IN VITRO INCORPORATION OF [3H]TdR IN HUMAN AND MURINE SOLID TUMOURS

Abstract

ABSTRACTABSTRACTUsing in vitro labelling with [3H]TdR, we measured the variation in mean grain count (MGC) with the distance from the periphery of the biopsy in twenty‐nine human solid tumours (seventeen squamous cell carcinomas of the oral cavity, seven mesenchymal sarcomas and five embryonal tumours). We found a decrease for two histological types of tumours (from 32 to 8 grains for squamous cell carcinomas and 19 to 9 grains for embryonal tumours, comparing the outer 0–40 μm zone to the inner 81–120 μm zone). The number of grains per cell was usually sufficient to provide a satisfactory estimation of the labelling index (LI) in the zone which is routinely studied (80 to 100 μm from the periphery). However, for squamous cell carcinomas for instance, we found the maximal LI between 21 and 40 μm (135% of the mean global LI) and only 77% in the region situated between 81 and 100 μm. Therefore, the probability of underestimating the LI in deeper regions should not be neglected (problems of penetration, metabolism or incorporation of [3H]TdR). This is why we have employed more sophisticated labelling methods to try to improve the results.In a murine mammary tumour (EMT6), we studied the influence of either hyperbaric oxygen (HPO) or 5‐FU or a combination of the two (5‐FU + HPO) on the change with depth in MGC and LI. In this murine tumour, as in the human tumours studied, MGC decreases slowly with increasing depth (MGC is 30 grains in 0–20 μm zone and 13 in 180–200 μm, and LI in the same zones, 29 and 16%). However, in neither case is the LI maximal at the periphery in spite of maximal MGC; this is probably due to local trauma. In two of the treated groups (5‐FU and 5‐FU + HPO), the MGC is significantly higher than controls (mean ratios: treated/control 1.3 and 1.4 respectively), whereas in the presence of hyperbaric oxygen alone no significant difference is observed. However, LI is greater in all three treated groups than in controls (mean ratios in presence of: HPO or 5‐FU or 5‐FU + HPO/conventional method 1.3, 1.3 and 1.2 respectively) and their change with depth follows a similar profile. In spite of the LI decrease with depth, if the area examined is chosen correctly, these improved techniques which preserve tissue integrity should provide a better LI estimation than conventional labelling methods.