Tumor cell SPTBN1 inhibits M2 polarization of macrophages by suppressing CXCL1 expression.

Tumor-associated macrophages (TAMs) are the most abundant immune cells in the tumor microenvironment, and the M2-type TAMs can promote tumor growth, invasion and angiogenesis, and suppress antitumor immune responses. It has been reported that spectrin beta, non-erythrocytic 1 (SPTBN1) may inhibit the infiltration of macrophages in Sptbn1+/-  mouse liver, but whether tumor SPTBN1 affects TAMs polarization remains unclear. This study investigated the effect and mechanism of tumor cell SPTBN1 on polarization and migration of TAMs in hepatoma and breast cancer. By analyzing tumor immune databases, we found a negative correlation between SPTBN1 and abundance of macrophages and myeloid-derived suppressor cells (MDSCs) in the tumor microenvironment. By reverse transcription-quantitative real-time PCR assays and cell migration assays, the migration and M2 polarization of macrophages were enhanced by the culture medium from hepatocellular carcinoma cell line PLC/PRF/5, SNU449, and breast cancer cell line MDA-MB-231 with SPTBN1 suppression, which could be reversed by CXCL1 neutralizing antibody MAB275. Meanwhile, the ability of migration and colony formation of PLC/PRF/5, SNU449, and MDA-MB-231 cells were promoted when coculture with M2 macrophages. We also found that SPTBN1 regulated CXCL1 through p65 by cytoplasmic-nuclear protein isolation experiments and ChIP-qPCR. Our data suggest that tumor cell SPTBN1 inhibits migration and M2-type polarization of TAMs by reducing the expression and secretion of CXCL1 via inhibiting p65 nuclear localization.

Biomimetic-mineralized bifunctional nanoflowers for enzyme-free and colorimetric immunological detection of protein biomarker.

Detection of protein biomarkers relies largely on the development of modern immunological methods. Herein, a new enzyme-free immunological method is proposed to detect protein biomarkers. Employment of antibody-Cu3(PO4)2 hybrid nanoflowers, which are prepared through a facile and mild biomimetic-mineralizing process, is the core concept of the method. These nanoflowers can perform functions: one is to bind to target protein biomarkers with high specificity; the other is to release large amounts of Cu2+ upon acid treatment, which can interact with creatinine and exert peroxidase-mimicking enzyme activity, therefore producing a distinctly amplified signal. Using osteocalcin, a well-known circulating protein biomarker for bone formation, as a model, the method affords a linear range from 0.1 to 50 ng/mL with a detection limit of 0.042 ng/mL, which is superior to reported methods. Moreover, the method shows considerable specificity, desirable performance in serum samples and eliminates the use of enzymes, so a great potential for this method is expected to meet the need of the clinical diagnosis.