6-Mercaptopurine potently inhibits recruitment of SHP2 by phosphorylated PD-1 to inhibit PD-1 signalling and enhance T cell function.

Antibody inhibitors that block PD-1/PD-L1 interaction have been approved for oncological clinics, yielding impressive treatment effects. Small molecules inhibiting PD-1 signalling are at various stages of development, given that small molecular drugs are expected to outperform protein drugs in several ways. Currently, a significant portion of these small molecular inhibitors achieve this purpose by binding to a limited region of the PD-L1 protein, thereby limiting the choice of chemical structures. Alternative strategies for developing small-molecular PD-1 inhibitors are urgently needed to broaden the choice of chemical structures. Here, we report that 6-mercaptopurine (6-MP) inhibits PD-1 signalling, activates T cell function in vitro and in vivo and shrinks tumours by activating cytotoxic T cells. Mechanistically, 6-MP potently inhibited PD-1 signalling by blocking the recruitment of SHP2 by PD-1. Considering that 6-MP is a chemotherapeutic agent already approved by the FDA for childhood leukaemia, our work revealed a novel anti-tumour mechanism for this drug and suggests that 6-MP warrants further clinical evaluation for other tumour types.

In vivo genome-wide CRISPR screening identifies ZNF24 as a negative NF-κB modulator in lung cancer.

Systemic identification of tumor suppressor genes (TSGs) and elucidation of their signaling provide a new angle for understanding of tumorigenesis, which is important for developing successful treatment for lung cancer patients. In our current work, we conducted an in vivo screen for lung cancer TSGs through CRISPR/Cas9 mediated knockout of genes at genome-wide scale. We found that ZNF24 was a potent and clinically relevant TSG of lung cancer. Ectopic expression of ZNF24 arrested lung cancer cells in S phase. Mechanistically, ZNF24 bound to promoter region of P65 to negatively regulate its transcription and thereby the signaling activity of NF-κB pathway. This signaling cascade is clinically relevant. Importantly, we found that combinational inhibition of KRAS, NF-κB, and PD-1 effectively shrank autochthonous KrasG12D/ZNF24-/- lung cancers in transgenic mouse model. Our current work thus revealed an important role played by loss of function of ZNF24 in lung tumorigenesis and shed new light in precision medicine for a portion of lung cancer patients.

Discovery of Isoform-Selective Akt3 Degraders Overcoming Osimertinib-Induced Resistance in Non-Small Cell Lung Cancer Cells.

EGFR inhibitor therapies have brought significant benefit to NSCLC patients. However, all patients gradually progress to acquired resistance via diverse mechanisms. Akt3 overexpression but not Akt1/2 is one of the found molecular events that mediate osimertinib (1) resistance in NSCLC patients. Here, we report 12l as the first bona fide isoform-selective Akt3 degrader which potently induced proteasomal degradation of the target both in vitro and in vivo, whereas its effects on Akt1/2 were minimal. Using 12l as a tool, non-canonical function of Akt3 was validated to contribute greatly to survival of 1-resistant H1975OR NSCLC cells. Degrader 12l potently suppressed the growth of H1975OR as well as several NSCLC cell lines with low nanomolar IC50 values and demonstrated promising in vivo antitumor efficacy in nude mice bearing H1975OR or PC9 NSCLC xenograft models. Selective degradation of Akt3 may be considered as a novel strategy for human cancer therapy.