Localization of collagen modifying enzymes on fibroblastic reticular cells and follicular dendritic cells in non-neoplastic and neoplastic lymphoid tissues

Mechanisms of lymphoma-stromal interactions focusing on tumor-associated macrophages, fibroblastic reticular cells, and follicular dendritic cells

The interaction between cancer cells and stromal cells contributes to the pathogenesis of various types of tumors in the tumor microenvironment (TME). Macrophages (Mφs), a type of stromal cell, are transformed into tumor-associated Mφs (TAMs) after integrating within solid tumors. TAMs are known to interact with cancer cells and induce tumor progression. Thus, the cancer cells construct an organ-specific TME, which is advantageous for the survival of cancer cells in the TME. The density of stromal cells is known to be involved in the prognosis of patients with lymphomas. A higher density of stromal cells increases the interaction between lymphoma cells and stromal cells, promoting lymphoma progression. This review focuses on stromal cells in lymphoid tissues, such as TAMs, fibroblastic reticular cells (FRCs), and follicular dendritic cells (FDCs). This review also focuses on the signal transduction caused by stromal cells and tumor cells via factors such as cytokines. IL-10 and other cytokines secreted by TAMs activate the JAK/STAT pathway in lymphoma cells of follicular lymphoma, classic Hodgkin lymphoma, and diffuse large B-cell lymphoma. FRCs play roles in tumor promotion in follicular lymphoma and diffuse large B-cell lymphoma. Cytokines/chemokines secreted by FDCs play essential roles in lymphoma cell survival, proliferation, invasion, and migration in follicular lymphoma. In conclusion, TAMs, FRCs, and FDCs play crucial roles in the TME of lymphomas. Furthermore, histological spatial analysis revealing the positional relationship of each cell could highlight lymphoma-stromal interactions.

Activation of fibroblasts by plasma cells via PDGF/PDGFR signaling in IgG4-related sialadenitis

IgG4-related sialadenitis (IgG4-SA) is one of the IgG4-related disease. The histological features of IgG4-SA include dense lymphoplasmacytic infiltrates and fibrosis. This study aimed to reveal the involvement of plasma cells in the development of fibrosis and the mechanism underlying fibrosis in IgG4-SA. Hematoxylin-eosin staining, Azan staining, silver staining, and immunohistochemistry (IHC) were performed on IgG4-SA and chronic sialadenitis specimens, and theses samples were analyzed by image analysis software. Histological spatial analysis was used to analyze the localization of IHC-positive cells and the distances between these cells. In the IgG4-SA group, many secondary lymphoid follicles with germinal centers were found, and many collagen fibers developed around these germinal centers. Collagen fibers composed mainly of type I collagen was abundant at sites away from secondary lymphoid follicles, and reticular fibers composed of type III collagen was abundant near secondary lymphoid follicles. Many FAP+ fibroblasts and MUM1+ plasma cells were localized near secondary lymphoid follicles. Histological spatial analysis demonstrated that 90.4% of MUM1+ plasma cells accumulated within 20 µm of FAP+ fibroblasts. Multiple immunofluorescence assays revealed that MUM1+ plasma cells expressed platelet-derived growth factor (PDGF) β, and FAP+ fibroblasts expressed PDGF receptor (PDGFR) β and pSTAT3 in IgG4-SA. We have shown that fibrosis is localized around secondary lymphoid follicles and that fibroblasts are activated by plasma cells via PDGF/PDGFR signaling in IgG4-SA.

The Tumor Microenvironment in Follicular Lymphoma: Its Pro-Malignancy Role with Therapeutic Potential

In the follicular lymphoma (FL) microenvironment, CXCR5⁺ICOS⁺PD1⁺BCL6⁺ follicular helper T (Tfh) cells, which closely correlate with FL B cells in neoplastic follicles, play a major role in supporting FL. Interleukin-4 secreted by Tfh cells triggers the upregulation of the lymphocyte chemoattractant CXCL12 in stromal cell precursors, in particular by fibroblastic reticular cells (FRCs). In turn, mesenchymal stem cells (MSCs) can be committed to FRC differentiation in the bone marrow and lymph nodes involved by FL. Noteworthy, MSCs can promote the differentiation of Tfh cells into highly immunosuppressive T-follicular regulatory cells. The tumor suppressor HVEM is highly mutated in FL cells, and its deficiency increases Tfh cell frequency. In contrast, PI3Kδ inhibition impedes the recruitment of Tfh/regulatory T cells and impairs the proliferation of follicular dendritic cells (FDCs) and FDC-induced angiogenesis. Since TIGIT ligands are expressed by FDCs, the immune checkpoint receptor TIGIT plays an important role in tumor-infiltrating T cells. Thus, TIGIT blockade might invigorate cytotoxic T cells in the FL microenvironment. Given their potential to simultaneously reduce the neoplastic B cells, Tfh, and TFR cells could also reinforce the effects of the cytotoxic T cells. This combinatory strategy should be explored as a treatment option to tackle FL.

Cytokeratin-positive interstitial reticulum cell (CIRC) tumor in the lymph node: a case report of the transformation from the epithelioid cell type to the spindle cell type

Background

Cytokeratin-positive interstitial reticulum cells (CIRCs), which are a subgroup of fibroblastic reticular cells (FRCs), are known to be present in the lymph nodes. There have been only a few cases of tumors derived from CIRCs.

Case presentation

We have reported a new case involving a CIRC tumor in a 75-year-old man and reviewed the literature. The resected mediastinal lymph nodes showed epithelial-like proliferation of large atypical round and polygonal epithelioid cells. The tumor cells expressed CK8, CK18, CAM5.2, AE1/AE3, epithelial membrane antigen, vimentin, fascin, and some FRC markers, which is consistent with the diagnosis of a CIRC tumor. Following chemotherapy, the CIRC tumor was observed to have responded very well and became difficult to confirm on imaging, but a small cell lung carcinoma developed 12 months later. Chemoradiotherapy was performed, but the patient passed away 29 months after the initial diagnosis. The autopsy revealed the recurrence of the CIRC tumor, residual small cell lung carcinoma, and a very small latent carcinoma of the prostate. The relapsed CIRC tumor cells had a spindle shape; they were highly pleomorphic and had invaded the superior vena cava.

Conclusion

We first reported autopsy findings of CIRC tumors and demonstrated the transformation of the tumor from the epithelioid cell type to the spindle cell type.

Good prognosis for follicular lymphoma with estrogen receptor α-positive follicular dendritic cells

Follicular lymphoma (FL) has a meshwork of follicular dendritic cells (FDCs). We previously demonstrated the presence of estrogen receptor alpha (ERα)⁺CD23⁺ FDCs in grades 1‐2 FL. The significance of FDCs as a prognostic factor in FL remains unknown. The current study aimed to compare clinicopathological features, including prognosis, between FL with and without ERα⁺ FDCs. This study evaluated the clinicopathological significance of ERα expression in 70 FL patients by immunostaining. The presence of ERα mRNA on FDCs from 5 FL patients was confirmed by CD21/ERα double staining (immunohistochemistry and in situ hybridization). We defined patients with frequent ERα expression as the ERα^high group and those with infrequent ERα expression as the ERα^low group. Thirty‐two patients were assigned to the ERα^high group (45.7%), and 38 patients were assigned to the ERα^low group (54.3%). Both overall survival (OS) and progression‐free survival (PFS) were significantly better in the ERα^high group than in the ERα^low group (OS, log‐rank, P = .0465; PFS, log‐rank, P = .0336). Moreover, high ERα expression on FDCs was an independent prognostic factor for OS in both the univariate ([hazard ratio] HR, 0.163; P = .0260) and multivariate (HR, 0.050; P = .0188) analyses and for PFS in both the univariate (HR, 0.232; P = .0213) and multivariate (HR, 0.084; P = .0243) analyses. ERα mRNA expression was detected in CD21⁺ FDCs within the neoplastic follicles of FL patients. In conclusion, a neoplastic follicular microenvironment with ERα‐positive FDCs might affect the grade and presence of the follicular pattern of FL and improve patient prognosis.

Advancing CAR T-Cell Therapy for Solid Tumors: Lessons Learned from Lymphoma Treatment

Chimeric antigen receptor (CAR) immunotherapy is one of the most promising modern approaches for the treatment of cancer. To date only two CAR T-cell products, Kymriah^® and Yescarta^®, have been approved by the Food and Drug Administration (FDA) for the treatment of lymphoblastic leukemia and B-cell lymphoma. Administration of CAR T-cells to control solid tumors has long been envisaged as one of the most difficult therapeutic tasks. The first two clinical trials conducted in sarcoma and neuroblastoma patients showed clinical benefits of CAR T-cells, yet multiple obstacles still hold us back from having accessible and efficient therapy. Why did such an effective treatment for relapsed and refractory hematological malignancies demonstrate only relatively modest efficiency in the context of solid tumors? Is it due to the lucky selection of the “magic” CD19 antigen, which might be one of a kind? Or do lymphomas lack the immunosuppressive features of solid tumors? Here we review the existing knowledge in the field of CAR T-cell therapy and address the heterogeneity of solid tumors and their diverse strategies of immunoevasion. We also provide an insight into prospective developments of CAR T-cell technologies against solid tumors.

Differential expression of estrogen receptor-α on follicular dendritic cells from patients with grade 1-2 and grade 3 follicular lymphoma

Hormone therapy has been used for patients with estrogen receptor alpha (ERα)–positive breast cancers. Recently, some studies reported the expression of ERα on neoplastic cells from B‐cell lymphomas. However, there has been only one report of ERα expression on the follicular dendritic cells (FDCs) that structurally and functionally support the microenvironment of follicular lymphomas (FLs). The objective of this study was to investigate the frequency of ERα expression on FDCs in nonneoplastic reactive lymphoid tissues and to compare the frequency of ERα expression on FDCs in the axillary lymph nodes between patients with and without antiestrogen therapy and among patients with grades 1‐3 of FL. Reverse transcription–polymerase chain reaction was performed to detect ERα mRNA in FL. In nonneoplastic germinal centers (GCs) from patients with tonsillitis or reactive lymphadenitis, ERα was expressed in the light zone. ERα‐positive cells strongly correlated with the width of GCs (r_s = 0.81, P < 0.01) and the CD21‐positive (r_s = 0.69, P < 0.01) and CD23‐positive (r_s = 0.83, P < 0.01) FDC meshwork. The axillary lymph nodes had fewer ERα‐positive cells, smaller GCs, and a looser CD21‐ and CD23‐positive FDC meshwork with hormone therapy than without hormone therapy (P < 0.01). Neoplastic follicles of G1‐2 FL had more ERα‐positive cells and a larger CD23⁺ FDC meshwork than those of G3 FL (P < 0.01). ERα mRNA was detected in both G1‐2 FL and G3 FL by reverse transcription–polymerase chain reaction. In conclusion, these results suggested that antiestrogen hormone therapy may decrease the number of ERα‐positive FDCs and that the responses mediated by the estrogen‐ERα interaction on FDCs may differ between G1‐2 FL and G3 FL.