CELLULAR AND MOLECULAR MECHANISMS OF METASTASIS AS APPLIED TO CARCINOMATOUS MENINGITIS

Cancer cells as well as bacteria metastasize to the subarachnoidal spa ce (SAS) causing meningitis. Primary brain tumors, although not formin g distant metastases, disseminate via the cerebrospinal fluid and occu py the meninges. The multistep process of cancer or bacterial dissemin ation is regulated through molecular crosstalk between invaders and ho st cells. Such crosstalks establish invasion-promoter and invasion-sup pressor complexes. In carcinomatous and bacterial meningitis, the part icipation of host cells is prominent since leukocytes and inflammatory cytokines are the major determinants of malignancy. We propose a mode l in which bacterial breakdown products activate endothelial cells, a process leading to leukocyte extravasation. This initiates a cascade o f inflammatory processes opening up the blood cerebrospinal fluid barr ier and producing access for new invaders.