Abstract A061: Nuclear lamin content as a biomarker for prostate cancer progression

Lamins are proteins that help to structure the cellular nucleus via the formation of an intermediate filament weave that grants rigidity to the nuclear membrane. Lamins also tether the chromatin to the nuclear envelope, contributing to the formation of heterochromatin, necessary for adequate gene expression control. The purpose of this study was to use a combination of immunostaining, ChIP-seq, and chromosome conformation capture (Hi-C) to a) characterize the expression and deposition patterns of Lamin A, Lamin B1, and Lamin B2 in cell lines and patient samples, b) to evaluate chromatin associations with the lamina and, c) to characterize chromatin organization phenomena related to lamina conformation. In this study, we used a collection of cells that model the continuum of progression in vitro as follows: RWPE (normal prostate epithelium), LNCaP (adenocarcinoma), VCaP and MDAPCa2a/b (bone metastatic). We also evaluated whether the phenotypes for lamin deposition observed in vitro correlate with that of patient samples, via immunohistochemistry of tissue microarrays. We have identified that Lamin A content is significantly lower in bone metastatic cell lines. While VCaP cells lack Lamin A deposition, MDAPCa2a cells have a heterogeneous distribution: cells that grow in contact with the cell culture surface express Lamin A while cells that grow atop 3D clusters of cells do not. In contrast, Lamin B1 and B2 content is consistent across cell lines. Analysis of tissue microarray immunohistochemistry showed congruent results to the in vitro findings: patient samples derived from higher-grade adenocarcinomas show a decreased number of lamin A positive cells.​ This endogenous lack of Lamin A in VCaP results in an altered lamin-associated domain distribution that can potentially result in abnormal heterochromatin formation, as characterized by ChIP-seq. Further,​through a comprehensive analysis of genome architecture via chromosome conformation capture, we observe a change in the radial positioning of the chromosomes when comparing cells that model normal epithelium, adenocarcinoma, and bone metastasis. Given that the primary metastatic site for prostate cancer is the bone, we evaluated the effect of bioavailable calcium on lamin expression in vitro. Interestingly, we find that in cells cultured on vessels coated in amorphous calcium phosphate, lamin expression is ablated both in normal epithelium and adenocarcinoma cell lines, independent of testosterone levels. Taken together, our results show that lamin content, and in particular loss of lamin A, could be an early predictor of disease progression potential, affecting nucleus mechanics and pliability, ultimately facilitating metastasis. Further, the altered chromatin organization dynamics can potentially act as a prelude for pro-metastatic transcription Citation Format: Rebeca San Martin, Priyojit Das, Sanaz Hossain, Rachel Patton McCord. Nuclear lamin content as a biomarker for prostate cancer progression [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr A061.