title: Resistance to paclitaxel therapy is related with Bcl-2 expression through an estrogen receptor mediated pathway in breast cancer.
abstract: Taxanes are approved for the treatment of breast cancer that has spread to the lymph nodes, following surgery and doxorubicin containing chemotherapy. Taxanes have improved the survival of breast cancer patients, especially in estrogen receptor (ER) negative population in clinical settings. This time we examined the relationship between chemosensitivity to Taxanes and expresson of ERalpha in breast cancer cell lines. In vitro effects of paclitaxel in 4 ER-positive and 3 ER-negative breast cancer cell lines were investigated by MTT assay. We also investigated members of Bcl-2 family by Western blotting and RT-PCR to clarify their role in paclitaxel resistance both in ER-positive and in ER-negative cells. ER-negative cell lines were more sensitive to paclitaxel than ER-positive cells. ER-negative KPL-4 and ZR-75-30 cells, which were sensitive to paclitaxel, became resistant when they were treated with demethylation agent, 5-aza-2'-deoxycytidine. Analysis of proapoptotic (Bax) and antiapoptotic (Bcl-2) molecules suggested that Bcl-2 is likely to have a role in the resistance of ER-positive cells. Bcl-2 expression was increased in a time-dependent manner after treatment of ER-positive cell lines with estrogen (E2). On the other hand, Bcl-2 was not detected in ER-negative cell lines. However, no significant difference was detected for Bax mRNA levels before and after E2 treatment in ER-positive and negative cell lines. Activation of ER gene expression in ER-negative KPL-4 cells by 5-aza-2'-deoxycytidine resulted in up-regulation of Bcl-2 mRNA. To support our data, we examined paclitaxel sensitivity in ER-negative MDA-MB-231 and ER stable transfectant cells S30 and JM6. This experiment also showed ER-negative cells were sensitive to paclitaxel but ER-positive cells were resistant to it. These results suggest that ER influenced chemosensitivity to paclitaxel through regulation of Bcl-2 family and regulation of the pathway may be crucial to increase the efficacy of taxanes in ER-positive breast cancer.
authors.affiliation: Department of Gastroenterological Surgery, Transplant, and Surgical Oncology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, and Department of Surgery, Okayama City Hospital, Okayama 700-8558, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Tabuchi
authors.forename: Junji
authors.initials: J
authors.lastname: Matsuoka
authors.forename: Mehmet
authors.initials: M
authors.lastname: Gunduz
authors.forename: Takako
authors.initials: T
authors.lastname: Imada
authors.forename: Ryoko
authors.initials: R
authors.lastname: Ono
authors.forename: Mitsuya
authors.initials: M
authors.lastname: Ito
authors.forename: Takayuki
authors.initials: T
authors.lastname: Motoki
authors.forename: Tomoki
authors.initials: T
authors.lastname: Yamatsuji
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Shirakawa
authors.forename: Munenori
authors.initials: M
authors.lastname: Takaoka
authors.forename: Minoru
authors.initials: M
authors.lastname: Haisa
authors.forename: Noriaki
authors.initials: N
authors.lastname: Tanaka
authors.forename: Junichi
authors.initials: J
authors.lastname: Kurebayashi
authors.forename: V Craig
authors.initials: VC
authors.lastname: Jordan
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Naomoto
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000627:therapeutic use*; D017209:Apoptosis; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D019008:Drug Resistance, Neoplasm; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D019254:Genes, bcl-2; D006801:Humans; D017239:Paclitaxel / Q000627:therapeutic use*; D011960:Receptors, Estrogen / Q000187:drug effects / Q000235:genetics / Q000502:physiology*
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D011960:Receptors, Estrogen; D004958:Estradiol; D017239:Paclitaxel