DISTRIBUTION OF HYPOXIA AND PROLIFERATION-ASSOCIATED MARKERS IN SPONTANEOUS CANINE TUMORS

The therapeutic response of malignant tumors depends on a number of fa ctors associated with tumor microenvironments including the possibilit y that these microenvironments change during treatment. Two factors, t umor hypoxia and cell proliferation, have been examined in spontaneous canine tumors undergoing multifraction radiation therapy. The approac h utilizes immunohistochemical analyses of hypoxia (CCI-103F) and prol iferation associated (PCNA) antigens in biopsy samples taken before an d after 5 daily fractions of 3 Gy (total dose 15 Gy). The tissue sampl es were formalin-fixed and paraffin-embedded for the immunohistochemic al study. Immunostaining of the sections for PCNA and hypoxia marker r eveals little or no overlap when the analysis is made prior to irradia tion. An increased degree of overlap seems to occur after 15 Gy but th e situation is complicated by a change towards more diffuse PCNA immun ostaining in the cells of the irradiated tissues.