Targeting the mitochondrial trifunctional protein restrains tumor growth in oxidative lung carcinomas.

Metabolic reprogramming is a common hallmark of cancer, but a large variability in tumor bioenergetics exists between patients. Using high-resolution respirometry on fresh biopsies of human lung adenocarcinoma, we identified 2 subgroups reflected in the histologically normal, paired, cancer-adjacent tissue: high (OX+) mitochondrial respiration and low (OX-) mitochondrial respiration. The OX+ tumors poorly incorporated [18F]fluorodeoxy-glucose and showed increased expression of the mitochondrial trifunctional fatty acid oxidation enzyme (MTP; HADHA) compared with the paired adjacent tissue. Genetic inhibition of MTP altered OX+ tumor growth in vivo. Trimetazidine, an approved drug inhibitor of MTP used in cardiology, also reduced tumor growth and induced disruption of the physical interaction between the MTP and respiratory chain complex I, leading to a cellular redox and energy crisis. MTP expression in tumors was assessed using histology scoring methods and varied in negative correlation with [18F]fluorodeoxy-glucose incorporation. These findings provide proof-of-concept data for preclinical, precision, bioenergetic medicine in oxidative lung carcinomas.

Fatty acid beta oxidation enzyme HADHA is a novel potential therapeutic target in malignant lymphoma.

Cancer cells, including malignant lymphoma cells, alter their metabolism, termed "metabolic reprograming," on initiation of malignant transformation as well as upon accumulation of genetic abnormalities. Here, to identify a novel therapeutic target involved in the metabolic changes during malignant lymphoma, we performed global analyses combined with shotgun proteomics, in silico database analysis, and clinic-pathologic analysis of nonneoplastic lymphoid tissue and malignant lymphoma tissue and verified the molecular functions in vitro. In total, 2002 proteins were detected from both samples and proteins related to fatty acid beta-oxidation (FAO) were detected more frequently in malignant lymphoma tissue. Consequently, the most frequently detected protein, the mitochondrial trifunctional enzyme subunit-alpha (HADHA), was identified as a potential target. Immunohistochemical analyses revealed that HADHA tended to be overexpressed in a high-grade subtype of malignant lymphoma tissue. Clinicopathologic study revealed that HADHA overexpression was correlated with significantly worse overall survival (P = 0.013) and was an independent prognostic predictor in diffuse large B-cell lymphoma (P = 0.027). In vitro, downregulation of HADHA negatively regulated cell growth by causing G0/G1 arrest (P = 0.0008) similar to treatment with etomoxir, an inhibitor of FAO (P = 0.032). Moreover, downregulation of HADHA increased the susceptibility to doxorubicin (P = 0.002) and etoposide (P = 0.004). Moreover, these phenotypes were confirmed in an HADHA knockout system. Thus, we provide a basis for a novel therapeutic strategy through the regulation of HADHA and FAO in patients with refractory malignant lymphoma.

Association of HADHA with human RNA silencing machinery.

In RNA silencing, small RNAs produced by dicer mediate target repression guided by RNA induced silencing complex (RISC). To effectively mediate this response, one or more proteins are employed at each stage. In the present study, we investigated HADHA, a new component in the human RNA silencing machinery. Immunoprecipitation analysis revealed that, HADHA associates with dicer complex and immunohistochemical studies confirmed its co localization with Dicer in the cytoplasm. Further, over expression of HADHA resulted in higher abundance levels of mature miRNA against a reduction in respective precursor levels and vice versa in HADHA knocked down cells. These findings suggest an auxiliary role for HADHA in miRNA biogenesis and help in better understanding of molecular mechanisms underlying RNAi pathway in mammals.