The first successful heterotransplantation of a human carcinoid tumor into nude mice is reported. CSH, a voluminous hepatic metastasis of a primary bronchial carcinoid tumor (CSB) was resected and transplanted into three irradiated nude (Swiss-nu/nu) mice both by subcutaneous (SC) and intramuscular (IM) routes; the success rate was five of six. Heterotransplanted tumors took 4 to 5 months to appear in the mice and 1 month to attain a width of 0.5 cm. Both human and mouse tumors (named CSH-SC and CSH-IM) were studied by light and electron microscopy. They were Grimelius-positive, neuron-specific enolase-positive, and bombesin-negative by immunocytochemistry. Furthermore, CSH-SC cells presented characteristic (pear-shaped, rod-shaped, or tadpole-shaped) neurosecretory granules. Although CSB and CSH were slightly serotonin positive by immunocytochemistry, only a few serotonin-positive cells were found in CSH-SC and none in CSH-IM, suggesting partial loss of differentiation or an increase in serotonin catabolism during transplantation.
Retrovirus-like intracisternal R-type particles (IRP) are structures present in Syrian hamster (Mesocricetus auratus) cells cultured in vitro where they appear either spontaneously or under chemical induction conditions. We have tested several chemical inducers and ten different cell lines, looking for the best IRP induction conditions. BHK21 cl. 13 showed the highest inducibility one day after a 24 h treatment with 1 microgram/ml of 5-aza-2'-deoxycytidine. Using detergent treatments and sucrose gradients, we obtained semi-purified IRP cores. A 7.2 kb RNA associated with the core fraction was revealed by hybridization with total Syrian hamster genomic DNA, but not with Syrian hamster intracisternal A particle (IAP) specific probes. This suggests that the IRP genes are distinct from IAP ones.
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