E3 Ubiquitin Ligase TRIP12 Controls Exit from Mitosis via Positive Regulation of MCL-1 in Response to Taxol.

Chemotherapy resistance is a major hurdle in cancer treatment. Taxol-based chemotherapy is widely used in the treatment of cancers including breast, ovarian, and pancreatic cancer. Loss of function of the tumor suppressor F-box WD-40 domain containing 7 (FBW7) mutations leads to the accumulation of its substrate MCL-1 which is associated with Taxol resistance in human cancers. We recently showed that E3 ubiquitin ligase TRIP12 is a negative regulator of FBW7 protein. In this study, we find that Taxol-induced mitotic block in cancer cells is partly controlled by TRIP12 via its positive regulation of MCL-1 protein. Genetic inhibition of TRIP12 accelerates MCL-1 protein degradation in mitosis. Notably, introducing double-point mutations in lysines 404/412 of FBW7 to arginine which makes it resistant to proteasomal degradation, leads to the sharp reduction of MCL-1 protein levels and sensitizes cancer cells to Taxol-induced cell death. Finally, TRIP12 deletion leads to enhanced mitotic arrest and cell death in an FBW7 and MCL-1 dependent manner in multiple cell lines including colorectal and ovarian cancer but not in breast cancer. Thus, the TRIP12/FBW7/MCL-1 axis may provide a therapeutic target to overcome Taxol-associated chemotherapy resistance in cancer.

Control of TGFß signalling by ubiquitination independent function of E3 ubiquitin ligase TRIP12.

Transforming growth factor ß (TGFß) pathway is a master regulator of cell proliferation, differentiation, and death. Deregulation of TGFß signalling is well established in several human diseases including autoimmune disorders and cancer. Thus, understanding molecular pathways governing TGFß signalling may help better understand the underlying causes of some of those conditions. Here, we show that a HECT domain E3 ubiquitin ligase TRIP12 controls TGFß signalling in multiple models. Interestingly, TRIP12 control of TGFß signalling is completely independent of its E3 ubiquitin ligase activity. Instead, TRIP12 recruits SMURF2 to SMAD4, which is most likely responsible for inhibitory monoubiquitination of SMAD4, since SMAD4 monoubiquitination and its interaction with SMURF2 were dramatically downregulated in TRIP12-/- cells. Additionally, genetic inhibition of TRIP12 in human and murine cells leads to robust activation of TGFß signalling which was rescued by re-introducing wildtype TRIP12 or a catalytically inactive C1959A mutant. Importantly, TRIP12 control of TGFß signalling is evolutionary conserved. Indeed, genetic inhibition of Drosophila TRIP12 orthologue, ctrip, in gut leads to a reduced number of intestinal stem cells which was compensated by the increase in differentiated enteroendocrine cells. These effects were completely normalised in Drosophila strain where ctrip was co-inhibited together with Drosophila SMAD4 orthologue, Medea. Similarly, in murine 3D intestinal organoids, CRISPR/Cas9 mediated genetic targeting of Trip12 enhances TGFß mediated proliferation arrest and cell death. Finally, CRISPR/Cas9 mediated genetic targeting of TRIP12 in MDA-MB-231 breast cancer cells enhances the TGFß induced migratory capacity of these cells which was rescued to the wildtype level by re-introducing wildtype TRIP12. Our work establishes TRIP12 as an evolutionary conserved modulator of TGFß signalling in health and disease.

Proteasomal degradation of the tumour suppressor FBW7 requires branched ubiquitylation by TRIP12.

The tumour suppressor FBW7 is a substrate adaptor for the E3 ubiquitin ligase complex SKP1-CUL1-F-box (SCF), that targets several oncoproteins for proteasomal degradation. FBW7 is widely mutated and FBW7 protein levels are commonly downregulated in cancer. Here, using an shRNA library screen, we identify the HECT-domain E3 ubiquitin ligase TRIP12 as a negative regulator of FBW7 stability. We find that SCFFBW7-mediated ubiquitylation of FBW7 occurs preferentially on K404 and K412, but is not sufficient for its proteasomal degradation, and in addition requires TRIP12-mediated branched K11-linked ubiquitylation. TRIP12 inactivation causes FBW7 protein accumulation and increased proteasomal degradation of the SCFFBW7 substrate Myeloid Leukemia 1 (MCL1), and sensitizes cancer cells to anti-tubulin chemotherapy. Concomitant FBW7 inactivation rescues the effects of TRIP12 deficiency, confirming FBW7 as an essential mediator of TRIP12 function. This work reveals an unexpected complexity of FBW7 ubiquitylation, and highlights branched ubiquitylation as an important signalling mechanism regulating protein stability.

Evaluation of osteoinductive and endothelial differentiation potential of Platelet-Rich Plasma incorporated Gelatin-Nanohydroxyapatite Fibrous Matrix.

In this study, platelet-rich plasma (PRP) was incorporated into gelatin-nanohydroxyapatite fibrous scaffold in two forms (PRP gel as coating on the scaffold [PCSC] and PRP powder within the scaffold [PCSL] and investigated for (a) growth factor release; (b) stability of scaffold at different temperature; (c) stability of scaffold before and after ETO sterilization; and (d) osteogenic and endothelial differentiation potential using mesenchymal stem cells (MSCs). PCSC demonstrated a high and burst growth factor release initially followed by a gradual reduction in its concentration, while PCSL showed a steady state release pattern for 30 days. The stability of growth factors released from PCSL was not altered either through ETO sterilization or through its storage at different temperature. PRP-loaded scaffolds induced the differentiation of MSCs into osteogenic and endothelial lineage without providing any induction factors in the cell culture medium and the differentiation rate was significantly higher when compared to the scaffolds devoid of PRP. PCSC performed better than PCSL. In general, PRP in combination with composite fibrous scaffold could be a promising candidate for bone tissue engineering applications.

Composite hydrogel of chitosan-poly(hydroxybutyrate-co-valerate) with chondroitin sulfate nanoparticles for nucleus pulposus tissue engineering.

Intervertebral disc degeneration, occurring mainly in nucleus pulposus (NP), is a leading cause of low back pain. In seeking to mitigate this condition, investigators in the field of NP tissue engineering have increasingly studied the use of hydrogels. However, these hydrogels should possess appropriate mechanical strength and swelling pressure, and concurrently support the proliferation of chondrocyte-like cells. The objective of this study was to develop and validate a composite hydrogel for NP tissue engineering, made of chitosan-poly(hydroxybutyrate-co-valerate) (CP) with chondroitin sulfate (CS) nanoparticles, without using a cross linker. The water uptake ability, as well as the viscoelastic properties of this composite hydrogel, was similar to native tissue, as reflected in the complex shear modulus and stress relaxation values. The hydrogel could withstand varying stress corresponding to daily activities like lying down (0.01 MPa), sitting (0.5 MPa) and standing (1.0 MPa) under dynamic conditions. The hydrogels were stable in PBS for 2 weeks and its stiffness, elastic and viscous modulus did not alter significantly during this period. Both CP and CP-CS hydrogels could assist the viability and adhesion of adipose derived rat mesenchymal stem cells (ADMSCs). The viability and chondrogenic differentiation of MSCs was significantly enhanced in presence of CS nanoparticles. Thus, CS nanoparticles-incorporated chitosan-PHBV hydrogels offer great potential for NP tissue engineering.

A novel polymorphism in BRCA2 exon 8 and breast cancer risk in South India.

In India the incidence of breast cancer is on the rise and it is rapidly becoming the number one cancer in females, pushing cervical cancer to the second spot. The contribution of BRCA2 to the development of the sporadic form of breast cancer remains undefined. To assess the role of SNPs in exon 8 of the BRCA2 gene in breast cancer development in India, a population-based study was here carried out on 107 breast cancer patients and 96 controls by PCR-RFLP and DNA sequencing. T-C transitions at positions 29 bp and 44 bp in relation to the total sequence of exon 8 were identified. Characterization of BRCA genes is relevant in a prevention setting as well as for the clinical management of hereditary breast cancer patients. The presently identified novel mutation in exon8 of the BRCA2 gene might have clinical significance.

Cytogenetic biomonitoring of road paving workers occupationally exposed to polycyclic aromatic hydrocarbons.

Road pavement workers are exposed to many known carcinogens in their complex occupational environment. The study makes an attempt to investigate exposure to polycyclic aromatic hydrocarbons (PAH) from the bitumen fumes among the road pavement workers engaged in different pavement sites at Coimbatore, Tamil Nadu and to thereby determine the genotoxic effects associated with it. The study included 36 road pavers and 37 control subjects with similar mean ages, smoking prevalence and alcohol consumption and was analyzed for DNA damage in blood leucocytes by Micronucleus assay (MN) and the Comet assay. The mean urinary 1-OHP concentration in road pavers (1.68 ∓ 0.93) was significantly higher than in controls (0.55 ∓ 0.42). The results of MN test and comet assay showed that the mean micronuclei rate in workers was significantly higher than those in controls (P <0.05). The results of our study indicated that the genetic damage was detectable in road paving workers occupationally exposed to bitumen and also demonstrate the high sensitivity of comet assay to assess early oxidative effects induced by exposure to bitumen fumes at low doses and confirm the suitability of urinary 1-OHP as a biomarker of PAH exposure.

Genotoxic effects of textile printing dye exposed workers in India detected by micronucleus assay.

The textile printing industry in South India employs a great number of workers that may possibly be exposed to toxic compounds. In the present study, subjects from textile printing units were investigated for the presence of genetic damage in their peripheral blood lymphocytes using micronucleus assay. Proliferation was also investigated using a nuclear division index. It was found that the micronucleus frequency was considerably greater in exposed subjects than in non exposed control subjects, but division was not increased in a statistically significant way. For the time being, this investigation should be considered as a preliminary study in which the influence of potential confounders could be adequately assessed. However, our results are non-ambiguous, indicating a potential health risk in these workers.

XRCC1399 and hOGG1326 polymorphisms and frequencies of micronuclei, comet and chromosomal aberrations among tobacco chewers: a South Indian population study.

DNA repair plays a critical role in protecting the genome of the cell from the insults of cancer-causing agents such as those found in tobacco. Reduced DNA repair capacity may constitute a significant risk factor for cancers. Recently, a number of polymorphisms in several DNA repair genes have been discovered, these polymorphisms may affect DNA repair capacity and thus modulate cancer susceptibility in exposed populations. In the present study, we explored the relationship between polymorphisms in the DNA repair gene XRCC1399 and hOGG1326 genotypes using polymerase chain reaction-restriction fragment length polymorphism (PCR/RFLP) and risk of cancer development. 156 smokeless tobacco users and 70 controls without significant exposure to mutagens were recruited. Questionnaires were completed to obtain detailed occupational, smoking, and medical histories. A standard micronucleus assay, comet assay and chromosomal aberration assays were used as a marker of genetic damage. There were significant differences in the micronucleus (MN), Comet scores and chromosomal aberrations (CA) between smokeless tobacco users and control subjects by Student's t-test (P< 0.05). These findings provide evidence for the view that polymorphisms in DNA repair genes may modify individual susceptibility to tobacco related cancers and justify additional studies to investigate their potential role in development of cancer.