Immunocytochemical detection of homeobox B3, B4, and C6 gene product expression in lung carcinomas

The so-called homeobox (HOX) was described as a highly conserved DNA motif of 183 base pairs, encoding the 61 amino acid DNA-binding homeodomain. Nume rous HOX genes have subsequently been shown to bind to DNA and regulate the transcription of other genes. In humans the class I HOX genes are placed i n four clusters on different chromosomes. The order of the genes within eac h of these clusters is evolutionarily conserved to a high degree and sugges ts that such an organization may be essential in the function of these gene s during normal embryo- and histogenesis. Reexpression of HOX gene products has been reported in a wide variety of neoplastically transformed cells an d it seems very likely that the HOX genes represent yet another class of on cofetal antigens involved in both normal development and cellular carcinoge nesis, as well as tumor progression. The expression pattern of three homeob ox gene products (HOX-B3, HOX-B4 and HOX-C6) all shown to be involved in lu ng tissue development, was examined immunocytochemically, in human lung car cinoma (LC) tissues. In all observed LC cases, HOX-C6 was present in over 6 0% of neoplastic cells (+++) demonstrating a medium grade (B and C) stainin g intensity. A smaller number of neoplastically transformed epithelial cell s also expressed the proteins HOX-B3 and -B4 (10% to 60% or + + to +++ and a medium grade staining intensity or B and C). The significance of these no vel oncofetal antigens in tumor cell biology and as target molecules in the immunotherapy of lung carcinomas should be established by future studies.