Tumor-derived microparticles induce bone marrow-derived cell mobilization and tumor homing: a process regulated by osteopontin.

Acute chemotherapy can induce rapid bone-marrow derived pro-angiogenic cell (BMDC) mobilization and tumor homing, contributing to tumor regrowth. To study the contribution of tumor cells to tumor regrowth following therapy, we focused on tumor-derived microparticles (TMPs). EMT/6 murine-mammary carcinoma cells exposed to paclitaxel chemotherapy exhibited an increased number of TMPs and significantly altered their angiogenic properties. Similarly, breast cancer patients had increased levels of plasma MUC-1(+) TMPs following chemotherapy. In addition, TMPs from cells exposed to paclitaxel induced higher BMDC mobilization and colonization, but had no increased effect on angiogenesis in Matrigel plugs and tumors than TMPs from untreated cells. Since TMPs abundantly express osteopontin, a protein known to participate in BMDC trafficking, the impact of osteopontin-depleted TMPs on BMDC mobilization, colonization, and tumor angiogenesis was examined. Although EMT/6 tumors grown in mice inoculated with osteopontin-depleted TMPs had lower numbers of BMDC infiltration and microvessel density when compared with EMT/6 tumors grown in mice inoculated with wild-type TMPs, no significant difference in tumor growth was seen between the two groups. However, when BMDCs from paclitaxel-treated mice were injected into wild-type EMT/6-bearing mice, a substantial increase in tumor growth and BMDC infiltration was detected compared to osteopontin-depleted EMT/6-bearing mice injected with BMDCs from paclitaxel-treated mice. Collectively, our results suggest that osteopontin expressed by TMPs play an important role in BMDC mobilization and colonization of tumors, but is not sufficient to enhance the angiogenic activity in tumors.

Addition of poly(A) and poly(A)-rich tails during RNA degradation in the cytoplasm of human cells.

Polyadenylation of RNA is a posttranscriptional modification that can play two somewhat opposite roles: stable polyadenylation of RNA encoded in the nuclear genomes of eukaryote cells contributes to nuclear export, translation initiation, and possibly transcript longevity as well. Conversely, transient polyadenylation targets RNA molecules to rapid exonucleolytic degradation. The latter role has been shown to take place in prokaryotes and organelles, as well as the nucleus of eukaryotic cells. Here we present evidence of hetero- and homopolymeric adenylation of truncated RNA molecules within the cytoplasm of human cells. RNAi-mediated silencing of the major RNA decay machinery of the cell resulted in the accumulation of these polyadenylated RNA fragments, indicating that they are degradation intermediates. Together, these results suggest that a mechanism of RNA decay, involving transient polyadenylation, is present in the cytoplasm of human cells.

Host response to immune checkpoint inhibitors contributes to tumor aggressiveness.

BACKGROUND: Immune checkpoint inhibitors (ICIs) have made a paradigm shift in clinical oncology due to unprecedented long-term remissions. However, only a small proportion of patients respond to ICI therapy. It is, therefore, essential to understand the mechanisms driving therapy resistance and to develop strategies for increasing response rates. We previously demonstrated that in response to various cancer treatment modalities, the host activates a range of biological processes that promote tumor regrowth and metastasis. Here, we characterize the host-mediated response to ICI therapy, and investigate its contribution to therapy resistance. METHODS: Tumor cell migration, invasion and motility were assessed in the presence of plasma from ICI-treated mice and patients. Immune cell composition in peripheral blood and tumors of ICI-treated mice was assessed by flow and mass cytometry. Plasma host factors driving tumor aggressiveness were identified by proteomic profiling, followed by bioinformatic analysis. The therapeutic effect of inhibiting host-mediated processes in ICI-treated mice was assessed in a tumor model. RESULTS: Tumor cells exhibit enhanced migratory and invasive properties in vitro on exposure to plasma from anti-PD1-treated mice. Moreover, mice intravenously injected with plasma-exposed tumor cells display increased metastatic burden and mortality rate in comparison to control arms. Furthermore, tumors from anti-PD1-treated mice as well as Matrigel plugs containing plasma from anti-PD1-treated mice are highly infiltrated with immune cell types associated with both antitumor and protumor activity. These collective findings suggest that anti-PD1 treatment induces a systemic host response that potentially counteracts the drug's therapeutic activity. Proteomic profiling of plasma from anti-PD1-treated mice reveals an activation of multiple biological pathways associated with tumor aggressiveness. Consequently, blocking IL-6, one of the key drivers of the identified biological pathways, counteracts ICI-induced metastatic properties in vitro and improves ICI treatment efficacy in vivo. Lastly, plasma samples from ICI-treated non-small cell lung cancer patients differentially affect tumor cell aggressiveness in vitro, with enhanced tumor cell motility correlating with a worse clinical outcome. CONCLUSIONS: ICI therapy induces host-mediated processes that contribute to therapy resistance. Identification and analysis of such processes may lead to the discovery of biomarkers for clinical response and strategies for overcoming therapy resistance.

The antiangiogenic role of the pro-inflammatory cytokine interleukin-31.

Pro-inflammatory cytokines in the tumor microenvironment are known for their ability to either inhibit or promote cancer progression. Here we evaluated the role of Interleukin-31 (IL31), a protein belonging to the pro-inflammatory IL-6 cytokine family which has been characterized in autoimmune disease, in tumorigenesis. We show that IL31 and its receptor, IL31RA, are highly expressed in various human and mouse cancer cell lines, as well as in tumor specimens from cancer patients. MC38 murine colon carcinoma cells depleted of IL31 exhibit an increase in invasive and migratory properties in vitro, effects that are reversed by supplementing the cells with exogenous IL31. In vivo, IL31-depleted MC38 tumor cells implanted to mice grow faster than control tumors. In contrast, MC38 tumor-bearing mice infused with recombinant IL31, exhibit a significant reduction in tumor growth than control mice. Furthermore, IL31 infusion reduces the number of metastatic lesions in the lungs of mice bearing 4T1 murine metastatic breast carcinoma. Lastly, injecting tumor-bearing, chemotherapy-treated mice with a long-lived IL31-IgG fusion protein reduces tumor growth, angiogenesis and pulmonary metastasis to a greater extent than when chemotherapy is used alone. The IL31 anti-tumor activity is explained, in part, by the anti-angiogenic effects demonstrated both in vitro and in vivo highlighting the potential use of IL31 as an anti-cancer drug.

Blocking IL1ß Pathway Following Paclitaxel Chemotherapy Slightly Inhibits Primary Tumor Growth but Promotes Spontaneous Metastasis.

Acquired resistance to therapy is a major obstacle in clinical oncology, and little is known about the contributing mechanisms of the host response to therapy. Here, we show that the proinflammatory cytokine IL1ß is overexpressed in response to paclitaxel chemotherapy in macrophages, subsequently promoting the invasive properties of malignant cells. In accordance, blocking IL1ß, or its receptor, using either genetic or pharmacologic approach, results in slight retardation of primary tumor growth; however, it accelerates metastasis spread. Tumors from mice treated with combined therapy of paclitaxel and the IL1 receptor antagonist anakinra exhibit increased number of M2 macrophages and vessel leakiness when compared with paclitaxel monotherapy-treated mice, indicating a prometastatic role of M2 macrophages in the IL1ß-deprived microenvironment. Taken together, these findings demonstrate the dual effects of blocking the IL1 pathway on tumor growth. Accordingly, treatments using "add-on" drugs to conventional therapy should be investigated in appropriate tumor models consisting of primary tumors and their metastases.

Small but mighty: microparticles as mediators of tumor progression.

A wide spectrum of both normal and diseased cell types shed extracellular vesicles that facilitate intercellular communication without direct cell-to-cell contact. Microparticles (MPs) are a subtype of extracellular vesicles that participate in multiple biological processes. They carry abundant bioactive molecules including different forms of nucleic acids and proteins that can markedly modulate cellular behavior. MPs are involved in several hallmarks of cancer such as drug resistance, thrombosis, immune evasion, angiogenesis, tumor invasion and metastasis. Such MPs originate from either cancer or other host cells. As MPs are secreted and can be detected in various body fluids, they can be used as potential diagnostic and prognostic biomarkers as well as vehicles for delivery of cytotoxic drugs. This review summarizes accumulating evidence on the biological properties of MPs in cancer, with reference to their potential usage in clinical settings.

Anti-VEGF-A affects the angiogenic properties of tumor-derived microparticles.

Tumor derived microparticles (TMPs) have recently been shown to contribute to tumor re-growth partially by inducing the mobilization and tumor homing of specific bone marrow derived pro-angiogenic cells (BMDCs). Since antiangiogenic drugs block proangiogenic BMDC mobilization and tumor homing, we asked whether TMPs from cells exposed to an antiangiogenic drug may affect BMDC activity and trafficking. Here we show that the level of VEGF-A is reduced in TMPs from EMT/6 breast carcinoma cells exposed to the anti-VEGF-A antibody, B20. Consequently, these TMPs exhibit reduced angiogenic potential as evaluated by a Matrigel plug and Boyden chamber assays. Consistently, BMDC mobilization, tumor angiogenesis, microvessel density and BMDC-colonization in growing tumors are reduced in mice inoculated with TMPs from B20-exposed cells as compared to mice inoculated with control TMPs. Collectively, our results suggest that the neutralization of VEGF-A in cultured tumor cells can block TMP-induced BMDC mobilization and colonization of tumors and hence provide another mechanism of action by which antiangiogenic drugs act to inhibit tumor growth and angiogenesis.

Differential therapeutic effects of anti-VEGF-A antibody in different tumor models: implications for choosing appropriate tumor models for drug testing.

We previously reported that the host response to certain chemotherapies can induce primary tumor regrowth, angiogenesis, and even metastases in mice, but the possible impact of anti-VEGF-A therapy in this context has not been fully explored. We, therefore, used combinations of anti-VEGF-A with chemotherapy on various tumor models in mice, including primary tumors, experimental lung metastases, and spontaneous lung metastases of 4T1-breast and CT26-colon murine cancer cell lines. Our results show that a combined treatment with anti-VEGF-A and folinic acid/5-fluorouracil/oxaliplatin (FOLFOX) but not with anti-VEGF-A and gemcitabine/cisplatinum (Gem/CDDP) enhances the treatment outcome partly due to reduced angiogenesis, in both primary tumors and experimental lung metastases models. However, neither treatment group exhibited an improved treatment outcome in the spontaneous lung metastases model, nor were changes in endothelial cell numbers found at metastatic sites. As chemotherapy has recently been shown to induce tumor cell invasion, we tested the invasion properties of tumor cells when exposed to plasma from FOLFOX-treated mice or patients with cancer. While plasma from FOLFOX-treated mice or patients induced invasion properties of tumor cells, the combination of anti-VEGF-A and FOLFOX abrogated these effects, despite the reduced plasma VEGF-A levels detected in FOLFOX-treated mice. These results suggest that the therapeutic impact of antiangiogenic drugs varies in different tumor models, and that anti-VEGF-A therapy can block the invasion properties of tumor cells in response to chemotherapy. These results may implicate an additional therapeutic role for anti-VEGF-A when combined with chemotherapy.

Anti-Bv8 antibody and metronomic gemcitabine improve pancreatic adenocarcinoma treatment outcome following weekly gemcitabine therapy.

Weekly gemcitabine therapy is the major treatment offered for patients with pancreatic adenocarcinoma cancer; however, relative resistance of tumor cells to chemotherapy, rapid regrowth, and metastasis are the main causes of death within a year. Recently, the daily continuous administration of chemotherapy in low doses--called metronomic chemotherapy (MC)--has been shown to inhibit primary tumor growth and delay metastases in several tumor types; however, its use as a single therapy is still in question due to its moderate therapeutic benefit. Here, we show that the combination of weekly gemcitabine with MC of the same drug delays tumor regrowth and inhibits metastasis in mice implanted orthotopically with pancreatic tumors. We further demonstrate that weekly gemcitabine, but not continuous MC gemcitabine or the combination of the two drug regimens, promotes rebound myeloid-derived suppressor cell (MDSC) mobilization and increases angiogenesis in this tumor model. Furthermore, Bv8 is highly expressed in MDSCs colonizing pancreatic tumors in mice treated with weekly gemcitabine compared to MC gemcitabine or the combination of the two regimens. Blocking Bv8 with antibodies in weekly gemcitabine-treated mice results in a significant reduction in tumor regrowth, angiogenesis, and metastasis. Overall, our results suggest that pro-tumorigenic effects induced by weekly gemcitabine are mediated in part by MDSCs expressing Bv8. Therefore, both Bv8 inhibition and MC can be used as legitimate 'add-on' treatments for preventing post-chemotherapy pancreatic cancer recurrence, progression, and metastasis following weekly gemcitabine therapy.