Abstract 1326: Perineural invasion and bone metastases in prostate cancer - is there a link

Abstract Bone metastases are the most common secondary lesions in prostate cancer (PCa) patients. Typically, initial bone metastases develop in the lower part of the spine and pelvis. While this metastatic pattern is not consistent with the random nature of the arterial osseous dissemination, previous reports suggested the role of the retrograde venous spread in this phenomenon. However, clinical data also indicate a positive association between the degree of perineural invasion (PNI) and bone metastases in PCa patients. Yet, the mechanism linking these two means of dissemination remains unknown. To identify the processes involved in the initial PCa dissemination we used the PC3-ML cell line, which was previously shown to trigger bone metastases, in the orthotopic xenograft model. To this end, the cells were injected into the prostates of male SCID/Bg mice and tumor development and progression was followed by magnetic resonance imaging (MRI) and histopathology. MRI indicated local invasion of the primary tumor, which later resulted in the formation of multiple secondary lesions along the lower spine. However, histopathological analysis revealed that these lesions were initiated in the soft tissues surrounding the vertebral column, while the subsequent invasion of the vertebra was the secondary event. The staining for neuronal markers, neurofilament (NF), tyrosine hydroxylase (TH) and neuropeptide Y (NPY), revealed that PCa cells created multicellular clusters spreading longitudinally along the small nerve fibers, particularly in the paraspinal muscle compartment. The staining for the endothelial cell marker, CD31, detected small vessels present within PCa clusters. However, no evident encapsulation of the PCa cells within blood vessels consistent with the retrograde venous spread was observed. Altogether, these results suggest PNI as the main route of the initial local dissemination of the PCa cells toward the bone, which then triggers bone invasion and subsequent hematogenous spread to distant bones. Further mechanistic studies are required to confirm this hypothesis. Citation Format: Dawid Sigorski, Susana Galli, Sung Hyeok Hong, Ewa Iżycka-Świeszewska, Joanna B. Kitlinska. Perineural invasion and bone metastases in prostate cancer - is there a link [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 1326.