Cytokeratin-positive subserosal myofibroblasts in gastroduodenal ulcer; another type of myofibroblasts

Microenvironment‑driven resistance to B‑Raf inhibition in a melanoma patient is accompanied by broad changes of gene methylation and expression in distal fibroblasts

The incidence of malignant melanoma is rapidly increasing and current medicine is offering only limited options for treatment of the advanced disease. For B‑Raf mutated melanomas, treatment with mutation‑specific drug inhibitors may be used. Unfortunately, tumors frequently acquire resistance to the treatment. Tumor microenvironment, namely cancer‑associated fibroblasts, largely influence this acquired resistance. In the present study, fibroblasts were isolated from a patient suffering from acrolentiginous melanoma (Breslow, 4.0 mm; Clark, IV; B‑Raf V600E mutated). The present study focused on the expression of structural and functional markers of fibroblast activation in melanoma‑associated fibroblasts (MAFs; isolated prior to therapy initiation) as well as in autologous control fibroblasts (ACFs) of the same patient isolated during B‑Raf inhibitor therapy, yet before clinical progression of the disease. Analysis of gene transcription was also performed, as well as DNA methylation status analysis at the genomic scale of both isolates. MAFs were positive for smooth muscle actin (SMA), which is a marker of myofibroblasts and the hallmark of cancer stoma. Surprisingly, ACF isolated from the distant uninvolved skin of the same patient also exhibited strong SMA expression. A similar phenotype was also observed in control dermal fibroblasts (CDFs; from different donors) exclusively following stimulation by transforming growth factor (TGF)‑β1. Immunohistochemistry confirmed that melanoma cells potently produce TGF‑β1. Significant differences were also identified in gene transcription and in DNA methylation status at the genomic scale. Upregulation of SMA was observed in ACF cells at the protein and transcriptional levels. The present results support recent experimental findings that tumor microenvironment is driving resistance to B‑Raf inhibition in patients with melanoma. Such an activated microenvironment may be viable for the growth of circulating melanoma cells.

The possible role of isolated lymphoid follicles in colonic mucosal repair

The continuous reformation and rapid repair of the colonic mucosa is essential for avoiding the aggregation of pernicious mutations induced by bacterial, toxic, or mitogenic factors. Gut-associated lymphoid tissue is supposed to play a central role in the organization of the repair mechanisms. In inflammatory conditions, the number, the diameter and the density of isolated lymphoid follicles (ILFs) are increasing. They are involved not just in immune surveillance, but their presence is also indispensable in normal mucosal regeneration of the colon. The relation of ILFs to the components of mucosal renewal such as bone marrow derived stem cells, follicular dendritic cells, subepithelial myofibroblasts or crypt formation has not been directly studied, and data about their putative organizer role are scattered in scientific literature. Whether they act as a regenerative pool containing stem cells in case of mucosal damage, or they are responsible only for the optimal cytokine milieu for the differentiation of immigrating stem cells is a question under debate. Our aim is to review the relation of ILFs to the different elements of colonic mucosal repair.

CAM5.2-positive subserosal myofibroblasts in appendicitis

In this study, we examined the distribution and origin of myofibroblasts around the perforations of appendicitis. Stromal cells of 45 cases were studied by immunohistochemistry. In the normal appendix, myofibroblasts were restricted to the mucosa, and CD34-positive stromal cells were distributed in the submucosal and subserosal layers. Some mesothelial cells were positive for cytokeratin CAM5.2, cytokeratin 5, or mesothelial cells (HBME-1). In perforation of appendicitis with both abscess and granulation tissue, a small to moderate or a moderate to large number of myofibroblasts appeared in the subserosal area around the perforation, respectively, but CD34-positive stromal cells were completely absent there. In the subserosal area of the perforation of appendicitis with abscess, cytokeratin 5-positive stromal cells were absent. However, a small to moderate number of cytokeratin CAM5.2-positive stromal cells were observed there. Double immunostaining showed the coexpression of alpha-smooth muscle actin (ASMA) and cytokeratin CAM5.2 and the coexpression of cytokeratin 5 and cytokeratin CAM5.2 in many or some stellate-shaped or spindle-shaped stromal cells existing in the subserosal area with granulation tissue around the perforation of appendicitis, respectively. Finally, many myofibroblasts appearing in the subserosal area of the perforation of appendicitis may be derived from submesothelial cells or mesothelial cells.