title: Lapatinib-resistant cancer cells possessing epithelial cancer stem cell properties develop sensitivity during sphere formation by activation of the ErbB/AKT/cyclin D2 pathway.
abstract: Lapatinib, a dual inhibitor of epidermal growth factor receptor (EGFR)/ErbB2, has antiproliferative effects and is used to treat patients with ErbB2-positive metastatic breast cancer. In the present study, we examined the effects of lapatinib on growth of oral and prostate cancer cells. Oral squamous cell carcinoma (OSCC) cell lines HSC3, HSC4 and Ca9-22 were sensitive to the antiproliferative effects of lapatinib in anchorage-dependent culture, but the OSCC cell lines KB and SAS and the prostate cancer cell line DU145 were resistant to lapatinib. Phosphorylation levels of EGFR in all cell lines decreased during lapatinib treatment in anchorage‑dependent culture. Furthermore, the phosphorylation levels of ErbB2, ErbB3 and Akt and the protein levels of cyclin D1 were decreased by lapatinib treatment of HSC3, HSC4 and Ca9-22 cells. ErbB3 was not expressed and cyclin D1 protein levels were not altered by lapatinib treatment in KB, DU145 and SAS cells. The phosphorylation of ErbB2 and AKT was not affected by lapatinib in SAS cells and was not detected in KB and DU145 cells. Lapatinib-resistant cell lines exhibited sphere-forming ability, and SAS cells developed sensitivity to lapatinib during sphere formation. The phosphorylation levels of ErbB2 and AKT and protein levels of cyclin D2 increased during sphere formation of SAS cells and decreased with lapatinib treatment. In addition, sphere formation of SAS cells was inhibited by the AKT inhibitor MK2206. AKT phosphorylation and cyclin D2 levels in SAS spheres were decreased by MK2206 treatment. SAS cells expressed E-cadherin, but not vimentin and KB cells expressed vimentin, but not E-cadherin. DU145 cells expressed vimentin and E-cadherin. These results suggested that phosphorylation of EGFR and ErbB2 by cell detachment from the substratum induces the AKT pathway/cyclin D2-dependent sphere growth in SAS epithelial cancer stem-like cells, thereby rendering SAS spheres sensitive to lapatinib treatment.
authors.affiliation: Department of Cell Biology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Ohnishi
authors.affiliation: Department of Cell Biology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Yasui
authors.affiliation: Second Department of Oral and Maxillofacial Surgery, Osaka Dental University, Hirakata, Osaka 573-1121, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Kakudo
authors.affiliation: Department of Cell Biology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan.
authors.forename: Masami
authors.initials: M
authors.lastname: Nozaki
mesh_terms: D015820:Cadherins / Q000096:biosynthesis; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D045744:Cell Line, Tumor; D019938:Cyclin D1 / Q000096:biosynthesis* / Q000235:genetics; D056742:Cyclin D2 / Q000096:biosynthesis* / Q000235:genetics; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D066246:ErbB Receptors / Q000096:biosynthesis / Q000235:genetics; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D000077341:Lapatinib; D008297:Male; D009062:Mouth Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D010766:Phosphorylation; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D051057:Proto-Oncogene Proteins c-akt / Q000096:biosynthesis* / Q000235:genetics; D011799:Quinazolines / Q000008:administration & dosage; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis* / Q000235:genetics; D020893:Receptor, ErbB-3 / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D015820:Cadherins; D019938:Cyclin D1; D056742:Cyclin D2; D066246:ErbB Receptors; D000077341:Lapatinib; D051057:Proto-Oncogene Proteins c-akt; D011799:Quinazolines; D018719:Erb-b2 Receptor Tyrosine Kinases; D020893:Receptor, ErbB-3; C530104:CCND1 protein, human; C080336:CCND2 protein, human; C512478:EGFR protein, human; C508053:ERBB2 protein, human; C581292:ERBB3 protein, human