Background & objective: We have identified a novel gene HERV-H-X from colon cancer tissue recently. This research was to analyze the deletion of the env region of HERV-H-X, to compare its expression with that of the env open reading frames (ORFs) in other HERV-H proviruses, and to study its differential expression in colon cancer and normal colon tissues.
Methods: Multiple alignments were performed for HERV-H-X and 3 other HERV-H proviruses (HERV-H/env62, HERV-H/env60, and HERV-H/env59) containing intact env ORF. HERV-H-X-specific polymerase chain reaction (PCR) and env ORF-common PCR for HERV-H/env62, env60 and env59 were conducted to study their expression in 8 pairs of colon cancer and adjacent normal tissues. Real-time quantitative PCR was conducted to study the differential expression of HERV-H-X in 17 pairs of colon cancer and adjacent normal tissues.
Results: The missing part in the env region of HERV-H-X corresponded to env ORFs in HERV-H/env62, HERV-H/env60 and HERV-H/env59. HERV-H-X was only detected in colon cancer tissues, while env ORFs were detected both in cancer and normal tissues. The expression of HERV-H-X was up-regulated in colon cancer tissues by 24.9 folds of that in normal tissues (P<0.01).
Conclusion: HERV-H-X is highly expressed in colon cancer, but its up-regulation is not related to env gene as it lacks an env ORF.