HPIP and RUFY3 are noncanonical guanine nucleotide exchange factors of Rab5 to regulate endocytosis-coupled focal adhesion turnover.

While the role of endocytosis in focal adhesion turnover-coupled cell migration has been established in addition to its conventional role in cellular functions, the molecular regulators and precise molecular mechanisms that underlie this process remain largely unknown. In this study, we report that proto-oncoprotein hematopoietic PBX-interacting protein (HPIP) localizes to focal adhesions as well as endosomal compartments along with RUN FYVE domain-containing protein 3 (RUFY3) and Rab5, an early endosomal protein. HPIP contains two coiled-coil domains (CC1 and CC2) that are necessary for its association with Rab5 and RUFY3 as CC domain double mutant, that is, mtHPIPΔCC1-2 failed to support it. Furthermore, we show that HPIP and RUFY3 activate Rab5 by serving as noncanonical guanine nucleotide exchange factors of Rab5. In support of this, either deletion of coiled-coil domains or silencing of HPIP or RUFY3 impairs Rab5 activation and Rab5-dependent cell migration. Mechanistic studies further revealed that loss of HPIP or RUFY3 expression severely impairs Rab5-mediated focal adhesion disassembly, FAK activation, fibronectin-associated-ß1 integrin trafficking, and thus cell migration. Together, this study underscores the importance of HPIP and RUFY3 as noncanonical guanine nucleotide exchange factors of Rab5 and in integrin trafficking and focal adhesion turnover, which implicates in cell migration.

Genotypic and haplotype analysis of Interleukin-6 and -18 gene polymorphisms in association with clinicopathological factors in breast cancer.

Cytokines are multifunctional glycoproteins that play a vital role in the tumor microenvironment and progression of breast cancer. Genetic polymorphisms may influence the immune responses restrained by pro- and anti-inflammatory cytokine expression in tumors. Hence, the present study evaluated the contribution of Interleukin (IL) 6 (rs1800797, rs1800796, and rs1800795) and IL18 (rs1946518, rs187238, and rs549908) genotypes and their haplotypes to the risk, progression of breast cancer in South Indian population. The polymorphisms of IL6 -597G > A, -572C > G & -174G > C, and IL18 -607C > A, -137G > C, 105A > T were genotyped through PCR-RFLP and As-PCR assays in the blood DNA of 600 subjects. We have performed haplotype, LD, univariate, multivariate logistic regression, and Kaplan-Meier analyses for the obtained data. The frequency of AA genotype & A-allele of IL6 -597G > A, and CC genotype & C-allele of IL6 -174G > C polymorphism was higher in breast cancer patients and was found to be significantly associated with late (advanced) stage, metastasis, etc. Further, IL18 -607C > A, -137G > C, and 105A > T polymorphisms were found to be associated with lobular carcinoma subtype, PgR -ve, and HER2 +ve breast cancer patients. In survival analysis, we have observed that the C-allele of IL6 -174G > C polymorphism to be significantly associated with 5 years of overall survival in breast cancer subjects. All SNPs of the IL6 and IL18 genes showed perfect LD; the G-C-C, A-G-G, and A-C-C haplotype combinations of IL6 gene conferred 2.09, 2.25, and 4.72 folds risk for breast cancer respectively. Hence, our results suggest the importance of genotypic and haplotype analysis of IL6 and IL18 gene variants in the progression and risk prediction of breast cancer.

Amino acid starvation sensing dampens IL-1ß production by activating riboclustering and autophagy.

Activation of the amino acid starvation response (AAR) increases lifespan and acute stress resistance as well as regulates inflammation. However, the underlying mechanisms remain unclear. Here, we show that activation of AAR pharmacologically by Halofuginone (HF) significantly inhibits production of the proinflammatory cytokine interleukin 1ß (IL-1ß) and provides protection from intestinal inflammation in mice. HF inhibits IL-1ß through general control nonderepressible 2 kinase (GCN2)-dependent activation of the cytoprotective integrated stress response (ISR) pathway, resulting in rerouting of IL-1ß mRNA from translationally active polysomes to inactive ribocluster complexes-such as stress granules (SGs)-via recruitment of RNA-binding proteins (RBPs) T cell-restricted intracellular antigen-1(TIA-1)/TIA-1-related (TIAR), which are further cleared through induction of autophagy. GCN2 ablation resulted in reduced autophagy and SG formation, which is inversely correlated with IL-1ß production. Furthermore, HF diminishes inflammasome activation through suppression of reactive oxygen species (ROS) production. Our study unveils a novel mechanism by which IL-1ß is regulated by AAR and further suggests that administration of HF might offer an effective therapeutic intervention against inflammatory diseases.

Hematopoietic PBX-interacting protein is a substrate and an inhibitor of the APC/C-Cdc20 complex and regulates mitosis by stabilizing cyclin B1.

Proper cell division relies on the coordinated regulation between a structural component, the mitotic spindle, and a regulatory component, anaphase-promoting complex/cyclosome (APC/C). Hematopoietic PBX-interacting protein (HPIP) is a microtubule-associated protein that plays a pivotal role in cell proliferation, cell migration, and tumor metastasis. Here, using HEK293T and HeLa cells, along with immunoprecipitation and immunoblotting, live-cell imaging, and protein-stability assays, we report that HPIP expression oscillates throughout the cell cycle and that its depletion delays cell division. We noted that by utilizing its D box and IR domain, HPIP plays a dual role both as a substrate and inhibitor, respectively, of the APC/C complex. We observed that HPIP enhances the G2/M transition of the cell cycle by transiently stabilizing cyclin B1 by preventing APC/C-Cdc20-mediated degradation, thereby ensuring timely mitotic entry. We also uncovered that HPIP associates with the mitotic spindle and that its depletion leads to the formation of multiple mitotic spindles and chromosomal abnormalities, results in defects in cytokinesis, and delays mitotic exit. Our findings uncover HPIP as both a substrate and an inhibitor of APC/C-Cdc20 that maintains the temporal stability of cyclin B1 during the G2/M transition and thereby controls mitosis and cell division.

A transcriptional repressive role for epithelial-specific ETS factor ELF3 on oestrogen receptor alpha in breast cancer cells.

Oestrogen receptor-α (ERα) is a ligand-dependent transcription factor that primarily mediates oestrogen (E2)-dependent gene transcription required for mammary gland development. Coregulators critically regulate ERα transcription functions by directly interacting with it. In the present study, we report that ELF3, an epithelial-specific ETS transcription factor, acts as a transcriptional repressor of ERα. Co-immunoprecipitation (Co-IP) analysis demonstrated that ELF3 strongly binds to ERα in the absence of E2, but ELF3 dissociation occurs upon E2 treatment in a dose- and time-dependent manner suggesting that E2 negatively influences such interaction. Domain mapping studies further revealed that the ETS (E-twenty six) domain of ELF3 interacts with the DNA binding domain of ERα. Accordingly, ELF3 inhibited ERα's DNA binding activity by preventing receptor dimerization, partly explaining the mechanism by which ELF3 represses ERα transcriptional activity. Ectopic expression of ELF3 decreases ERα transcriptional activity as demonstrated by oestrogen response elements (ERE)-luciferase reporter assay or by endogenous ERα target genes. Conversely ELF3 knockdown increases ERα transcriptional activity. Consistent with these results, ELF3 ectopic expression decreases E2-dependent MCF7 cell proliferation whereas ELF3 knockdown increases it. We also found that E2 induces ELF3 expression in MCF7 cells suggesting a negative feedback regulation of ERα signalling in breast cancer cells. A small peptide sequence of ELF3 derived through functional interaction between ERα and ELF3 could inhibit DNA binding activity of ERα and breast cancer cell growth. These findings demonstrate that ELF3 is a novel transcriptional repressor of ERα in breast cancer cells. Peptide interaction studies further represent a novel therapeutic option in breast cancer therapy.

Functional regulation of pre-B-cell leukemia homeobox interacting protein 1 (PBXIP1/HPIP) in erythroid differentiation.

Pre-B-cell leukemia homeobox interacting protein 1 or human PBX1 interacting protein (PBXIP1/HPIP) is a co-repressor of pre-B-cell leukemia homeobox 1 (PBX1) and is also known to regulate estrogen receptor functions by associating with the microtubule network. Despite its initial discovery in the context of hematopoietic cells, little is yet known about the role of HPIP in hematopoiesis. Here, we show that lentivirus-mediated overexpression of HPIP in human CD34(+) cells enhances hematopoietic colony formation in vitro, whereas HPIP knockdown leads to a reduction in the number of such colonies. Interestingly, erythroid colony number was significantly higher in HPIP-overexpressing cells. In addition, forced expression of HPIP in K562 cells, a multipotent erythro-megakaryoblastic leukemia cell line, led to an induction of erythroid differentiation. HPIP overexpression in both CD34(+) and K562 cells was associated with increased activation of the PI3K/AKT pathway, and corresponding treatment with a PI3K-specific inhibitor, LY-294002, caused a reduction in clonogenic progenitor number in HPIP-expressing CD34(+) cells and decreased K562 cell differentiation. Combined, these findings point to an important role of the PI3K/AKT pathway in mediating HPIP-induced effects on the growth and differentiation of hematopoietic cells. Interestingly, HPIP gene expression was found to be induced in K562 cells in response to erythroid differentiation signals such as DMSO and erythropoietin. The erythroid lineage-specific transcription factor GATA1 binds to the HPIP promoter and activates HPIP gene transcription in a CCCTC-binding factor (CTCF)-dependent manner. Co-immunoprecipitation and co-localization experiments revealed the association of CTCF with GATA1 indicating the recruitment of CTCF/GATA1 transcription factor complex onto the HPIP promoter. Together, this study provides evidence that HPIP is a target of GATA1 and CTCF in erythroid cells and plays an important role in erythroid differentiation by modulating the PI3K/AKT pathway.

AMPK: An odyssey of a metabolic regulator, a tumor suppressor, and now a contextual oncogene.

Metabolic reprogramming is a unique but complex biochemical adaptation that allows solid tumors to tolerate various stresses that challenge cancer cells for survival. Under conditions of metabolic stress, mammalian cells employ adenosine monophosphate (AMP)-activated protein kinase (AMPK) to regulate energy homeostasis by controlling cellular metabolism. AMPK has been described as a cellular energy sensor that communicates with various metabolic pathways and networks to maintain energy balance. Earlier studies characterized AMPK as a tumor suppressor in the context of cancer. Later, a paradigm shift occurred in support of the oncogenic nature of AMPK, considering it a contextual oncogene. In support of this, various cellular and mouse models of tumorigenesis and clinicopathological studies demonstrated increased AMPK activity in various cancers. This review will describe AMPK's pro-tumorigenic activity in various malignancies and explain the rationale and context for using AMPK inhibitors in combination with anti-metabolite drugs to treat AMPK-driven cancers.

Hematopoietic PBX-interacting protein is a novel regulator of mammary epithelial cell differentiation.

Hematopoietic PBX-interacting protein (HPIP, also known as PBXIP1) is an estrogen receptor (ER) interacting protein that regulates estrogen-mediated breast cancer cell proliferation and tumorigenesis. However, its functional significance in the context of mammary gland development is unexplored. Here, we report that HPIP is required for prolactin (PRL)-induced lactogenic differentiation in vitro. Molecular analysis of HPIP expression in mice revealed its induced expression at pregnancy and lactation stages of mammary gland. Moreover, PRL is a lactogenic hormone that controls pregnancy as well as lactation and induces Hpip/Pbxip1 expression in a signal transducer and activator of transcription 5a-dependent manner. Using mammary epithelial and lactogenic-competent cell lines, we further show that HPIP plays a regulatory role in PRL-mediated mammary epithelial cell differentiation, which is measured by acini formation, ß-casein synthesis, and lipid droplet formation. Further mechanistic studies using pharmacological inhibitors revealed that HPIP modulates PRL-induced ß-casein synthesis via phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) activation. This study also identified HPIP as a critical regulator of autocrine PRL signaling as treatment with the PRL receptor antagonist Δ1-9-G129R-hPRL restrained HPIP-mediated PRL synthesis, AKT activation, and ß-casein synthesis in cultured HC11 cells. Interestingly, we also uncovered that microRNA-148a (miR-148a) antagonizes HPIP-mediated mammary epithelial cell differentiation. Together, our study identified HPIP as a critical regulator of PRL signaling and revealed a novel molecular circuitry involving PRL, HPIP, PI3K/AKT, and miR-148a that controls mammary epithelial cell differentiation in vitro.

A reciprocal feedback loop between HIF-1α and HPIP controls phenotypic plasticity in breast cancer cells.

While phenotypic plasticity is a critical factor contributing to tumor heterogeneity, molecular mechanisms underlying this process are largely unknown. Here we report that breast cancer cells display phenotypic diversity in response to hypoxia or normoxia microenvironments by operating a reciprocal positive feedback regulation of HPIP and HIF-1α. We show that under hypoxia, HIF-1α induces HPIP expression that establishes cell survival, and also promotes cell migration/invasion, EMT and metastatic phenotypes in breast cancer cells. Mechanistic studies revealed that HPIP interacts with SRP14, a component of signal recognition particle, and stimulates MMP9 synthesis under hypoxic stress. Whereas, in normoxia, HPIP stabilizes HIF-1α, causing the Warburg effect to support cell growth. Concurrently, mathematical modelling corroborates this reciprocal feedback loop in enabling cell-state transitions in cancer cells. Clinical data indicate that elevated levels of HPIP and HIF-1α correlate with unfavorable prognosis and shorter survival rates in breast cancer subjects. Together, this data shows a reciprocal positive feedback loop between HPIP and HIF-1α that was unknown hitherto. It unveils how the tumor microenvironment influences phenotypic plasticity that has an impact on tumor growth and metastasis and, further signifies considering this pathway as a potential therapeutic target in breast cancer.

Focal adhesion dynamics in cellular function and disease.

Acting as a bridge between the cytoskeleton of the cell and the extra cellular matrix (ECM), the cell-ECM adhesions with integrins at their core, play a major role in cell signalling to direct mechanotransduction, cell migration, cell cycle progression, proliferation, differentiation, growth and repair. Biochemically, these adhesions are composed of diverse, yet an organised group of structural proteins, receptors, adaptors, various enzymes including protein kinases, phosphatases, GTPases, proteases, etc. as well as scaffolding molecules. The major integrin adhesion complexes (IACs) characterised are focal adhesions (FAs), invadosomes (podosomes and invadopodia), hemidesmosomes (HDs) and reticular adhesions (RAs). The varied composition and regulation of the IACs and their signalling, apart from being an integral part of normal cell survival, has been shown to be of paramount importance in various developmental and pathological processes. This review per-illustrates the recent advancements in the research of IACs, their crucial roles in normal as well as diseased states. We have also touched on few of the various methods that have been developed over the years to visualise IACs, measure the forces they exert and study their signalling and molecular composition. Having such pertinent roles in the context of various pathologies, these IACs need to be understood and studied to develop therapeutical targets. We have given an update to the studies done in recent years and described various techniques which have been applied to study these structures, thereby, providing context in furthering research with respect to IAC targeted therapeutics.

Two decades of a protooncogene HPIP/PBXIP1: Uncovering the tale from germ cell to cancer.

Hematopoietic PBX interacting protein (HPIP or pre-B-cell leukemia transcription factor interacting protein (PBXIP1) was discovered two decades ago as a corepressor of pre-B-cell leukemia homeobox (PBX) 1 with a vital functional role in hematopoiesis. Later it emerged as a potential biomarker of poor prognosis and tumorigenesis for more than a dozen different cancers. It regulates aggressive cancer phenotypes, cell proliferation, metastasis, EMT, etc. The anomaly in the regulation of HPIP is linked with physiological disorders like renal fibrosis, chronic kidney disease and osteoarthritis. Scientists have unraveled more than twenty interacting proteins of HPIP and its functional role in various physiological and cellular processes that involves normal neuronal development, embryogenesis, endometrium decidualization, and germ cell proliferation. Over the past 20 years, we have witnessed the emerging role of HPIP and its association with a myriad of cellular activities ranging from germ cell proliferation to cancer aggressiveness, modulating multitude of signaling cascades like TGF-ß1, PI3K/AKT, Wnt, mTOR, and Sonic hedgehog signaling pathways. This review will give the current understanding of HPIP, in terms of its diverse functions, theoretical ideas, and further explore cellular links and promising areas that need to be investigated. We also provide a comprehensive overview of the transcript variants of HPIP and distinct sets of transcription factors regulating their expression, which may help to understand the role of HPIP in various cellular or physiological conditions.

HPIP protooncogene differentially regulates metabolic adaptation and cell fate in breast cancer cells under glucose stress via AMPK and RNF2 dependent pathways.

While cancer cells rewire metabolic pathways to sustain growth and survival under metabolic stress in solid tumors, the molecular mechanisms underlying these processes remain largely unknown. In this study, cancer cells switched from survival to death during the early to late phases of metabolic stress by employing a novel signaling switch from AMP activated protein kinase (AMPK)-Forkhead box O3 (FOXO3a)-hematopoietic PBX1-interacting protein (HPIP) to the ring finger protein 2 (RNF2)-HPIP-ubiquitin (Ub) pathway. Acute metabolic stress induced proto-oncogene HPIP expression in an AMPK-FOXO3a-dependent manner in breast cancer (BC) cells. HPIP depletion reduced cell survival and tumor formation in mouse xenografts, which was accompanied by diminished intracellular ATP levels and increased apoptosis in BC cells in response to metabolic (glucose) stress. Glutamine flux (13C-labeled) analysis further suggested that HPIP rewired glutamine metabolism by controlling the expression of the solute carrier family 1 member 5 (SLC1A5) and glutaminase (GLS) genes by acting as a coactivator of MYC to ensure cell survival upon glucose deprivation. However, in response to chronic glucose stress, HPIP was ubiquitinated by the E3-Ub ligase, RNF2, and was concomitantly degraded by the proteasome-mediated pathway, ensuring apoptosis. In support of these data, clinical analyses further indicated that elevated levels of HPIP correlated with AMPK activation in BC. Taken together, these data suggest that HPIP is a signal coordinator during metabolic stress and thus serves as a potential therapeutic target in BC.

Effective in vitro delivery of paclitaxel by nanocargo of mesoporous polycaprolactone against triple negative breast cancer cells by minimalizing drug dose.

Among the breast cancers, triple negative breast cancer (TNBC) has relatively poor outcomes with a lower survival rate and personalised chemotherapy is the only option available for treatment. Currently in the biomedical domain, nanomaterials with porous morphology have revealed their tremendous possibilities to be used as a nanocarrier in treating cancer by offering void space to encapsulate/entrap biological agents. However, the development of nanocarrier-based targeted therapy with high therapeutic efficacy and fewer side effects to normal cells is always a challenge. Here, we have developed nanocargos based on biodegradable mesoporous PCL (polycaprolactone) of approx. diameter of 75 nm by template removal synthesis techniques. Succeeding the comparative analysis of the nanocarriers, the efficiencies of core shell PCL-mZnO (PZ) and mesoporous PCL (HPZ) to deliver paclitaxel (Taxol/T) into breast cancer cells, is investigated. We found that HPZ nanocapsules have less cytotoxicity and drug loading efficiency of about 600 µg mg-1. The Taxol-loaded nanoparticles (T-HPZ) have exhibited more cytotoxicity than Taxol alone treated cancer cells. Furthermore, T-HPZ treated MDA-MB231 cells are accumulated at G2/M phase of the cell cycle and eventually undergo apoptosis. In support of this, anchorage independent growth of MDA-MB231 cells are significantly inhibited by T-HPZ treatment. Together, our findings suggest that T-HPZ-based paclitaxel (Taxol/T) loaded nanoparticles provide a novel therapeutic option in the treatment of TNBC.

Zirconia-containing wollastonite ceramics derived from biowaste resources for bone tissue engineering.

Zirconia-containing wollastonite (CaSiO3) ceramics with partial substitution of zirconia (1, 3 and 5 mol%) were prepared using eggshells and rice husk ash as source materials for calcium oxide and silica, respectively, through a sol-gel technique. The effect of incorporation of zirconia on in vitro bioactivity, mechanical properties, degradability and cytocompatibility of wollastonite was studied. Bioactivity was evaluated by in vitro assay using simulated body fluid while degradability was tested in Tris-HCl buffer solution for different time periods (1, 3, 7, 14 and 21 d) according to the ISO 10 993-14 standard. Human osteosarcoma (MG-63) cells were used to assess cytocompatibility with the MTT assay. X-ray diffractometry, Fourier transform infrared spectroscopy and scanning electron microscopy-energy dispersive spectroscopy were used to characterize the ceramics before and after in vitro studies. The results obtained showed that increasing the zirconia content in the wollastonite phase increases microhardness, compressive strength, bending strength and the elasticity modulus, while slightly decreasing the rate of formation of the hydroxyapatite layer. Moreover, the samples doped with zirconia had a lower degradation rate and it was noticed that cell viability is unaffected by the incorporation of zirconia.

IITZ-01, a novel potent lysosomotropic autophagy inhibitor, has single-agent antitumor efficacy in triple-negative breast cancer in vitro and in vivo.

Autophagy is a homeostatic process that recycles damaged organelles and long-lived proteins by delivering them in double-membrane vesicles to lysosomes for degradation. Autophagy has a prominent role in survival, proliferation, and resistance of tumors in metabolic and chemotherapeutic stress conditions. Clinical trials with chloroquine-a known autophagy inhibitor-were unable to achieve complete autophagy inhibition in vivo, warranting the search for more potent autophagy inhibitors. In a process of exploring the mechanism of action of previously identified cytotoxic s-triazine analogs, we discovered that both IITZ-01 and IITZ-02 act as potent autophagy inhibitors. Treatment with these compounds resulted in the vacuolated appearance of cells due to their specific accumulation in lysosomes. In addition, these basic compounds also deacidify lysosomes as evidenced by the decrease in lysotracker red staining and inhibit maturation of lysosomal enzymes leading to lysosomal dysfunction. IITZ-01 and IITZ-02 enhance autophagosome accumulation but inhibit autophagosomal degradation by impairing lysosomal function, finally resulting in the inhibition of autophagy. Interestingly, compound IITZ-01 exhibited more than 10-fold potent autophagy inhibition along with 12- to 20-fold better cytotoxic action than CQ. IITZ-01 and IITZ-02 also abolished mitochondrial membrane potential and triggered apoptosis through the mitochondria-mediated pathway. Furthermore, IITZ-01 and IITZ-02 displayed potent antitumor action in vivo through autophagy inhibition and apoptosis induction in MDA-MB-231 breast cancer xenograft model with IITZ-01 exhibiting superior anticancer efficacy. Overall, these data demonstrate that IITZ-01 is potent autophagy inhibitor with single-agent anticancer activity and awaits further preclinical development as potential anticancer therapeutic.

An inherent role of integrin-linked kinase-estrogen receptor alpha interaction in cell migration.

Integrin-linked kinase (ILK) and estrogen receptor (ER)-alpha modulate cell migration. However, the crosstalk between ERalpha and ILK and the role of ILK in ERalpha-mediated cell migration remain unexplored. Here, we report that ILK participates in ERalpha signaling in breast cancer cells. We found that ILK binds ERalpha in vitro and in vivo through a LXXLL motif in ILK. Estrogen prevented ERalpha-ILK binding, resulting in phosphatidylinositol 3-kinase (PI3K)-dependent increase in ILK kinase activity. Furthermore, the regulation of ERalpha-ILK interaction was dependent on the PI3K pathway. Unexpectedly, transient knockdown or inhibition of ILK caused hyperphosphorylation of ERalpha Ser(118) in an extracellular signal-regulated kinase/mitogen-activated protein kinase pathway-dependent manner and an enhanced ERalpha recruitment to the target chromatin and gene expression, a process reversed by overexpression of ILK. Compatible with these interactions, estrogen regulated cell migration via the PI3K/ILK/AKT pathway with stable ILK overexpression hyperactivating cell migration. Thus, status of ILK signaling may be an important modifier of ER signaling in breast cancer cells and this pathway could be exploited for therapeutic intervention in breast cancer cells.

Increased expression of tissue transglutaminase in pancreatic ductal adenocarcinoma and its implications in drug resistance and metastasis.

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive neoplastic diseases and is virtually incurable. The molecular mechanisms that contribute to the intrinsic resistance of PDAC to various anticancer therapies are not well understood. Recently, we have observed that several drug-resistant and metastatic tumors and tumor cell lines expressed elevated levels of tissue transglutaminase (TG2). Because PDAC exhibits inherent resistance to various drugs, we determined the constitutive expression of TG2 in 75 PDAC and 12 PDAC cell lines. Our results showed that 42 of 75 (56%) PDAC tumor samples expressed higher basal levels of TG2 compared with the normal pancreatic ducts [odds ratio (OR), 2.439; P = 0.012]. The increased expression of TG2 in PDAC was strongly associated with nodal metastasis (OR, 3.400; P = 0.017) and lymphovascular invasion (OR, 3.055; P = 0.045). Increased expression of TG2 was also evident in all 12 cell lines examined. The elevated expression of TG2 in PDAC cell lines was associated with gemcitabine resistance and increased invasive potential. Overexpression of catalytically active or inactive (C(277)S mutant) TG2 induced focal adhesion kinase (FAK) activation and augmented invasive functions in the BxPC-3 cell line. Conversely, down-regulation of TG2 by small interfering RNA attenuated FAK phosphorylation. Immunoprecipitation and confocal microscopy data revealed that TG2 was associated with FAK protein in PDAC cells. The activated FAK colocalized with TG2 at focal adhesion points. These results show for the first time that elevated expression of TG2 can induce constitutive activation of FAK and thus may contribute to the development of drug resistance and invasive phenotypes in PDAC.

Nimbolide, a neem limonoid inhibits cytoprotective autophagy to activate apoptosis via modulation of the PI3K/Akt/GSK-3ß signalling pathway in oral cancer.

Of late, nimbolide, a limonoid from the neem tree (Azadirachta indica) has gained increasing research attention owing to its potent antiproliferative and apoptosis-inducing effects. The present study was designed to investigate the effect of nimbolide on autophagy and the time point at which the phosphorylation status of GSK-3ß and PI3K dictate the choice between autophagy and apoptosis in SCC131 and SCC4 oral cancer cells. Additionally, we analysed changes in the expression of proteins involved in autophagy and apoptosis after therapeutic intervention with nimbolide in a hamster model of oral oncogenesis. Furthermore, we also demonstrate changes in the expression of key genes involved in apoptosis and autophagy during the stepwise evolution of hamster and human OSCCs. Nimbolide-induced stereotypical changes in oral cancer cells characteristic of both apoptosis and autophagy. Time-course experiments revealed that nimbolide induces autophagy as an early event and then switches over to apoptosis. Nimbolide negatively regulates PI3K/Akt signalling with consequent increase in p-GSK-3ßTyr216, the active form of GSK-3ß that inhibits autophagy. Downregulation of HOTAIR, a competing endogenous RNA that sponges miR-126 may be a major contributor to the inactivation of PI3K/Akt/GSK3 signalling by nimbolide. Analysis of key markers of apoptosis and autophagy as well as p-AktSer473 during sequential progression of hamster and human OSCC revealed a gradual evolution to a pro-autophagic and antiapoptotic phenotype that could confer a survival advantage to tumors. In summary, the results of the present study provide insights into the molecular mechanisms by which nimbolide augments apoptosis by overcoming the shielding effects of cytoprotective autophagy through modulation of the phosphorylation status of Akt and GSK-3ß as well as the ncRNAs miR-126 and HOTAIR. Development of phytochemicals such as nimbolide that target the complex interaction between proteins and ncRNAs that regulate the autophagy/apoptosis flux is of paramount importance in cancer prevention and therapeutics.

Proline-, glutamic acid-, and leucine-rich protein-1 is essential in growth factor regulation of signal transducers and activators of transcription 3 activation.

Proline-, glutamic acid-, and leucine-rich protein-1 (PELP1) is a novel estrogen receptor coactivator that plays an important role in the genomic and nongenomic actions of estrogen receptor by interacting with histones and src-mitogen-activated protein kinase pathway, respectively. A great deal of information has emerged in recent years about the possible role of PELP1 in estrogen receptor signaling. However, the participation and significance of PELP1 in other cellular signaling pathways remains unknown. Using a yeast two-hybrid screen, we identified PELP1 as a novel interacting protein of signal transducers and activators of transcription 3 (STAT3) and found evidence of physiologic interaction between PELP1 and STAT3. We also found that these interactions played a mechanistic role in the positive regulation of STAT3 transcription from synthetic promoters and endogenous target genes such as cyclin D1, c-myc, and c-fos. Overexpression of PELP1 enhanced phosphorylation of STAT3 at Ser727 in a src-mitogen-activated protein kinase-sensitive manner and, conversely, down-regulation of PELP1 compromised growth factor-mediated induction of STAT3 target genes. We also discovered that PELP1 interacts with STAT3 in the nuclear compartment and down-regulation of PELP1 interfered with the recruitment of STAT3 to its target gene promoters. In summary, our results highlight a novel role for PELP1 in growth factor signaling and indicate that PELP1-mediated genomic and nongenomic functions play a role in the growth factor-mediated STAT3 transactivation functions. Such regulatory interactions of PELP1 may have important functional implications in the cross-talk of estrogen receptor and growth factor signaling.