Carboxypeptidase A3 expression in canine mast cell tumors and tissue-resident mast cells

Mast cell tumors (MCTs) are one of the most common cutaneous malignancies in dogs. Previous studies have reported expression of mast cell–specific proteases chymase and tryptase in canine cutaneous MCTs and in connective tissue and mucosal mast cells. In humans and rodents, mast cells express an additional specific protease, carboxypeptidase A3 (CPA3). In this article, we describe CPA3 immunoreactivity in connective tissue, visceral, mucosal, and neoplastic mast cells in dogs. Positive immunolabeling for CPA3 was observed in nonneoplastic mast cells in 20/20 formalin-fixed paraffin-embedded normal tissues (skin, liver, spleen, intestine), and in 63/63 MCTs irrespective of their histological grade. CPA3 protein expression was comparable to that of c-kit in both the nonneoplastic and neoplastic mast cells. Three distinct labeling patterns (membranous, diffuse, and focal cytoplasmic) were observed for CPA3 in MCTs. The focal cytoplasmic labeling pattern was associated with high-grade MCTs staged with the Kiupel 2-tier grading criteria. We propose CPA3 as a novel immunohistochemical marker for canine mast cells in health and disease.

Measures of gene expression in sputum cells can identify TH2-high and TH2-low subtypes of asthma

BACKGROUND

The 3-gene signature of periostin, chloride channel accessory 1 (CLCA1), and Serpin β2 (SERPINB2) in airway epithelial brushings is used to classify asthma into TH2-high and TH2-low endotypes. Little is known about the utility of gene profiling in sputum as a molecular phenotyping method.

OBJECTIVE

We sought to determine whether gene profiling in sputum cells can identify T(H)2-high and T(H)2-low subtypes of asthma.

METHODS

In induced sputum cell pellets from 37 asthmatic patients and 15 healthy control subjects, PCR was used to profile gene expression of the epithelial cell signature of IL-13 activation (periostin, CLCA1, and SERPINB2), TH2 genes (IL4, IL5, and IL13), and other genes associated with airway TH2 inflammation.

RESULTS

Gene expression levels of CLCA1 and periostin, but not SerpinB2, were significantly higher than normal in sputum cells from asthmatic subjects. Expression levels of IL-4, IL-5, and IL-13 were also significantly increased in asthmatic patients and highly correlated within individual subjects. By combining the expression levels of IL-4, IL-5, and IL-13 in a single quantitative metric ("T(H)2 gene mean"), 26 (70%) of the 37 asthmatic patients had T(H)2-high asthma, which was characterized by more severe measures of asthma and increased blood and sputum eosinophilia. TH2 gene mean values tended to be stable when initial values were very high or very low but fluctuated above or below the T(H)2-high cutoff when initial values were intermediate.

CONCLUSION

IL-4, IL-5, and IL-13 transcripts are easily detected in sputum cells from asthmatic patients, and their expression levels can be used to classify asthma into T(H)2-high and T(H)2-low endotypes.

Human mast cells arise from a common circulating progenitor

BACKGROUND

Human tissue mast cells (MCs) have the potential to express several neutral granule proteases, which are the most precise markers of the phenotypic heterogeneity of MCs. However, the full extent of such heterogeneity is limited by the fact that MCs containing either tryptase only or tryptase and chymase have long been considered to be the sole MC phenotypes. Moreover, the potential developmental relationship between human MCs of different protease phenotypes has remained a matter of dispute.

OBJECTIVE

We attempted to define how human MCs with different protease phenotypes relate to their circulating progenitors.

METHODS

MCs were generated from human peripheral blood-derived CD34(+) progenitors in the presence of kit ligand (KITLG) and the cytokines IL-3, IL-9, and IL-6 under serum-free conditions, or by KITLG alone in the presence or absence of serum. The expression of chymase, carboxypeptidase A3, cathepsin G, granzyme B, and the tryptases derived from the TPSAB1, TPSB2, TPSD1, and TPSG1/PRSS31 genes were determined weekly at the mRNA and/or protein levels.

RESULTS

Incubation of CD34(+) progenitors in the presence of KITLG and the cytokines IL-3, IL-9, and IL-6 promoted the development of a single population of MCs with a uniform tryptase(+), chymase(+), CPA3(+), cathepsin G(+), and granzyme B(+) phenotype. Interestingly, the presence of KITLG alone was sufficient to induce the expression of all the above proteases.

CONCLUSION

All circulating human MC progenitors have the potential to differentiate into MCs expressing the complete panel of neutral granule proteases, implying that human MCs originate from a common MC-committed progenitor.