c-mos immunoreactivity is an indicator of good prognosis in lung cancer

Aims: Reports concerning the expression of cytoplasmic components of the mi togen-activating protein kinase (MAPK) pathway in lung cancer are limited. One of the molecules participating in this pathway is the product of the c- mos proto-oncogene. In vitro investigations, in somatic cells, have shown t hat c-mos expression has opposing effects on cell cycle progression suggest ing that it may represent an important determinant of aberrant cell functio n. In this study we analysed, by immunohistochemical means, its status in a series of lung carcinomas and correlated the findings with clinicopatholog ical parameters and survival of the patients. Methods and results: Sixty cases of lung carcinomas were included in the st udy. These comprised 52 non-small (NSCLCs) and eight small cell lung carcin omas (SCLCs). Sections from the carcinomas were immunostained with the poly clonal anti-c-mos antibody P-19. Specificity was tested by using the approp riate control peptide and control cell lines. Expression was observed in 63 % of the cases, with NSCLCs showing higher reactivity (67%) than SCLCs (37. 5%). Staining was observed mainly to the cytoplasm and membranes of the can cerous cells, but some nuclei reacted as well. An intratumour heterogeneous immunoreactivity was noticed. The most interesting and unexpected finding was that c-mos positive staining was associated with better recurrence-free survival in our series, regardless of histological type (P = 0.035). Furth ermore, favourable disease-related and recurrence-free survival was observe d in the SqC group with c-mos immunoreactivity (P < 0.001). Conclusions: c-mos proto-oncogene is expressed in a significant proportion of lung carcinomas and may play a role in its development. The fact that it s expression is associated with a relatively good prognosis may be indicati ve of a negative impact on tumour growth.