Epstein-Barr virus (EBV) genome-positive nasopharyngeal carcinomas (NPCs) regularly express the virus-coded nuclear antigen EBNA1, but not other EBNAs, and a subset of tumors also appear to be latent membrane protein LMP1 positive; the status of NPCs with respect to a second virus-coded latent membrane protein LMP2 is unknown.
Epstein-Barr virus (EBV) genome-positive nasopharyngeal carcinomas (NPCs) regularly express the virus-coded nuclear antigen EBNA1, but not other EBNAs, and a subset of tumors also appear to be latent membrane protein LMP1 positive; the status of NPCs with respect to a second virus-coded latent membrane protein LMP2 is unknown.
Although the expression of the CD23 antigen in transplantable NPCs has been reported, our study demonstrates that expression of this antigen in human undifferentiated NPCs is rare.
Furthermore, the inflammatory cytokines whose genes are classically induced by IL-1 and TNF were found expressed only in C17 and C19 suggesting another level of heterogeneity among NPCs.
Furthermore, the inflammatory cytokines whose genes are classically induced by IL-1 and TNF were found expressed only in C17 and C19 suggesting another level of heterogeneity among NPCs.
Furthermore, the inflammatory cytokines whose genes are classically induced by IL-1 and TNF were found expressed only in C17 and C19 suggesting another level of heterogeneity among NPCs.
Our results seem to indicate that mutations in the p53 gene contribute to a significant number of cases of the head and neck tumors including 20% of nasopharyngeal carcinoma biopsies.
Polymerase chain reaction-single-stranded conformational polymorphism analysis and direct sequencing failed to detect sequence alterations in exons 5 through 8 of the p53 gene in the 15 tumors and in the 4 NPC xenografts, all of which tested positive for Epstein-Barr virus.
We conclude from this study that mutational or other alterations of the p53 gene are not common in nasopharyngeal carcinogenesis and that a codon-280 mutation of p53 may be involved in less than 10% of NPC cases.
However, 100% frequency of complete loss of heterozygosity was observed at two chromosomal loci: RAF-1 locus (ten of ten cases at 3p25) and D3S3 locus (nine of nine cases at 3p14), in all evaluable NPC patients, suggesting the presence of putative tumor suppressor gene(s) within or close to these defined regions.
However, 100% frequency of complete loss of heterozygosity was observed at two chromosomal loci: RAF-1 locus (ten of ten cases at 3p25) and D3S3 locus (nine of nine cases at 3p14), in all evaluable NPC patients, suggesting the presence of putative tumor suppressor gene(s) within or close to these defined regions.