Macromolecular Complex Including MLL3, Carabin and Calcineurin Regulates Cardiac Remodeling

BACKGROUND

Cardiac hypertrophy is an intermediate stage in the development of heart failure. The structural and functional processes occurring in cardiac hypertrophy include extensive gene reprogramming, which is dependent on epigenetic regulation and chromatin remodeling. However, the chromatin remodelers and their regulatory functions involved in the pathogenesis of cardiac hypertrophy are not well characterized.

METHODS

Protein interaction was determined by immunoprecipitation assay in primary cardiomyocytes and mouse cardiac samples subjected or not to transverse aortic constriction for 1 week. Chromatin immunoprecipitation and DNA sequencing (ChIP-seq) experiments were performed on the chromatin of adult mouse cardiomyocytes.

RESULTS

We report that the calcium-activated protein phosphatase CaN (calcineurin), its endogenous inhibitory protein carabin, the STK24 (STE20-like protein kinase 3), and the histone monomethyltransferase, MLL3 (mixed lineage leukemia 3) form altogether a macromolecular complex at the chromatin of cardiomyocytes. Under basal conditions, carabin prevents CaN activation while the serine/threonine kinase STK24 maintains MLL3 inactive via phosphorylation. After 1 week of transverse aortic constriction, both carabin and STK24 are released from the CaN-MLL3 complex leading to the activation of CaN, dephosphorylation of MLL3, and in turn, histone H3 lysine 4 monomethylation. Selective cardiac MLL3 knockdown mitigates hypertrophy, and chromatin immunoprecipitation and DNA sequencing analysis demonstrates that MLL3 is de novo recruited at the transcriptional start site of genes implicated in cardiomyopathy in stress conditions. We also show that CaN and MLL3 colocalize at chromatin and that CaN activates MLL3 histone methyl transferase activity at distal intergenic regions under hypertrophic conditions.

CONCLUSIONS

Our study reveals an unsuspected epigenetic mechanism of CaN that directly regulates MLL3 histone methyl transferase activity to promote cardiac remodeling.

Cancer patients with COVID-19: a retrospective study of 51 patients in the district of Piacenza, Northern Italy

Background:

Cancer patients are considered a highly fragile group in the current coronavirus disease 2019 (COVID-19) pandemic.

Material & methods:

In this study, patients with COVID-19 and cancer, hospitalized in Piacenza, Italy, from 4 April to 4 May 2020 were included. Risk factors for death were analyzed.

Results:

Fifty-one COVID-19 cancer patients were included, of which the median age was 71.02 years (range: 51–86) and 70.59% were male. Cancer types included gastrointestinal (25.49%), genitourinary (25.49%) and lung (23.53%). Forty-five (88.24%) patients received hydroxychloroquine-based therapy. In addition, 25 of 51 patients died (49%): 12 of 51 (23.53%) owing to cancer and 13 of 51 (25.49%) owing to COVID-19.

Conclusion:

The risks for death were related to later onset of treatment for COVID-19, severe/critical COVID-19, age, elevated basal CRP and elevated lactate dehydrogenase.

The effect of COVID-19 on cancer patients is of high concern during the COVID-19 outbreak. Here we expand on our initial analysis of 25 patients, presenting 51 patients with COVID-19 and cancer and examining their risk factors for mortality considering indicators such as age and treatment history. We confirm that risk of mortality is greater for cancer patients, and also confirm well-known risk factors for mortality in this group.