Combination of genistein with ionizing radiation on androgen-independent prostate cancer cells.
OBJECTIVE
To study the effect of the combined use of genistein and ionizing radiation (IR) on prostate DU145 cancer cells.


METHODS
DU145, an androgen-independent human prostate cancer cell line, was used in the experiment. Clonogenic assay was used to compare the survival of DU145 cells after treatments with genistein alone and in combination with graded IR. Apoptosis was assayed by DNA ladder and TUNEL stain. Cell cycle alterations were observed by flow cytometry and related protein expressions by immunoblotting.


RESULTS
Clonogenic assay demonstrated that genistein, even at low to medium concentrations, enhanced the radiosensitivity of DU145 cells. Twenty-four hours after treatment with IR and/or genistein, apoptosis was mainly seen with genistein at high concentrations and was minimally related to IR. At 72 h, apoptosis also occurred in treatment with lower concentration of genistein, especially when combined with IR. While both IR and genistein led to G2/M cell cycle arrest, combination of them further increased the DU145 cells at G2/M phase. This G2/M arrest was largely maintained at 72 h, accompanied by increasing apoptosis and hyperdiploid cell population. Cell-cycle related protein analysis disclosed biphasic changes in cyclin B1 and less dramatically cdc-2, but stably elevated p21 cip1 levels with increasing genistein concentrations.


CONCLUSIONS
Genistein enhanced the radiosensitivity of DU145 prostate cancer cells. The mechanisms might be involved in the increased apoptosis, prolonged cell cycle arrest and impaired damage repair.
Yan
Sen-Xiang
SX
Department of Radiology, First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou 310003, China.
Ejima
Yasuo
Y
Sasaki
Ryohei
R
Zheng
Shu-Sen
SS
Demizu
Yusuke
Y
Soejima
Toshinori
T
Sugimura
Kazuro
K
D000728:Androgens / Q000502:physiology*; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D004273:DNA, Neoplasm / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics; D005434:Flow Cytometry; D019833:Genistein / Q000494:pharmacology*; D006801:Humans; D015151:Immunoblotting; D020287:In Situ Nick-End Labeling; D008297:Male; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000532:radiotherapy*; D014410:Tumor Stem Cell Assay
D000728:Androgens; D016588:Anticarcinogenic Agents; D004273:DNA, Neoplasm; D019833:Genistein