Abstract 2205: KRTAP 2-3 is a novel potential biomarker of cells in the polyaneuploid cancer cell (PACC) state to predict cancer recurrence
Authors: Mendez Sabrina A. , Sharma Reema , Pienta Kenneth J. , Amend Sarah R. 
Published: April 2023

Abstract
Prostate cancer (PCa) is the second leading cause of death in American men. PCa death is primarily attributed to therapeutic resistance. Our group and others have recently discovered a stress-induced adaptive cell state that plays a key role in therapy resistance: the polyaneuploid cancer cell (PACC) state. Cells in the polyaneuploid cancer cell (PACC) state are characterized by large cell size and polyploidization of the baseline aneuploid genome. Cells in the PACC state (e.g., pleomorphic giant cells, polyploid giant cancer cells, osteoclast like cells) have been reported in patient tumor specimens of multiple cancer types. We recently reported that in primary tumor specimens of PCa patients undergoing radical prostatectomy with curative intent, the number of cells in the PACC state is a statistically significant negative prognostic factor for metastasis-free survival (data adjusted for CAPRA-S). These data highlight the promise of the PACC state as a predictive biomarker for recurrence. In our previous work, cells in the PACC state were identified and quantified through EpCAM immunohistochemistry (IHC) to visualize cell membranes, manually including cells with &gt3x increased nuclear area compared to adjacent non-polyploid cancer cells. However, this method is labor intensive and highly subjective. There are currently no biomarkers to distinguish cells in the PACC state. To identify candidate PACC state biomarkers, we performed RNA sequencing to identify differentially expressed genes. Across two independent RNA sequencing datasets of PC3 cells induced to enter the PACC state with IC50 cisplatin or IC90 docetaxel, the most differentially expressed gene was KRTAP2-3 (Log2FC=4.3 and 5.51, respectively). The Keratin Associated Protein 2-3 (KRTAP2-3) is encoded by one of the homologous KRTAP genes classified by high sulfur content and is primarily expressed in the cortex of the hair follicle. It has not been previously implicated in PCa or in chemotherapy resistance. Due to its differential RNA expression in the PACC state and its low expression in most normal tissues, we hypothesize that KRTAP2-3 can be used as a biomarker to distinguish cells in the PACC state in patient tumor samples. To test this directly, we optimized RNA in situ-hybridization (RNAish) for KRTAP2-3. In initial experiments utilizing PC3 cell line plugs, we found that the KRTAP2-3 RNAish signal successfully distinguished cells in the PACC state (50.6 average punctae/cell) from non-polyploid cells (0.19 average punctae/cell) reflecting 96% percent accuracy using sensitivity and specificity metrics. We have further confirmed positive KRTAP2-3 signal on PC3 cells induced to access the PACC state in response to cisplatin, docetaxel, and etoposide treatment. Future work will evaluate the utility of the KRTAP2-3 gene as a prognostic biomarker that marks cells in the PACC state within PCa patient tissue microarrays.
Citation Format: Sabrina A. Mendez, Reema Sharma, Kenneth J. Pienta, Sarah R. Amend. KRTAP 2-3 is a novel potential biomarker of cells in the polyaneuploid cancer cell (PACC) state to predict cancer recurrence [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2205.