Abstract Background: Despite the high prevalence of prostate cancer (PC), there are relatively few cell lines and they are not sufficient to cover the genetic and phenotypic diversity of the disease. Patient derived xenografts (PDX) provide a useful toolset for studying human PC, but cell line models are still important assets for their ease of use, including genetic engineering and scalability for large-scale screens. We adapted the LuCaP189. 4 PDX into a 2D cell line, called LuCaP189. 4CL, and characterized its genetic and phenotypic features and suitability as an experimental model. Of particular note, this line carries natural CDK12 bi-allelic loss (BAL), making it an especially useful for understanding this aggressive disease subtype that accounts for 5-7% of metastatic castration resistant PC. Methods: LuCaP189. 4 PDX tumors were serially passaged to adapt to common cell culture conditions. DNA was analyzed by karyotyping and exome sequencing. Growth rates of the cell line were measured at different passages and RNA was collected for transcriptome analysis. Cells were also grown in 3D culture conditions and re-implanted into mice to generate cell-line derived xenograft tumors (CDX). LNCaPFGC and NCI-H660 were also grown as cell lines, 3D, or CDX and analyzed by RNA-seq for comparison. LuCaP 189. 4CL was immunoblotted for key tumor suppressors and immunostained for lineage markers. Cells were tested for sensitivity to common PC therapies and additional genomic characteristics were assayed by enzymatic methyl DNA sequencing and S9. 6 R-loop chromatin profiling. Results: The LuCaP189. 4CL maintained key characteristics of the PDX model, including high AR activity and AR splice variant expression and loss of CDK12. LuCaP189. 4CL cells are smaller than LNCaPFGC or 22Rv1 and growth rate is partially density dependent. The line is mostly diploid and amenable to lentiviral transduction at roughly one quarter efficiency relative to LNCaPFGC. LuCaP189. 4CL successfully established CDX tumors when implanted in mice (11/12 take rate). DNA mutations and tandem duplicator phenotype (TDP), a hallmark of CDK12 loss, were matched between the cell line and PDX. LuCaP189. 4CL also exhibits genomic patterns of high DNA methylation and R-loop activity. LuCaP189. 4CL did not respond to enzalutamide or supraphysiologic androgen and showed less sensitivity to carboplatin, olaparib, and docetaxel compared to LNCaPFGC and 22Rv1. However, the line showed enhanced sensitivity to the RNA Pol2 inhibitor α-amanitin. Conclusions: The LuCaP189. 4CL model is a new cell line that retains key characteristics of the PDX and human mCRPC, including high AR activity and CDK12 loss. Transcriptomic analysis of various culture conditions is ongoing. This line is not sensitive to most standard therapies, concordant with observations in patients with CDK12-BAL, and exhibits rare genomic features of DNA methylation, TDP, and high R-loop activity. This cell line adds to the genetic and phenotypic representation of PC cell line models with the potential to enhance future PC research. Citation Format: Sander Frank, Dapei Li, Xiulan Yang, Tarana Arman, Galina Semenova, Armand Bankhead, Brian Hanratty, Jessica Maruwan, Emily Distler, Jared Lucas, Ruth Dumpit, Ilsa Coleman, Reza A. Ghodsi, Colm Morrissey, Eva Corey, Michael Haffner, Peter S. Nelson. LuCaP189. 4CL: a novel 2D model of AR -high, CDK12 -mutant mCRPC suitable for studies of genetic and therapeutic vulnerabilities abstract. In: Proceedings of the AACR Special Conference in Cancer Research: Innovations in Prostate Cancer Research and Treatment; 2026 Jan 20-22; Philadelphia PA. Philadelphia (PA): AACR; Cancer Res 2026;86 (2Suppl): Abstract nr B022.
Frank et al. (Tue,) studied this question.