Tumor-induced STAT3 activation in monocytic myeloid-derived suppressor cells enhances stemness and mesenchymal properties in human pancreatic cancer.

Pancreatic cancer (PC) mobilizes myeloid cells from the bone marrow to the tumor where they promote tumor growth and proliferation. Cancer stem cells (CSCs) are a population of tumor cells that are responsible for tumor initiation. Aldehyde dehydrogenase-1 activity in PC identifies CSCs, and its activity has been correlated with poor overall prognosis in human PC. Myeloid cells have been shown to impact tumor stemness, but the impact of immunosuppressive tumor-infiltrating granulocytic and monocytic myeloid-derived suppressor cells (Mo-MDSC) on ALDH1(Bright) CSCs and epithelial to mesenchymal transition is not well understood. In this study, we demonstrate that Mo-MDSC (CD11b(+)/Gr1(+)/Ly6G(-)/Ly6C(hi)) significantly increase the frequency of ALDH1(Bright) CSCs in a mouse model of PC. Additionally, there was significant upregulation of genes associated with epithelial to mesenchymal transition. We also found that human PC converts CD14(+) peripheral blood monocytes into Mo-MDSC (CD14(+)/HLA-DR(low/-)) in vitro, and this transformation is dependent on the activation of the STAT3 pathway. In turn, these Mo-MDSC increase the frequency of ALDH1(Bright) CSCs and promote mesenchymal features of tumor cells. Finally, blockade of STAT3 activation reversed the increase in ALDH1(Bright) CSCs. These data suggest that the PC tumor microenvironment transforms monocytes to Mo-MDSC by STAT3 activation, and these cells increase the frequency of ALDH1(Bright) CSCs. Therefore, targeting STAT3 activation may be an effective therapeutic strategy in targeting CSCs in PC.

The clonal evolution of metastatic colorectal cancer.

Tumor heterogeneity and evolution drive treatment resistance in metastatic colorectal cancer (mCRC). Patient-derived xenografts (PDXs) can model mCRC biology; however, their ability to accurately mimic human tumor heterogeneity is unclear. Current genomic studies in mCRC have limited scope and lack matched PDXs. Therefore, the landscape of tumor heterogeneity and its impact on the evolution of metastasis and PDXs remain undefined. We performed whole-genome, deep exome, and targeted validation sequencing of multiple primary regions, matched distant metastases, and PDXs from 11 patients with mCRC. We observed intricate clonal heterogeneity and evolution affecting metastasis dissemination and PDX clonal selection. Metastasis formation followed both monoclonal and polyclonal seeding models. In four cases, metastasis-seeding clones were not identified in any primary region, consistent with a metastasis-seeding-metastasis model. PDXs underrepresented the subclonal heterogeneity of parental tumors. These suggest that single sample tumor sequencing and current PDX models may be insufficient to guide precision medicine.

Mutations in the rat myelin basic protein gene are associated with specific alterations in other myelin gene expression.

The Long Evans shaker (les) rat is a myelin basic protein (MBP) mutant that exhibits severe central nervous system (CNS) dysmyelination. We used a combination of immunohistochemistry, immunoblot and Northern blot analyses to determine the effect of MBP deficits on the expression of other CNS myelin genes in this mutant. Immunohistochemistry revealed a marked reduction in all major myelin proteins and differences in their intracellular distribution. Immunoblots confirmed the decreased expression of these proteins and indicated that relative levels of proteolipid protein (PLP) and DM20 were altered in this mutant. Quantitation of mRNA levels indicated that decreases in PLP and DM20 were a result of changes in mRNA levels but detected no change in other myelin gene transcripts.

Inflammatory monocyte mobilization decreases patient survival in pancreatic cancer: a role for targeting the CCL2/CCR2 axis.

PURPOSE: To determine the role of the CCL2/CCR2 axis and inflammatory monocytes (CCR2(+)/CD14(+)) as immunotherapeutic targets in the treatment of pancreatic cancer. EXPERIMENTAL DESIGN: Survival analysis was conducted to determine if the prevalence of preoperative blood monocytes correlates with survival in patients with pancreatic cancer following tumor resection. Inflammatory monocyte prevalence in the blood and bone marrow of patients with pancreatic cancer and controls was compared. The immunosuppressive properties of inflammatory monocytes and macrophages in the blood and tumors, respectively, of patients with pancreatic cancer were assessed. CCL2 expression by human pancreatic cancer tumors was compared with normal pancreas. A novel CCR2 inhibitor (PF-04136309) was tested in an orthotopic model of murine pancreatic cancer. RESULTS: Monocyte prevalence in the peripheral blood correlates inversely with survival, and low monocyte prevalence is an independent predictor of increased survival in patients with pancreatic cancer with resected tumors. Inflammatory monocytes are increased in the blood and decreased in the bone marrow of patients with pancreatic cancer compared with controls. An increased ratio of inflammatory monocytes in the blood versus the bone marrow is a novel predictor of decreased patient survival following tumor resection. Human pancreatic cancer produces CCL2, and immunosuppressive CCR2(+) macrophages infiltrate these tumors. Patients with tumors that exhibit high CCL2 expression/low CD8 T-cell infiltrate have significantly decreased survival. In mice, CCR2 blockade depletes inflammatory monocytes and macrophages from the primary tumor and premetastatic liver resulting in enhanced antitumor immunity, decreased tumor growth, and reduced metastasis. CONCLUSIONS: Inflammatory monocyte recruitment is critical to pancreatic cancer progression, and targeting CCR2 may be an effective immunotherapeutic strategy in this disease.

His36Pro point-mutated proteolipid protein retained in the endoplasmic reticulum of oligodendrocytes in the shaking pup.

The shaking pup (shp) is a canine mutation that affects the myelin protein proteolipid protein (PLP) and its smaller and less abundant isoform, DM20, with proline replacing histidine(36), resulting in a severe myelin deficiency in the central nervous system. We present evidence that the mutation leads to disrupted trafficking of the shp PLP/DM20 within oligodendrocytes. Immunohistochemical studies revealed significantly reduced levels of PLP/DM20 and other major myelin components such as myelin basic protein (MBP), myelin associated glycoprotein (MAG), and 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP) in shp myelin. The distribution of shp PLP/DM20 proteins were altered and mostly retained in perinuclear cytoplasm and proximal processes, which co-localized with distended rough endoplasmic reticulum (RER) within oligodendrocytes. No abnormal accumulation of MAG, MBP, or CNP in the cell body was found. These results suggest that mutated PLP/DM20 in the shp could be selectively retained in RER, causing disruption of their translocation to the periphery to myelinate axons.

Suppression of activated microglia promotes survival and function of transplanted oligodendroglial progenitors.

To evaluate the functional consequence of microglial activation in vivo, oligodendroglial progenitors were transplanted into the spinal cord of Long Evans shaker, a myelin mutant rat in which myelin defects are associated with progressive microglial activation. Cells grafted into neonatal rats at the initiation of gliosis successfully myelinated axons. However, cells transplanted during peak microglial activation did not lead to myelination due to death of the grafted cells within 3 days after transplantation. Pretreatment of these animals with minocycline, a tetracycline derivative, resulted in cell survival and myelination by the grafted cells. In culture, minocycline did not affect the survival, proliferation, or differentiation of oligodendroglial progenitors. Hence, minocycline likely modulates the function of reactive glia in vivo to promote the survival and myelination of transplanted oligodendroglial progenitors.

Inhibition of autoimmune encephalomyelitis by a tetracycline.

We have explored the use of minocycline, a tetracycline with antiinflammatory properties, to treat chronic relapsing-remitting experimental allergic encephalomyelitis, an animal model of multiple sclerosis. Therapeutic treatment with minocycline dramatically suppresses ongoing disease activity and limits disease progression. Disease suppression is associated with immune deviation in the periphery and with suppression of the inflammatory cascade in the central nervous system. This association is demonstrated by inhibition of microglial activation and metalloproteinase-2 expression, which results in a concomitant decrease in inflammation and demyelination. As an established antiinflammatory drug with neuroprotective properties, minocycline may provide a novel therapeutic agent for relapsing-remitting multiple sclerosis.