bioRxiv2025
It is well-known that the cells die when a cancer cell line is continuously cultured without passage, even though it was kept in a fresh medium. However, none of this phenomenons decisive causes and mechanism(s) have been elucidated yet. After the cancer cell death, the medium exserted cytocidality. This cancer cell death (e.g., spontaneous, apoptosis, programmed) was found to be caused by only one kind of cytocidal substance (MW<1kDa) (named CSS) produced from the cells own component(s) by the cells themselves. CSS mammalian specifically by cancer cell lines but not nontumor cell lines and the CSS exerted cytocidality against other cell lines and vice versa regardless of species in mammalian. In vivo, CSS showed a significant life-prolonging effect without any adverse event. An established cell line derived from human renal cell carcinoma (HRC23) was used in this study as CSS was found and characterized by this cell line first. HighlightsO_LIOnly one kind of low molecular substance exerting cytocidality was found only in a medium after cancer cells death in the culture but not in non-tumor cell lines one. C_LIO_LIThe cytocidal substance (named CSS: cancer cell suicide substance) was a small molecule (MW<1kDa) with a slightly positively charged highly hydrophilic character. C_LIO_LICSS was produced regardless of extracellular nutritional condition, even in glucose-free HBSS (Nutrition-Free Method.) C_LIO_LICSS exserted cytocidality against other cancer cell lines irrespective of the histological patterns and the species of mammalian cells and vice versa. C_LIO_LICSS can be considered as a direct and critical substance produced from cell component(s) themselves by the cancer cells themselves. C_LIO_LIProduction of CSS was specific for cancer cells. This clear functional difference between cancer and nontumor cells should be meaningful embryologically. C_LIO_LIIn vivo, CSS showed complete anti-metastasis during administration period against Lewis Lung Carcinoma (LLC) transplanted mouse without any adverse event. CSS may have high potential as a new type of cancer therapy drug. C_LI In shortThis study is so simple, absolutely reproducible and anyone can reproduce this study with an easy basic method. A critical substance CSS (cancer cell suicide substance) of spontaneous cancer cell death was found in a medium after the cancer cells had been dead. Only one kind of small-size substance with MW<1kDa with a highly water-soluble and positively charged character is made only from cell own component(s) itself by the cells themselves. Even in a nutrition-free physiologically balanced salt solution, CSS was produced regardless of extracellular nutritional condition. Only cancer cell lines produced CSS, but not by non-tumor cell lines. CSS exserted cytocidality against other histologically different patterns of cancer cell lines regardless of species and vice versa. The anticancer effect of HRC23 produced CSS in vivo against mouse LLC (Lewis Lung Carcinoma)-transplanted mice showed a clear life-prolonging effect without any adverse event. Thus, CSS may have the possibility to be a cancer therapy drug. And, in view of embryologically, this clear difference of CSS production between cancer cells and nontumor cells will be important event.