1. Cancer Center & Department of Breast and Thyroid Surgery, Xiang'an Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, China.
2. Cancer Research Center, School of Medicine, Xiamen University, Xiamen, Fujian, China.
3. Clinical Central Research Core and Key Laboratory for Endocrine-Related Cancer Precision Medicine of Xiamen, Xiang'an Hospital of Xiamen University, Xiamen, Fujian, China.
4. The Breast Center, Cancer Hospital of Shantou University Medical College, Shantou, Guangdong, China.
5. Guangdong Provincial Key Laboratory for Breast Cancer Diagnosis and Treatment, Cancer Hospital of Shantou University Medical College, Shantou 515041, China.
6. Present address: Department of Thyroid and Breast Surgery, The Eighth Affiliated Hospital, Sun Yat-sen University, Shenzhen, Guangdong, China.
*These authors contributed equally to this study.
Visualization of cell-cycle G1 phase for monitoring the early response of cell cycle specific drug remains challenging. In this study, we developed genetically engineered bioluminescent reporters by fusing full-length cyclin E to the C-terminal luciferase (named as CycE-Luc and CycE-Luc2). Next, HeLa cell line or an ER-positive breast cancer cell line MCF-7 was transfected with these reporters. In cellular assays, the bioluminescent signal of CycE-Luc and CycE-Luc2 was accumulated in the G1 phase and decreased after exiting from the G1 phase. The expression of CycE-Luc and CycE-Luc2 fusion protein was regulated in a cell cycle-dependent manner, which was mediated by proteasome ubiquitination and degradation. Next, our in vitro and in vivo experiment confirmed that the cell cycle arrested by anti-cancer agents (palbociclib or 5-FU) was monitored quantitatively and dynamically by bioluminescent imaging of these reporters in a real-time and non-invasive manner. Thus, these optical reporters could reflect the G1 phase alternation of cell cycle, and might become a future clinically translatable approach for predicting and monitoring response to palbociclib in patients with ER-positive breast cancer.
Keywords: CDK4/6, bioluminescence, cyclin E, the G1 phase of the cell cycle, non-invasive molecular imaging