Absence of APOBEC-1 mediated mRNA editing in human carcinomas

Abstract

The transgene expression of the catalytic subunit APOBEC-1 of the apo B mRNA editing enzymecomplex can cause hepatocellular carcinoma in mice and rabbits. It has been proposed that aberrant editing of mRNA may represent a novel oncogenic principle. This investigation aimed to de®ne whether such aberrant hyperediting mediated by APOBEC-1 occurs in human carcinomas. Editing and hyperediting of apo B, NAT1 or NF1 mRNA was not identi®ed in any of 28 resected tumor specimens, including hepatocellular, bile duct, gastric, colorectal, pancreatic adeno-and neuroendocrine, lung adeno-, medullary thyroid and breast carcinoma, soft tissue sarcoma and neuroblastoma. In most types of carcinoma, signi®cant levels for full-length APOBEC-1 mRNA could not be detected. Low level expression of APOBEC-1 was found in colorectal and gastric carcinoma where most of the APOBEC-1 mRNA is inactivated by alternate splicing. The`auxiliary' components of the apo B mRNA editing enzyme-complex are missing in many tumors including colorectal and gastric carcinoma, but are highly expressed in hepatocellular, lung adeno-and breast carcinoma all of which lack APOBEC-1. Taken together, either APOBEC-1 or the`auxiliary' components of the apo B mRNA editing enzyme-complex or both are missing in human carcinomas resulting in the absence of mRNA editing. Currently, there is no evidence that aberrant editing mediated by APOBEC-1 contributes to the tumorigenesis of natural human carcinomas.

Toxicogenomics of Kojic Acid on Gene Expression Profiling of A375 Human Malignant Melanoma Cells

“…59,60) Furthermore, most of human carcinomas were caused by APOBEC1 mediated mRNA editing. [61][62][63] Thus, the down-regulated APOBEC1 may potentially allow deactivating the tumor progression of A375 melanoma cells. ARHGEF16 (Rho guanine exchange factor (GEF) 16) is one of the multiple GEF members that have a crucial role in activating small GTPase by exchanging GDP for GTP and regulate various cellular functions including actin cytoskeleton organization, activation of kinase cascades, mitogenesis, transcriptional activation and stimulation of DNA synthesis.…”

Expression of activation-induced cytidine deaminase in human B-cell non-Hodgkin lymphomas

“…25 Total RNA from human lymphoma tissues (10 g) was coprecipitated with 2 ϫ 10 4 cpm ␣-32 P-labeled AID antisense RNA probe. Hybridization and RNA digestion with the Ribonuclease Protection Assay II Kit (Ambion, Austin, TX) and analysis of the protected RNAs on denaturing polyacrylamide sequencing gels was performed as described.…”

“…Hybridization and RNA digestion with the Ribonuclease Protection Assay II Kit (Ambion, Austin, TX) and analysis of the protected RNAs on denaturing polyacrylamide sequencing gels was performed as described. 25,26 Analysis of somatic hypermutation of the variable region of the immunoglobulin heavy-chain gene Recombined V(D)J segments of the IgH transcripts of the lymphoma specimens were amplified from the respective cDNA pools by PCR using a set of degenerate oligonucleotides exactly as described. 27 …”

“…PCR reactions were performed as described 24,25 using the following conditions-AID s-1 and AID as-2: 30 cycles at 94°C for 30 seconds, 58°C for 30 seconds, and 72°C for 30 seconds; AID 3 and AID 7: 30 cycles at 94°C for 30 seconds, 55°C for 30 seconds, and 72°C for 30 seconds; AID 5 and AID 6: 30 cycles at 94°C for 30 seconds, 55°C for 30 seconds, and 72°C for 30 seconds; nested PCR with AID 14 and AID 6 and 30 cycles using the same PCR conditions; ␤-actin s-1 and ␤-actin as-1: 25 cycles at 94°C for 30 seconds, 55°C for 30 seconds, and 72°C for 30 seconds; Bcl-6 s-1 and Bcl-6 as-1: 30 cycles at 94°C for 30 seconds, 55°C for 30 seconds, and 72°C for 30 seconds; blimp-1 s-a and blimp-1 as-1: 30 cycles at 94°C for 30 seconds, 55°C for 30 seconds, and 72°C for 30 seconds; c-myc s-1 and c-myc as-1: 30 cycles at 94°C for 30 seconds, 55°C for 30 seconds, and 72°C for 30 seconds. PCR products were hybridized with 32 P-labeled internal oligonucleotides.…”

“…PCR products were hybridized with 32 P-labeled internal oligonucleotides. 25 Quantitative PCR was performed with a Light Cycler (Roche, Basel, Switzerland) using standard software for quantification as recommended by the manufacturer. Expression levels were normalized to the expression level of ␤-actin mRNA.…”