ABSTRACT
This study is to observe whether platycodin D has the guiding role in treatment of mouse lung cancer with doxorubicin and explore its guiding mechanism. In vitro, platycodin D and doxorubicin(alone or in combination) were added into Lewis lung cancer(LLC) cells to detect the cell proliferation and doxorubicin uptake. Cell morphological changes were analyzed by cell holographic analysis system; cell gap junctional intercellular communication(GJIC) was tested by fluorescent yellow tracer; lyso-tracker red was used to examine lysosomal function; LC-3 B(Light chain 3 beta)and P62(heat shock 90-like protein)staining were used to test auto-phagy and autophagic degradation respectively; and P-glycoprotein(P-gp) expression was examined by Western blot. In vivo, lung solid tumor was formed in mouse LLC cells via intravenous injection. Platycodin D and doxorubicin(alone or in combination) were used to treat tumor-bearing mice for four weeks, and then the tumor size was examined, mouse survival time was recorded, doxorubicin uptake in lung tissues was tested, and lung tissues were stained for observation by HE(hematoxylin-eosin) and immunohistochemistry. The results showed that platycodin D at the experimental concentration had no effect on LLC cell proliferation but decreased LLC cell volume, promoted the cells to uptake doxorubicin and enhanced the inhibitory action of doxorubicin on cell proliferation. Platycodin D could promote GJIC and lysosomal function, increase autophagy and autophagic degradation and suppress P-gp expression. Platycodin D at the experimental dose in this study had no effect on LLC lung solid tumors in mice, increased doxorubicin uptake in lung tissues and enhanced the therapeutic efficacy of doxorubicin on lung solid tumors. Platycodin D could improve the extracellular matrix deposition in lung solid tumors, decreased the lung mucin 5 AC secretion and pulmonary vessel permeability. In summary, platycodin D had the guiding role in treating mouse lung cancer with doxorubicin, and its guiding mechanism may be associated with the promotion of cell communication, lysosomal function, and improvement of extracellular environment.