300 s. The dissociation of the interaction was subsequently measured for 300 s. Systematic baseline drift correction was done by subtracting the shift recorded for sensors loaded with ligand but incubated without analyte. Data analysis and curve fitting were done using Octet software version 11.0. Experimental data were fitted with the binding equations available for a 1:1 interaction with local fitting and the mean ± standard error of the mean (SEM) values of k on and k off were calculated from the data of five different concentrations of an analyte. The K D was calculated as the ratio of k off /k on. cell immunostaining. The human cervical cancer cell line HeLa and human gastric cancer cell line N87 or human breast cancer cells expressing firefly luciferase SK-BR-3/Luc were obtained from the RIKEN Bio-Resource Center (Tsukuba, Japan) or JCRB Cell Bank (Osaka, Japan), respectively, and maintained at 37 °C in 5% FBS-DMEM (Nacalai Tesque, Kyoto, Japan) supplemented with penicillin (100 U/ml) and streptomycin (100 µg/ml) (Nacalai Tesque). The cells (1.0 × 10 4 cells/well) were seeded on a slide chamber plate, cultured for 16 h and fixed by treatment with a 4% paraformaldehyde solution (Nacalai Tesque) for 10 min at 25 °C. The cells were blocked with 1% BSA/PBS for 1 h at 25 °C. After the addition of 50 nM purified His-tagged FLAPs or 5 nM trastuzumab in 1% BSA/PBS to the chamber, the cells were incubated for 16 h at 4 °C. Thousand-fold diluted Alexa Fluor 488-conjugated mouse anti-His tag secondary antibody (Medical & Biological Laboratories, Aichi, Japan) or Alexa Fluor 488-conjugated mouse anti-human IgG Fc secondary antibody in 1% BSA/PBS were used to fluorescently label the His-tagged FLAPs or trastuzumab, respectively. After washing three times with PBS, the stained cells were mounted with Fluoromount (Diagnostic ByoSystems, CA, USA) containing 1/1000 Hoechst 33342 (Nacalai Tesque). All photos were taken using a BZ-X700 microscope (Keyence, Osaka, Japan). Statistical analysis. Data are presented as means ± SEM and were statistically analysed with a two-sided Student's t-test; p values of < 0.05 were considered statistically significant.

Triple-negative breast cancer (TNBC) is a highly metastatic and aggressive disease with limited treatment options. Recently, the combination of the immune checkpoint inhibitor (ICI) atezolizumab (anti-PD-L1) with nab-paclitaxel was approved following a clinical trial that showed response rates in at least 43% of patients. While this approval marks a major advance in the treatment of TNBC it may be possible to improve the efficacy of ICI therapies through further modulation of the suppressive tumor immune microenvironment (TIME). Several factors may limit immune response in TNBC including aberrant growth factor signaling, such as VEGFR2 and cMet signaling, inefficient vascularization, poor delivery of drugs and immune cells, and the skewing of immune cell populations toward immunosuppressive phenotypes. Here we investigate the immune-modulating properties of AXT201, a novel 20 amino-acid integrin-binding peptide in two syngeneic mouse TNBC models: 4T1-BALB/c and NT4-FVB. AXT201 treatment improved survival in the NT4 model by 20% and inhibited the growth of 4T1 tumors by 47% over 22 days postinoculation. Subsequent immunohistochemical analyses of 4T1 tumors also showed a 53% reduction in vascular density and a 184% increase in pericyte coverage following peptide treatment. Flow cytometry analyses demonstrated evidence of a more favorable anti-tumor immune microenvironment following treatment with AXT201, including significant decreases in the populations of T regulatory cells, monocytic myeloid-derived suppressor cells, and PD-L1 expressing cells and increased expression of T cell functional markers. Together, these findings demonstrate immune-activating properties of AXT201 that could be developed in combination with other immunomodulatory agents in the treatment of TNBC.

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Background Retroviruses exist as exogenous infectious agents and as endogenous retroviruses (ERVs) integrated into host chromosomes. Such endogenous retroviruses (ERVs) are grouped into three classes roughly corresponding to the seven genera of infectious retroviruses: class I (gamma-, epsilonretroviruses), class II (alpha-, beta-, delta-, lentiretroviruses) and class III (spumaretroviruses). Some ERVs have counterparts among the known infectious retroviruses, while others represent paleovirological relics of extinct or undiscovered retroviruses. Results Here we identify an intact ERV in the Anuran amphibian, Xenopus tropicalis. XtERV-S has open reading frames (ORFs) for gag, pol (polymerase) and env (envelope) genes, with a small additional ORF in pol and a serine tRNA primer binding site. It has unusual features and domain relationships to known retroviruses. Analyses based on phylogeny and functional motifs establish that XtERV-S gag and pol genes are related to the ancient env-less class III ERV-L family but the surface subunit of env is unrelated to known retroviruses while its transmembrane subunit is class I-like. LTR constructs show transcriptional activity, and XtERV-S transcripts are detected in embryos after the maternal to zygotic mid-blastula transition and before the late tailbud stage. Tagged Gag protein shows typical subcellular localization. The presence of ORFs in all three protein-coding regions along with identical 5’ and 3’ LTRs (long terminal repeats) indicate this is a very recent germline acquisition. There are older, full-length, nonorthologous, defective copies in Xenopus laevis and the distantly related African bullfrog, Pyxicephalus adspersus. Additional older, internally deleted copies in X. tropicalis carry a 300 bp LTR substitution. Conclusions XtERV-S represents a genera-spanning member of the largely env-less class III ERV that has ancient and modern copies in Anurans. This provirus has an env ORF with a surface subunit unrelated to known retroviruses and a transmembrane subunit related to class I gammaretroviruses in sequence and organization, and is expressed in early embryogenesis. Additional XtERV-S-related but defective copies are present in X. tropicalis and other African frog taxa. XtERV-S is an unusual class III ERV variant, and it may represent an important transitional retroviral form that has been spreading in African frogs for tens of millions of years.