BACKGROUNDTo investigate the relationship between expression of fragile histidine triad gene protein, Fhit, and clinicopathological characteristics of human lung cancer.

METHODSFhit protein expression was detected in 92 cases of formalin-fixed, paraffin-embedded human lung cancer by citrate-microwave-SP immunohistochemical method, of which 52 were non-small cell cancer (NSCLC) and 40 small cell cancer (SCLC). Its relationship to histological grade, lymph node metastasis and histological classification were analysed.

RESULTSThe loss of Fhit protein expression were found in 62.0% (57/92) and 4.3% (4/92) of cancer tissue and normal lung tissue, respectively and there was a significant difference in the expression of Fhit protein between cancer and normal tissue (P=0.000). 53.8% (28/52) of the cases of NSCLC showed a marked loss or absence of Fhit expression, 46.2% (24/52) of cases were negative, 7.7% (4/52) showed a higher expression and 38.5% (20/52) equal to the level of Fhit expression compared with the matched normal tissues. The loss of Fhit expression was closely related to histological grade (P=0.003), to lymph node metastasis (P=0.029), and to histological classification of the cases (P=0.003). There was a significant difference between grade I+II (38.2%; 13/34) and grade III cancer (83.3%; 15/18), between cancers with lymph node metastasis (70.8%; 17/24) and those without (39.3%; 11/28), and between squamous cell carcinoma ( 68.6%; 24/35) and adenocarcinoma (23.5%; 4/17). The loss of Fhit protein expression was found in 33 of 40 cases of SCLC (82.5%) and the remainder 7 cases (17.5%) showed the same quantity of expression of Fhit, compared with the normal bronchial mucosa.

CONCLUSIONSThe expression of Fhit protein may be associated with the decreasing differentiation, lymph node metastasis and histological classification in NSCLC, and be corresponding to the occurrence and evolution of SCLC. These results suggest that the decreased Fhit expression plays an important role in the development and progression of the tumor, and thus may become a new prognostic marker in human lung cancer.