Comment re: Temozolomide preferentially depletes cancer stem cells

Beier and colleagues ( 1), in contrast to previous studies ( 2– 4), show that temozolomide depletes clonogenic and highly tumorigenic cells in glioblastoma cultures and reduces tumorigenicity in vivo. The in vivo studies, however, raise concerns. Tumor xenografts were measured on T2-weighted magnetic resonance images (MRI; TR/TE 4,000/73 ms). In Fig. 6A of their report, the hyperintense signal of the xenograft is similar to cerebrospinal fluid (CSF). At this TR/TE value, a glial tumor without necrotic or cystic areas is expected to be less hyperintense than CSF. Although the MRI appearance may depend on transplantation techniques, the hyperintense signal of the xenografts seems related to regressive phenomena ( 5). The ventricles homolateral to the tumor are not compressed or displaced as expected; conversely, they seem slightly enlarged. Furthermore, the untreated xenograft in Fig. 6A of ref. 1 (upper left) shows an extra-axial CSF collection that does not favor the presence of an underlying mass lesion.