Homeobox B3, B4, and C6 gene product expression in osteosarcomas as detected by immunocytochemistry

Osteosarcoma (OS) is a malignant neoplastic disease of the bone, of mesench ymal origin and with considerable morphologic heterogeneity consisting of m alignant stroma with evidence of malignant osteoid, bone and/or cartilage p roduction. The mammalian homeobox (HOX) represents a highly conserved DNA m otif of 183 base pairs, encoding the 61 amino acid DNA-binding homeodomain, through which the HOX gene products regulate the transcription of other ge nes involved in onto-and histogenesis. Re-expression of HOX proteins has be en identified in a wide variety of neoplastically transformed cell types an d it seems that the HOX genes represent yet another family of oncofetal ant igens involved in both normal development and oncogenesis, as' well as tumo r tissue progression. During this study, the expression pattern of three HO X gene produces (HOX-C6, -B3, and -B4) was examined immunocytochemically in human osteosarcoma (OS) tissues. In all observed (16/16) OS cases, HOX-C6 was present in over 90% of the neoplastically transformed cells (+ + + +), demonstrating a high to medium grade (A to B) staining intensity Similar re sults were obtained in OS cells for the other two observed proteins (HOX-B3 and -B4; over 90% or + + + + and a high to medium grade staining intensity or A and B). The significance of the expression of class I HOX proteins in the pathobiology, diagnosis and prognostication of human OS should be esta blished by further investigations.