Non-migratory tumorigenic intrinsic cancer stem cells ensure breast cancer metastasis by generation of CXCR4(+) migrating cancer stem cells.

Although the role of metastatic cancer stem cells (mCSCs) in tumor progression has been well documented, our study reveals a hitherto unidentified role of tumorigenic intrinsic CSCs (iCSCs) in breast cancer metastasis. We show that unlike highly migratory mCSCs residing in the breast tumor disseminating/peripheral regions, iCSCs populate the inner mass of the tumor and are non-migratory. However iCSCs, via paracrine signaling, induce conversion of non-stem cancer cells to CSCs that (i) are identical to the previously reported mCSCs, and (ii) in contrast to iCSCs, express chemokine receptor, chemokine (C-X-C motif) receptor 4 (CXCR4), which is crucial for their metastatic potential. These mCSCs also demonstrate high in vivo tumorigenicity. Physical non-participation of iCSCs in metastasis is further validated in vivo, where only mCSCs are found to exist in the metastatic sites, lymph nodes and bone marrow, whereas the primary tumor retains both iCSCs and mCSCs. However, iCSCs ensure metastasis since their presence is crucial for deliverance of highly metastatic CXCR4(+) mCSCs to the migrating fraction of cells. Cumulatively, these results unveil a novel role of iCSCs in breast cancer metastasis as parental regulators of CXCR4(+) mCSCs, and highlight the therapeutic requisite of targeting iCSCs, but not CXCR4(+) mCSCs, to restrain breast cancer metastasis from the root by inhibiting the generation of mCSCs from iCSCs. Considering the pivotal role of iCSCs in tumor metastasis, the possibility of metastasis to be a 'stem cell phenomena' is suggested.

Cytokine gene therapy or infusion as treatment for solid human cancer.

In the induction of tissue-directed immune responses, cytokines tend to be released within the affected tissues. We used two strategies to expose tumor tissues to continuous high levels of cytokines: First, a vaccinia interleukin (IL)2 recombinant was injected directly intratumorally 3-weekly at 10(7) pfus/dose in six patients with the solid tumor malignant mesothelioma (MM). No virus excretion was detectable. At each cycle vaccinia-IL-2 mRNA (SQ [semi-quantitative] reverse transcription polymerase chain reaction) was maximal 24-72 h following injection reduced at 8 days and faded by 21 days. No tumor regression occurred. Second, based on the success of granulocyte macrophage colony-stimulating factor (GM-CSF) in gene transfer experiments, we conducted a study using continuous intratumoral GM-CSF infusion in eight patients with MM using a portable pump at doses of 10 micro/cg/24 h over 8 weeks. Systemic neutrophil agglutination and local catheter-related difficulties occurred. Two patients demonstrated tumor necrosis, one of whom had a marked progressive mononuclear cell infiltration of the tumor associated with a partial response (>50% reduction in tumor area). Murine studies using our MM model in CBA and BALB/C mice have demonstrated that B7-1 and allo-class I transfections induce strong tumor-specific cytotoxic T lymphocyte responses: GM-CSF, IL-12, and IL-2 induced mixed nonspecific plus specific responses, whereas B7-2 and class II transfections were not effective. We conclude that increased intratumoral cytokine concentrations can be generated using both gene transfer and cytokine infusion approaches; however, both have their limitations and, at this stage, have not produced dramatic antitumor effects in humans.