Browsing by Author "Sarkar, Susobhan"

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    In Vivo MR Imaging of Tumor-Associated Macrophages: The Next Frontier in Cancer Imaging
    (SAGE Publications, 2018-03-22) Yang, Runze; Sarkar, Susobhan; Yong, Voon Wee E.; Dunn, Jeff F.
    There is a complex interaction between cancer and the immune system. Tumor-associated macrophages (TAMs) can be subverted by the cancer to adopt a pro-tumor phenotype to aid tumor growth. These anti-inflammatory, pro-tumor TAMs have been shown to contribute to a worsened outcome in several different types of cancer. Various strategies aimed at combating the pro-tumor TAMs have been developed. Several therapies, such as oncolytic viral therapy and high-intensity focused ultrasound, have been shown to stimulate TAMs and suppress tumor growth. Targeting TAMs is a promising way to combat cancer, but sensitive imaging methods that are capable of detecting these therapeutic responses are needed. A promising idea is to use imaging contrast agents to label TAMs to determine their relative number and location within, and around the tumor. This can provide information about the efficacy of TAM depletion therapies, as well as macrophage-stimulating therapies. In this review, we describe various in vivo MRI methods capable of tracking TAMs, and conclude with a short section on tracking TAMs in patients.
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    Therapeutic activation of macrophages and microglia to suppress brain tumor-initiating cells
    (Nature Publishing Group, 2013-12-08) Sarkar, Susobhan; Doring, Axinia; Zemp, Franz J; Silva, Claudia; Lun, Xueqing; Wang, Xiuling; Kelly, John; Hader, Walter; Hamilton, Mark; Mercier, Philippe; Dunn, Jeffery F.; Kinniburgh, Dave; van Rooijen, Nico; Robbins, Stephen; Forsyth, Peter; Cairncross, Gregory; Weiss, Samuel; Yong, V Wee
    Brain tumor initiating cells (BTICs) contribute to the genesis and recurrence of gliomas. We examined whether the microglia and macrophages that are abundant in gliomas alter BTIC growth. We found that microglia derived from non-glioma human subjects markedly mitigated the sphere-forming capacity of glioma patient–derived BTICs in culture by inducing the expression of genes that control cell cycle arrest and differentiation. This sphere-reducing effect was mimicked by macrophages, but not by neurons or astrocytes. Using a drug screen, we validated amphotericin B (AmpB) as an activator of monocytoid cells and found that AmpB enhanced the microglial reduction of BTIC spheres. In mice harboring intracranial mouse or patient-derived BTICs, daily systemic treatment with non-toxic doses of AmpB substantially prolonged life. Notably, microglia and monocytes cultured from glioma patients were inefficient at reducing the sphere-forming capacity of autologous BTICs, but this was rectified by AmpB. These results provide new insights into the treatment of gliomas.