Abstract 3804: Multiparameter cell-cycle measurement enables a better assessment of cancer aggressiveness than Ki67 LI alone

Abstract Background: Ki67 is expressed in the G1, S, G2 and M phase of the cell cycle. Immunohistochemical determination of the Ki67 labeling index (LI) is a clinically well-established tool for assessing the proliferative activity of tumors and critical clinical decisions are based on this parameter. Other cell cycle associated proteins have been evaluated for clinical utility much less intensively. This for example includes minichromosome maintenance-3 (MCM3) which is expressed earlier in the cell cycle than Ki67. Design: To evaluate the difference and potential synergy between of Ki67 and MCM3 based proliferation indices, both proteins were analyzed by multiplex fluorescent immunohistochemistry in more than 1, 580 colorectal carcinomas that were available in a tissue microarray format and results were compared with clinico-pathological parameters (pT, pN, grade, MSI, p53 status). A deep learning-based framework comprising a deep-learning based algorithm for automated cell and marker detection was used for image analysis. Results: In our 1, 583 evaluable colorectal cancers, the average Ki67 LI was 69% and the average MCM3-LI was 67%. There was a significant overlap between Ki67 and MCM3 staining: Of all panCK positive tumor cells, 56% were positive for both Ki67 and MCM3, 11% were only positive for Ki67, 8% showed positivity only for MCM3, and 25% were negative for both markers. According to the expression of Ki67 and MCM3, the following compartments of proliferating cells were defined: early (MCM3+/Ki67−), intermediate (MCM3+/Ki67+), and late phase of the cell cycle (MCM3−/Ki67+) as well as full proliferation (MCM3+ or Ki67+). Comparison with clinico-pathological parameters revealed the best p-values for the MCM3 LI in the comparison with pT (p=2. 7e−8), nodal metastasis (p=0. 0002), and p53 alterations (p=6e−11) while the “full proliferation” LI was most tightly linked to microsatellite instability (p=1e−10). The Ki67 LI was best correlated to the grade (p=0. 01). Conclusion: The combined analysis of MCM3 and Ki67 enables the distinction of cells in early, intermediate, and late phase of the cell cycle. At least in colorectal cancer - a highly proliferative neoplasm - MCM3 quantification alone or in combination with Ki67 often resulted in stronger relationships with clinicopathological parameters than the Ki67 LI alone. These results suggest that a more subtle analysis of cell cycle proteins might enable a better evaluation of cancer aggressiveness than Ki67 measurement alone. Citation Format: Jan H. Mueller, Julia Ebner, Zhihao Huang, Maximilian Lennartz, Claudia Hube-Magg, Frank Jacobsen, Stefan Steurer, Christian Bernreuther, Till S. Clauditz, Andreas H. Marx, Till Krech, Eike Burandt, Guido Sauter, Ronald Simon, Sarah Minner, Elena Bady. Multiparameter cell-cycle measurement enables a better assessment of cancer aggressiveness than Ki67 LI alone abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 3804.