Protein Signaling Profile of Prostate Tumor Metastasis Treated with Pembrolizumab: A Case Study

The immune system is heavily influenced by protein signaling pathways that drive the growth and metastasis of prostate tumors. Understanding the activation changes of immune-related proteins before, during, and after treatment can provide valuable information regarding treatment efficacy. This study aimed to investigate the protein signaling expression changes occurring within a patient’s tumor diagnosed with prostate cancer that metastasized into the bladder while being treated with Pembrolizumab. Nine biopsies were obtained at different times throughout the duration of treatment that were then used in our analysis. Using the instruments’ manufacturing recommendations, tumor cells were isolated from formalin fixed paraffin embedded (FFPE) tissue sections from the nine individual prostate cancer biopsies. In following lab procedures, these slides were deparaffinized, dehydrated, and hematoxylin stained before Laser Capture Microdissection (LCM). LCM caps were lysed using extraction buffer. The lysates that were obtained were then printed onto nitrocellulose slides using Reverse Phase Protein Array (RPPA) and stained with a group of antibodies selected to examine immune signaling and DNA damage repair endpoints. A laser scanner was used to scan the slides and the images produced were analyzed with MicroVigene software. Upon reviewing our results, biomarkers FoxP3, MSH2, CD3 zeta, and MLH1 showed elevated activation levels. In addition, Chk-1 (S345), Chk-2 (S33/35), STAT1 (Y701), PD-L1 (22-c-3), and PD-L1(E1L3N) appeared to be less expressed. Further research is needed on a larger sample size to support our results.