Liposome-mediated delivery of the p21 activated kinase-1 (PAK-1) inhibitor IPA-3 limits prostate tumor growth in vivo

Targeted Liposomal Drug Delivery: Overview of the Current Applications and Challenges

In drug development, it is not uncommon that an active substance exhibits efficacy in vitro but lacks the ability to specifically reach its target in vivo. As a result, targeted drug delivery has become a primary focus in the pharmaceutical sciences. Since the approval of Doxil® in 1995, liposomes have emerged as a leading nanoparticle in targeted drug delivery. Their low immunogenicity, high versatility, and well-documented efficacy have led to their clinical use against a wide variety of diseases. That being said, every disease is accompanied by a unique set of physiological conditions, and each liposomal product must be formulated with this consideration. There are a multitude of different targeting techniques for liposomes that can be employed depending on the application. Passive techniques such as PEGylation or the enhanced permeation and retention effect can improve general pharmacokinetics, while active techniques such as conjugating targeting molecules to the liposome surface may bring even further specificity. This review aims to summarize the current strategies for targeted liposomes in the treatment of diseases.

PAK inhibitor FRAX486 decreases the metastatic potential of triple-negative breast cancer cells by blocking autophagy

BACKGROUND

Triple-negative breast cancer (TNBC) is a unique breast cancer subtype with a high risk of metastasis and recurrence and a poor prognosis. Epithelial-mesenchymal transition (EMT) endows epithelial cells with the ability to move to distant sites, which is essential for the metastasis of TNBC to organs, including the lung. Autophagy, an intracellular degradation process that involves formation of double-layered lipid autophagosomes that transport cytosolic cargoes into lysosomes via autophagosome-lysosome fusion, is involved in various diseases, including cancer and neurodegenerative, metabolic, cardiovascular, and infectious diseases. The relationship between autophagy and cancer has become relatively clear. However, research on pharmacological drugs that block cancer EMT by targeting autophagy is still in the initial stages. Therefore, the re-evaluation of old drugs for their potential in blocking both autophagy and EMT was conducted.

METHODS

More than 2000 small molecule chemicals were screened for dual autophagy/EMT inhibitors, and FRAX486 was identified as the best candidate inhibitor of autophagy/EMT. The functions of FRAX486 in TNBC metastasis were detected by CCK-8, migration and wound healing assays. The effects of FRAX486 on autophagy and its target PAK2 were determined by immunoblotting, immunofluorescence, immunoprecipitation analysis and transmission electron microscopy. The findings were validated in mouse models.

RESULTS

Here, we report that FRAX486, a potent P21-activated kinase 2 (PAK2) inhibitor, facilitates TNBC suppression both in vitro and in vivo by blocking autophagy. Mechanistically, FRAX486 inhibits autophagy in TNBC cells by targeting PAK2, leading to the ubiquitination and proteasomal degradation of STX17, which mediates autophagosome-lysosome fusion. The inhibition of autophagy by FRAX486 causes upregulation of the epithelial marker protein E-cadherin and thus suppresses the migration and metastasis of TNBC cells.

CONCLUSIONS

The effects of FRAX486 on TNBC metastasis suppression were verified to be dependent on PAK2 and autophagy inhibition. Together, our results provide a molecular basis for the application of FRAX486 as a potential treatment for inhibiting the metastasis of TNBC.

PAK1 and Therapy Resistance in Melanoma

Malignant melanoma claims more lives than any other skin malignancy. While primary melanomas are usually cured via surgical excision, the metastatic form of the disease portents a poor prognosis. Decades of intense research has yielded an extensive armamentarium of anti-melanoma therapies, ranging from genotoxic chemo- and radiotherapies to targeted interventions in specific signaling pathways and immune functions. Unfortunately, even the most up-to-date embodiments of these therapies are not curative for the majority of metastatic melanoma patients, and the need to improve their efficacy is widely recognized. Here, we review the reports that implicate p21-regulated kinase 1 (PAK1) and PAK1-related pathways in the response of melanoma to various therapeutic modalities. Ample data suggest that PAK1 may decrease cell sensitivity to programmed cell death, provide additional stimulation to growth-promoting molecular pathways, and contribute to the creation of an immunosuppressive tumor microenvironment. Accordingly, there is mounting evidence that the concomitant inhibition of PAK1 enhances the potency of various anti-melanoma regimens. Overall, the available information suggests that a safe and effective inhibition of PAK1-dependent molecular processes would enhance the potency of the currently available anti-melanoma treatments, although considerable challenges in implementing such strategies still exist.

Lyophilization of Nanoparticles, Does It Really Work? Overview of the Current Status and Challenges

Nanoparticles are being increasingly used as drug delivery systems to enhance the delivery to and uptake by target cells and to reduce off-target toxicity of free drugs. However, although the advantages of nanoparticles as drug carriers are clear, there are still some limitations, especially in maintaining their long-term stability. Lyophilization, also known as freeze-drying, has been heavily investigated as a solution to this problem. This strategy has been shown to be effective in increasing both the long-term stability of nanoparticles and the shelf life of the drug product. However, the process is still in need of improvement in several aspects, such as the process parameters, formulation factors, and characterization techniques. This review summarizes the advantages and limitations of nanoparticles for the treatment of disease, advantages and limitations, and the status of the lyophilization of nanoparticles for therapeutic use and provides insight into both the advantages and the limitations.

Use of Liposome-encapsulated estetrol for treatment of Neonatal Hypoxic-Ischemic encephalopathy

Estetrol (E4) is a natural estrogen synthesized only during pregnancy. It has strong neuroprotective and antioxidative activities. The aim of the present study was to define the neuroprotective potency of E4 encapsulated either in liposome (Lipo-E4) or in drug-in cyclodextrin (HP-β-CD) in liposome (DCL) system, and compare them with a single use of E4. In vitro studies were performed in an oxidative stress model of primary hippocampal neuronal cell cultures, followed by the lactate dehydrogenase activity and cell proliferation assays. In vivo studies were conducted by using a model of neonatal hypoxic-ischemic encephalopathy in immature rat pups. Brain samples were studied by (immuno)histochemistry for the detection of survived cells, expression of microtubule-associated protein-2, myelin basic protein, doublecortin and vascular-endothelial growth factor. Concentrations of glial fibrillary acidic protein in blood serum were studied by ELISA. In vitro, cell proliferation was significantly up-regulated in cultures treated either by DCL-E4 or E4 compared to the control cells, whereas DCL-E4 treated cells had significantly higher survival rate than the cells treated by E4 alone. Evaluation of brain samples showed that DCL-E4 and a high dose of E4 alone significantly preserve the grey and the white matter loses, and diminish GFAP expression in blood. Although DCL-E4 and E4 have similar effect on neurogenesis in the hippocampus and the cortex, DCL-E4 treatment significantly up-regulates angiogenesis in the hippocampus compared to a single use of E4. Present work reveals for the first time that liposome-encapsulated E4 might be a better alternative to a single use of E4.

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.

Liposomes in Cancer Therapy: How Did We Start and Where Are We Now

Since their first discovery in the 1960s by Alec Bangham, liposomes have been shown to be effective drug delivery systems for treating various cancers. Several liposome-based formulations received approval by the U.S. Food and Drug Administration (FDA) and European Medicines Agency (EMA), with many others in clinical trials. Liposomes have several advantages, including improved pharmacokinetic properties of the encapsulated drug, reduced systemic toxicity, extended circulation time, and targeted disposition in tumor sites due to the enhanced permeability and retention (EPR) mechanism. However, it is worth noting that despite their efficacy in treating various cancers, liposomes still have some potential toxicity and lack specific targeting and disposition. This explains, in part, why their translation into the clinic has progressed only incrementally, which poses the need for more research to focus on addressing such translational limitations. This review summarizes the main properties of liposomes, their current status in cancer therapy, and their limitations and challenges to achieving maximal therapeutic efficacy.

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.

PAK1 Is Involved in the Spindle Assembly during the First Meiotic Division in Porcine Oocytes

P21-activated kinase 1 (PAK1), as a member of the PAK family, has been implicated in various functions during somatic mitosis; however, less is known about its role during oocyte meiosis. Herein, we highlight the indispensable role of PAK1 in regulating spindle assembly and cell cycle progression during the first meiotic division of porcine oocytes. First, we found that the activated PAK1 expressed dynamically, and its subcellular localization was tightly associated with the spindle dynamics during meiosis in porcine oocytes. Specific inhibition of PAK1 activity by inhibitor targeting PAK1 activation-3 (IPA-3) led to impaired extrusion of the first polar body (PB1); with most of the IPA-3-treated oocytes arrested at germinal vesicle breakdown (GVBD) and subjected to failure of bipolar spindle formation. However, the adverse effects caused by IPA-3 on oocytes could be restored by reducing disulfide bonds between PAK1 and IPA-3 with dithiothreitol (DTT) treatment. Furthermore, the co-immunoprecipitation assay revealed that PAK1 interacted directly with Aurora A and transforming acidic coiled coil 3 (TACC3), providing an additional explanation for the similar localization of Aurora A and activated PAK1. Additionally, inhibiting the activity of PAK1 decreased the expression of p-Aurora A and p-TACC3; however, the reduced activity of Aurora A and TACC3 could be restored by DTT. In conclusion, PAK1 plays a crucial role in the proper assembly of the spindle during the first meiotic division of porcine oocytes, and the regulation of PAK1 is associated with its effects on p-Aurora A and p-TACC3 expression.

The trilogy of P21 activated kinase, autophagy and immune evasion in pancreatic ductal adenocarcinoma

Pancreatic Ductal Adenocarcinoma (PDA) is one of the most lethal types of cancer with a dismal prognosis. KRAS mutation is a commonly identified oncogene in PDA tumorigenesis and P21-activated kinases (PAKs) are its downstream mediator. While PAK1 is more well-studied, PAK4 also attracted increasing interest. In PDA, PAK inhibition not only reduces cancer cell viability but also sensitises it to chemotherapy. While PDA remains resistant to existing immunotherapies, PAK inhibition has been shown to increase cancer immunogenicity of melanoma, glioblastoma and PDA. Furthermore, autophagy plays an important role in PDA immune evasion, and accumulating evidence has pointed to a connection between PAK and cancer cell autophagy. In this literature review, we aim to summarize currently available studies that have assessed the potential connection between PAK, autophagy and immune evasion in PDA biology to guide future research.

Blocking PI3K p110β Attenuates Development of PTEN-Deficient Castration-Resistant Prostate Cancer

A common outcome of androgen deprivation in prostate cancer therapy is disease relapse and progression to castration-resistant prostate cancer (CRPC) via multiple mechanisms. To gain insight into the recent clinical findings that highlighted genomic alterations leading to hyperactivation of PI3K, we examined the roles of the commonly expressed p110 catalytic isoforms of PI3K in a murine model of Pten-null invasive CRPC. While blocking p110α had negligible effects in the development of Pten-null invasive CRPC, either genetic or pharmacologic perturbation of p110β dramatically slowed CRPC initiation and progression. Once fully established, CRPC tumors became partially resistant to p110β inhibition, indicating the acquisition of new dependencies. Driven by our genomic analyses highlighting potential roles for the p110β/RAC/PAK1 and β-catenin pathways in CRPC, we found that combining p110β with RAC/PAK1 or tankyrase inhibitors significantly reduced the growth of murine and human CRPC organoids in vitro and in vivo. Because p110β activity is dispensable for most physiologic processes, our studies support novel therapeutic strategies both for preventing disease progression into CRPC and for treating CRPC.

IMPLICATIONS

This work establishes p110β as a promising target for preventing the progression of primary PTEN-deficient prostate tumors to CRPC, and for treating established CRPC in combination with RAC/PAK1 or tankyrase inhibitors.

The Use of Nanomedicine to Target Signaling by the PAK Kinases for Disease Treatment

P21-activated kinases (PAKs) are serine/threonine kinases involved in the regulation of cell survival, proliferation, inhibition of apoptosis, and the regulation of cell morphology. Some members of the PAK family are highly expressed in several types of cancer, and they have also been implicated in several other medical disorders. They are thus considered to be good targets for treatment of cancer and other diseases. Although there are several inhibitors of the PAKs, the utility of some of these inhibitors is reduced for several reasons, including limited metabolic stability. One way to overcome this problem is the use of nanoparticles, which have the potential to increase drug delivery. The overall goals of this review are to describe the roles for PAK kinases in cell signaling and disease, and to describe how the use of nanomedicine is a promising new method for administering PAK inhibitors for the purpose of disease treatment and research. We discuss some of the basic mechanisms behind nanomedicine technology, and we then describe how these techniques are being used to package and deliver PAK inhibitors.

Safe Nanoparticles: Are We There Yet?

The field of nanotechnology has grown over the last two decades and made the transition from the benchtop to applied technologies. Nanoscale-sized particles, or nanoparticles, have emerged as promising tools with broad applications in drug delivery, diagnostics, cosmetics and several other biological and non-biological areas. These advances lead to questions about nanoparticle safety. Despite considerable efforts to understand the toxicity and safety of these nanoparticles, many of these questions are not yet fully answered. Nevertheless, these efforts have identified several approaches to minimize and prevent nanoparticle toxicity to promote safer nanotechnology. This review summarizes our current knowledge on nanoparticles, their toxic effects, their interactions with mammalian cells and finally current approaches to minimizing their toxicity.

Distinct effects of pharmacological inhibition of stromelysin1 on endothelial-to-mesenchymal transition and myofibroblast differentiation

Endothelial-to-mesenchymal transition (EndMT) and fibroblast-to-myofibroblast (FibroMF) differentiation are frequently reported in organ fibrosis. Stromelysin1, a matrix metalloprotease-3 (MMP3) has been indicated in vascular pathologies and organ injuries that often lead to fibrosis. In the current study, we investigated the role of stromelysin1 in EndMT and FibroMF differentiation, which is currently unknown. In our results, whereas TGFβ2 treatment of endothelial cells (ECs) induced EndMT associated with increased expression of stromelysin1 and mesenchymal markers such as α-smooth muscle actin (αSMA), N-cadherin, and activin linked kinase-5 (ALK5), inhibition of stromelysin1 blunted TGFβ2-induced EndMT. In contrast, treatment of NIH-3T3 fibroblasts with TGFβ1 promoted FibroMF differentiation accompanied by increased expression of αSMA, N-cadherin, and ALK5. Intriguingly, stromelysin1 inhibition in TGFβ1-stimulated myofibroblasts further exacerbated fibroproliferation with increased FibroMF marker expression. Gene Expression Omnibus (GEO) data analysis indicated increased stromelysin1 expression associated with EndMT and decreased stromelysin1 expression in human pulmonary fibrosis fibroblasts. In conclusion, our study has identified that EndMT and FibroMF differentiation are reciprocally regulated by stromelysin1.

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.

Sterically stabilized liposomes targeting P21 (RAC1) activated kinase-1 and secreted phospholipase A2 suppress prostate cancer growth and metastasis

Metastatic prostate cancer (PCa) has a very high mortality rate in men, in Western countries and lacks reliable treatment. The advanced-stage PCa cells overexpress P21 (RAC1) activated kinase-1 (PAK1) and secreted phospholipase A2 (sPLA2) suggesting the potential utility of pharmacologically targeting these molecules to treat metastatic PCa. The small molecule, inhibitor targeting PAK1 activation-3 (IPA3) is a highly specific allosteric inhibitor of PAK1; however, it is metabolically unstable once in the plasma thus, limiting its utility as a chemotherapeutic agent. In the present study, the efficacy and specificity of IPA3 were combined with the stability and the sPLA2-targeted delivery method of two sterically stabilized liposomes [sterically stabilized long-circulating liposomes (SSL)-IPA3 and sPLA2 responsive liposomes (SPRL)-IPA3, respectively] to inhibit PCa growth and metastasis. It was found that twice-a-week administration of either SSL-IPA3 or SPRL-IPA3 for 3 weeks effectively suppressed the growth of PC-3 cell tumor xenografts implanted in athymic nude mice. Both drug formulations also inhibited the metastasis of intravenously administered murine RM1 PCa cells to the lungs of C57BL/6 mice. Whereas the twice-a-week administration of SSL-IPA3 significantly inhibited the spontaneous PCa metastasis to the lungs in Transgenic Adenocarcinoma of the Mouse Prostate mice, the administration of free IPA3 had no significant therapeutic benefit. The results present two novel IPA3 encapsulated liposomes to treat metastatic PCa.

Differential regulation of TGFβ type-I receptor expressions in TGFβ1-induced myofibroblast differentiation

Fibroblast-to-myofibroblast (FibroMF) differentiation is crucial for embryogenesis and organ fibrosis. Although transforming growth factor-β (TGFβ) is the primary mediator of FibroMF differentiation, the type-I receptor (TGFβRI) responsible for this has not yet been confirmed. In the current study, we investigated the ALK1 and ALK5 expressions in TGFβ1-stimulated NIH 3T3 fibroblasts to compare with the data from the Gene Expression Omnibus (GEO) repository. In our results, whereas TGFβ1 treatment promoted FibroMF differentiation accompanied by increased ALK5 expression and reduced ALK1 expression, TGFβ1-induced FibroMF differentiation and increased α-smooth muscle actin (αSMA) and ALK5 expression were inhibited by co-treatment with ALK5 inhibitor SB431542. GEO database analysis indicated increased ALK5 expression and reduced ALK1 expression in fibrotic compared to normal mouse or human tissues correlating with organ fibrosis progression. Finally, the inhibitors of Akt, mTOR, and β-catenin suppressed TGFβ1-induced ALK5 expression, indicating that the Akt pathway promotes FibroMF differentiation via ALK5 expression and fibrosis.

PAK1 inhibitor IPA-3 mitigates metastatic prostate cancer-induced bone remodeling

Metastatic prostate cancer (PCa) has high mortality and a poor 5-year survival rate primarily due to the lack of effective treatments. Bone is the primary site of PCa metastasis in humans and the development of reliable therapeutic options for bone metastatic PCa will make a huge impact in reducing the mortality among these patients. Although P21 activated kinases (PAKs) have been studied in the past for their role in cancer, the efficacy of targeting PAKs to treat lung and bone metastatic PCa has not been tested yet. In the current study, we report that targeting PAK1 using IPA-3, an allosteric inhibitor of PAK1 kinase activity, significantly inhibits the murine metastatic PCa (RM1) cell proliferation and motility in vitro, and metastasis to the lungs in vivo. More importantly, we demonstrate for the first time that treatment with IPA-3 can blunt metastatic PCa-induced bone remodeling in vivo as analyzed by the 3-dimensional microcomputer tomography analysis. Our study has identified IPA-3 as a potential drug to treat bone metastatic PCa.

Liposomes and drug-in-cyclodextrin-in-liposomes formulations encapsulating 17β-estradiol: An innovative drug delivery system that prevents the activation of the membrane-initiated steroid signaling (MISS) of estrogen receptor α

The encapsulation into liposomes of several types of molecules presents the advantages to protect the activity of these molecules and to target specific tissues. Nevertheless, a major obstacle remains the incomplete understanding of nano-bio interactions. Specifically, the impact that inclusion of drug into liposomes or of drug-in-cyclodextrin-in liposomes (DCL) could have on the molecular and cellular mechanism of drug action is largely unknown. As a proof of concept, we evaluated the impact of 17β-estradiol (E2) included into liposomes or DCL on estrogen receptor (ER)α signaling pathways. Indeed, ERα relays the pleiotropic actions of E2 in physiology and pathophysiology through two major pathways: (1) the genomic/nuclear effects associated to the transcriptional activity of the ERα and (2) the rapid/nongenomic/membrane-initiated steroid signaling (MISS) effects related to the induction of fast signaling pathways occurring when ERα is anchored to the plasma membrane. We evidenced that the inclusion of E2 into liposomes (Lipo-E2) or into DCL (DCL-E2) prevented the activation of the rapid/nongenomic/extranuclear/MISS pathway of ERα, while the activation of the genomic/nuclear pathway was maintained. These results support that Lipo-E2 and DCL-E2 could be a useful tool to delineate the complex molecular mechanisms associated to ERα. In conclusion, this study supports the notion that inclusion of drugs into liposomes or DCL could modify some specific pathways of their molecular and cellular mechanisms of action. These results emphasized that attention should be paid to nano-bio interactions induced by the use of nanovectors in medicine.

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.

Genome atlas analysis based profiling of Akt pathway genes in the early and advanced human prostate cancer

Recent studies conducted in the mouse and cellular models suggest a stage-specific, differential effect of Akt activity modulation on tumor growth and metastasis in various cancers. In prostate cancer (PCa), although the deletion of Akt1 gene in a neuroendocrine model of TRansgenic Adenocarcinoma of the Mouse Prostate (TRAMP) blunted oncogenic transformation and tumor growth, Akt1 suppression in the advanced PCa resulted in the activation of transforming growth factor-β pathway and enhanced metastasis to the lungs. Such a dual role for the Akt isoforms and its signaling partners has not been investigated in human PCa. In the current study, we performed genomic database analysis of Akt isoforms and associated pathway molecules in human prostate adenocarcinoma, castration-resistant PCa, neuroendocrine PCa and metastatic PCa for mutations, genetic alterations, mRNA and protein expressions and activating phosphorylations from cBioportal. Results from the protein data analysis from the cBioportal were compared to the results of our data on human PCa tissue analysis and the cellular effects of Akt1 suppression using MK-2206 on PCa cell aggressiveness. Our study indicates the existence of a dual role for Akt1 in PCa and warrants a large-scale analysis of the early and advanced stage PCa clinical samples for further clarity.

Targeting p21-activated kinase 1 inhibits growth and metastasis via Raf1/MEK1/ERK signaling in esophageal squamous cell carcinoma cells

Background

p21-activated kinase 1 (PAK1) plays a fundamental role in promoting the development and progression of several cancers and is a potential therapeutic target. However, the biological function and underlying mechanism of PAK1 in esophageal squamous cell carcinoma (ESCC) remain unclear.

Methods

The expression of PAK1 was detected in both ESCC cell lines and clinical samples. Cell growth was measured by MTT, focus formation and soft agar assays. Cell migration and invasion were detected by wound healing and transwell assays. Animal models of subcutaneous tumourigenicity and tail vein metastasis were performed to determine the inhibitory effect of pharmacological inhibitor IPA-3 on tumor growth and metastasis of ESCC cells.

Results

We found that PAK1 was frequently overexpressed in ESCC. Ectopic expression of PAK1 promoted cellular growth, colony formation and anchorage-independent growth. Overexpressing PAK1 also enhanced migration, invasion and the expression of MMP-2 and MMP-9 in ESCC cells. In contrast, silencing PAK1 by lentiviral knockdown or a specific inhibitor IPA-3 resulted in a contrary effect. Subsequent investigations revealed that Raf1/MEK1/ERK signaling pathway was involved in PAK1-mediated effect. Enhanced expression of Raf1 attenuated the inhibitory functions of PAK1 shRNA. Whereas blocking of Raf1 by shRNA or specific inhibition of MEK1 by U0126 antagonized the oncogenetic effect of PAK1 on ESCC cells. More importantly, Pharmacological inhibition of PAK1 by IPA-3 significantly suppressed tumor growth and lung metastasis of ESCC cells in vivo.

Conclusions

These data support that PAK1 is an ideal target for the development of potential therapeutic drugs for ESCC patients even with metastasis.

Electronic supplementary material

The online version of this article (10.1186/s12964-019-0343-5) contains supplementary material, which is available to authorized users.

Translational Multi-Disciplinary Approach for the Drug and Gene Delivery Systems for Cancer Treatment

Over the last several decades, nanoparticulate delivery systems have emerged as advanced drug and gene delivery tools for cancer therapy. However, their translation into clinical use still poses major challenges. Even though many innovative nanoparticulate approaches have shown very positive results both in vitro and in vivo, few of them have found a place in clinical practice. Possible factors responsible for the existing gap in the translation of nanomedicine to clinical practice may include oversimplification of enhanced permeability and retention effect, lack of correlation between the in vivo animal data vs their translation in human, and challenging multiple biological steps experienced during systemic delivery of nanomedicine. Understanding these challenges and coming up with solutions to overcome them is an important step in effective translation of nanomedicine into clinical practice. This review focuses on advancements in the field of nanomedicine used for anti-cancer therapy, including passive targeting, active targeting, and stimuli-controlled delivery. The review further reveals some of the challenges that are currently faced by pharmaceutical scientists in translation of nanomedicine; these include lack of adequate models for preclinical testing that can predict efficacy in humans, absence of appropriate regulatory guidelines for their approval processes, and difficulty in scale-up of the manufacturing of nanodrug delivery systems. A better understanding of these challenges will help us in filling the gap between the bench and bedside in cancer therapy.

Recent Advances in Drug Delivery System for Bioactive Glycosides from Traditional Chinese Medicine

Traditional Chinese Medicine (TCM) has been used in China for thousands of years for the prevention and treatment of various diseases. The materials that exert a therapeutic effect are called the active ingredients. The bioactive glycosides are important active ingredients from TCM that can make significant contributions to treating diseases. Because of the possibilities of various clinical applications, the properties and administration of these bioactive glycosides deserve further investigation. Their promising treatment effects, however, are hindered by their poor solubility, poor stability and rapid elimination. Therefore, it is necessary that we improve the therapeutic efficacy of bioactive glycosides by overcoming these problems. Meanwhile, some practical design strategies and novel drug delivery vehicles based on drug delivery systems provide favorable support in clinical practice for these active ingredients. This review summarizes diverse pharmacological activities of bioactive glycosides and focuses on recent advances in delivery system for these active constitutes; in particular, some glycol glycosides can effectively cure intractable diseases through targeted drug delivery. This review elucidates some design strategies for drug delivery system that are mainly based on two methods (avoiding physical barriers by changing dosage forms and enhancing the ability to bind to receptors or proteins after administration) and indicate the current challenges during the combination of delivery vehicles and these glycosides in hopes of promoting the process of receiving ideal therapeutic efficacy of them in future studies.

Toxicological status of nanoparticles: What we know and what we don't know

The field of nanotechnology has grown exponentially during the last few decades, due in part to the use of nanoparticles in many manufacturing processes, as well as their potential as clinical agents for treatment of diseases and for drug delivery. This has created several new avenues by which humans can be exposed to nanoparticles. Unfortunately, investigations assessing the toxicological impacts of nanoparticles (i.e. nanotoxicity), as well as their possible risks to human health and the environment, have not kept pace with the rapid rise in their use. This has created a gap-in-knowledge and a substantial need for more research. Studies are needed to help complete our understanding of the mechanisms of toxicity of nanoparticles, as well as the mechanisms mediating their distribution and accumulation in cells and tissues and their elimination from the body. This review summarizes our knowledge on nanoparticles, including their various applications, routes of exposure, their potential toxicity and risks to human health.

Paving the Rho in cancer metastasis: Rho GTPases and beyond

Malignant carcinomas are often characterized by metastasis, the movement of carcinoma cells from a primary site to colonize distant organs. For metastasis to occur, carcinoma cells first must adopt a pro-migratory phenotype and move through the surrounding stroma towards a blood or lymphatic vessel. Currently, there are very limited possibilities to target these processes therapeutically. The family of Rho GTPases is an ubiquitously expressed division of GTP-binding proteins involved in the regulation of cytoskeletal dynamics and intracellular signaling. The best characterized members of the Rho family GTPases are RhoA, Rac1 and Cdc42. Abnormalities in Rho GTPase function have major consequences for cancer progression. Rho GTPase activation is driven by cell surface receptors that activate GTP exchange factors (GEFs) and GTPase-activating proteins (GAPs). In this review, we summarize our current knowledge on Rho GTPase function in the regulation of metastasis. We will focus on key discoveries in the regulation of epithelial-mesenchymal-transition (EMT), cell-cell junctions, formation of membrane protrusions, plasticity of cell migration and adaptation to a hypoxic environment. In addition, we will emphasize on crosstalk between Rho GTPase family members and other important oncogenic pathways, such as cyclic AMP-mediated signaling, canonical Wnt/β-catenin, Yes-associated protein (YAP) and hypoxia inducible factor 1α (Hif1α) and provide an overview of the advancements and challenges in developing pharmacological tools to target Rho GTPase and the aforementioned crosstalk in the context of cancer therapeutics.

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.