Sustainable production of 2,3,5,6-tetramethylpyrazine at high titer in engineered Corynebacterium glutamicum.

The industrial amino acid production workhorse, Corynebacterium glutamicum naturally produces low levels of 2,3,5,6-tetramethylpyrazine (TMP), a valuable flavor, fragrance and commodity chemical. Here we demonstrate TMP production (∼0.8 ​g L-1) in C. glutamicum type strain ATCC13032 via overexpression of acetolactate synthase and/or alpha-acetolactate decarboxylase from Lactococcus lactis in CGXII minimal medium supplemented with 40 g L-1 glucose. This engineered strain also demonstrated growth and TMP production when the minimal medium was supplemented with up to 40% (v v-1) hydrolysates derived from ionic liquid pretreated sorghum biomass. A key objective was to take the fully engineered strain developed in this study and interrogate media parameters that influence the production of TMP, a critical post strain engineering optimization. Design of experiments in a high throughput plate format identified glucose, urea and their ratio as significant components affecting TMP production. These two components were further optimized using response surface methodology. In the optimized CGXII medium, the engineered strain could produce up to 3.56 g L-1 TMP (4-fold enhancement in titers and 2-fold enhancement in yield, mol mol-1) from 80 g L-1 glucose and 11.9 g L-1 urea in shake flask batch cultivation.

Obg-like ATPase 1 exacerbated gemcitabine drug resistance of pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is a highly malignant disease with a poor prognosis due to inefficient diagnosis and tenacious drug resistance. Obg-like ATPase 1 (OLA1) is overexpressed in many malignant tumors. The molecular mechanism of OLA1 underlying gemcitabine (GEM)-induced drug resistance was investigated in this study. An enhanced expression of OLA1 was observed in a GEM acquired resistant pancreatic cancer cell lines and in patients with pancreatic cancer. Overexpressed OLA1 showed poor overall survival rates in patients with pancreatic cancer. Dysregulation of the OLA1 reduced expression of CD44+/CD133+, and improved the sensitivity of pancreatic cancer cells to GEM. OLA1 highly expression facilitated the formation of the OLA1/Sonic Hedgehog (SHH)/Hedgehog-interacting protein (HHIP) complex in nuclei, resulting in the inhibition of negative feedback of Hedgehog signaling induced by HHIP. This study suggests that OLA1 may be developed as an innovative drug target for an effective therapy of pancreatic cancer.

Advance in microRNA as a potential biomarker for early detection of pancreatic cancer.

Pancreatic cancer is characterized as a disease with low survival and high mortality because of no effective diagnostic and therapeutic strategies available in clinic. Conventional clinical diagnostic methods including serum markers and radiological imaging (CT, MRI, EUS, etc.) often fail to detect precancerous or early stage lesions. Development of effective biomarkers is unmet for reduction of mortality of pancreatic cancer. MicroRNAs (miRNAs) are a group of small non-protein-coding RNAs playing roles in regulation of cell physiology including tumorigenesis, apoptotic escape, proliferation, invasion, epithelial-mesenchymal transition (EMT), metastasis and chemoresistance. Various altered signaling pathways involving in molecular pathogenesis of pancreatic cancer are mediated by miRNAs as a role of either oncogenes or tumor suppressors. Among biomarkers developed including protein, metabolites, DNA, RNA, epigenetic mutation, miRNAs are superior because of its unique chemical property. Recent study suggests that miRNAs may be promising biomarkers used for early detection of pancreatic cancer. This review will update the progression made in early detection of pancreatic cancer.