Differential immunohistochemical expression of hTERT in lung cancer patients with and without idiopathic pulmonary fibrosis

Background

Human telomerase reverse transcriptase (hTERT) is the catalytic subunit of telomerase enzyme, which adds nucleotides to telomeres and counteracts their length shortening. The development of a telomere maintenance mechanism represents a hallmark of cancer. On the other hand, idiopathic pulmonary fibrosis (IPF) is associated with mutations in telomerase genes and shorter telomeres. IPF is frequently complicated with lung cancer.

Aim

To investigate the expression of hTERT in lung cancer with co-existing IPF and to compare with lung cancer without fibrosis.

Methods

Diagnostic lung cancerous biopsies were retrieved from 18 patients with lung cancer and concomitant IPF, as well as 18 age and gender matched controls with lung cancer without pulmonary fibrosis. The expression of hTERT was studied with immunohistochemistry. ImajeJ software was used to quantitate subcellular stain intensity. Immunohistochemical investigation of two senescence-associated markers, p16 and p21, was also performed in all 36 cases.

Results

Both groups highly expressed hTERT, without significant difference (100% vs 95%, p = 0.521). Evaluation of p16 and p21 immunostaining revealed negative to minimal immunoreactivity in both groups. hTERT localization exhibited higher median nuclear intensity in the group of lung cancer with IPF (0.62 vs 0.45, p = 0.016), while cytoplasmic intensity did not differ significantly (0.17 vs 0.15, p = 0.463). Higher median nuclear intensity was also correlated with small cell lung cancer subtype in the whole study sample (0.69 vs 0.45, p = 0.09).

Conclusion

hTERT is highly expressed in lung cancer with concomitant IPF, but with differential localization compared to lung cancer without IPF, implying differences in pathogenicity and requiring further investigation.