Targeting bortezomib-induced aggresome formation using vinorelbine enhances the cytotoxic effect along with ER stress loading in breast cancer cell lines.
The ubiquitin-proteasome and autophagy-lysosome pathways are two major self-digestive systems for cellular proteins. Ubiquitinated misfolded proteins are degraded mostly by proteasome. However, when ubiquitinated proteins accumulate beyond the capacity of proteasome clearance, they are transported to the microtubule-organizing center (MTOC) along the microtubules to form aggresomes, and subsequently some of them are degraded by the autophagy-lysosome system. We previously reported that macrolide antibiotics such as azithromycin and clarithromycin block autophagy flux, and that concomitant treatment with the proteasome inhibitor bortezomib (BZ) and macrolide enhances endoplasmic reticulum (ER) stress-mediated apoptosis in breast cancer cells. As ubiquitinated proteins are concentrated at the aggresome upon proteasome failure, we focused on the microtubule as the scaffold of this transport pathway for aggresome formation. Treatment of metastatic breast cancer cell lines (e.g., MDA-MB‑231 cells) with BZ resulted in induction of aggresomes, which immunocytochemistry detected as a distinctive eyeball-shaped vimentin-positive inclusion body that formed in a perinuclear lesion, and that electron microscopy detected as a sphere of fibrous structure with some dense amorphous deposit. Vinorelbine (VNR), which inhibits microtubule polymerization, more effectively suppressed BZ-induced aggresome formation than paclitaxel (PTX), which stabilizes microtubules. Combined treatment using BZ and VNR, but not PTX, enhanced the cytotoxic effect and apoptosis induction along with pronounced ER stress loading such as upregulation of GRP78 and CHOP/GADD153. The addition of azithromycin to block autophagy flux in the BZ plus VNR-containing cell culture further enhanced the cytotoxicity. These data suggest that suppression of BZ-induced aggresome formation using an inhibitory drug such as VNR for microtubule polymerization is a novel strategy for metastatic breast cancer therapy.
Department of Breast Surgery, Tokyo Medical University, Tokyo, Japan.
Kana
K
Miyahara
Department of Biochemistry, Tokyo Medical University, Tokyo, Japan.
Hiromi
H
Kazama
Laboratory of Electron Microscopy, Tokyo Medical University, Tokyo, Japan.
Hiroko
H
Kokuba
Department of Breast Surgery, Tokyo Medical University, Tokyo, Japan.
Seiichiro
S
Komatsu
Department of Biochemistry, Tokyo Medical University, Tokyo, Japan.
Ayako
A
Hirota
Department of Biochemistry, Tokyo Medical University, Tokyo, Japan.
Jun
J
Takemura
Department of Otolaryngology (Head and Neck Surgery), Tokyo Medical University, Tokyo, Japan.
Kazuhiro
K
Hirasawa
Department of Biochemistry, Tokyo Medical University, Tokyo, Japan.
Shota
S
Moriya
Department of Biochemistry, Tokyo Medical University, Tokyo, Japan.
Akihisa
A
Abe
Department of Biochemistry, Tokyo Medical University, Tokyo, Japan.
Masaki
M
Hiramoto
Department of Breast Surgery, Tokyo Medical University, Tokyo, Japan.
Takashi
T
Ishikawa
Department of Biochemistry, Tokyo Medical University, Tokyo, Japan.
Keisuke
K
Miyazawa
D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001343:Autophagy / Q000187:drug effects; D015153:Blotting, Western; D000069286:Bortezomib / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D049109:Cell Proliferation / Q000187:drug effects; D004357:Drug Synergism; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D005260:Female; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects*; D014407:Tumor Cells, Cultured; D014747:Vinblastine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000077235:Vinorelbine
D000970:Antineoplastic Agents; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D014747:Vinblastine; D000069286:Bortezomib; D046988:Proteasome Endopeptidase Complex; D000077235:Vinorelbine