Introduction: Cu-64-diacetyl-bis (N-4-methylthiosemicarbazone) (Cu-64-ATSM) is a potential imaging agent of hypoxic tumor for use with PET. Recent literature demonstrated that cancer cells expressing CD 133, which is a frequently used marker for so-called cancer stem cells or cancer stem cell-like cells (collectively referred to here as CSCs), contribute to tumor's therapeutic resistance and metastasis ability. Culturing under hypoxia is also reported to enlarge the proportion of CD133(+) cells, which would indicate survival advantage of CD133(+) cells under hypoxia. Here, we investigated the relationships between Cu-64-ATSM accumulation and existence of CD133(+) cells using mouse colon carcinoma (colon-26) tumor.
Methods: Intratumor distribution of Cu-64-ATSM and F-18-fluorodeoxyglucose ((18)FDG) was compared with immunohistochemical staining for CD133 with a colon-26 model. In vitro characterization of CD133(+) colon-26 cells was also performed.
Results: In colon-26 tumors, Cu-64-ATSM localized preferentially in regions with a high density of CDI33(+) cells. The percentage of CD133(+) cells was 11-fold higher in Cu-64-ATSM high-uptake regions compared with (18)FDG high- (but Cu-64-ATSM low-) uptake regions. CD133(+) colon-26 cells showed characteristics previously linked with CSCs in other cancer cell lines, such as high colony-forming ability, high tumor-initiating ability and enrichment under hypoxic cultivation. The proportion of CD133(+) cells was enlarged by culturing under glucose starvation as well as hypoxia, and Cu-64-ATSM uptake was increased under such conditions.
Conclusions: Our findings showed that, in colon-26 tumors, Cu-64-ATSM accumulates in rich regions of CD133(+) cells with characteristics of CSCs. Therefore Cu-64-ATSM could be a potential imaging agent for rich regions of CD133(+) cells, associated with CSCs, within tumors. (C) 2010 Elsevier Inc. All rights reserved.