Therapeutic Targeting of Golgi Phosphoprotein 2 (GOLPH2) with Armed Antibodies: A Preclinical Study of Anti-GOLPH2 Antibody Drug Conjugates in Lung and Colorectal Cancer Models of Patient Derived Xenografts (PDX).

BACKGROUND: Golgi phosphoprotein 2 (GOLPH2) has been shown to be involved in chronic inflammatory processes and carcinogenesis. GOLPH2 is prominently overexpressed in hepatocellular carcinoma, melanoma, glioblastoma, prostate, lung, and colorectal cancer. With a low and tightly regulated expression in non-malignant tissues, GOLPH2 has been proposed as an attractive target for cancer therapy. However, GOLPH2 is predominantly located intracellularly and when situated outside of the cell it is proteolytically cleaved and shed from the cell surface. Until now, GOLPH2 has been regarded as an "undruggable" target. OBJECTIVE: We sought to create antibodies that specifically bind to GOLPH2 overexpressing tumor cells. PATIENTS AND METHODS: Antibodies binding to membranous GOLPH2 despite shedding of the protein were generated from a scFV library screening. These antibodies target the part of GOLPH2 that remains at the cell surface after proteolytic cleavage. These antibodies were then tested in vitro and in vivo. RESULTS: Two candidates (G2-1 and G2-2) showed target specific binding in vitro. Utilizing a tumor array (n = 128 tumors) with G2-2 and a reference antibody, a GOLPH2 expression scoring system was established. Rapid internalization of the antibodies was noted so this was exploited to deliver a toxic payload of pyrrolobenzodiazepine (PBD). In two patient-derived xenograft (PDX)-models, colorectal and lung cancer, the G2-2 antibody drug conjugate (ADC) displayed high efficacy with significant tumor responses (P = 0.001; P = 0.013) and improved survival (P = 0.0001; P = 0.0011) compared with controls. CONCLUSIONS: Treatment with GOLPH2-directed antibodies induces durable responses in colorectal and lung cancer models. With a robust companion assay for GOLPH2 positivity at hand our findings prepare for the translation into a clinical trial.

Humanized Monoclonal Antibody Blocking Carbonic Anhydrase 12 Enzymatic Activity Leads to Reduced Tumor Growth In Vitro.

BACKGROUND/AIM: Carbonic anhydrase 12 (CA12) is a membrane-associated enzyme that is highly expressed on many human cancers. It is a poor prognostic marker and hence an attractive target for cancer therapy. This study aimed to develop a humanized CA12-antibody with anti-cancer activity. MATERIALS AND METHODS: Antibody libraries were constructed and screened by the Retrocyte display®. Antibody binding and blocking properties were determined by ELISA, flow cytometry and enzymatic activity assays. Spheroid viability was determined by Cell-Titer-Fluor assay. RESULTS: We developed a novel humanized CA12-specific antibody, 4AG4, which recognized CA12 as an antigen and blocked CA12 enzymatic activity. Our humanized CA12-antibody significantly inhibited spheroid growth of lung adenocarcinoma A549-cells in vitro by blocking CA12 enzymatic activity. Similar anti-tumor effects were recapitulated with CA12-gene knockout of A549-cells. CONCLUSION: Our newly identified humanized CA12-antibody with anti-cancer activity, represents a new tool for the treatment of CA12-positive tumors.

RP1 is a phosphorylation target of CK2 and is involved in cell adhesion.

RP1 (synonym: MAPRE2, EB2) is a member of the microtubule binding EB1 protein family, which interacts with APC, a key regulatory molecule in the Wnt signalling pathway. While the other EB1 proteins are well characterized the cellular function and regulation of RP1 remain speculative to date. However, recently RP1 has been implicated in pancreatic cancerogenesis. CK2 is a pleiotropic kinase involved in adhesion, proliferation and anti-apoptosis. Overexpression of protein kinase CK2 is a hallmark of many cancers and supports the malignant phenotype of tumor cells. In this study we investigate the interaction of protein kinase CK2 with RP1 and demonstrate that CK2 phosphorylates RP1 at Ser(236) in vitro. Stable RP1 expression in cell lines leads to a significant cleavage and down-regulation of N-cadherin and impaired adhesion. Cells expressing a Phospho-mimicking point mutant RP1-ASP(236) show a marked decrease of adhesion to endothelial cells under shear stress. Inversely, we found that the cells under shear stress downregulate endogenous RP1, most likely to improve cellular adhesion. Accordingly, when RP1 expression is suppressed by shRNA, cells lacking RP1 display significantly increased cell adherence to surfaces. In summary, RP1 phosphorylation at Ser(236) by CK2 seems to play a significant role in cell adhesion and might initiate new insights in the CK2 and EB1 family protein association.