Summary The transcription factor Dmp1 is a Ras/HER2-activated haplo-insufficient tumor suppressor that activates the Arf/p53 pathway of cell cycle arrest. Recent evidence suggests that Dmp1 may activate p53 independently of Arf in certain cell types. Here we report findings supporting this concept with the definition an Arf-independent function for Dmp1 in tumor suppression. We found that Dmp1 and p53 can interact directly in mammalian cells via the carboxyl-terminus of p53 and the DNA-binding domain of Dmp1. Expression of Dmp1 antagonized ubiquitination of p53 by Mdm2 and promoted nuclear localization of p53. Dmp1-p53 binding significantly increased the level of p53, independent of Dmp1’s DNA-binding activity. Mechanistically, p53 target genes were activated synergistically by co-expression of Dmp1 and p53 in p53−/−; Arf−/−cells and genotoxic responses of these genes were hampered more dramatically in Dmp1−/− and p53−/− cells than in Arf−/− cells. Together, our findings identify a robust new mechanism of p53 activation mediated through by direct physical interaction between Dmp1 and p53.

Stratifying patients on the basis of molecular signatures could facilitate development of therapeutics that target pathways specific to a particular disease or tissue location. Previous studies suggest that pathogenesis of rheumatoid arthritis (RA) is similar in all affected joints. Here we show that distinct DNA methylation and transcriptome signatures not only discriminate RA fibroblast-like synoviocytes (FLS) from osteoarthritis FLS, but also distinguish RA FLS isolated from knees and hips. Using genome-wide methods, we show differences between RA knee and hip FLS in the methylation of genes encoding biological pathways, such as IL-6 signalling via JAK-STAT pathway. Furthermore, differentially expressed genes are identified between knee and hip FLS using RNA-sequencing. Double-evidenced genes that are both differentially methylated and expressed include multiple HOX genes. Joint-specific DNA signatures suggest that RA disease mechanisms might vary from joint to joint, thus potentially explaining some of the diversity of drug responses in RA patients.

Objective Aminopeptidase N (CD13, EC 3.4.11.2) is a metalloproteinase expressed by fibroblast like synoviocytes (FLS). It has been suggested that CD13 can act chemotactically for T cells in rheumatoid arthritis (RA). The goals of this study were to measure CD13 in vivo and in vitro-in RA samples, and to determine whether CD13 could play a role in homing of T cells to the RA joint. Methods IL-17 treated FLS were used to immunize mice, from which a novel anti-human CD13 monoclonal antibody (591.1D7.34) was developed. 1D7 and a second anti-CD13 monoclonal, WM15, were used to develop a novel ELISA for CD13, and CD13 enzymatic activity was measured in parallel. Chemotaxis of cytokine activated T cells (Tck) was measured by an under-agarose assay. Result We detected substantial amounts of CD13 in synovial fluids, sera, FLS lysates, and culture supernatants by ELISA, with a significant increase in CD13 in RA synovial fluids when compared to osteoarthritis (OA). CD13 accounted for most but not all of the CD13-like enzymatic activity in synovial fluid. Recombinant human CD13 was chemotactic for Tck through a G-protein-coupled-receptor and contributed to the chemotactic properties of synovial fluid independently of enzymatic activity. Conclusion CD13 is released from FLS into culture supernatants and is found in synovial fluid. CD13 induces chemotaxis of Tck, a T cell population similar to that found in RA synovium. This data suggest that CD13 could play an important role as a T cell chemoattractant, in a positive feedback loop that contributes to RA synovitis.

• Plasma concentrations of CXCL9 are elevated at the onset of cGVHD diagnosis, but not in patients with cGVHD for more than 3 months.• Plasma concentrations of CXCL9 are impacted by immunosuppressive therapy.There are no validated biomarkers for chronic GVHD (cGVHD). We used a protein microarray and subsequent sequential enzyme-linked immunosorbent assay to compare 17 patients with treatment-refractory de novo-onset cGVHD and 18 time-matched control patients without acute or chronic GVHD to identify 5 candidate proteins that distinguished cGVHD from no cGVHD: CXCL9, IL2Ra, elafin, CD13, and BAFF. We then assessed the discriminatory value of each protein individually and in composite panels in a validation cohort (n 5 109). CXCL9 was found to have the highest discriminatory value with an area under the receiver operating characteristic curve of 0.83 (95% confidence interval, 0.74-0.91). CXCL9 plasma concentrations above the median were associated with a higher frequency of cGVHD even after adjustment for other factors related to developing cGVHD including age, diagnosis, donor source, and degree of HLA matching (71% vs 20%; P < .001). A separate validation cohort from a different transplant center (n 5 211) confirmed that CXCL9 plasma concentrations above the median were associated with more frequent newly diagnosed cGVHD after adjusting for the aforementioned factors (84% vs 60%; P 5 .001). Our results confirm that CXCL9 is elevated in patients with newly diagnosed cGVHD. (Blood. 2014;123(5):786-793)

Synopsis Understanding the pathogenesis of joint inflammation and destruction in rheumatoid arthritis involves dissection of the cellular and molecular interactions that occur in synovial tissue. Development of effective targeted therapies has been based on progress in achieving such insights. Safer and more specific approaches to treatment could flow from discovery of cell-cell interaction pathways that are relatively specific for inflammation of the joint, and less important in defense against systemic infection. This chapter highlights selected cell-cell interactions in rheumatoid arthritis synovium that may be worthy of evaluation as future therapeutic targets.