Abstract 3370: CD133 and CD87 in small cell lung cancer cells are not sufficient markers of cancer stem cells, showing chemoresistant populations
Authors: Kubo Toshio , Takigawa Nagio , Osawa Masahiro , Ochi Nobuaki , Harada Daijiro , Yasugi Masayuki , Ninomiya Takashi , Tanimoto Mitsune , Kiura Katsuyuki 
Published: February 2011

Abstract
Background: More than 80% of all patients with small cell lung cancer (SCLC) receiving chemotherapy achieve an objective response; however, most responders eventually relapse because of drug resistance. Tumors are presumed to contain a small population of cancer stem cells (CSCs) that initiate tumor growth and promote tumor spreading. Multidrug resistance in CSCs is thought to allow the tumor to evade conventional therapy. This study focused on the expression of CD133 and CD87, because CD133 is a putative marker of CSCs in some cancers including brain, colon and lung and CD87 is associated with stem cell like properties in SCLC.
Material and methods: This study used six SCLC cell lines (SBC-3, 4, 5, 6, 7, 9) established in the laboratory. The sensitivities of these cell lines to cisplatin, etoposide, paclitaxel, SN-38 (active metabolite of irinotecan), and amrubicinol (active metabolite of amrubicin) were determined by an MTT assay. The expression levels of CD133 and CD87 were analyzed by real-time quantitative reverse transcriptase-PCR assay and flow cytometry. CD133+/− and CD87+/− cells were isolated by flow cytometry and were subsequently cloned twice. Cell cycle traverse perturbations were analyzed by flow cytometry using propidium iodide and Pyronin Y. NOD/SCID mice were used for the tumor formation assay.
Results: The SBC-7 cells showed the highest expression levels of both CD133 and CD87 among the six cell lines. CD133-/CD87-, CD133+/CD87-, and CD133-/CD87+ cells were successfully isolated from SBC-7 cells; however, double positive cells could not be isolated. Both CD133+/CD87- and CD133-/CD87+ sub-populations showed higher resistance to chemotherapeutic drugs and repopulating ability, and contained more G0 quiescent cells than the CD133-/CD87- sub-population in vitro. Contrary to expectations, the CD133-/CD87- as well as the CD133+/CD87- sub-populations showed higher tumorigenic potential than the CD133-/CD87+ sub-population in vivo. When 5000 (or 2000) CD133+/CD87-, CD133-/CD87+, and CD133-/CD87- cells were inoculated into NOD/SCID mice, the tumors were detected in 100% (or 50%), 67% (or 0%) and 100% (or 100%), respectively. The drugs were screened for their ability to overcome the high resistance of CD133+/CD87- cells to chemotherapy and zoledronic acid was thus found to restore the sensitivity of CD133+/CD87- cells to amrubicinol in vitro.
Conclusions: Both CD133 and CD87 proved to be inadequate markers for CSCs, however, they were able to predict resistance to chemotherapy. Amrubicin in combination with zoledronic acid might be beneficial for the treatment of SCLC patients who are refractory to conventional chemotherapy.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3370.