Increased drug resistance of cultured human cancer cell lines in three‐dimensional cellular growth assay using collagen gel matrix

Toshiharu Furukawa, Tetsuro Kubota, Masahiko Watanabe, Suguru Kase, Yoshiro Saikawa, Hideki Nishibori, Tsong‐Hong ‐H Kuo, Susumu Kodaira, Kyuya Ishibiki, Masaki Kitajima