapies for advanced disease. Epigenetic alterations may constitute novel and attractive therapeutic targets, owing to their ubiquity in cancer and their reversible nature. Herein, we offer an overview of the most important studies which compared differences in expression of enzymes that mediate epigenetic alterations between oesophageal cancer and normal mucosa, as well as in vitro data addressing the role of these genes/proteins in oesophageal cancer. Furthermore, The Cancer Genome Atlas database was interrogated for the correlation between expression of these epigenetic markers and standard clinicopathological features. We concluded that most epigenetic players studied thus far are overexpressed in tumours compared to normal tissue. Furthermore, functional assays suggest an oncogenic role for most of those enzymes, supporting their potential as therapeutic targets in oesophageal cancer.

Primary small cell carcinoma of the esophagus: progression in the last decade

Primary small cell carcinoma of the esophagus (PSCCE) is a highly malignant tumor that is diagnosed by endoscopic biopsy and immunohistochemistry. Because of its low incidence, a high degree of malignancy, and rapid progress, it is difficult to conduct large, randomized controlled trials and to establish a standard treatment plan for this disease. In recent years, several retrospective studies have been reported, and with the rise of emerging therapies, PSCCE has gradually become a focus of thoracic surgery. This paper reviews progress in the diagnosis and treatment of PSCCE in recent years.

Systemic analysis of the expression and prognostic significance of PAKs in breast cancer

PAKs (p21-activated kinases) are reported to play crucial roles in a variety of cellular processes and participate in the progression of human cancers. However, the expression and prognostic values of PAKs remain poorly explored in breast cancers. In our study, we examined the mRNA and protein expression levels of PAKs and the prognostic value. We also analyzed the interaction network, genetic alteration, and functional enrichment of PAKs. The results showed that the mRNA levels of PAK1, PAK2, PAK4 and PAK6 were significantly up-regulated in breast cancer compared with normal tissues, while the reverse trend for PAK3 and PAK5 was found, furthermore, the proteins expression of PAK1, PAK2 and PAK4 in breast cancer tissues were higher than that in normal breast tissues. Survival analysis revealed breast cancer patients with low mRNA expression of PAK3 and PAK5 showed worse RFS, conversely, elevated PAK4 levels predicted worse RFS. In addition, the breast cancer patients with PAKs genetic alterations correlated with worse OS. These results indicated that PAKs might be promising potential biomarkers for breast cancer.

Tumor-Infiltrating Immune Cells and PD-L1 as Prognostic Biomarkers in Primary Esophageal Small Cell Carcinoma

Primary esophageal small cell carcinoma (PESCC) is a weakly prevalent but lethal malignancy with early metastasis and a poor prognosis. Currently, neither effective prognostic indicators nor curative therapies are available for PESCC. Immunotherapy has now evolved into one of the most promising therapies for cancer patients. Tumor-infiltrating immune cells which are integral to the tumor immune microenvironment (TIME) are recognized as highly important for prognosis prediction, while the responsiveness to immune checkpoint blockade may be subject to the features of TIME. In this study, we aim to identify the TIME and provide indication for the applicability of immune checkpoint therapy in PESCC. We found that PD-L1 expression was detected in 33.33% (27/81) of all the patients, mostly exhibiting a stroma-only pattern and that it was positively associated with tumor-infiltrating immune cells (CD4⁺, CD8⁺, and CD163⁺). In 74.07% of PD-L1-positive specimens, PD-L1⁺CD163⁺ cells were colocalized more with CD4⁺ than CD8⁺ T cells. 83.95% (68/81) of all the specimens were infiltrated with more CD4⁺ than CD8⁺ T cells. Further analysis showed FoxP3⁺ Tregs constituted 13-27% of the total CD4⁺ T cell population. The Kaplan--Meier analysis indicated several factors that contribute to poor survival, including negative PD-L1 expression, rich CD4 expression, rich FoxP3 expression, a low CD8/CD4 ratio, and a high FoxP3/CD8 ratio. A nomogram model was constructed and showed good performance for survival prediction. These results highlight that a suppressive TIME contributes to poor survival of patients with PESCC. TIME analyses might be a promising approach to evaluate the possibility and effect of immune checkpoint-based immunotherapeutics in PESCC patients.

p-21 Activated Kinase as a Molecular Target for Chemoprevention in Diabetes

Hypothesis: Anti-diabetic drugs modulate p-21 activated kinase (PAK) signaling. Introduction: Type 2 diabetes mellitus (T2DM) is a chronic inflammatory disease associated with increased cancer risk. PAK signaling is implicated in cellular homeostasis when regulated, and cancer when unrestrained. Recent reports provided a role for PAK signaling in glucose homeostasis, but the role of PAKs in the pathogenesis of T2DM is unknown. Here, we performed a mini-meta-analysis to explore if anti-diabetic drugs modify PAK signaling pathways, and provide insight regarding modulation of these pathways, to potentially reduce diabetes-associated cancer risk. Methods: PAK interacting partners in T2DM were identified using the online STRING database. Correlation studies were performed via systematic literature review to understand the effect of anti-diabetic drugs on PAK signaling. A mini-meta-analysis correlated multiple clinical studies and revealed the overall clinical response rate and percentage of adverse events in piogliazone (n = 53) and metformin (n = 91) treated patients with PAK-associated diseases. Results: A total of 30 PAK interacting partners were identified (10: reduced beta-cell mass; 10: beta-cell dysfunction; 10: obesity-insulin resistance), which were highly associated with Wnt, and G-protein signaling. The anti-diabetic drug metformin activated signaling pathways upstream; whereas pioglitazone inhibited pathways downstream of PAK. Overall, clinical response upon pioglitazone treatment was 53%. Seventy-nine percent of pioglitazone and 75% of metformin treated patients had adverse events. Pioglitazone reduced molecular-PAK biomarkers of proliferation (Ki67 and CyclinD1), and metformin had the opposite effect. Conclusions: PAK signaling in T2DM likely involves Wnt and G-protein signaling, which may be altered by the anti-diabetic drugs metformin and pioglitazone. Apart from the therapeutic limitations of adverse events, pioglitazone may be promising in chemoprevention. However long-term multi-centered studies, which initiate pioglitazone treatment early will be required to fully assess the full potential of these drugs.

The oncogenic roles of nuclear receptor coactivator 1 in human esophageal carcinoma

Nuclear receptor coactivator 1 (NCOA1) plays crucial roles in the regulation of gene expression mediated by a wide spectrum of steroid receptors such as androgen receptor (AR), estrogen receptor α (ER α), and estrogen receptor β (ER β). Therefore, dysregulations of NCOA1 have been found in a variety of cancer types. However, the clinical relevance and the functional roles of NCOA1 in human esophageal squamous cell carcinoma (ESCC) are less known. We found in this study that elevated levels of NCOA1 protein and/or mRNA as well as amplification of the NCOA1 gene occur in human ESCC. Elevated levels of NCOA1 due to these dysregulations were not only associated with more aggressive clinic-pathologic parameters but also poorer survival. Results from multiple cohorts of ESCC patients strongly suggest that the levels of NCOA1 could serve as an independent predictor of overall survival. In addition, silencing NCOA1 in ESCC cells remarkably decreased proliferation, migration, and invasion. These findings not only indicate that NCOA1 plays important roles in human ESCC but the levels of NCOA1 also could serve as a potential prognostic biomarker of ESCC and targeting NCOA1 could be an efficacious strategy in ESCC treatment.

Identification and Validation of Fibroblast Growth Factor 12 Gene as a Novel Potential Biomarker in Esophageal Cancer Using Cancer Genomic Datasets

Esophageal squamous cell carcinoma (ESCC) has a complex, multifactorial etiology in which environmental, geographical, and genetic factors play major roles. It is the second most common cancer among men and the fourth most common among women in India, with a particularly high prevalence in Northeast India. In this study, an integrative in silico [DAVID, NCG5.0, Oncomine, Cancer Cell Line Encyclopedia, and The Cancer Genome Atlas (TCGA)] approach was used to identify the potential biomarkers by using the available three genomic datasets on ESCC from Northeast India followed by its in vitro functional validation. Fibroblast Growth Factor 12 (FGF12) gene was overexpressed in ESCC. The upregulation of FGF12 was also observed on ESCC of TCGA OncoPrint portal, whereas very low expression of FGF12 gene was mapped in normal esophageal tissue on the GTEx database. Silencing of FGF12 showed significant inhibition in activity of tumor cell proliferation, colony formation, and cell migration. The upregulation of FGF12 showed significantly reduced survival in ESCC patients. The protein interaction analysis of FGF12 found the binding with MAPK8IP2 and MAPK13. High expression of FGF12 along with MAPK8IP2, and MAPK13 proteins correlate with poor survival in ESCC patients. Tissue microarray also showed expression of these proteins in patients with ESCC. These results indicate that FGF12 has a potential role in ESCC and suggest that cancer genomic datasets with application of in silico approaches are instrumental for biomarker discovery research broadly and specifically, for the identification of FGF12 as a putative biomarker in ESCC.

p21 Activated kinase 1: Nuclear activity and its role during DNA damage repair

p21-activated kinase 1 (PAK1) is a serine/threonine kinase activated by the small GTPases Rac1 and Cdc42. It is located in the chromosome 11q13 and is amplified and/or overexpressed in several human cancer types including 25-30% of breast tumors. This enzyme plays a pivotal role in the control of a number of fundamental cellular processes by phosphorylating its downstream substrates. In addition to its role in the cytoplasm, it is well documented that PAK1 also plays crucial roles in the nucleus participating in mitotic events and gene expression through its association and/or phosphorylation of several transcription factors, transcriptional co-regulators and cell cycle-related proteins, including Aurora kinase A (AURKA), polo-like kinase 1 (PLK1), the forkhead transcription factor (FKHR), estrogen receptor α (ERα), and Snail. More recently, PAK signaling has emerged as a component of the DNA damage response (DDR) as PAK1 activity influences the cellular sensitivity to ionizing radiation and promotes the expression of several genes involved in the Fanconi Anemia/BRCA pathway. This review will focus on the nuclear functions of PAK1 and its role in the regulation of DNA damage repair.

Reduced PAK1 activity sensitizes FA/BRCA-proficient breast cancer cells to PARP inhibition

Cells that are deficient in homologous recombination, such as those that have mutations in any of the Fanconi Anemia (FA)/BRCA genes, are hypersensitive to inhibition of poly(ADP-ribose) polymerase (PARP). However, FA/BRCA-deficient tumors represent a small fraction of breast cancers, which might restrict the therapeutic utility of PARP inhibitor monotherapy. The gene encoding the serine-threonine protein kinase p21-activated kinase 1 (PAK1) is amplified and/or overexpressed in several human cancer types including 25-30% of breast tumors. This enzyme controls many cellular processes by phosphorylating both cytoplasmic and nuclear substrates. Here, we show that depletion or pharmacological inhibition of PAK1 down-regulated the expression of genes involved in the FA/BRCA pathway and compromised the ability of cells to repair DNA by Homologous Recombination (HR), promoting apoptosis and reducing colony formation. Combined inhibition of PAK1 and PARP in PAK1 overexpressing breast cancer cells had a synergistic effect, enhancing apoptosis, suppressing colony formation, and delaying tumor growth in a xenograft setting. Because reduced PAK1 activity impaired FA/BRCA function, inhibition of this kinase in PAK1 amplified and/or overexpressing breast cancer cells represents a plausible strategy for expanding the utility of PARP inhibitors to FA/BRCA-proficient cancers.

Growth hormone-releasing hormone receptor antagonists inhibit human gastric cancer through downregulation of PAK1-STAT3/NF-κB signaling

Gastric cancer (GC) ranks as the fourth most frequent in incidence and second in mortality among all cancers worldwide. The development of effective treatment approaches is an urgent requirement. Growth hormone-releasing hormone (GHRH) and GHRH receptor (GHRH-R) have been found to be present in a variety of tumoral tissues and cell lines. Therefore the inhibition of GHRH-R was proposed as a promising approach for the treatment of these cancers. However, little is known about GHRH-R and the relevant therapy in human GC. By survival analyses of multiple cohorts of GC patients, we identified that increased GHRH-R in tumor specimens correlates with poor survival and is an independent predictor of patient prognosis. We next showed that MIA-602, a highly potent GHRH-R antagonist, effectively inhibited GC growth in cultured cells. Further, this inhibitory effect was verified in multiple models of human GC cell lines xenografted into nude mice. Mechanistically, GHRH-R antagonists target GHRH-R and down-regulate the p21-activated kinase 1 (PAK1)-mediated signal transducer and activator of transcription 3 (STAT3)/nuclear factor-κB (NF-κB) inflammatory pathway. Overall, our studies establish GHRH-R as a potential molecular target in human GC and suggest treatment with GHRH-R antagonist as a promising therapeutic intervention for this cancer.

Expression of P21-activated kinase 1 and cell division control protein 42 homolog correlates with clinicopathological features and prognosis in cervical carcinoma

AIM

This study investigated P21-activated kinase 1 (PAK1) and cell division control protein 42 homolog (CDC42) expression and their correlation with clinicopathological features and prognosis in cervical carcinoma.

METHODS

Cervical carcinoma (n = 55), cervical intraepithelial neoplasias (CIN, n = 93), and normal cervix (n = 26) tissues were sampled. PAK1 and CDC42 expressions were determined using real-time quantitative polymerase chain reaction, Western blot and immunohistochemistry. Correlation analysis of PAK1 and CDC42 expression was performed using a Pearson correlation test. Survival rate was calculated using the Kaplan-Meier method. Independent prognostic factors were analyzed by Cox proportional hazard model.

RESULTS

PAK1 and CDC42 expression were positively correlated in all tissues. PAK1 and CDC42 expression in cervical carcinoma tissues were higher than those in normal tissues. PAK1 and CDC42 protein expression in normal cervix, CINI, CINII, CINIII and cervical carcinoma tissues showed a gradually increasing trend. PAK1 and CDC42 expression were correlated with lymph node metastasis, the depth of tumor invasion, the degree of tumor differentiation, histological type and lymphovascular space invasion (LVSI; all P < 0.05). Cox regression analysis showed that the degree of tumor differentiation, PAK1 protein expression, histological type and LVSI are independent risk factors for prognosis of cervical carcinoma.

CONCLUSION

High PAK1 and CDC42 expressions are closely related to the clinicopathological features and poor prognosis of cervical carcinoma, serving as unfavorable prognostic factors.

PAKs in Human Cancer Progression: From Inception to Cancer Therapeutic to Future Oncobiology

Since the initial recognition of a mechanistic role of p21-activated kinase 1 (PAK1) in breast cancer invasion, PAK1 has emerged as one of the widely overexpressed or hyperactivated kinases in human cancer at-large, allowing the PAK family to make in-roads in cancer biology, tumorigenesis, and cancer therapeutics. Much of our current understanding of the PAK family in cancer progression relates to a central role of the PAK family in the integration of cancer-promoting signals from cell membrane receptors as well as function as a key nexus-modifier of complex, cytoplasmic signaling network. Another core aspect of PAK signaling that highlights its importance in cancer progression is through PAK's central role in the cross talk with signaling and interacting proteins, as well as PAK's position as a key player in the phosphorylation of effector substrates to engage downstream components that ultimately leads to the development cancerous phenotypes. Here we provide a comprehensive review of the recent advances in PAK cancer research and its downstream substrates in the context of invasion, nuclear signaling and localization, gene expression, and DNA damage response. We discuss how a deeper understanding of PAK1's pathobiology over the years has widened research interest to the PAK family and human cancer, and positioning the PAK family as a promising cancer therapeutic target either alone or in combination with other therapies. With many landmark findings and leaps in the progress of PAK cancer research since the infancy of this field nearly 20 years ago, we also discuss postulated advances in the coming decade as the PAK family continues to shape the future of oncobiology.