S-adenosylmethionine synthetase (SAMS) catalyzes the formation of S-adenosylmethionine (SAM) and is essential to normal cell function. There are two forms of SAMS, liver-specific and nonliver-specific (often referred to as "kidney"), which are products of two different genes. SAMS isoenzymes differ greatly in kinetic parameters and sensitivity to inhibition by methionine analogs. The current work studied changes in SAMS and their significance in liver cancer. Northern blot analysis showed that while normal liver expresses only liver-specific SAMS, both HepG2 and HuH-7 cells express only nonliver-specific SAMS. Absence of liver-specific SAMS messenger RNA (mRNA) was not because of gene deletion or rearrangement but complete lack of gene transcription. Reverse-transcription polymerase chain reaction (RT-PCR) with liver- and kidney-specific SAMS primers showed that liver-specific SAMS mRNA was absent with only kidney SAMS mRNA present in HepG2, HuH-7, Hep3B, and HuH-1 cells, and four consecutive hepatocellular carcinoma (HCC) specimens. Normal liver tissues from the same patients express both forms of SAMS mRNA. As a result of the change in SAMS expression, SAMS activity was higher in HepG2 and HuH-7 cells at physiologically relevant methionine concentrations but lower at high (mmol/L) methionine concentrations than rat hepatocytes. Treatment with ethionine and seleno-D,L-ethionine, two inhibitors known to have I50 values 50 to 60 times lower against SAMS purified from Novikoff hepatoma cells as compared with SAMS purified from normal rat liver, resulted in increased cell lysis in HepG2 and HuH-7 cells but not cultured rat hepatocytes. These agents did not affect cellular adenosine triphosphate (ATP) levels but inhibited SAMS activity in HepG2 and HuH-7 cells when added to their protein extracts. In summary, expression of SAMS is altered in human liver cancer. This occurrence may provide a potentially exploitable target for cancer chemotherapy.

Supplemental Table 3A. Importantly, much like DP103, the highest levels of MMP9 were found in primary breast tumors that showed metastasis compared with nonmetastatic or benign tumors (Figure 3E). Importantly, the correlation between DP103 and MMP9 a strong positive clinical correlation between expression of DP103 and MMP9 (P < 0.001 in both cohorts). To further substantiate this finding, we next investigated whether a similar correlation between DP103 and MMP9 expression existed in the cohort from 1-3) or pBO-BI-DP103 (lanes 4-6) were either left untreated or treated with CPT (10 μM) for indicated times. Protein extracts analyzed by EMSA and Western blotting using anti-DP103 and anti-β-actin antibodies (top panel). (G) MDA-MB-231 cells transfected with either control siRNA (ctsi) or siRNA against DP103 and subjected to CPT (10 μM) stimulation at the indicated times. Cells were harvested and lysates evaluated by Western blotting for the indicated proteins. Fold difference in protein DNA binding indicated in E and F for EMSA and for protein expression changes indicated in G for Western blot.

No abstract

Myeloid-derived suppressor cells (MDSC) are regulators of immune responses in cancer. The differentiation and function of these MDSCs may be regulated through multiple factors, such as microRNAs. However, the effect of long noncoding RNAs (lncRNA) on the differentiation and function of MDSCs is poorly understood. We identified a long noncoding RNA (lncRNA) named in MDSCs, which may control suppressive functions of MDSCs. could be induced in and tumor and inflammatory environments. It regulated a set of target transcripts, such as Arg-1, NOS2, NOX2, and COX2, to control immune-suppressive function and differentiation of MDSCs. This lncRNA was also able to bind to the C/EBPβ isoform LIP to inhibit the activation of C/EBPβ. We also found that the conserved homologue has a similar function to murine These findings suggest a negative feedback role for in controlling the immunosuppressive functions of MDSC in the tumor environment..

Proliferative R28 cells retain functional neuronal properties that may prove useful in future studies of neuronal differentiation and development.