Jeffrey R. Lee

Expression of indoleamine 2,3-dioxygenase by plasmacytoid dendritic cells in tumor-draining lymph nodes

One mechanism contributing to immunologic unresponsiveness toward tumors may be presentation of tumor antigens by tolerogenic host APCs. We show that mouse tumor-draining LNs (TDLNs) contained a subset of plasmacytoid DCs (pDCs) that constitutively expressed immunosuppressive levels of the enzyme indoleamine 2,3-dioxygenase (IDO). Despite comprising only 0.5% of LN cells, these pDCs in vitro potently suppressed T cell responses to antigens presented by the pDCs themselves and also, in a dominant fashion, suppressed T cell responses to third-party antigens presented by nonsuppressive APCs. Adoptive transfer of DCs from TDLNs into naive hosts created profound local T cell anergy, specifically toward antigens expressed by the transferred DCs. Anergy was prevented by targeted disruption of the IDO gene in the DCs or by administration of the IDO inhibitor drug 1-methyl-D-tryptophan to recipient mice. Within the population of pDCs, the majority of the functional IDO-mediated suppressor activity segregated with a novel subset of pDCs coexpressing the B-lineage marker CD19. We hypothesize that IDO-mediated suppression by pDCs in TDLNs creates a local microenvironment that is potently suppressive of host antitumor T cell responses.

Activation of Gpr109a, receptor for niacin and the commensal metabolite butyrate, suppresses colonic inflammation and carcinogenesis

Commensal gut microflora and dietary fiber protect against colonic inflammation and colon cancer through unknown targets. Butyrate, a bacterial product from fermentation of dietary fiber in the colon, has been implicated in this process. GPR109A (encoded by Niacr1) is a receptor for butyrate in the colon. GPR109A is also a receptor for niacin, which is also produced by gut microbiota and suppresses intestinal inflammation. Here we showed that Gpr109a signaling promoted anti-inflammatory properties in colonic macrophages and dendritic cells and enabled them to induce differentiation of Treg cells and IL-10-producing T cells. Moreover, Gpr109a was essential for butyrate-mediated induction of IL-18 in colonic epithelium. Consequently, Niacr1(-/-) mice were susceptible to development of colonic inflammation and colon cancer. Niacin, a pharmacological Gpr109a agonist, suppressed colitis and colon cancer in a Gpr109a-dependent manner. Thus, Gpr10a has an essential role in mediating the beneficial effects of gut microbiota and dietary fiber in colon.

ArticleActivation of Gpr109a, Receptor for Niacin and the Commensal Metabolite Butyrate, Suppresses Colonic Inflammation and Carcinogenesis

Commensal gut microflora and dietary fiber protect against colonic inflammation and colon cancer through unknown targets. Butyrate, a bacterial product from fermentation of dietary fiber in the colon, has been implicated in this process. GPR109A (encoded by Niacr1) is a receptor for butyrate in the colon. GPR109A is also a receptor for niacin, which is also produced by gut microbiota and suppresses intestinal inflammation. Here we showed that Gpr109a signaling promoted anti-inflammatory properties in colonic macrophages and dendritic cells and enabled them to induce differentiation of Treg cells and IL-10-producing T cells. Moreover, Gpr109a was essential for butyrate-mediated induction of IL-18 in colonic epithelium. Consequently, Niacr1(-/-) mice were susceptible to development of colonic inflammation and colon cancer. Niacin, a pharmacological Gpr109a agonist, suppressed colitis and colon cancer in a Gpr109a-dependent manner. Thus, Gpr10a has an essential role in mediating the beneficial effects of gut microbiota and dietary fiber in colon.

Gastrointestinal autonomic nerve tumor: immunohistochemical and molecular identity with gastrointestinal stromal tumor.

Gastrointestinal autonomic nerve tumor (GANT) is a gastrointestinal neoplasm that ultrastructurally recapitulates the enteric neural plexus. This study identifies and defines the features of 10 cases of this rare mesenchymal tumor and compares its clinicopathologic and molecular genetic features with the data on gastrointestinal stromal tumor (GIST). The majority of patients in this series presented at an older age (mean 64 years). Tumors arose from the stomach (6), small intestine (2), and retroperitoneum (2). Mean tumor size was 14 cm; however, four neoplasms were <6 cm. Histologically, tumors were spindled or epithelioid; one epithelioid tumor demonstrated a previously undescribed rhabdoid histologic phenotype. All tumors were positive for CD117 (KIT), while eight of 10 were positive for CD34. In contrast, only two were positive for S-100, and all were negative for actin and desmin. Five GANTs demonstrated GIST-specific gain-of-function mutations in the juxtamembrane domain of the c-kit gene (50%). Three of 10 patients died of disease in 22–30 months, one patient died in the postoperative period, and one patient died of complications of CML. The clinicopathologic, histologic, immunohistologic, and molecular features of GANT are similar to GIST, indicating that GANT merely represents a phenotypic variant of GIST.

Pattern of Recruitment of Immunoregulatory Antigen-Presenting Cells in Malignant Melanoma

The mechanism by which the immune system of a tumor-bearing host acquires tolerance toward tumor antigens is still elusive. Antigen-presenting cells (APCs) are critical regulators of the decision between immune response and tolerance. APCs that express the tryptophan-degrading enzyme indoleamine 2,3-dioxygenase (IDO) have been found to inhibit T-cell responses both in vitro and in vivo. We hypothesized that malignant tumors exploit this mechanism by recruiting IDO-expressing APCs to the tumor-draining lymph nodes. To test this hypothesis, archival tissues and records of 26 cases of lymph node dissection for invasive cutaneous melanoma were obtained. IDO immunohistochemistry was performed on 14 cutaneous tumors and 328 regional lymph nodes. Abnormal accumulations of IDO-positive cells with a monocytoid or plasmacytoid morphology were identified in the perisinusoidal regions of draining lymph nodes in 45% of nodes studied. Recruitment of IDO-positive cells was seen in nodes with and without malignancy. We hypothesize that these IDO-positive APCs may contribute mechanistically to acquired tolerance to tumor antigens. Immunostaining of tumor-draining lymph nodes for abnormal accumulation of IDO-expressing cells might thus constitute an adverse prognostic factor and could contribute to the decision process and the appropriate care of patients with this deadly disease.

Indoleamine 2,3-dioxygenase, immunosuppression and pregnancy

Pharmacologic inhibition of indoleamine 2,3-dioxygenase (IDO) activity during murine pregnancy results in maternal T-cell-mediated rejection of allogeneic but not syngeneic conceptuses. Increased risk of allogeneic pregnancy failure induced by exposure to IDO inhibitor is strongly correlated with maternal C3 deposition at the maternal-fetal interface. Here we review evidence that cells expressing IDO contribute to immunosuppression by inhibiting T-cell responses to tumor antigens and tissue allografts, as well as fetal tissues.

NF-κB directly regulates Fas transcription to modulate Fas-mediated apoptosis and tumor suppression

Background: The functions of NF-κB in apoptosis and tumor development are controversial. Results: Fas functions as a tumor suppressor, and NF-κB directly binds to multiple sites in the Fas promoter region to regulate Fas transcription. Conclusion: Canonical NF-κB is a Fas transcription activator, whereas alternate NF-κB is a Fas transcription repressor. Significance: Inhibition of NF-κB in cancer therapy might suppress Fas-mediated apoptosis to impair host immune cell-mediated tumor suppression. Fas is a member of the death receptor family. Stimulation of Fas leads to induction of apoptotic signals, such as caspase 8 activation, as well as “non-apoptotic” cellular responses, notably NF-κB activation. Convincing experimental data have identified NF-κB as a critical promoter of cancer development, creating a solid rationale for the development of antitumor therapy that suppresses NF-κB activity. On the other hand, compelling data have also shown that NF-κB activity enhances tumor cell sensitivity to apoptosis and senescence. Furthermore, although stimulation of Fas activates NF-κB, the function of NF-κB in the Fas-mediated apoptosis pathway remains largely undefined. In this study, we observed that deficiency of either Fas or FasL resulted in significantly increased incidence of 3-methylcholanthrene-induced spontaneous sarcoma development in mice. Furthermore, Fas-deficient mice also exhibited significantly greater incidence of azoxymethane and dextran sodium sulfate-induced colon carcinoma. In addition, human colorectal cancer patients with high Fas protein in their tumor cells had a longer time before recurrence occurred. Engagement of Fas with FasL triggered NF-κB activation. Interestingly, canonical NF-κB was found to directly bind to the FAS promoter. Blocking canonical NF-κB activation diminished Fas expression, whereas blocking alternate NF-κB increased Fas expression in human carcinoma cells. Moreover, although canonical NF-κB protected mouse embryo fibroblast (MEF) cells from TNFα-induced apoptosis, knocking out p65 diminished Fas expression in MEF cells, resulting in inhibition of FasL-induced caspase 8 activation and apoptosis. In contrast, knocking out p52 increased Fas expression in MEF cells. Our observations suggest that canonical NF-κB is a Fas transcription activator and alternate NF-κB is a Fas transcription repressor, and Fas functions as a suppressor of spontaneous sarcoma and colon carcinoma.

Spasmolytic polypeptide-expressing metaplasia (SPEM) associated with gastric cancer in Iceland

Recent studies have described a spasmolytic polypeptide-expressing metaplastic cell lineage (SPEM) in the gastric fundic mucosa associated with both chronic H. pylori infection and gastric adenocarcinoma. We investigated the association of SPEM both with early gastric adenocarcinoma and in biopsies taken from patients prior to diagnosis of cancer. Two cohorts were examined. First, gastric resections from 29 patients with early gastric cancer were examined. Second, biopsies taken from 18 patients prior to the diagnosis of gastric cancer were compared with their respective resection specimens as well as with control biopsies from a cohort of 19 patients diagnosed with gastritis without subsequent development of cancer. The presence of SPEM and intestinal metaplasia (IM) adjacent to and distant from the cancer was compared and spasmolytic polypeptide (SP) immunostaining within dysplastic/cancerous cells was identified. SPEM was present adjacent to cancer in all early cancer cases where the tumor was located in the body or at the body/antrum junction, and was present in the body mucosa distant from the cancer in 76% of cases. Intestinal metaplasia was found adjacent to the tumor in 76% of cases and in body sections in 52% of resections. SP immunostaining was noted within cancer cells in 62% of tumors, and within dysplastic cells in 76% of resections where dysplasia was present. SPEM was present in 82% of the biopsies obtained prior to the diagnosis of cancer, compared with only 37% in the gastritis cohort. IM was present in only 57% of biopsies. In conclusion, SPEM is strongly associated with early gastric cancers and is observed in gastric biopsies prior to the development of cancer. In addition, early gastric cancers demonstrated a high incidence of SP expression. These results suggest that SPEM merits consideration as an important pre-neoplastic gastric lesion.

Identification of spasmolytic polypeptide expressing metaplasia (SPEM) in remnant gastric cancer and surveillance postgastrectomy biopsies

Following gastrectomy, the remnant oxyntic mucosa is at increased risk of developing adenocarcinoma. Alkaline pancreaticoduodenal reflux, carcinogen production from intragastric bacterial overgrowth, denervation, and devascularization have been implicated in this malignant transformation. Recent reports have described a novel spasmolytic polypeptide (SP) expressing metaplastic lineage designated as SPEM. This lineage has been identified in the mucosa surrounding gastric adenocarcinomas, and SP staining has been observed in the cells of surface dysplasia and invasive malignancy. In this study we describe 19 cases of remnant gastric adenocarcinoma from Japan. In addition, we studied surveillance biopsies in 90 patients who underwent antrectomy for carcinoma. SPEM was identified in the mucosa surrounding 88% of the remnant cancers, as well as in 61% of the surveillance biopsies. In the malignant resections, 67% of the surface dysplasia displayed SP positive cells, and 25% revealed SP immunostaining within invasive malignant cells. These findings implicate SPEM as a potential precursor lesion of gastric adenocarcinoma.

P21 Activated Kinase-1 (Pak1) Promotes Prostate Tumor Growth and Microinvasion via Inhibition of Transforming Growth Factor β Expression and Enhanced Matrix Metalloproteinase 9 Secretion

Background: The significance of Pak1 in prostate cancer remains unclear. Results: Pak1 knockdown impaired prostate tumor growth via increased expression of TGFβ and reduced secretion of MMP9. Conclusions: We demonstrated that Pak1 is a more potent mediator of prostate cancer cell migration and tumor growth than Pak6, the predominant isoform in the prostate. Significance: A novel role of Pak1 in prostate cancer is identified. P21-activated kinases (Paks) are major effectors downstream of the small Rho family of GTPases. Among the six isoforms, Pak1 is the most ubiquitous and the best characterized member. Previous studies have shown that inhibition of Pak6, which is predominantly present in the prostate compared with other tissues, inhibits prostate tumor growth in vivo. Even though Pak1 has been identified in normal prostatic epithelial cells and cancer cells, its specific role in the development of prostate cancer remains unclear. We report here that highly invasive prostate cancer cells express significantly higher levels of Pak1 protein compared with non-invasive prostate cancer cells. Furthermore, prostate tumor tissues and prostate cancer metastasized to lungs showed a higher expression of Pak1 compared with normal tissues. Interestingly, Pak6 protein expression levels did not change with the invasive/metastatic potential of the cancer cells or tumors. Although inhibition of Pak1, and not Pak6, resulted in impaired PC3 cell migration, the effects of Pak1 knockdown on transendothelial migration (microinvasion), tumor growth, and tumor angiogenesis was higher compared with Pak6 knockdown. Finally, gene array data revealed reduced expression of matrix metalloproteinase 9 with the ablation of either Pak1 or Pak6 gene expression in PC3 cells, whereas protein levels of TGFβ was elevated significantly with specific modulation of Pak1 activity or ablation of the Pak1 gene. Our observations suggest that although some level of functional redundancy exists between Pak1 and Pak6 in prostate cancer cells, targeting Pak1 is a potential option for the management of prostate tumor growth, microinvasion, and metastasis.