Selective methioninase-induced trap of cancer cells in S/G2 phase visualized by FUCCI imaging confers chemosensitivity

// Shuya Yano 1,2,3 , Shukuan Li 1 , Qinghong Han 1 , Yuying Tan 1 , Michael Bouvet 2 , Toshiyoshi Fujiwara 3 and Robert M. Hoffman 1,2 1 AntiCancer, Inc, San Diego, CA 2 Department of Surgery, University of California, San Diego, CA 3 Department of Gastroenterological Surgery, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan Correspondence: Robert M. Hoffman, email: // Keywords : cell cycle, FUCCI, imaging, S/G 2 phase block, recombinant methioninase, rMETase, chemotherapy, HeLa cells, MCF-7 cells Received : July 18, 2014 Accepted : August 18, 2014 Published : August 19, 2014 Abstract A major impediment to the response of tumors to chemotherapy is that the large majority of cancer cells within a tumor are quiescent in G 0 /G 1 , where cancer cells are resistant to chemotherapy. To attempt to solve this problem of quiescent cells in a tumor, cancer cells were treated with recombinant methioninase (rMETase), which selectively traps cancer cells in S/G 2 . The cell cycle phase of the cancer cells was visualized with the fluorescence ubiquitination-based cell cycle indicator cell cycle indicator (FUCCI). At the time of rMETase-induced S/G 2 -phase blockage, identified by the cancer cells’ green fluorescence by FUCCI imaging, the cancer cells were administered S/G 2 -dependent chemotherapy drugs, which interact with DNA or block DNA synthesis such as doxorubicin, cisplatin, or 5-fluorouracil. Treatment of cancer cells with drugs only, without rMETase-induced S/G 2 phase blockage, led to the majority of the cancer-cell population being blocked in G 0 /G 1 phase, identified by the cancer cells becoming red fluorescent in the FUCCI system. The G 0 /G 1 blocked cells were resistant to the chemotherapy. In contrast, trapping of cancer cells in S/G 2 phase by rMETase treatment followed by FUCCI-imaging-guided chemotherapy was highly effective in killing the cancer cells.