Summary The treatment of colorectal cancer (CRC) with FOLFOX shows some efficacy, but these tumors quickly develop resistance to this treatment. We have observed increased phosphorylation of AKT1/mTO Show more
Summary The treatment of colorectal cancer (CRC) with FOLFOX shows some efficacy, but these tumors quickly develop resistance to this treatment. We have observed increased phosphorylation of AKT1/mTOR/4EBP1 and levels of p21 in FOLFOX-resistant CRC cells. We have identified a small molecule, NSC49L, that stimulates protein phosphatase 2A (PP2A) activity, downregulates the AKT1/mTOR/4EBP1-axis, and inhibits p21 translation. We have provided evidence that NSC49L- and TRAIL-mediated sensitization is synergistically induced in p21-knockdown CRC cells, which is reversed in p21-overexpressing cells. p21 binds with procaspase 3 and prevents the activation of caspase 3. We have shown that TRAIL induces apoptosis through the activation of caspase 3 by NSC49L-mediated downregulation of p21 translation, and thereby cleavage of procaspase 3 into caspase 3. NSC49L does not affect global protein synthesis. These studies provide a mechanistic understanding of NSC49L as a PP2A agonist, and how its combination with TRAIL sensitizes FOLFOX-resistant CRC cells. Show less
The NAD+-dependent deacetylase SIRT1 controls key metabolic functions by deacetylating target proteins and strategies that promote SIRT1 function such as SIRT1 overexpression or NAD+ boosters alleviat Show more
The NAD+-dependent deacetylase SIRT1 controls key metabolic functions by deacetylating target proteins and strategies that promote SIRT1 function such as SIRT1 overexpression or NAD+ boosters alleviate metabolic complications. We previously reported that SIRT1-depletion in 3T3-L1 preadipocytes led to C-Myc activation, adipocyte hyperplasia, and dysregulated adipocyte metabolism. Here, we characterized SIRT1-depleted adipocytes by quantitative mass spectrometry-based proteomics, gene-expression and biochemical analyses, and mitochondrial studies. We found that SIRT1 promoted mitochondrial biogenesis and respiration in adipocytes and expression of molecules like leptin, adiponectin, matrix metalloproteinases, lipocalin 2, and thyroid responsive protein was SIRT1-dependent. Independent validation of the proteomics dataset uncovered SIRT1-dependence of SREBF1c and PPARα signaling in adipocytes. SIRT1 promoted nicotinamide mononucleotide acetyltransferase 2 (NMNAT2) expression during 3T3-L1 differentiation and constitutively repressed NMNAT1 and 3 levels. Supplementing preadipocytes with the NAD+ booster nicotinamide mononucleotide (NMN) during differentiation increased expression levels of leptin, SIRT1, and PGC-1α and its transcriptional targets, and reduced levels of pro-fibrotic collagens (Col6A1 and Col6A3) in a SIRT1-dependent manner. Investigating the metabolic impact of the functional interaction of SIRT1 with SREBF1c and PPARα and insights into how NAD+ metabolism modulates adipocyte function could potentially lead to new avenues in developing therapeutics for obesity complications. Show less