Antitumor effect and enhancement of cytotoxic drug activity by cetuximab in nasopharyngeal carcinoma cells.

BACKGROUND: Nasopharyngeal carcinoma (NPC) is the most common head and neck cancer in southern China and South East Asia. Epidermal growth factor receptor (EGFR) has been proposed as a new target for anticancer therapy. EGFR was over-expressed in 85% of NPC tissues and was associated with poor prognosis. MATERIALS AND METHODS: EGFR protein expression in four NPC cell lines, CNE-2, HONE-1, HK1 and C666-1, was examined by Western immunoblotting. The antitumor effect of cetuximab was studied in the cell lines, either alone or in combination with cisplatin or paclitaxel. RESULTS: EGFR protein expression was highest in the HK1 cell line, moderate in CNE-2 and HONE-1, and lowest in C666-1. Single agent cetuximab demonstrated significant antitumor effect in the HK1 and HONE-1 cell lines, but minimal activity in CNE-2 and C666-1 cells. When cetuximab was combined with cisplatin or paclitaxel in the HK1 and HONE-1 cell lines, an additive enhancement of cytotoxic drug activity was demonstrated. CONCLUSION: Cetuximab demonstrated single agent activity selectively in NPC cell lines with moderate to high EGFR protein expression. Cetuximab could also additively enhance the antitumor effects of cisplatin or paclitaxel in these NPC cell lines. These results support the rationale of combining cetuximab with current standard chemotherapy to further improve the therapeutic ratio in the treatment of NPC. Future studies should aim at defining the predictive markers for response to cetuximab in order to select the responsive tumor for the correctly targeted agents.

Epstein-Barr virus-encoded small RNA induces insulin-like growth factor 1 and supports growth of nasopharyngeal carcinoma-derived cell lines.

To assess the role of insulin-like growth factor 1 (IGF-1) in the growth of nasopharyngeal carcinoma (NPC), three NPC-derived cell lines, C666-1, CNE1 and HONE1, were examined. C666-1 cells maintained NPC phenotype of Epstein-Barr virus (EBV) expression and were positive for IGF-1 secretion, and their growth was strikingly inhibited by treatment with an anti-IGF-1 antibody under low serum condition. On the other hand, CNE1 and HONE1 cells were EBV-negative and did not secrete IGF-1. Although they could not grow under low serum condition, addition of recombinant IGF-1 made them grow. EBV conversion of CNE1 and HONE1 cells reproduced NPC phenotype of EBV expression and accompanied IGF-1 expression. Although they could grow under low serum condition, their growth was strikingly inhibited by treatment with the anti-IGF-1 antibody. These results suggest that EBV infection induces IGF-1 in NPC cell lines, and that the secreted IGF-1 acts as an autocrine growth factor. These findings seem to be operative in vivo, as NPC biopsies consistently express IGF-1. Further studies demonstrated that increased IGF-1 expression reflected transcriptional activation, and EBV-encoded small RNA (EBER) was responsible for IGF-1 induction. EBER is invariably expressed in EBV-associated malignancies, including NPC. The present findings strongly suggest that EBER directly affects the pathogenesis of NPC.

Frequent chromosome 9p losses in histologically normal nasopharyngeal epithelia from southern Chinese.

Nasopharyngeal carcinoma (NPC) is a common cancer among the Chinese population in the southern part of China. The incidence of this cancer drops markedly in northern China. A 6- to 24-fold difference exists between southern and northern Chinese. To investigate the early genetic events involved in the development of this cancer, we have examined loss of heterozygosity (LOH) on chromosome 9p, being one of the most frequent genetic alterations in NPC, in nasopharyngeal tissues including normal epithelia (NP), dysplastic lesions (DNP) and invasive carcinoma (NPC) from high-risk and low-risk regions. We found similar frequencies of 9p LOH in NPC from high-risk (77.8%) and low-risk (63.6%) regions (p = 0.43). In contrast, 45% of normal nasopharyngeal epithelia from the high-risk region showed 9p LOH, while none of the NP from the low-risk region showed such abnormalities (p = 0.002). Deletions of chromosome 9p were found in 66.7% dysplastic nasopharyngeal lesions. These findings suggest that LOH of chromosome 9p is an early event in the tumorigenesis of NPC. The increased risk of NPC in southern Chinese may be related to early loss of genetic materials as indicated by 9p LOH in the NP from high- and low-risk regions. We also reported previously that Epstein-Barr virus (EBV) latent infection was present in all high-grade DNP and NPC but not in any NP from fetuses or normal adults. Thus, early genetic alterations such as 9p LOH may take place prior to EBV latent infection and expand clonally thereafter.

Promoter hypermethylation of multiple genes in nasopharyngeal carcinoma.

PURPOSE: The methylation profile of nasopharyngeal carcinoma (NPC) has been investigated by a candidate gene approach. EXPERIMENTAL DESIGN: Four NPC cell lines, 4 NPC xenografts, 33 NPC primary tumors, and 6 samples of normal nasopharyngeal epithelium were subjected to methylation-specific PCR for analysis of promoter methylation of eight cancer-related genes. These eight genes were RASSF1A, RARbeta2, DAP-kinase, p16, p15, p14, MGMT, and GSTP1. The correlation between methylation status of these genes and clinical features such as stage, local-regional recurrence, distant metastasis, and survival has been analyzed. RESULTS: The incidence of promoter methylation in NPC samples was 84% for RASSF1A, 80% for RARbeta2, 76% for DAP-kinase, 46% for p16, 17% for p15, 20% for p14, 20% for MGMT, and 3% for GSTP1. No methylation of these genes was detected in the six normal nasopharyngeal epithelium samples. All NPC tumor samples in this study displayed aberrant methylation in at least one of these eight genes. No significant correlation between methylation status of these genes and clinical parameters of the patients was found. CONCLUSIONS: A high frequency of aberrant methylation of the 5' CpG island of the RASSF1A, RARbeta2, DAP-kinase, and p16 genes in the present study was noted. Our findings suggest that methylation of the genes in the critical pathways is common in NPC.