(-)-Gossypol enhances response to radiation therapy and results in tumor regression of human prostate cancer.

Radioresistance markedly impairs the efficacy of tumor radiotherapy and involves antiapoptotic signal transduction pathways that prevent radiation-induced cell death. The majority of human prostate cancers overexpress the important antiapoptotic proteins Bcl-2 and/or Bcl-xL, which render tumors resistant to radiation therapy. (-)-Gossypol, a natural polyphenol product from cottonseed, has recently been identified as a potent small molecule inhibitor of both Bcl-2 and Bcl-xL. In the current study, we investigated the antitumor activity of (-)-gossypol in prostate cancer and tested our hypothesis that (-)-gossypol may improve prostate cancer's response to radiation by potentiating radiation-induced apoptosis and thus making cancer cells more sensitive to ionizing radiation. Our data show that (-)-gossypol potently enhanced radiation-induced apoptosis and growth inhibition of human prostate cancer PC-3 cells, which have a high level of Bcl-2/Bcl-xL proteins. Our in vivo studies using PC-3 xenograft models in nude mice show that orally given (-)-gossypol significantly enhanced the antitumor activity of X-ray irradiation, leading to tumor regression in the combination therapy. In situ terminal deoxynucleotidyl transferase-mediated nick end labeling staining showed that significantly more apoptotic cells were induced in the tumors treated with (-)-gossypol plus radiation than either treatment alone. Anti-CD31 immunohistochemical staining indicates that (-)-gossypol plus radiation significantly inhibited tumor angiogenesis. Our results show that the natural polyphenol inhibitor of Bcl-2/Bcl-xL, (-)-gossypol, can radiosensitize prostate cancer in vitro and in vivo without augmenting toxicity. (-)-Gossypol may improve the outcome of current prostate cancer radiotherapy and represents a promising novel anticancer regime for molecular targeted therapy of hormone-refractory prostate cancer with Bcl-2/Bcl-xL overexpression.

[1]  Shaomeng Wang,et al.  (-)-Gossypol acts directly on the mitochondria to overcome Bcl-2- and Bcl-X(L)-mediated apoptosis resistance. , 2005, Molecular cancer therapeutics.

[2]  Dajun Yang,et al.  Molecular mechanism of gossypol-induced cell growth inhibition and cell death of HT-29 human colon carcinoma cells. , 2003, Biochemical pharmacology.

[3]  Han Ml,et al.  A comparative study on rapid and slow loading of gossypol in the treatment of gynecological diseases , 1984 .

[4]  E. Chang,et al.  Transferrin-liposome-mediated systemic p53 gene therapy in combination with radiation results in regression of human head and neck cancer xenografts. , 1999, Human gene therapy.

[5]  B D Kahan,et al.  The Synergistic Effects Of Cyclosporine, Sirolimus, And Brequinar On Heart Allograft Survival In Mice , 1995, Transplantation.

[6]  A. Rehemtulla,et al.  The role of apoptosis in 2',2'-difluoro-2'-deoxycytidine (gemcitabine)-mediated radiosensitization. , 2001, Clinical cancer research : an official journal of the American Association for Cancer Research.

[7]  J. Winfield,et al.  In vitro and in vivo cytotoxicity of gossypol against central nervous system tumor cell lines. , 1994, Journal of neuro-oncology.

[8]  S. Nicosia,et al.  Akt Phosphorylation and Stabilization of X-linked Inhibitor of Apoptosis Protein (XIAP)* , 2004, Journal of Biological Chemistry.

[9]  H. Pehamberger,et al.  Bcl-xL Antisense Oligonucleotides Chemosensitize Human Glioblastoma Cells , 2002, Chemotherapy.

[10]  M. Gleave,et al.  Targeting Anti-Apoptotic Genes Upregulated by Androgen Withdrawal Using Antisense Oligonucleotides to Enhance Androgen- and Chemo-Sensitivity in Prostate Cancer , 2002, Investigational New Drugs.

[11]  D. Hochhauser,et al.  Gossypol inhibition of mitosis, cyclin D1 and Rb protein in human mammary cancer cells and cyclin-D1 transfected human fibrosarcoma cells. , 1997, British Journal of Cancer.

[12]  R. Motzer,et al.  Computerized quantitation of synergism and antagonism of taxol, topotecan, and cisplatin against human teratocarcinoma cell growth: a rational approach to clinical protocol design. , 1994, Journal of the National Cancer Institute.

[13]  M. Scarsella,et al.  Treatment of melanoma cells with a bcl-2/bcl-xL antisense oligonucleotide induces antiangiogenic activity , 2003, Oncogene.

[14]  N. Kyprianou,et al.  bcl‐2 over‐expression delays radiation‐induced apoptosis without affecting the clonogenic survival of human prostate cancer cells , 1997, International journal of cancer.

[15]  A. Raffo,et al.  Antisense RNA down-regulation of bcl-xL Expression in prostate cancer cells leads to diminished rates of cellular proliferation and resistance to cytotoxic chemotherapeutic agents. , 2002, Cancer research.

[16]  A. Tari,et al.  Bcl-2-related antisense therapy. , 2002, Seminars in oncology.

[17]  John Calvin Reed,et al.  Immunohistochemical analysis of bcl-2, bax, bcl-X, and mcl-1 expression in prostate cancers. , 1996, The American journal of pathology.

[18]  E. Chang,et al.  Self-assembly of a virus-mimicking nanostructure system for efficient tumor-targeted gene delivery. , 2002, Human gene therapy.

[19]  M. Gleave,et al.  Synergistic chemosensitization and inhibition of progression to androgen independence by antisense Bcl‐2 oligodeoxynucleotide and paclitaxel in the LNCaP prostate tumor model , 2001, International journal of cancer.

[20]  T. Chou,et al.  Schedule-dependent synergism of taxol or taxotere with edatrexate against human breast cancer cells in vitro , 1995, Cancer Chemotherapy and Pharmacology.

[21]  John Calvin Reed,et al.  Expression of bcl-2 and the progression of human and rodent prostatic cancers. , 1996, Clinical cancer research : an official journal of the American Association for Cancer Research.

[22]  H. Pehamberger,et al.  Small interfering RNA targeting bcl-2 sensitizes malignant melanoma. , 2003, Oligonucleotides.

[23]  M. Han,et al.  [A comparative study on rapid and slow loading of gossypol in the treatment of gynecological diseases]. , 1984, Zhongguo yi xue ke xue yuan xue bao. Acta Academiae Medicinae Sinicae.

[24]  Guy S. Salvesen,et al.  X-linked IAP is a direct inhibitor of cell-death proteases , 1997, Nature.

[25]  Debabrata Banerjee,et al.  Sequence-dependent synergistic cytotoxicity of ecteinascidin-743 and paclitaxel in human breast cancer cell lines in vitro and in vivo. , 2002, Cancer research.

[26]  L. Beckett,et al.  BCL2 antisense reduces prostate cancer cell survival following irradiation. , 2002, Cancer biotherapy & radiopharmaceuticals.

[27]  D. Kuban,et al.  Bcl-2 is significantly overexpressed in localized radio-recurrent prostate carcinoma, compared with localized radio-naive prostate carcinoma. , 2003, International journal of radiation oncology, biology, physics.

[28]  S. Nicosia,et al.  Akt phosphorylation and stabilization of XIAP: A major mechanism of Akt-induced cell survival at post-mitochondrial level , 2004 .

[29]  M. Wannenmacher,et al.  Radiosensitization by pemetrexed of human colon carcinoma cells in different cell cycle phases. , 2003, International journal of radiation oncology, biology, physics.

[30]  T. Chou,et al.  Assessment of synergistic and antagonistic effects of chemotherapeutic agents in vitro. , 1994, Contributions to gynecology and obstetrics.

[31]  S. Shangary,et al.  Recent advances in the development of anticancer agents targeting cell death inhibitors in the Bcl-2 protein family , 2003, Leukemia.

[32]  M. Benito,et al.  cIAP‐1, but not XIAP, is cleaved by caspases during the apoptosis induced by TGF‐β in fetal rat hepatocytes , 2002, FEBS letters.

[33]  T. Chou,et al.  Quantitation of the synergistic interaction of edatrexate and cisplatin in vitro , 2004, Cancer Chemotherapy and Pharmacology.

[34]  H. H. Van Horn,et al.  Effects of gossypol from cottonseed on hematological responses and plasma alpha-tocopherol concentration of dairy cows. , 2002, Journal of dairy science.

[35]  R. D'Amato,et al.  Angiogenic potential of prostate carcinoma cells overexpressing bcl-2. , 2001, Journal of the National Cancer Institute.

[36]  M. Mego.  Telomerase inhibitors in anticancer therapy: gossypol as a potential telomerase inhibitor. , 2002, Bratislavske lekarske listy.

[37]  D. W. Fry,et al.  Anticancer therapy targeting the erbB family of receptor tyrosine kinases. , 2001, Seminars in oncology.

[38]  M. Gleave,et al.  Antisense targets to enhance hormone and cytotoxic therapies in advanced prostate cancer. , 2003, Current drug targets.

[39]  C. Coleman,et al.  Apoptosis and clonogenic cell death in PC3 human prostate cancer cells after treatment with gamma radiation and suramin. , 1997, Radiation research.

[40]  F. W. Cox,et al.  Biochemical correlates of the antitumor and antimitochondrial properties of gossypol enantiomers. , 1990, Molecular pharmacology.

[41]  M. Ergun,et al.  Apoptotic effect of gossypol on human lymphocytes , 2003, Cell biology international.

[42]  E. Chang,et al.  Systemic tumor-targeted gene delivery by anti-transferrin receptor scFv-immunoliposomes. , 2002, Molecular cancer therapeutics.

[43]  Mansoor M Ahmed,et al.  Didox (A Novel Ribonucleotide Reductase Inhibitor) Overcomes bcl-2 Mediated Radiation Resistance in Prostate Cancer Cell Line PC-3 , 2002, Cancer biology & therapy.

[44]  John Calvin Reed,et al.  Discovery, characterization, and structure-activity relationships studies of proapoptotic polyphenols targeting B-cell lymphocyte/leukemia-2 proteins. , 2003, Journal of medicinal chemistry.

[45]  Shaomeng Wang,et al.  In vitro Effects of the BH3 Mimetic, (−)-Gossypol, on Head and Neck Squamous Cell Carcinoma Cells , 2004, Clinical Cancer Research.

[46]  S. R. Datta,et al.  BAD and glucokinase reside in a mitochondrial complex that integrates glycolysis and apoptosis , 2003, Nature.

[47]  E. Chang,et al.  Transferrin-liposome-mediated p53 sensitization of squamous cell carcinoma of the head and neck to radiation in vitro. , 1997, Human gene therapy.

[48]  S. Grant,et al.  Induction of apoptotic DNA fragmentation and cell death in HL-60 human promyelocytic leukemia cells by pharmacological inhibitors of protein kinase C. , 1994, Cancer research.

[49]  S. Korsmeyer,et al.  Function of BID – a Molecule of the bcl-2 Family – in Ischemic Cell Death in the Brain , 2002, European Surgical Research.

[50]  E. Chang,et al.  Systemic p53 Gene Therapy of Cancer with Immunolipoplexes Targeted by Anti-Transferrin Receptor scFv , 2001, Molecular medicine.

[51]  C. Hudis,et al.  Oral Gossypol in the Treatment of Patients with Refractory Metastatic Breast Cancer: A Phase I/II Clinical Trial , 2001, Breast Cancer Research and Treatment.

[52]  T. Chou,et al.  Synergistic effects of new chemopreventive agents and conventional cytotoxic agents against human lung cancer cell lines. , 1999, Cancer research.

[53]  M. Koutsilieris,et al.  Response of PC-3 prostate cancer cells to combination therapy using irradiation with glucocorticoids or doxorubicin. , 1999, Anticancer research.

[54]  Non-viral gene delivery for p53. , 2000, Current opinion in molecular therapeutics.

[55]  D. Hossfeld,et al.  Indirect radiation leukemogenesis in DBA/2 mice: increased expression of B2 repeats in FDC-P1 cells transformed by intracisternal A-particle transposition , 1998, Annals of Hematology.

[56]  Jitsuo Usuda,et al.  Promotion of Photodynamic Therapy-Induced Apoptosis by the Mitochondrial Protein Smac/DIABLO: Dependence on Bax¶ , 2002, Photochemistry and photobiology.

[57]  A. Tolcher.  Preliminary phase I results of G3139 (bcl-2 antisense oligonucleotide) therapy in combination with docetaxel in hormone-refractory prostate cancer. , 2001, Seminars in oncology.

[58]  G. Hanks,et al.  Radiation inactivation of human prostate cancer cells: the role of apoptosis. , 1996, Radiation research.

[59]  H. Asgari,et al.  Gossypol effects on endothelial cells and tumor blood flow. , 1991, Life sciences.

[60]  Richard E. Moore,et al.  Transplantable Syngeneic Rodent Tumors , 2002 .

[61]  K. Chou,et al.  Gossypol, a component in cottonseed, induced increases in cytosolic Ca2+ levels in Chang liver cells. , 2002, Toxicon : official journal of the International Society on Toxinology.

[62]  D. Gandara,et al.  Antisense oligonucleotides in the treatment of non-small-cell lung cancer. , 2003, Clinical lung cancer.