Microbial Chemistry Research Foundation

Vasculogenic mimicry (VM) is a process by which tumor cells form vessel-like network to secure oxygen and nutrients essential for tumor growth. Intercellular junctions, including tight junctions, may play a critical role in this process, important for VM. Here, we investigated the role of angulin-1/LSR (Ang-1), a key component of tricellular tight junctions, in VM regulation. We performed VM assay using Ang-1 knockout (KO) breast cancer cells. Compared with control cells, Ang-1/KO cells exhibited significantly enhanced VM formation, accompanied by increasing epithelial-mesenchymal transition (EMT) features. In a xenograft model, tumors derived from Ang-1/KO cells showed increased mass and elevated VM ratios. Re-expression of Ang-1 isoforms 3, 4 or 6-2 in Ang-1/KO cells suppressed VM formation, whereas isoforms 1, 2 and 6 had no effect. RT-PCR analysis of breast cancer patient tissues confirmed the lower expression of Ang-1 isoform 6-2, which suppresses VM. These findings identify Ang-1 as a novel regulator of VM and suggest that specific isoforms, particularly isoform 6-2, may serve as isoform-specific diagnostic markers or therapeutic targets in breast cancer.

The inhibition of kynurenine production is considered a promising target for cancer immunotherapy. In this study, an amino acid derivative, compound 1 was discovered using a cell-based assay with our screening library. Compound 1 suppressed kynurenine production without inhibiting indoleamine 2,3-dioxygenase 1 (IDO1) activity. The activity of 1 was derived from the inhibition of IDO1 by a metabolite of 1, O-benzylhydroxylamine (OBHA, 2a). A series of N-substituted 2a derivatives that exhibit potent activity in cell-based assays may represent effective prodrugs. Therefore, we synthesized and evaluated novel N,O-substituted hydroxylamine derivatives. The structure-activity relationships revealed that N,O-substituted hydroxylamine 2c inhibits kynurenine production in a cell-based assay. We conducted an in vivo experiment with 2c, although the effectiveness of O-substituted hydroxylamine derivatives in vivo has not been previously reported. The results indicate that N,O-substituted hydroxylamine derivatives are promising IDO1 inhibitors.

Overexpression of human epidermal growth factor receptor 2 (HER2) in breast and gastric cancers is associated with a poor prognosis, making it an important therapeutic target. Here, we establish a novel cancer-specific anti-HER2 antibody, H₂Mab-214. H₂Mab-214 reacts with HER2 on cancer cells, but unlike the therapeutic antibody trastuzumab, it does not react with HER2 on normal cells in flow cytometry measurements. A crystal structure suggests that H₂Mab-214 recognizes a structurally disrupted region in the HER2 domain IV, which normally forms a β-sheet. We show that this misfolding is inducible by site-directed mutagenesis mimicking the disulfide bond defects that also may occur in cancer cells, indicating that the local misfolding in the Cys-rich domain IV governs the cancer-specificity of H₂Mab-214. Furthermore, we show that H₂Mab-214 effectively suppresses tumor growth in xenograft mouse models. Our findings offer a potential strategy for developing cancer-specific therapeutic antibodies that target partially misfolded cell surface receptors.