we have demonstrated that the s.c. co-inoculation of fibroblasts with different kinds of tumor cells of animal origin [ rat rhabdomyosarcoma ( rms ) 9-4/0 , rat hepato-carcinoma fao ] or human origin ( colonic adenocarcinoma ht29 , ewing 's sarcoma pleural metastasis ew-s1 ) is necessary for tumor take and growth when the number of tumor cells alone is below the tumorigenic dose .
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fibroblasts
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cells