Czernin, J. | bioRxiv Science

bioRxiv2024

Development of a LRRC15-Targeted Radio-Immunotheranostic Approach to Deplete Pro-tumorigenic Mechanisms and Immunotherapy Resistance

Leucine-rich repeat containing 15 (LRRC15) has emerged as an attractive biomarker and target for cancer therapy. We have developed a humanized monoclonal antibody (mAb), DUNP19, that specifically binds to a phylogenetically conserved LRRC15 epitope and is internalized by target-expressing cancer and stromal cells. In xenograft mouse models, Lutetium-177 labeled DUNP19 ([177Lu]-DUNP19) enables non-invasive imaging and precise radiotherapy to LRRC15-expressing cancer cells and murine cancer-associated fibroblasts (CAFs), halting tumor progression and prolonging survival with minimal toxicity. Transcriptomic analyses of [177Lu]-DUNP19-treated tumors reveal a loss of pro-tumorigenic mechanisms, including a transforming growth factor beta (TGF{beta})-driven and LRRC15+ signature associated with immunotherapy resistance. Together, these results demonstrate that radio-theranostic targeting of LRRC15 with DUNP19 is a compelling precision medicine platform for image-guided diagnosis, eradication, and reprogramming of LRRC15+ tumor tissue that drives immuno-resistance and aggressive disease. SIGNIFICANCEWe introduce a pioneering LRRC15-guided radio-theranostic approach integrating clinical imaging and radioimmunotherapy. Our strategy utilizes a mAb, DUNP19, to target LRRC15-expressing cancer cells and fibroblasts, demonstrating significant tumor reduction, prolonged survival, and reversal of TGF{beta}-driven treatment resistance. This approach offers a promising strategy for improving outcomes in aggressive cancers.

pharmacology and toxicology↗

bioRxiv2019

Defective Nucleotide Catabolism Defines a Subset of Cancers Sensitive to Purine Nucleoside Phosphorylase Inhibition

Small molecule inhibitors of purine nucleoside phosphorylase (PNP) have been explored as a treatment strategy for leukemia and lymphoma, however, the determinants of response to this class of drugs are incompletely understood. PNP inhibitors impair cell proliferation by preventing catabolism of the nucleoside deoxyguanosine (dG) which induces toxic imbalances amongst intracellular deoxyribonucleotide triphosphate (dNTP) pools following its phosphorylation and trapping by nucleoside kinases. We hypothesized that differential nucleoside uptake or catabolism defines cancer cell lines as either sensitive or resistant to PNP inhibition. Among cancer cell lines we found that T-cell acute lymphoblastic leukemia (T-ALL) cells are uniquely and acutely sensitive to PNP inhibition whereas the B-cell leukemia and solid tumor models are completely resistant. We determined that although the nucleoside scavenging kinase deoxycytidine kinase (dCK) was active in all cells tested, PNP inhibitors only induced dGTP pool increases in sensitive models. By evaluating the expression of key genes involved in nucleotide scavenging, biosynthesis, and phosphohydrolysis in a panel of sensitive and resistant cell lines we found that the dNTP phosphohydrolase SAM histidine aspartate containing protein 1 (SAMHD1) was exclusively expressed in resistant models. Using CRISPR/Cas9 SAMHD1 knockout cell lines, we verified that PNP inhibitor sensitivity is a function of SAMHD1 expression and determined that the pharmacological inhibition of dCK or genetic restoration of SAMHD1 conferred resistance to PNP inhibition. Importantly, we determined that low expression of SAMHD1 is not limited to T-ALL as subset of established and primary solid tumors models are SAMHD1-deficient. These solid tumor models were consistently acutely sensitive to PNP inhibitors which indicates that the utility of PNP inhibitors extends beyond hematological malignancies. Additionally, we found that deoxycytidine (dC) can limit the anti-proliferative effects of PNP inhibitors by competing with dG for phosphorylation by dCK but this effect can be overcome by expression of dC-catabolizing gene cytidine deaminase (CDA). Collectively, these results indicate that SAMHD1, dCK and CDA are critical biomarkers that must be used to stratify patients in clinical trials evaluating pharmacological PNP inhibition.

cancer biology↗