Validation of novel LY6K targeting small molecule inhibitors and their structural analogues for treatment of triple negative breast cancer

This study presents a proof-of-principle pharmacological approach to target Lymphocyte Antigen 6K (LY6K) in cancer cells using small molecules. LY6K is a member of the LY6 family located on human chromosome 8q24, a region often amplified in cancers. LY6K expression is largely restricted in normal tissues to testis, but is elevated across multiple solid tumor types and is associated with poor survival outcomes in cervical, breast, ovarian, lung, head and neck, bladder, esophageal, and colorectal cancers. Prior functional studies show that genetic knockdown of LY6K reduces tumor growth and that LY6K overexpression correlates with enhanced TGFβ signaling and tumor progression, supporting LY6K as a cancer-selective therapeutic target.

To test whether LY6K can be directly targeted with small molecules, the investigators screened approximately 2,600 compounds from the NCI small molecule library for direct binding to recombinant LY6K using a surface plasmon resonance (SPR) assay. From this screen they identified NSC243928 as a direct binder of LY6K. NSC243928 demonstrated binding to both the full-length and mature forms of LY6K, while showing no detectable binding to closely related LY6 family members LY6D or LY6E, indicating selectivity in this initial characterization. Functional follow-up showed that NSC243928 inhibits growth of HeLa cells that express LY6K, providing early evidence that small-molecule binding of LY6K can translate into inhibition of cancer cell viability.

These results establish NSC243928 as a first-in-class LY6K-binding small molecule and validate the broader strategy of pharmacologically inhibiting LY6K as a therapeutic approach. The study emphasizes LY6K’s suitability as a drug target for cancers where its expression is high and potentially oncogenic, and notes particular relevance to difficult-to-treat malignancies including cervical, pancreatic, ovarian, head and neck, lung, gastric, and triple-negative breast cancers (TNBC). Because LY6K’s normal expression is largely limited to testicular germ cells, targeting LY6K may offer a therapeutic window with potentially limited impact on most normal tissues.

The work documents both a screening strategy (SPR-based direct binding assays against recombinant protein) and an early lead compound with demonstrated biochemical selectivity and cellular activity. By showing that a small molecule can directly bind LY6K and inhibit LY6K-expressing cancer cell growth, the study sets groundwork for medicinal chemistry optimization of NSC243928 and related analogues, expanded biochemical and cellular profiling, structural studies of the LY6K–ligand interaction, and preclinical evaluation in in vivo tumor models. Collectively, the findings position LY6K as a tractable and promising target for targeted therapeutics, particularly in cancers such as TNBC where new targeted options are urgently needed.