Search

We have recently cloned a novel splice variant of cyclin D2 termed as cycD2SV. CycD2SV overexpression in several immortalized cell lines led to formation of ubiquitinated protein aggregates accompanied by a significant decrease in cell proliferation. Based on immuno co-localization and ultrastructural analysis experiments, cycD2SV protein aggregates were frequently found in various subcellular compartments such as endosomes, autophagosomes, lysosomes and the microtubule organizing centre. Secondary structure analysis revealed that the amino terminal α-helix in cycD2SV is not tightly packed with the cyclin box suggesting a misfolded conformation compared to other cyclins. Deletion analysis suggests that 1-53 amino acid region of cycD2SV may be required for protein aggregation and 54-136 amino acid region may mediate cell cycle inhibition. Based on co-immunoprecipitation experiments, we have shown that cycD2SV binds to cycD2 as well as CDK4. In addition, gene expression analysis demonstrated an upregulation in GADD45α and dynamin 2 mRNA levels in cycD2SV overexpressing cells. These two proteins are known to play critical roles in the DNA damage response and apoptosis pathways. TUNEL experiments were negative for apoptosis, however, cycD2SV expressing cells were more sensitive to cell death induced by external stressors such as trypsinization. Collectively our results suggest that cycD2SV mediates cell cycle inhibition by sequestering endogenous cell cycle proteins, such as cycD2 and CDK4, and possibly targeting them for ubiquitin mediated protein degradation.

The mechanism by which HIV and HCV cooperatively accelerate hepatocyte damage is not clearly understood; however, each virus affects the TRAIL: TRAIL-receptor system. We, therefore, questioned whether the independent effects of HCV and HIV combine to synergistically result in TRAIL dependent hepatocyte killing. We describe that Huh7 hepatocytes treated with HIV gp120 results in both increase TRAIL-R2 expression and an acquired sensitivity to TRAIL mediated killing. Moreover HCV infection and HCV core expression alone in Huh7 cells upregulates TRAIL. Co-incubation of HIV gp120 primed hepatocytes with HCV core expressing hepatocytes results in the selective death of the HIV gp120 primed hepatocytes that is selectively blocked by TRAIL-R2-Fc fusion protein. Liver biopsies from HIV mono-infected patients have increased TRAIL-R2; biopsies from HCV infected patients have increased TRAIL, while co-infected liver biopsies have increased PARP cleavage within hepatocytes indicating enhanced apoptosis. These findings suggest a pathogenic model to understand why HIV/HCV co-infection accelerates liver injury.

Doxorubicin (Dox) is an anthracycline used to effectively treat several forms of cancer. Unfortunately, the use of Dox is limited due to its association with cardiovascular complications which are manifested as acute and chronic cardiotoxicity. The pathophysiological mechanism of Dox induced cardiotoxicity appears to involve increased expression of the tumor suppressor protein p53 in cardiomyocytes, followed by cellular apoptosis. It is not known whether downregulation of p53 expression in cardiomyocytes would result in decreased rates of myocardial fibrosis which occurs in response to cardiomyocyte loss. Further, it is not known whether Dox can induce perivascular necrosis and associated fibrosis in the heart. In this study we measured the effects of acute Dox treatment on myocardial and perivascular apoptosis and fibrosis in a conditional knockout (CKO) mouse model system which harbours inactive p53 alleles specifically in cardiomyocytes. CKO mice treated with a single dose of Dox (20 mg/kg), did not display lower levels of myocardial apoptosis or reactive oxygen and nitrogen species (ROS/RNS) compared to control mice with intact p53 alleles. Interestingly, CKO mice also displayed higher levels of interstitial and perivascular fibrosis compared to controls 3 or 7 days after Dox treatment. Additionally, the decrease in levels of the microtubule protein α-tubulin, which occurs in response to Dox treatment, was not prevented in CKO mice. Overall, these results indicate that selective loss of p53 in cardiomyocytes is not sufficient to prevent Dox induced myocardial ROS/RNS generation, apoptosis, interstitial fibrosis and perivascular fibrosis. Further, these results support a role for p53 independent apoptotic pathways leading to Dox induced myocardial damage and highlight the importance of vascular lesions in Dox induced cardiotoxicity.

The combination of panobinostat, bortezomib and dexamethasone (PanBorDex) is available as a treatment option for relapsed refractory multiple myeloma (RRMM) based on the PANORAMA-1 trial which investigated this triplet in early relapse. In routine clinical care, PanBorDex is used primarily in later relapses and is commonly administered in attenuated dosing schedules to mitigate the treatment-related toxicity. We set out to evaluate efficacy and safety outcomes with PanBorDex later in the disease course and evaluate the role of attenuated dosing schedules. This was a retrospective evaluation of patients treated in routine clinical practice between 2016-2019 across seven heamatology centres in the UK; patients who received at least one dose of PanBorDex were eligible for inclusion. The dosing schedule of panobinostat (10mg, 15mg or 20mg, twice or three times a week) and bortezomib (0.7mg/m2, 1mg/m2 or 1.3mg/m2 once or twice weekly) was as per treating physician choice. Patients received treatment until disease progression or unacceptable toxicity. The primary outcome is response rates according to IMWG criteria. Key secondary endpoints include progression-free survival (PFS) and overall survival (OS). Other secondary endpoints include rates of adverse events according to CTCAE criteria. In total, 61 patients were eligible for inclusion and received PanBorDex primarily as ≥5th line of treatment. One third of patients received PanBorDex at full dose, for the remaining two thirds, treatment was given in reduced dose intensities. The overall response rate was 44.2%, including 14.7% very good partial response (VGPR) rates; 68.8% of patients derived clinical benefit with stable disease or better. The median PFS was 3.4 months; non-refractory patients and those who achieved VGPR benefited from prolonged PFS of 11.4 months and 17.7 months, respectively. The median OS was 9.5 months. The triplet was associated with 45% and 18% incidence of grade 3-4 thrombocytopenia and diarrhea, respectively., Competing Interests: I have read the journal’s policy and the authors of this manuscript have the following competing interests: N. Maouche: Takeda UK; honorarium, consultancy fees, speaker fees, conference attendance, grant, Celgene; speaker fees, Novartis; speaker fees, Janssen; conference fees, Abbvie; conference fees. B. Kishore: Celgene; consultancy, Takeda UK; conference attendance, BMS; conference attendance, Janssen; conference attendance, Shire; advisory board. Z. Bhatti: None Declared. B. Supratik: None Declared. F. Karim: None Declared. S. Sundararaman: None Declared. F. Collings: Celgene; Speaker fees, Takeda; Speaker fees. B. Tseu: None Declared. H. Leary: None Declared. N. Ryman: None Declared. U. Reddy: None Declared. G. Vallance: Jazz Pharmaceuticals; grant, Takeda UK; grant. J. Kothari: None Declared. K. Ramasamy: Janssen; grant, speaker fees, advisory board, Novartis; advisory board. This does not alter our adherence to PLOS ONE policies on sharing data and materials.