Elevated p21-activated kinase 2 activity results in anchorage-independent growth and resistance to anticancer drug-induced cell death

PAK2 as a therapeutic target in cancer: Mechanisms, challenges, and future perspectives

P21-activated kinases (PAKs) are crucial regulators within cellular signaling pathways and have been implicated in a range of human diseases, including cancer. Among the PAK family, PAK2 is widely expressed across various tissues and has emerged as a significant driver of cancer progression. However, systematic studies on PAK2 remain limited. This review provides a comprehensive overview of PAK2's role in cancer, focusing on its involvement in processes such as angiogenesis, metastasis, cell survival, metabolism, immune response, and drug resistance. We also explore its function in key cancer signaling pathways and the potential of small-molecule inhibitors targeting PAK2 for therapeutic purposes. Despite promising preclinical data, no PAK2 inhibitors have reached clinical practice, underscoring challenges related to their specificity and therapeutic application. This review highlights the biological significance of PAK2 in cancer and its interactions with critical signaling pathways, offering valuable insights for future research. We also discuss the major obstacles in developing PAK inhibitors and propose strategies to overcome these barriers, paving the way for their clinical translation.

Proteomic and Phosphoproteomic Profiling of Matrix Stiffness-Induced Stemness-Dormancy State Transition in Breast Cancer Cells

The dormancy of cancer stem cells is a major factor leading to drug resistance and a high rate of late recurrence and mortality in estrogen receptor-positive (ER+) breast cancer. Previously, we demonstrated that a stiffer matrix induces tumor cell dormancy and drug resistance, whereas a softened matrix promotes tumor cells to exhibit a stem cell state with high proliferation and migration. In this study, we present a comprehensive analysis of the proteome and phosphoproteome in response to gradient changes in matrix stiffness, elucidating the mechanisms behind cell dormancy-induced drug resistance. Overall, we found that antiapoptotic and membrane transport processes may be involved in the mechanical force-induced dormancy resistance of ER+ breast cancer cells. Our research provides new insights from a holistic proteomic and phosphoproteomic perspective, underscoring the significant role of mechanical forces stemming from the stiffness of the surrounding extracellular matrix as a critical regulatory factor in the tumor microenvironment.

The up-regulation of PAK2 indicates unfavorable prognosis in patients with serous epithelial ovarian cancer and contributes to paclitaxel resistance in ovarian cancer cells

BACKGROUND

The main challenge in treating ovarian cancer is chemotherapy resistance. Previous studies have shown that PAK2 is highly expressed in various cancers. This research investigates whether increased PAK2 expression contributes to chemo-resistance and poor prognosis in ovarian cancer.

METHODS

Initially, bioinformatics analysis was used to assess the importance of PAK2 mRNA up-regulation in ovarian cancer. This was then validated using tissue microarray to confirm PAK2 protein expression and localization in clinical samples. Univariate and multivariate logistic regression analyses were carried out to identify potential risk factors for chemo-resistance in serous epithelial ovarian cancer (EOC), while multivariate Cox regression and Kaplan-Meier analysis were conducted to ascertain prognostic factors for overall survival (OS) and disease-free survival (DFS) in patients with serous EOC. In vitro experiments were conducted to verify if inhibiting PAK2 expression could increase A2780/Taxol cells' sensitivity to paclitaxel, as shown by evaluating cell proliferation, apoptosis, transwell, and clone formation. Additionally, the interaction between PAK2, lnc-SNHG1, and miR-216b-5p was verified using RIP and luciferase reporter assays. Rescue experiments were undertaken to examine the influence of the lnc-SNHG1/miR-216b-5p/PAK2 axis on the development of paclitaxel resistance in A2780/Taxol cells.

RESULTS

The bioinformatics analysis indicated a notable increase in PAK2 expression in ovarian malignant tumors compared to adjacent tissues, particularly in patients with stage III-IV disease compared to those with stage I-II disease (P = 0.0056). Elevated levels of PAK2 were linked to reduced OS in ovarian cancer patients, although no significant association was observed with DFS. Immunohistochemistry findings further supported these results, showing positive PAK2 protein expression in chemo-resistant serous EOC tissues, predominantly localized in the cytoplasm, which correlated with poorer OS and DFS outcomes. In vitro experiments demonstrated that the downregulation of PAK2 in A2780/Taxol cells led to a reduction in colony formation, an increase in apoptosis, and a diminished capacity for cell invasion. Subsequent analysis confirmed that lnc-SNHG1 functions as a competitive endogenous RNA (ceRNA) by interacting with miR-216b-5p and regulating PAK2 expression. Rescue experiments demonstrated that lnc-SNHG1 induces resistance to paclitaxel in A2780/Taxol cells by modulating the miR-216b-5p/PAK2 axis.

CONCLUSIONS

PAK2 shows promise as a predictor of chemotherapy resistance and poor outcomes in ovarian cancer, indicating its potential use as a treatment target to overcome this resistance.

Targeting P21-Activated Kinase-1 for Metastatic Prostate Cancer

Metastatic prostate cancer (mPCa) has limited therapeutic options and a high mortality rate. The p21-activated kinase (PAK) family of proteins is important in cell survival, proliferation, and motility in physiology, and pathologies such as infectious, inflammatory, vascular, and neurological diseases as well as cancers. Group-I PAKs (PAK1, PAK2, and PAK3) are involved in the regulation of actin dynamics and thus are integral for cell morphology, adhesion to the extracellular matrix, and cell motility. They also play prominent roles in cell survival and proliferation. These properties make group-I PAKs a potentially important target for cancer therapy. In contrast to normal prostate and prostatic epithelial cells, group-I PAKs are highly expressed in mPCA and PCa tissue. Importantly, the expression of group-I PAKs is proportional to the Gleason score of the patients. While several compounds have been identified that target group-I PAKs and these are active in cells and mice, and while some inhibitors have entered human trials, as of yet, none have been FDA-approved. Probable reasons for this lack of translation include issues related to selectivity, specificity, stability, and efficacy resulting in side effects and/or lack of efficacy. In the current review, we describe the pathophysiology and current treatment guidelines of PCa, present group-I PAKs as a potential druggable target to treat mPCa patients, and discuss the various ATP-competitive and allosteric inhibitors of PAKs. We also discuss the development and testing of a nanotechnology-based therapeutic formulation of group-I PAK inhibitors and its significant potential advantages as a novel, selective, stable, and efficacious mPCa therapeutic over other PCa therapeutics in the pipeline.

Subtype-specific kinase dependency regulates growth and metastasis of poor-prognosis mesenchymal colorectal cancer

BACKGROUND

Colorectal cancer (CRC) can be divided into four consensus molecular subtypes (CMS), each with distinct biological features. CMS4 is associated with epithelial-mesenchymal transition and stromal infiltration (Guinney et al., Nat Med 21:1350-6, 2015; Linnekamp et al., Cell Death Differ 25:616-33, 2018), whereas clinically it is characterized by lower responses to adjuvant therapy, higher incidence of metastatic spreading and hence dismal prognosis (Buikhuisen et al., Oncogenesis 9:66, 2020).

METHODS

To understand the biology of the mesenchymal subtype and unveil specific vulnerabilities, a large CRISPR-Cas9 drop-out screen was performed on 14 subtyped CRC cell lines to uncover essential kinases in all CMSs. Dependency of CMS4 cells on p21-activated kinase 2 (PAK2) was validated in independent 2D and 3D in vitro cultures and in vivo models assessing primary and metastatic outgrowth in liver and peritoneum. TIRF microscopy was used to uncover actin cytoskeleton dynamics and focal adhesion localization upon PAK2 loss. Subsequent functional assays were performed to determine altered growth and invasion patterns.

RESULTS

PAK2 was identified as a key kinase uniquely required for growth of the mesenchymal subtype CMS4, both in vitro and in vivo. PAK2 plays an important role in cellular attachment and cytoskeletal rearrangements (Coniglio et al., Mol Cell Biol 28:4162-72, 2008; Grebenova et al., Sci Rep 9:17171, 2019). In agreement, deletion or inhibition of PAK2 impaired actin cytoskeleton dynamics in CMS4 cells and, as a consequence, significantly reduced invasive capacity, while it was dispensable for CMS2 cells. Clinical relevance of these findings was supported by the observation that deletion of PAK2 from CMS4 cells prevented metastatic spreading in vivo. Moreover, growth in a model for peritoneal metastasis was hampered when CMS4 tumor cells were deficient for PAK2.

CONCLUSION

Our data reveal a unique dependency of mesenchymal CRC and provide a rationale for PAK2 inhibition to target this aggressive subgroup of colorectal cancer.

Combination of PAKs inhibitors IPA-3 and PF-3758309 effectively suppresses colon carcinoma cell growth by perturbing DNA damage response

PURPOSE

PAKs proteins are speculated as new promising targets for cancer therapy due to their central role in many oncogenic pathways. Because PAKs proteins are very significant during carcinogenesis, we aimed to investigate the hypothesis that inhibition of PAKs with IPA-3 and PF-3758309 treatment could synergistically reduce colon carcinoma cell growth.

MATERIALS AND METHODS

The cytotoxic effects of both drugs were determined by a cell viability assay. Cell cycle and apoptosis were analyzed by flow cytometry. The effects of inhibitor drugs on marker genes of apoptosis, autophagy, cell cycle, and DNA damage were tested via immunoblotting.

RESULTS AND CONCLUSIONS

We found out the synergistic effect of these drugs in pair on five colon cancer cell lines. Combined treatment with IPA-3+PF-3758309 in SW620 and Colo 205 cells markedly suppressed colon formation and induced apoptosis, cell cycle arrest, and autophagy compared with treatment with each drug alone. Additionally, this combination sensitized colon cancer cells to ionizing radiation that resulted in inhibition of cell growth.

SIGNIFICANCE

Collectively, our findings show for the first time that cotreatment of IPA-3 with PF-3758309 exhibits superior inhibitory effects on colon carcinoma cell growth via inducing DNA damage-related cell death and also enforces a cell cycle arrest.

Expression of Marker PAK1 in Sinonasal Polyposis

Introduction Chronic rhinosinusitis with nasal polyposis involves mucosal lining of nose and paranasal sinuses. Numerous studies studied the mechanism leading to sinonasal polyposis. We attempted study the inflammatory mechanisms responsible for the recruitment and activation of leukocytes. Aim To study and compare the expression of the immunohistochemistry marker PAK1 in sinonasal polyposis and normal nasal mucosa. Material and Methods Prospective observational study done by comparing two groups of 30 each with Group A comprises Sinonasal polyposis and Group B comprises normal nasal mucosa. The specimens were subjected to PAK1 immunohistochemical staining. Results Immunihistrochemical staining showed higher intensity stain in sinonasal polyp when compared to normal nasal mucosa. Conclusion The upregulation of PAK1 in sinonasal polyposis when compared to normal nasal mucosa may indicate an increased cellular proliferation and turnover in the background of chronic inflammation.

miR-511-5p Suppresses Cell Migration, Invasion and Epithelial-Mesenchymal Transition Through Targeting PAK2 in Gastric Cancer

As a malignant tumor, gastric cancer (GC) is closely related with gastric mucosa and has a high mortality in the world. Since microRNA (miRNA) has become more and more important in tumor research, we intend to find out the functional role and mechanism of miR-511-5p in GC. Firstly, miR-511-5p level was examined in human GC cell lines and tissues, and its effect on cell migration and invasion of BGC-823 or HGC-27 cells was tested by migration assay and transwell assay. Then, we confirmed the association between miR-511-5p and p21 activated kinase 2 (PAK2) by the luciferase reporter assay, and further assessed their role in cell migration and invasion. Moreover, we verified the function of miR-511-5p and PAK2 in epithelial-mesenchymal transition (EMT). In our study, miR-511-5p was downregulated in GC cell lines and tissues, and inversely associated with PAK2. Luciferase reporter assay confirmed that miR-511-5p could bind to PAK2. MiR-511-5p mimics significantly upregulated E-cadherin and downregulated N-cadherin, Vimentin and Snail, and consequently inhibited cell migration and invasion. However, reintroduction of PAK2 reversed the inhibitory function of miR-511-5p on BGC-823 and HGC-27 cells. Our research suggested that tumor-suppressive function of miR-511-5p in GC was inhibited by PAK2, and miR-511-5p/PAK2 axis may serve as a new strategy in GC management.

CDK4/6 inhibition synergizes with inhibition of P21-Activated Kinases (PAKs) in lung cancer cell lines

Theoretically, small molecule CDK4/6 inhibitors (CDK4/6is) represent a logical therapeutic option in non-small cell lung cancers since most of these malignancies have wildtype RB, the key target of CDKs and master regulator of the cell cycle. Unfortunately, CDK4/6is are found to have limited clinical activity as single agents in non-small cell lung cancer. To address this problem and to identify effective CDK4/6i combinations, we screened a library of targeted agents for efficacy in four non-small cell lung cancer lines treated with CDK4/6 inhibitors Palbociclib or Abemaciclib. The pan-PAK (p21-activated kinase) inhibitor PF03758309 emerged as a promising candidate with viability ratios indicating synergy in all 4 cell lines and for both CDK4/6is. It is noteworthy that the PAKs are downstream effectors of small GTPases Rac1 and Cdc42 and are overexpressed in a wide variety of cancers. Individually the compounds primarily induced cell cycle arrest; however, the synergistic combination induced apoptosis, accounting for the synergy. Surprisingly, while the pan-PAK inhibitor PF03758309 synergizes with CDK4/6is, no synergy occurs with group I PAK inhibitors FRAX486 or FRAX597. Cell lines treated only with Ribociclib, FRAX486 or FRAX597 underwent G1/G0 arrest, whereas combination treatment with these compounds predominantly resulted in autophagy. Combining high concentrations of FRAX486, which weakly inhibits PAK4, and Ribociclib, mimics the autophagy and apoptotic effect of PF03758309 combined with Ribociclib. FRAX597, a PAKi that does not inhibit PAK4 did not reduce autophagy in combination with Ribociclib. Our results suggest that a unique combination of PAKs plays a crucial role in the synergy of PAK inhibitors with CDK4/6i. Targeting this unique PAK combination, could greatly improve the efficacy of CDK4/6i and broaden the spectrum of cancer treatment.

Investigating the response of paediatric leukaemia-propagating cells to BCL-2 inhibitors

Relapse of paediatric acute lymphoblastic leukaemia (ALL) may occur due to persistence of resistant cells with leukaemia‐propagating ability (LPC). In leukaemia, the balance of B‐cell lymphoma‐2 (BCL‐2) family proteins is disrupted, promoting survival of malignant cells and possibly LPC. A direct comparison of BCL‐2 inhibitors, navitoclax and venetoclax, was undertaken on LPC subpopulations from B‐cell precursor (BCP) and T‐cell ALL (T‐ALL) cases in vitro and in vivo. Responses were compared to BCL‐2 levels detected by microarray analyses and Western blotting. In vitro, both drugs were effective against most BCP‐ALL LPC, except CD34⁻/CD19⁻ cells. In contrast, only navitoclax was effective in T‐ALL and CD34⁻/CD7⁻ LPC were resistant to both drugs. In vivo, navitoclax was more effective than venetoclax, significantly improving survival of mice engrafted with BCP‐ and T‐ALL samples. Venetoclax was not particularly effective against T‐ALL cases in vivo. The proportions of CD34⁺/CD19⁻, CD34⁻/CD19⁻ BCP‐ALL cells and CD34⁻/CD7⁻ T‐ALL cells increased significantly following in vivo treatment. Expression of pro‐apoptotic BCL‐2 genes was lower in these subpopulations, which may explain the lack of sensitivity. These data demonstrate that some LPC were resistant to BCL‐2 inhibitors and sustained remission will require their use in combination with other therapeutics.

PAK2 activated by Cdc42 and caspase 3 mediates different cellular responses to oxidative stress-induced apoptosis

p21-activated protein kinase (PAK2) is a unique member of the PAK family kinases that plays important roles in stress signaling. It can be activated by binding to the small GTPase, Cdc42 and Rac1, or by caspase 3 cleavage. Cdc42-activated PAK2 mediates cytostasis, whereas caspase 3-cleaved PAK2 contributes to apoptosis. However, the relationship between these two states of PAK2 activation remains elusive. In this study, through protein biochemical analyses and various cell-based assays, we demonstrated that full-length PAK2 activated by Cdc42 was resistant to the cleavage by caspase 3 in vitro and within cells. When mammalian cells were treated by oxidative stress using hydrogen peroxide, PAK2 was highly activated through caspase 3 cleavage that led to apoptosis. However, when PAK2 was pre-activated by Cdc42 or by mild stress such as serum deprivation, it was no longer able to be cleaved by caspase 3 upon hydrogen peroxide treatment, and the subsequent apoptosis was also largely inhibited. Furthermore, cells expressing active mutants of full-length PAK2 became more resistant to hydrogen peroxide-induced apoptosis than inactive mutants. Taken together, this study identified two states of PAK2 activation, wherein Cdc42- and autophosphorylation-dependent activation inhibited the constitutive activation of PAK2 by caspase cleavage. The regulation between these two states of PAK2 activation provides a new molecular mechanism to support PAK2 as a molecular switch for controlling cytostasis and apoptosis in response to different types and levels of stress with broad physiological and pathological relevance.

PAK1, PAK1Δ15, and PAK2: similarities, differences and mutual interactions

P21-activated kinases (PAK) are key effectors of the small GTPases Rac1 and Cdc42, as well as of Src family kinases. In particular, PAK1 has several well-documented roles, both kinase-dependent and kinase-independent, in cancer-related processes, such as cell proliferation, adhesion, and migration. However, PAK1 properties and functions have not been attributed to individual PAK1 isoforms: besides the full-length kinase (PAK1-full), a splicing variant lacking the exon 15 (PAK1Δ15) is annotated in protein databases. In addition, it is not clear if PAK1 and PAK2 are functionally overlapping. Using fluorescently tagged forms of human PAK1-full, PAK1Δ15, and PAK2, we analyzed their intracellular localization and mutual interactions. Effects of PAK inhibition (IPA-3, FRAX597) or depletion (siRNA) on cell-surface adhesion were monitored by real-time microimpedance measurement. Both PAK1Δ15 and PAK2, but not PAK1-full, were enriched in focal adhesions, indicating that the C-terminus might be important for PAK intracellular localization. Using coimmunoprecipitation, we documented direct interactions among the studied PAK group I members: PAK1 and PAK2 form homodimers, but all possible heterocomplexes were also detected. Interaction of PAK1Δ15 or PAK2 with PAK1-full was associated with extensive PAK1Δ15/PAK2 cleavage. The impedance measurements indicate, that PAK2 depletion slows down cell attachment to a surface, and that PAK1-full is involved in cell spreading. Altogether, our data suggest a complex interplay among different PAK group I members, which have non-redundant functions.

PAK2 links cell survival to mechanotransduction and metabolism

Campbell et al. show that force stimulates PAK2 activation at cell–cell junctions, where it protects cells under force from death and plays a key role in linking force-induced mechanotransduction, metabolism, and cell survival.

Too little or too much force can trigger cell death, yet factors that ensure the survival of cells remain largely unknown. Here, we demonstrate that E-cadherin responds to force by recruiting and activating p21-activated protein kinase 2 (PAK2) to allow cells to stiffen, metabolize, and survive. Interestingly, PAK2 activation and its control of the apoptotic response are specific for the amplitude of force applied. Specifically, under low amplitudes of physiological force, PAK2 is protected from proteolysis, thereby ensuring cell survival. In contrast, under higher amplitudes of physiological force, PAK2 is left unprotected and stimulates apoptosis, an effect that is prevented by cleavage-resistant forms of the protein. Finally, we demonstrate that PAK2 protection is conferred by direct binding of AMPK. Thus, PAK2 mediates the survival of cells under force. These findings reveal an unexpected paradigm for how mechanotransduction, metabolism, and cell survival are linked.

Focus on Cdc42 in Breast Cancer: New Insights, Target Therapy Development and Non-Coding RNAs

Breast cancer is the most common malignant tumors in females. Although the conventional treatment has demonstrated a certain effect, some limitations still exist. The Rho guanosine triphosphatase (GTPase) Cdc42 (Cell division control protein 42 homolog) is often upregulated by some cell surface receptors and oncogenes in breast cancer. Cdc42 switches from inactive guanosine diphosphate (GDP)-bound to active GTP-bound though guanine-nucleotide-exchange factors (GEFs), results in activation of signaling cascades that regulate various cellular processes such as cytoskeletal changes, proliferation and polarity establishment. Targeting Cdc42 also provides a strategy for precise breast cancer therapy. In addition, Cdc42 is a potential target for several types of non-coding RNAs including microRNAs and lncRNAs. These non-coding RNAs is extensively involved in Cdc42-induced tumor processes, while many of them are aberrantly expressed. Here, we focus on the role of Cdc42 in cell morphogenesis, proliferation, motility, angiogenesis and survival, introduce the Cdc42-targeted non-coding RNAs, as well as present current development of effective Cdc42-targeted inhibitors in breast cancer.

PAK2-c-Myc-PKM2 axis plays an essential role in head and neck oncogenesis via regulating Warburg effect

The histone modifiers (HMs) are crucial for chromatin dynamics and gene expression; however, their dysregulated expression has been observed in various abnormalities including cancer. In this study, we have analyzed the expression of HMs in microarray profiles of head and neck cancer (HNC), wherein a highly significant overexpression of p21-activated kinase 2 (PAK2) was identified which was further validated in HNC patients. The elevated expression of PAK2 positively correlated with enhanced cell proliferation, aerobic glycolysis and chemoresistance and was associated with the poor clinical outcome of HNC patients. Further, dissection of molecular mechanism revealed an association of PAK2 with c-Myc and c-Myc-dependent PKM2 overexpression, wherein we showed that PAK2 upregulates c-Myc expression and c-Myc thereby binds to PKM promoter and induces PKM2 expression. We observed that PAK2-c-Myc-PKM2 axis is critical for oncogenic cellular proliferation. Depletion of PAK2 disturbs the axis and leads to downregulation of c-Myc and thereby PKM2 expression, which resulted in reduced aerobic glycolysis, proliferation and chemotherapeutic resistance of HNC cells. Moreover, the c-Myc complementation rescued PAK2 depletion effects and restored aerobic glycolysis, proliferation, migration and invasion in PAK2-depleted cells. The global transcriptome analysis of PAK2-depleted HNC cells revealed the downregulation of various genes involved in active cell proliferation, which indicates that PAK2 overexpression is critical for HNC progression. Together, these results suggest that the axis of PAK2-c-Myc-PKM2 is critical for HNC progression and could be a therapeutic target to reduce the cell proliferation and acquired chemoresistance and might enhance the efficacy of standard chemotherapy which will help in better management of HNC patients.

miR-26a inhibits proliferation and promotes apoptosis in porcine immature Sertoli cells by targeting the PAK2 gene

Accumulating reports have demonstrated that microRNAs (miRNAs) participate in regulating the complex processes of animal testis development and spermatogenesis; yet, the mechanisms by which miRNAs regulate spermatogenesis are poorly understood. miR-26a was identified as a miRNA that is differentially expressed among different pig testicular tissue developmental stages in our previous study. In this study, p21 activated kinase 2 (PAK2) gene was determined as one target gene of miR-26a by luciferase reporter assay, and miR-26a repressed the PAK2 mRNA abundance in porcine Sertoli cells. The Cell Counting Kit-8 (CCK8) assay, 5-Ethynyl-2'-deoxyuridine (EdU) assay and annexin V-FITC/PI staining assay results showed that miR-26a overexpression inhibited proliferation and promoted apoptosis in porcine Sertoli cells. These phenomena were similar to the siRNA-mediated knockdown of the PAK2 gene. Taken together, our results demonstrate that miR-26a inhibits proliferation and promotes apoptosis in porcine Sertoli cells by targeting the PAK2 gene, which may be a regulator of porcine spermatogenesis.

SIVcpz closely related to the ancestral HIV-1 is less or non-pathogenic to humans in a hu-BLT mouse model

The HIV-1 pandemic is a consequence of the cross-species transmission of simian immunodeficiency virus in wild chimpanzees (SIVcpz) to humans. Our previous study demonstrated SIVcpz strains that are closely related to the ancestral viruses of HIV-1 groups M (SIVcpzMB897) and N (SIVcpzEK505) and two SIVcpz lineages that are not associated with any known HIV-1 infections in humans (SIVcpzMT145 and SIVcpzBF1167), all can readily infect and robustly replicate in the humanized-BLT mouse model of humans. However, the comparative pathogenicity of different SIVcpz strains remains unknown. Herein, we compared the pathogenicity of the above four SIVcpz strains with HIV-1 using humanized-BLT mice. Unexpectedly, we found that all four SIVcpz strains were significantly less pathogenic or non-pathogenic compared to HIV-1, manifesting lower degrees of CD4+ T-cell depletion and immune activation. Transcriptome analyses of CD4+ T cells from hu-BLT mice infected with SIVcpz versus HIV-1 revealed enhanced expression of genes related to cell survival and reduced inflammation/immune activation in SIVcpz-infected mice. Together, our study results demonstrate for the first time that SIVcpz is significantly less or non-pathogenic to human immune cells compared to HIV-1. Our findings lay the groundwork for a possible new understanding of the evolutionary origins of HIV-1, where the initial SIVcpz cross-species transmission virus may be initially less pathogenic to humans.

PAK5 overexpression is associated with lung metastasis in osteosarcoma

p21-activated kinases (PAKs) are multifunctional effectors of Rho GTPases, which are associated with cytoskeletal organization, cellular morphogenesis, migration and survival. PAKs are overactive in a number of tumor tissues and have attracted attention as a potential target for cancer therapy. In the present study, PAK5 levels were analyzed in primary osteosarcoma (OS) samples (n=65) using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and immunohistochemistry (IHC) methods. In the primary OS tissue, increased PAK5 expression (IHC score >2, n=37) was associated with significantly decreased overall survival (P=0.036) compared with decreased PAK5 expression (IHC score ≤2, n=28). PAK5 expression was identified to be significantly associated with metastasis (P=0.010). The lung is the most common metastasis site for OS. In addition, the level of PAK5 in lung metastasis tissue (n=13) was detected using RT-qPCR and IHC methods. PAK5 expression was increased in lung metastasis tissue compared with in primary OS samples. PAK5 was silenced using short hairpin RNA in OS cell lines. Wound healing, migration and nude mice model assay results consistently demonstrated that PAK5 knockdown was able to significantly inhibit OS migration. In PAK5-knockdown cells, the alteration in the expression of a number of metastasis-associated factors, including epithelial cadherin, vimentin, fibronectin and matrix metalloproteinase 2 (MMP2), was analyzed. Only MMP2 expression was decreased significantly (P<0.05). The expression level of MMP2 was analyzed in primary OS tissue and lung metastasis tissue using RT-qPCR and IHC methods. Expression of MMP2 was identified to be associated with expression of PAK5. The results of the present study suggest that PAK5 promotes OS cell migration and that PAK5 expression may be used to predict lung metastasis.

MicroRNA miR-4779 suppresses tumor growth by inducing apoptosis and cell cycle arrest through direct targeting of PAK2 and CCND3

Depending on the function of their target genes, microRNAs (miRNAs) act as either tumor suppressors or oncogenes. Therefore, miRNAs represent a novel therapeutic strategy for prevention and management of cancer by targeting of onco-miRNAs or mimicking of tumor suppressor miRNAs. Herein, we identified novel tumor suppressor miRNAs and investigated their molecular mechanisms. To identify novel tumor suppressor miRNAs, we used 532 human miRNA mimic libraries and measured cell viability using MTS assays. The function of miR-4779 was then analyzed using cell cycle analyses and apoptosis, colony forming, and soft agar assays. Target genes of miR-4779 were predicted using TargetScan and miRDB databases and were confirmed using luciferase assays. Levels of miR-4779 and target genes in colon cancer tissue samples from patients were evaluated using qRT-PCR and western blotting analyses. Finally, in vivo tumor suppressive effects of miR-4779 were evaluated in HCT116 xenografts. In this study, miR-4779 inhibited cancer cell growth by inducing apoptosis and cell cycle arrest, and the putative survival factors PAK2 and CCND3 were identified as direct targets of miR-4779. In subsequent experiments, PAK2 knockdown induced cell cycle arrest and CCND3 knockdown induced cell cycle arrest and apoptosis. In addition, miR-4779 suppressed tumor growth and tumorigenesis in an in vivo HCT116 xenograft model. Finally, miR-4779 expression was low in 9 of 10 colon cancer tissues, whereas PAK2 and CCND3 expressions were significantly high in colon cancer tissues. The novel tumor suppressor miR-4779 inhibits cancer cell growth via cell cycle arrest and apoptosis by directly targeting PAK2 and CCND3. The present data indicate the potential of miR-4779 as a therapeutic target for miRNA-based cancer therapy.

COPD GWAS variant at 19q13.2 in relation with DNA methylation and gene expression

Chronic obstructive pulmonary disease (COPD) is among the major health burdens in adults. While cigarette smoking is the leading risk factor, a growing number of genetic variations have been discovered to influence disease susceptibility. Epigenetic modifications may mediate the response of the genome to smoking and regulate gene expression. Chromosome 19q13.2 region is associated with both smoking and COPD, yet its functional role is unclear. Our study aimed to determine whether rs7937 (RAB4B, EGLN2), a top genetic variant in 19q13.2 region identified in genome-wide association studies of COPD, is associated with differential DNA methylation in blood (N = 1490) and gene expression in blood (N = 721) and lungs (N = 1087). We combined genetic and epigenetic data from the Rotterdam Study (RS) to perform the epigenome-wide association analysis of rs7937. Further, we used genetic and transcriptomic data from blood (RS) and from lung tissue (Lung expression quantitative trait loci mapping study), to perform the transcriptome-wide association study of rs7937. Rs7937 was significantly (FDR < 0.05) and consistently associated with differential DNA methylation in blood at 4 CpG sites in cis, independent of smoking. One methylation site (cg11298343-EGLN2) was also associated with COPD (P = 0.001). Additionally, rs7937 was associated with gene expression levels in blood in cis (EGLN2), 42% mediated through cg11298343, and in lung tissue, in cis and trans (NUMBL, EGLN2, DNMT3A, LOC101929709 and PAK2). Our results suggest that changes of DNA methylation and gene expression may be intermediate steps between genetic variants and COPD, but further causal studies in lung tissue should confirm this hypothesis.

Deciphering the link between PI3K and PAK: An opportunity to target key pathways in pancreatic cancer?

The development of personalised therapies has ushered in a new and exciting era of cancer treatment for a variety of solid malignancies. Yet pancreatic ductal adenocarcinoma (PDAC) has failed to benefit from this paradigm shift, remaining notoriously refractory to targeted therapies. Chemotherapy is the cornerstone of management but can offer only modest survival benefits of a few months with 5-year survival rates rarely exceeding 3%. Despite these disappointing statistics, significant strides have been made towards understanding the complex biology of pancreatic cancer, with deep genomic sequencing identifying novel genetic aberrations and key signalling pathways. The PI3K-PDK1-AKT pathway has received great attention due to its prominence in carcinogenesis. However, efforts to target several components of this network have resulted in only a handful of drugs demonstrating any survival benefit in solid tumors; despite promising pre-clinical results. p-21 activated kinase 4 (PAK4) is a gene that is recurrently amplified or overexpressed in PDAC and both PAK4 and related family member PAK1, have been linked to aberrant RAS activity, a common feature in pancreatic cancer. As regulators of PI3K, PAKs have been highlighted as a potential prognostic marker and therapeutic target. In this review, we discuss the biology of pancreatic cancer and the close interaction between PAKs and the PI3K pathway. We also suggest proposals for future research that may see the development of effective targeted therapies that could finally improve outcomes for this disease.

Dual Site Phosphorylation of Caspase-7 by PAK2 Blocks Apoptotic Activity by Two Distinct Mechanisms

Caspases, the cysteine proteases that execute apoptosis, are tightly regulated via phosphorylation by a series of kinases. Although all apoptotic caspases work in concert to promote apoptosis, different kinases regulate individual caspases. Several sites of caspase-7 phosphorylation have been reported, but without knowing the molecular details, it has been impossible to exploit or control these complex interactions, which normally prevent unwanted proliferation. During dysregulation, PAK2 kinase plays an alternative anti-apoptotic role, phosphorylating caspase-7 and promoting unfettered cell growth and chemotherapeutic resistance. PAK2 phosphorylates caspase-7 at two sites, inhibiting activity using two different molecular mechanisms, before and during apoptosis. Phosphorylation of caspase-7 S30 allosterically obstructs its interaction with caspase-9, preventing intersubunit linker processing, slowing or preventing caspase-7 activation. S239 phosphorylation renders active caspase-7 incapable of binding substrate, blocking later events in apoptosis. Each of these mechanisms is novel, representing new opportunities for synergistic control of caspases and their counterpart kinases.

Gastrointestinal hormones/neurotransmitters and growth factors can activate P21 activated kinase 2 in pancreatic acinar cells by novel mechanisms

P-21-activated kinases (PAKs) are serine/threonine kinases comprising six isoforms divided in two groups, group-I (PAK1-3)/group-II (PAK4-6) which play important roles in cell cytoskeletal dynamics, survival, secretion and proliferation and are activated by diverse stimuli. However, little is known about PAKs ability to be activated by gastrointestinal (GI) hormones/neurotransmitters/growth-factors. We used rat pancreatic acini to explore the ability of GI-hormones/neurotransmitters/growth-factors to activate Group-I-PAKs and the signaling cascades involved. Only PAK2 was present in acini. PAK2 was activated by some pancreatic growth-factors [EGF, PDGF, bFGF], by secretagogues activating phospholipase-C (PLC) [CCK, carbachol, bombesin] and by post-receptor stimulants activating PKC [TPA], but not agents only mobilizing cellular calcium or increasing cyclic AMP. CCK-activation of PAK2 required both high- and low-affinity-CCK1-receptor-state activation. It was partially reduced by PKC- or Src-inhibition, but not with PI3K-inhibitors (wortmannin, LY294002) or thapsigargin. IPA-3, which prevents PAK2 binding to small-GTPases partially inhibited PAK2-activation, as well as reduced CCK-induced ERK1/2 activation and amylase release induced by CCK or bombesin. This study demonstrates pancreatic acini, possess only one Group-I-PAK, PAK2. CCK and other GI-hormones/neurotransmitters/growth-factors activate PAK2 via small GTPases (CDC42/Rac1), PKC and SFK but not cytosolic calcium or PI3K. CCK-activation of PAK2 showed several novel features being dependent on both receptor-activation states, having PLC- and PKC-dependent/independent components and small-GTPase-dependent/independent components. These results show that PAK2 is important in signaling cascades activated by numerous pancreatic stimuli which mediate their various physiological/pathophysiological responses and thus could be a promising target for the development of therapies in some pancreatic disorders such as pancreatitis.

PAK signalling during the development and progression of cancer

p21-Activated kinases (PAKs) are positioned at the nexus of several oncogenic signalling pathways. Overexpression or mutational activation of PAK isoforms frequently occurs in various human tumours, and recent data suggest that excessive PAK activity drives many of the cellular processes that are the hallmarks of cancer. In this Review, we discuss the mechanisms of PAK activation in cancer, the key substrates that mediate the developmental and oncogenic effects of this family of kinases, and how small-molecule inhibitors of these enzymes might be best developed and deployed for the treatment of cancer.

p21-Activated kinase 5: a pleiotropic kinase

The PAKs (p21-activated kinases) are highly conserved serine/threonine protein kinases which comprise six mammalian PAKs. PAK5 (p21-activated kinase 5) is the least understood member of PAKs that regulate many intracellular processes when they are stimulated by activated forms of the small GTPases Cdc42 and Rac. PAK5 takes an important part in multiple signal pathways in mammalian cells and controls a variety of cellular functions including cytoskeleton organization, cell motility and apoptosis. The main goal of this review is to describe the structure, mechanisms underlying its activity regulation, its role in apoptosis and the likely directions of further research.

Downregulation of PAK5 inhibits glioma cell migration and invasion potentially through the PAK5-Egr1-MMP2 signaling pathway

PAK5 (p21 activated kinase 5) is upregulated in human colorectal carcinoma cells and is a known tumor promoter in carcinogenesis of the colon. Little is known regarding the mechanisms underlying the downstream targets of PAK5, and information concerning its biological significance in glioma is lacking. In this study, we investigated the effects of PAK5 on proliferation, migration, invasion, and apoptosis in human U87 and U251 glioma cells and examined the underlying molecular mechanism. We performed cell growth assays and cell cycle analysis to observe the cell proliferation. Flow cytometry analysis was performed to evaluate apoptosis, and in vitro scratch assays, cell migration assays, and gelatin zymography were performed to examine cell migration. Western blot analysis was performed to examine signal transduction in the cells. We demonstrated that suppression of PAK5 in glioma cells significantly inhibited cell migration and invasion. We also observed that suppression of PAK5 in human glioma cell lines inhibited cell growth because of G1 phase arrest. Additionally, flow cytometry and Western blot analysis indicated that PAK5 could inhibit cell apoptosis. These results suggest that the PAK5-Egr1-MMP2 signaling pathway is involved in tumor progression and may have a potential role in cancer prevention and treatment.

Association of the epithelial-to-mesenchymal transition phenotype with responsiveness to the p21-activated kinase inhibitor, PF-3758309, in colon cancer models

The p21-activated kinase (PAK) family of serine/threonine kinases, which are overexpressed in several cancer types, are critical mediators of cell survival, motility, mitosis, transcription, and translation. In the study presented here, we utilized a panel of colorectal cancer (CRC) cell lines to identify potential biomarkers of sensitivity or resistance that may be used to individualize therapy to the PAK inhibitor PF-03758309. We observed a wide range of proliferative responses in the CRC cell lines exposed to PF-03758309, this response was recapitulated in other phenotypic assays such as anchorage-independent growth, three-dimensional (3D) tumor spheroid formation, and migration. Interestingly, we observed that cells most sensitive to PF-03758309 exhibited up-regulation of genes associated with a mesenchymal phenotype (CALD1, VIM, ZEB1) and cells more resistant had an up-regulation of genes associated with an epithelial phenotype (CLDN2, CDH1, CLDN3, CDH17) allowing us to derive an epithelial-to-mesenchymal transition (EMT) gene signature for this agent. We assessed the functional role of EMT-associated genes in mediating responsiveness to PF-3758309, by targeting known genes and transcriptional regulators of EMT. We observed that suppression of genes associated with the mesenchymal phenotype conferred resistance to PF-3758309, in vitro and in vivo. These results indicate that PAK inhibition is associated with a unique response phenotype in CRC and that further studies should be conducted to facilitate both patient selection and rational combination strategies with these agents.

Full-length Mst1 exhibits growth promoting function in human hepatocellular carcinoma cells

The putative tumor suppressor Mst1, when cleaved to its 36kDa cleaved form, amplifies apoptotic signals. We found that Mst1 was predominantly expressed in its full-length form in 76% (17/25 cases) of hepatocellular carcinoma (HCC) tumors. Mst1 cleavage was basically absent in HCC cells. Ectopic full-length Mst1 expression increased the growth of HCC cells by 55-80% within 3days after transfection. Expression of exogenous NORE1B, a tumor suppressor commonly lost in HCC tumors (~56% of our cohort), was sufficient to suppress the growth promotion of full-length Mst1. Hence, Mst1 exhibits a growth promoting activity in HCC cells upon NORE1B downregulation.

Proteomics-based strategy to delineate the molecular mechanisms of RhoGDI2-induced metastasis and drug resistance in gastric cancer

Rho GDP dissociation inhibitor 2 (RhoGDI2) was initially identified as a regulator of the Rho family of GTPases. Our recent works suggest that RhoGDI2 promotes tumor growth and malignant progression, as well as enhances chemoresistance in gastric cancer. Here, we delineate the mechanism by which RhoGDI2 promotes gastric cancer cell invasion and chemoresistance using two-dimensional gel electrophoresis (2-DE) on proteins derived from a RhoGDI2-overexpressing SNU-484 human gastric cancer cell line and control cells. Differentially expressed proteins were identified using matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF-MS). In total, 47 differential protein spots were identified; 33 were upregulated, and 14 were downregulated by RhoGDI2 overexpression. Upregulation of SAE1, Cathepsin D, Cofilin1, CIAPIN1, and PAK2 proteins was validated by Western blot analysis. Loss-of-function analysis using small interference RNA (siRNA) directed against candidate genes reveals the need for CIAPIN1 and PAK2 in RhoGDI2-induced cancer cell invasion and Cathepsin D and PAK2 in RhoGDI2-mediated chemoresistance in gastric cancer cells. These data extend our understanding of the genes that act downstream of RhoGDI2 during the progression of gastric cancer and the acquisition of chemoresistance.

The interconnectedness of cancer cell signaling

The elegance of fundamental and applied research activities have begun to reveal a myriad of spatial and temporal alterations in downstream signaling networks affected by cell surface receptor stimulation including G protein-coupled receptors and receptor tyrosine kinases. Interconnected biochemical pathways serve to integrate and distribute the signaling information throughout the cell by orchestration of complex biochemical circuits consisting of protein interactions and covalent modification processes. It is clear that scientific literature summarizing results from both fundamental and applied scientific research activities has served to provide a broad foundational biologic database that has been instrumental in advancing our continued understanding of underlying cancer biology. This article reflects on historical advances and the role of innovation in the competitive world of grant-sponsored research.

Phosphorylation of caspase-7 by p21-activated protein kinase (PAK) 2 inhibits chemotherapeutic drug-induced apoptosis of breast cancer cell lines

p21-activated kinase (PAK) 2, a member of the PAK family of serine/threonine protein kinases, plays an important role in physiological processes such as motility, survival, mitosis, and apoptosis. However, the role of PAK2 in resistance to chemotherapy is unclear. Here we report that PAK2 is highly expressed in human breast cancer cell lines and human breast invasive carcinoma tissue compared with a human non-tumorigenic mammary epithelial cell line and adjacent normal breast tissue, respectively. Interestingly, we found that PAK2 can bind with caspase-7 and phosphorylate caspase-7 at the Ser-30, Thr-173, and Ser-239 sites. Functionally, the phosphorylation of caspase-7 decreases its activity, thereby inhibiting cellular apoptosis. Our data indicate that highly expressed PAK2 mediates chemotherapeutic resistance in human breast invasive ductal carcinoma by negatively regulating caspase-7 activity.

Functional PAK-2 knockout and replacement with a caspase cleavage-deficient mutant in mice reveals differential requirements of full-length PAK-2 and caspase-activated PAK-2p34

p21-Activated protein kinase 2 (PAK-2) has both anti- and pro-apoptotic functions depending on its mechanism of activation. Activation of full-length PAK-2 by the monomeric GTPases Cdc42 or Rac stimulates cell survival, whereas caspase activation of PAK-2 to the PAK-2p34 fragment is involved in the apoptotic response. In this study we use functional knockout of PAK-2 and gene replacement with the caspase cleavage-deficient PAK-2D212N mutant to differentiate the biological functions of full-length PAK-2 and caspase-activated PAK-2p34. Knockout of PAK-2 results in embryonic lethality at early stages before organ development, whereas replacement with the caspase cleavage-deficient PAK-2D212N results in viable and healthy mice, indicating that early embryonic lethality is caused by deficiency of full-length PAK-2 rather than lack of caspase activation to the PAK-2p34 fragment. However, deficiency of caspase activation of PAK-2 decreased spontaneous cell death of primary mouse embryonic fibroblasts and increased cell growth at high cell density. In contrast, stress-induced cell death by treatment with the anti-cancer drug cisplatin was not reduced by deficiency of caspase activation of PAK-2, but switched from an apoptotic to a nonapoptotic, caspase-independent mechanism. Homozygous PAK-2D212N primary mouse embryonic fibroblasts that lack the ability to generate the proapoptotic PAK-2p34 show less activation of the effector caspase 3, 6, and 7, indicating that caspase activation of PAK-2 amplifies the apoptotic response through a positive feedback loop resulting in more activation of effector caspases.

Dinosaurs and ancient civilizations: reflections on the treatment of cancer

Research efforts in the area of palaeopathology have been seen as an avenue to improve our understanding of the pathogenesis of cancer. Answers to questions of whether dinosaurs had cancer, or if cancer plagued ancient civilizations, have captured the imagination as well as the popular media. Evidence for dinosaurian cancer may indicate that cancer may have been with us from the dawn of time. Ancient recorded history suggests that past civilizations attempted to fight cancer with a variety of interventions. When contemplating the issue why a generalized cure for cancer has not been found, it might prove useful to reflect on the relatively limited time that this issue has been an agenda item of governmental attention as well as continued introduction of an every evolving myriad of manmade carcinogens relative to the total time cancer has been present on planet Earth. This article reflects on the history of cancer and the progress made following the initiation of the "era of cancer chemotherapy."

Rac1 activity changes are associated with neuronal pathology and spatial memory long-term recovery after global cerebral ischemia

Excitotoxicity is the main event during neurological disorders producing drastic morphological and functional changes. Rac-GTPase is involved in cytoskeletal remodeling and survival. However, the role of Rac1 after cerebral ischemia has not been completely understood yet. In this study, we evaluated the activity of Rac1 and its immunoreactivity associated to neuropathological hallmarks and behavioral task analyses after global cerebral ischemia in an acute and long-term post-ischemia period. Our findings showed that during the acute phase (24h) after global cerebral ischemia, a decrease of the active state of Rac1 was detected in the hippocampus, together with a down-regulation of survival signaling. In this same post-ischemia time, Rac1 immunoreactivity was redistributed to cytoplasm and to aberrant neurites, accompanied by dendritic and actin cytoskeletal retraction both in vivo and in vitro in neuronal primary cultures treated with glutamate. Neurons transfected with the constitutively active mutant of Rac1 were recovered from the glutamate-induced affection in vitro. However, in the in vivo model an inactive state of Rac1, and its cellular localization remained one month after ischemia, with still decreased survival signaling, significant tauopathy, and learning and memory alterations. These neuropathological hallmarks were reversed two months post-ischemia, related with a Rac1 activity state similar to control, as well as a "normalization" of the learning and memory tasks in the ischemic rats. In summary, our data suggests that changes in Rac1 activity are involved in the neurodegenerative processes after cerebral ischemia, and also in its long-term recovery.

Pleiotropic functions of Rho GTPase signaling: a Trojan horse or Achilles' heel for breast cancer treatment?

Rho GTPase signaling is altered in human breast tumors, and elevated expression and activation of Rho GTPases correlate with tumor progression, metastasis, and poor prognosis. Here we review the evidence that Rho signaling functions as a key regulator of cell cycle, mitosis, apoptosis, and invasion during breast cancer growth and progression and discuss whether these pleiotropic actions enhance or limit the targetability of this network. We propose that depending on the stage and subtype of breast cancer, targeting Rho signaling may have chemopreventative, anti-tumor, and anti-metastatic efficacy. An understanding of how Rho signaling is perturbed in specific stages and subtypes of breast cancer and how it functions in the context of the complex in vivo environment during the stochastic process of tumor formation and progression are necessary in order to effectively target this signaling network for breast cancer treatment.

PAK1 as a therapeutic target

IMPORTANCE OF THE FIELD

P21-activated kinases (PAKs) are involved in multiple signal transduction pathways in mammalian cells. PAKs, and PAK1 in particular, play a role in such disorders as cancer, mental retardation and allergy. Cell motility, survival and proliferation, the organization and function of cytoskeleton and extracellular matrix, transcription and translation are among the processes affected by PAK1.

AREAS COVERED IN THIS REVIEW

We discuss the mechanisms that control PAK1 activity, its involvement in physiological and pathophysiological processes, the benefits and the drawbacks of the current tools to regulate PAK1 activity, the evidence that suggests PAK1 as a therapeutic target and the likely directions of future research.

WHAT THE READER WILL GAIN

The reader will gain a better knowledge and understanding of the areas described above.

TAKE HOME MESSAGE

PAK1 is a promising therapeutic target in cancer and allergen-induced disorders. Its suitability as a target in vascular, neurological and infectious diseases remains ambiguous. Further advancement of this field requires progress on such issues as the development of specific and clinically acceptable inhibitors, the choice between targeting one or multiple PAK isoforms, elucidation of the individual roles of PAK1 targets and the mechanisms that may circumvent inhibition of PAK1.

Caspase Activation of p21-Activated Kinase 2 Occurs during Cisplatin-Induced Apoptosis of SH-SY5Y Neuroblastoma Cells and in SH-SY5Y Cell Culture Models of Alzheimer's and Parkinson's Disease

p21-activated kinase 2 (PAK-2) appears to have a dual function in the regulation of cell survival and cell death. Activation of full-length PAK-2 by the p21 G-proteins Rac or Cdc42 stimulates cell survival. However, PAK-2 is unique among the PAK family because it is also activated through proteolytic cleavage by caspase 3 or similar caspases to generate the constitutively active PAK-2p34 fragment. Caspase activation of PAK-2 correlates with the induction of apoptosis in response to many stimuli and recombinant expression of PAK-2p34 has been shown to stimulate apoptosis in several human cell lines. Here, we show that caspase activation of PAK-2 also occurs during cisplatin-induced apoptosis of SH-SY5Y neuroblastoma cells as well as in SH-SY5Y cell culture models for Alzheimer's and Parkinson's disease. Inhibition of mitochondrial complex I or of ubiquitin/proteasome-mediated protein degradation, which both appear to be involved in Parkinson's disease, induce apoptosis and caspase activation of PAK-2 in SH-SY5Y cells. Overexpression of the amyloid precursor protein, which results in accumulation and aggregation of β-amyloid peptide, the main component of β-amyloid plaques in Alzheimer's disease, also induces apoptosis and caspase activation of PAK-2 in SH-SY5Y cells. Expression of the PAK-2 regulatory domain inhibits caspase-activated PAK-2p34 and prevents apoptosis in 293T human embryonic kidney cells, indicating that caspase activation of PAK-2 is directly involved in the apoptotic response. This is the first evidence that caspase activation of PAK-2 correlates with apoptosis in cell culture models of Alzheimer's and Parkinson's disease and that selective inhibition of caspase-activated PAK-2p34 could prevent apoptosis.

The War on Cancer rages on

In 1971, the "War on Cancer" was launched by the US government to cure cancer by the 200-year anniversary of the founding of the United States of America, 1976. This article briefly looks back at the progress that has been made in cancer research and compares progress made in other areas of human affliction. While progress has indeed been made, the battle continues to rage on.