Telomerase activity in Indian patients with carcinomas of the aerodigestive tract

Combined evaluation of expression of telomerase, survivin, and anti-apoptotic Bcl-2 family members in relation to loss of differentiation and apoptosis in human head and neck cancers

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) is one of the most common cancers, and it accounts for 5% of all adult cancers worldwide. Loss of growth control and a marked resistance to apoptosis are considered major mechanisms driving tumor progression. Little is known about the distribution of inhibitors of apoptosis in HNSCC or how they correlate with other biomarkers of malignancy, such as telomerase, an enzyme that plays a critical role in cellular immortalization. The objective of this study was to assess the protein expression of anti-apoptotic members of Bcl-2 family and survivin and correlate them with telomerase activity.

METHODS

We compared anti-apoptotic protein expression in tumor tissue sections of 50 HNSCC patients and 19 histopathologically normal tissues by immunohistochemistry and Western blotting. Apoptotic index was studied by TUNEL assay. Telomerase activity was determined by polymerase chain reaction (PCR)-enzyme-linked immunosorbent assay (ELISA).

RESULTS

Bcl-2, Bcl-XL, and survivin were found to be significantly upregulated in tumor tissues as compared with the normal tissue. Protein expression of Bcl-2 and survivin was significantly associated with the loss of differentiation in tumors and that of Bcl-XL with nodal metastasis. Telomerase activity was found to be upregulated in tumors as compared with the normal tissue (p <.001) and was found to be significantly associated with the loss of differentiation in tumors.

CONCLUSIONS

Mechanisms that promote both cell proliferation (telomerase activity) and cell survival (expression of inhibitors of apoptosis protein [IAPs]) appear to be activated in HNSCC. This is the first study of its kind to look into the correlation of the apoptotic pathway and proliferation promoting enzyme activity simultaneously in relation to loss of apoptosis and differentiation in HNSCCs. Telomerase activity in these tumors was found to be correlated with Bcl-2, Bcl-XL, and survivin overexpression and with reduced apoptosis, thereby suggesting that novel strategies can be developed to control cancer cell growth by co-targeting telomerase and apoptotic pathways.

Clinical usefulness of telomerase activation and telomere length in head and neck cancer

BACKGROUND

Telomere shortening at every replication cycle is postulated to limit the life span of human somatic cells. In contrast, activation of telomerase is proposed to be an essential step for cancer cell immortalization. Head and neck cancer is the most common malignancy in the Indian population compared with Western countries. However, there are very few reports on telomerase activity and telomere length in head and neck cancer.

METHODS

Telomerase activation and telomere length alterations were studied in tumor and adjacent normal tissues in 110 patients with head and neck cancer and 40 patients with precancerous/benign conditions. Telomerase activity and telomere lengths were determined by Telomeric Repeat Amplification Protocol (TRAP assay) and Southern blot analysis, respectively.

RESULTS

Telomerase activation was observed in 78.2% of the malignant tissues, 85% of the precancerous tissues, and 53.1% of the adjacent normal tissues. Peak terminal restriction fragment length (TRF) was observed to be significantly lower in malignant tissues compared with the adjacent normal tissues. No significant correlation could be observed between telomerase activation and clinicopathologic characteristics of the patients. Two-year disease-free survival analysis showed that patients showing telomerase activation in the adjacent normal tissues and patients showing higher telomere length in malignant tissues had poor disease-free survival.

CONCLUSIONS

Our results demonstrate the significant clinical usefulness of telomerase activation and telomere length for head and neck cancer patients. These markers may be helpful in predicting the clinical course of the disease and thus in identifying the patients in need of a close follow-up and vigorous adjuvant treatment.

Telomerase--a potential molecular marker of lung and cervical cancer

Telomerase, a ribonucleoprotein enzyme that adds hexameric TTAGGG nucleotide repeats onto telomeres is reactivated in most malignancies. Lung cancer is a common malignant disease worldwide as well as in India. Most patients present in advanced stages. As noninvasive diagnostic techniques are preferred, we assayed the telomerase activity in pre-bronchoscopy sputum and compared it with that of bronchial washings and bronchoscopic biopsies by telomeric repeat amplification protocol (TRAP) in 53 cases of lung cancer. These were corroborated with cytopathological/histopathological examinations. Telomerase activity was detected in 58.5% of sputum samples, 70% of bronchial washings and 74% of bronchoscopic biopsies thereby making it a good noninvasive diagnostic marker of lung cancer. Cervical cancer is the 7th most common cancer worldwide, with 100,000 new cases being reported annually in India. It is routinely screened by Papanicolaou's (Pap) smear. Human papilloma virus (HPV) is one of its etiological agents. We have assayed telomerase activity in relation to HPV-16/18 in cervical samples from 93 subjects ranging from normal to precancerous to frank cancers in tissue biopsies and cervical scrapings. HPV infection was detected by polymerase chain reaction (PCR) in 81% of tumor samples, in 6% of control hysterectomy samples and in 2% of cervical scrapings of normal healthy controls with HPV-16 being the predominant type. Telomerase activity was detected in 96.5% of cervical tumor samples, in 68.7% of premalignant cervical scrapings but was not detected in control hysterectomy samples, or in cervical scrapings of normal healthy controls. There was 71% correlation between telomerase activity and HPV-16/18 infection.