Impact of differing methodologies for serum miRNA-371a-3p assessment in stage I testicular germ cell cancer recurrence.

Introduction: Current evidence shows that serum miR-371a-3p can identify disease recurrence in testicular germ cell tumour (TGCT) patients and correlates with tumour load. Despite convincing evidence showing the advantages of including miR-371a-3p testing to complement and overcome the classical serum tumour markers limitations, the successful introduction of a serum miRNA based test into clinical practice has been impeded by a lack of consensus regarding optimal methodologies and lack of a universal protocol and thresholds. Herein, we investigate two quantitative real-time PCR (qRT-PCR) based pipelines in detecting disease recurrence in stage I TGCT patients under active surveillance, and compare the sensitivity and specificity for each method. Methods: Sequential serum samples collected from 33 stage I TGCT patients undergoing active surveillance were analysed for miR-371a-3p via qRT-PCR with and without an amplification step included. Results: Using a pre-amplified protocol, all known recurrences were detected via elevated miR-371a-3p expression, while without pre-amplification, we failed to detect recurrence in 3/10 known recurrence patients. For pre-amplified analysis, sensitivity and specificity was 90% and 94.4% respectively. Without amplification, sensitivity dropped to 60%, but exhibited 100% specificity. Discussion: We conclude that incorporating pre-amplification increases sensitivity of miR-371a-3p detection, but produces more false positive results. The ideal protocol for quantification of miR-371a-3p still needs to be determined. TGCT patients undergoing active surveillance may benefit from serum miR-371a-3p quantification with earlier detection of recurrences compared to current standard methods. However, larger cross-institutional studies where samples are processed and data is analysed in a standardised manner are required prior to its routine clinical implementation.

Detection of recurrences using serum miR-371a-3p during active surveillance in men with stage I testicular germ cell tumours.

BACKGROUND: MiR-371a-3p predicts the presence of a macroscopic non-teratomatous germ cell tumour (GCT). We hypothesised that miR-371a-3p can also detect recurrence during active surveillance (AS) of stage I GCT. METHODS: We prospectively collected serum samples of 33 men. Relative expression of serum miR-371a-3p levels was determined at each follow-up visit using real-time quantitative reverse transcription-polymerase chain reaction. RESULTS: Recurrence was detected using standard follow-up investigations in 10/33 patients (30%) after a median of 7 months. Directly after orchiectomy, miR-371a-3p levels were not elevated in any of the 15 patients with available post-orchiectomy samples. However, all ten recurring patients exhibited increasing miR-371a-3p levels during follow-up, while miR-371a-3p levels remained non-elevated in all but one patient without recurrence. MiR-371a-3p detected recurrences at a median of 2 months (range 0-5) earlier than standard follow-up investigations. CONCLUSIONS: MiR-371a-3p levels immediately post orchiectomy are not predictive for recurrences and unfortunately cannot support decision-making for AS vs. adjuvant treatment. However, miR-371a-3p detects recurrences reliably and earlier than standard follow-up investigations. If this can be confirmed in larger cohorts, monitoring miR-371a-3p could replace surveillance imaging in seminomatous GCT and reduce the amount of imaging in non-seminomatous GCT. Earlier detection of disease recurrence may also reduce the overall treatment burden.

Lymphatic endothelial cells attenuate inflammation via suppression of dendritic cell maturation.

Vascular endothelial growth factor-C (VEGF-C)-induced lymphangiogenesis and increased tissue drainage have been reported to inhibit acute and chronic inflammation, and an activated lymphatic endothelium might mediate peripheral tolerance. Using transgenic mice overexpressing VEGF-C in the skin, we found that under inflammatory conditions, VEGF-C-mediated expansion of the cutaneous lymphatic network establishes an immune-inhibitory microenvironment characterised by increased regulatory T (Treg) cells, immature CD11c+CD11b+ dendritic cells (DCs) and CD8+ cells exhibiting decreased effector function. Strikingly, lymphatic endothelial cell (LEC)-conditioned media (CM) potently suppress DC maturation with reduced expression of MHCII, CD40, and IL-6, and increased IL-10 and CCL2 expression. We identify an imbalance in prostaglandin synthase expression after LEC activation, favoring anti-inflammatory prostacyclin synthesis. Importantly, blockade of LEC prostaglandin synthesis partially restores DC maturity. LECs also produce TGF-ß1, contributing to the immune-inhibitory microenvironment. This study identifies novel mechanisms by which the lymphatic endothelium modulates cellular immune responses to limit inflammation.

G-CSF regulates macrophage phenotype and associates with poor overall survival in human triple-negative breast cancer.

Tumor-associated macrophages (TAMs) have been implicated in the promotion of breast cancer growth and metastasis, and a strong infiltration by TAMs has been associated with estrogen receptor (ER)-negative tumors and poor prognosis. However, the molecular mechanisms behind these observations are unclear. We investigated macrophage activation in response to co-culture with several breast cancer cell lines (T47D, MCF-7, BT-474, SKBR-3, Cal-51 and MDA-MB-231) and found that high granulocyte colony-stimulating factor (G-CSF) secretion by the triple-negative breast cancer (TNBC) cell line MDA-MB-231 gave rise to immunosuppressive HLA-DRlo macrophages that promoted migration of breast cancer cells via secretion of TGF-α. In human breast cancer samples (n = 548), G-CSF was highly expressed in TNBC (p < 0.001) and associated with CD163+ macrophages (p < 0.0001), poorer overall survival (OS) (p = 0.021) and significantly increased numbers of TGF-α+ cells. While G-CSF blockade in the 4T1 mammary tumor model promoted maturation of MHCIIhi blood monocytes and TAMs and significantly reduced lung metastasis, anti-CSF-1R treatment promoted MHCIIloF4/80hiMRhi anti-inflammatory TAMs and enhanced lung metastasis in the presence of high G-CSF levels. Combined anti-G-CSF and anti-CSF-1R therapy significantly increased lymph node metastases, possibly via depletion of the so-called "gate-keeper" subcapsular sinus macrophages. These results indicate that G-CSF promotes the anti-inflammatory phenotype of tumor-induced macrophages when CSF-1R is inhibited and therefore caution against the use of M-CSF/CSF-1R targeting agents in tumors with high G-CSF expression.

Manipulation of B-cell responses with histone deacetylase inhibitors.

Histone deacetylase inhibitors (HDACi) are approved for treating certain haematological malignancies, however, recent evidence also illustrates they are modulators of the immune system. In experimental models, HDACi are particularly potent against malignancies originating from the B-lymphocyte lineage. Here we examine the ability of this class of compounds to modify both protective and autoimmune antibody responses. In vitro, HDACi affect B-cell proliferation, survival and differentiation in an HDAC-class-dependent manner. Strikingly, treatment of lupus-prone Mrl/lpr mice with the HDACi panobinostat significantly reduces autoreactive plasma-cell numbers, autoantibodies and nephritis, while other immune parameters remain largely unaffected. Immunized control mice treated with panobinostat or the clinically approved HDACi vorinostat have significantly impaired primary antibody responses, but these treatments surprisingly spare circulating memory B cells. These studies indicate that panobinostat is a potential therapy for B-cell-driven autoimmune conditions and HDACi do not induce major long-term detrimental effects on B-cell memory.

A transgenic Prox1-Cre-tdTomato reporter mouse for lymphatic vessel research.

The lymphatic vascular system plays an active role in immune cell trafficking, inflammation and cancer spread. In order to provide an in vivo tool to improve our understanding of lymphatic vessel function in physiological and pathological conditions, we generated and characterized a tdTomato reporter mouse and crossed it with a mouse line expressing Cre recombinase under the control of the lymphatic specific promoter Prox1 in an inducible fashion. We found that the tdTomato fluorescent signal recapitulates the expression pattern of Prox1 in lymphatic vessels and other known Prox1-expressing organs. Importantly, tdTomato co-localized with the lymphatic markers Prox1, LYVE-1 and podoplanin as assessed by whole-mount immunofluorescence and FACS analysis. The tdTomato reporter was brighter than a previously established red fluorescent reporter line. We confirmed the applicability of this animal model to intravital microscopy of dendritic cell migration into and within lymphatic vessels, and to fluorescence-activated single cell analysis of lymphatic endothelial cells. Additionally, we were able to describe the early morphological changes of the lymphatic vasculature upon induction of skin inflammation. The Prox1-Cre-tdTomato reporter mouse thus shows great potential for lymphatic research.

An intact immune system is required for the anticancer activities of histone deacetylase inhibitors.

Cell-intrinsic effects such as induction of apoptosis and/or inhibition of cell proliferation have been proposed as the major antitumor responses to histone deacetylase inhibitors (HDACi). These compounds can also mediate immune-modulatory effects that may contribute to their anticancer effects. However, HDACi can also induce anti-inflammatory, and potentially immunosuppressive, outcomes. We therefore sought to clarify the role of the immune system in mediating the efficacy of HDACi in a physiologic setting, using preclinical, syngeneic murine models of hematologic malignancies and solid tumors. We showed an intact immune system was required for the robust anticancer effects of the HDACi vorinostat and panobinostat against a colon adenocarcinoma and two aggressive models of leukemia/lymphoma. Importantly, although HDACi-treated immunocompromised mice bearing established lymphoma succumbed to disease significantly earlier than tumor bearing, HDACi-treated wild-type (WT) mice, treatment with the conventional chemotherapeutic etoposide equivalently enhanced the survival of both strains. IFN-γ and tumor cell signaling through IFN-γR were particularly important for the anticancer effects of HDACi, and vorinostat and IFN-γ acted in concert to enhance the immunogenicity of tumor cells. Furthermore, we show that a combination of vorinostat with α-galactosylceramide (α-GalCer), an IFN-γ-inducing agent, was significantly more potent against established lymphoma than vorinostat treatment alone. Intriguingly, B cells, but not natural killer cells or CD8(+) T cells, were implicated as effectors of the vorinostat antitumor immune response. Together, our data suggest HDACi are immunostimulatory during cancer treatment and that combinatorial therapeutic regimes with immunotherapies should be considered in the clinic.

Molecular and biologic analysis of histone deacetylase inhibitors with diverse specificities.

Histone deacetylase inhibitors (HDACi) are anticancer agents that induce hyperacetylation of histones, resulting in chromatin remodeling and transcriptional changes. In addition, nonhistone proteins, such as the chaperone protein Hsp90, are functionally regulated through hyperacetylation mediated by HDACis. Histone acetylation is thought to be primarily regulated by HDACs 1, 2, and 3, whereas the acetylation of Hsp90 has been proposed to be specifically regulated through HDAC6. We compared the molecular and biologic effects induced by an HDACi with broad HDAC specificity (vorinostat) with agents that predominantly inhibited selected class I HDACs (MRLB-223 and romidepsin). MRLB-223, a potent inhibitor of HDACs 1 and 2, killed tumor cells using the same apoptotic pathways as the HDAC 1, 2, 3, 6, and 8 inhibitor vorinostat. However, vorinostat induced histone hyperacetylation and killed tumor cells more rapidly than MRLB-223 and had greater therapeutic efficacy in vivo. FDCP-1 cells dependent on the Hsp90 client protein Bcr-Abl for survival, were killed by all HDACis tested, concomitant with caspase-dependent degradation of Bcr-Abl. These studies provide evidence that inhibition of HDAC6 and degradation of Bcr-Abl following hyperacetylation of Hsp90 is likely not a major mechanism of action of HDACis as had been previously posited.

Modulation of antitumour immune responses by intratumoural Stat1 expression.

Signal transducer and activator of transcription 1 (Stat1) mediates anti-viral responses and cytokine-driven anti-proliferative, apoptotic and immunomodulatory activities. As de-regulated Stat1 function can affect tumour progression we sought to elucidate the effects of tumour cell-intrinsic Stat1 expression on immunosurveillance. Knockout of Stat1 enhanced the development of sarcomas induced by the chemical carcinogen 3-methylcholanthrene (MCA). Growth of transplanted MCA-induced Stat1⁻/⁻ sarcomas was suppressed in wild-type mice compared to growth in Stat1⁻/⁻ and immunocompromised recipients. Co-depletion of NK and CD8⁺ T cells from wild-type mice facilitated Stat1-deficient tumour growth whereas depletion of CD4⁺ T cells and CD8⁺ T cells did not. In vitro and in vivo analysis of the tumours implicated a role for NK cell-mediated, perforin-dependent killing of Stat1-deficient tumours. Interestingly, restoration of Stat1 expression in Stat1⁻/⁻ tumours resulted in diminished involvement of NK cells and increased contribution of CD8⁺ T cells in anti-tumour responses. Therefore, Stat1 expression within tumour cells modulated anti-tumour immune responses by altering the dominant immune effector cell involvement from NK cells to CD8⁺ T cells in the absence or presence of Stat1 respectively.

Non-invasive dynamic near-infrared imaging and quantification of vascular leakage in vivo.

Preclinical vascular research has been hindered by a lack of methods that can sensitively image and quantify vascular perfusion and leakage in vivo. In this study, we have developed dynamic near-infrared imaging methods to repeatedly visualize and quantify vascular leakage in mouse skin in vivo, and we have applied these methods to transgenic mice with overexpression of vascular endothelial growth factors VEGF-A or -C. Near-infrared dye conjugates were developed to identify a suitable vascular tracer that had a prolonged circulation lifetime and slow leakage into normal tissue after intravenous injection. Dynamic simultaneous imaging of ear skin and a large blood vessel in the leg enabled determination of the intravascular signal (blood volume fraction) from the tissue signal shortly after injection and quantifications of vascular leakage into the extravascular tissue over time. This method allowed for the sensitive detection of increased blood vascularity and leakage rates in K14-VEGF-A transgenic mice and also reliably measured inflammation-induced changes of vascularity and leakage over time in the same mice. Measurements after injection of recombinant VEGF-A surprisingly revealed increased blood vascular leakage and lymphatic clearance in K14-VEGF-C transgenic mice which have an expanded cutaneous lymphatic vessel network, potentially indicating unanticipated effects of lymphatic drainage on vascular leakage. Increased vascular leakage was also detected in subcutaneous tumors, confirming that the method can also be applied to deeper tissues. This new imaging method might facilitate longitudinal investigations of the in vivo effects of drug candidates, including angiogenesis inhibitors, in preclinical disease models.

The combination of histone deacetylase inhibitors with immune-stimulating antibodies has potent anti-cancer effects.

The use of immunotherapy to treat cancer is rapidly gaining momentum. Using pre-clinical mouse models, we have recently demonstrated potent and long lasting tumor regression can be elicited by immune-stimulating monoclonal antibodies (mAbs) when combined with histone deacetylase inhibitors (HDACi) and believe this therapy will have broad application in humans.

Eradication of solid tumors using histone deacetylase inhibitors combined with immune-stimulating antibodies.

Histone deacetylase inhibitors (HDACi) have been successfully used as monotherapies for the treatment of hematological malignancies; however, the single agent effects of HDACi against solid tumors are less robust. Using preclinical models of lymphoma, we have recently demonstrated that HDACi induce tumor cell-specific apoptosis and that this is essential for the therapeutic effects of these agents. Herein, we demonstrate that HDACi can be combined with immune-activating antibodies designed to promote the function of antigen-presenting cells (APCs) and enhance proliferation and survival of cytotoxic T cells (CTL) to stimulate a host antitumor immune response resulting in eradication of established solid tumors. This unique combination therapy was dependent on tumor cell apoptosis mediated by HDACi that stimulated the uptake of dead tumor cells by APCs. Tumor eradication was mediated by CD8(+) CTL that used perforin as the key immune effector molecule. This combination therapy was well tolerated and induced long-term immunological antitumor memory capable of mediating spontaneous tumor eradication upon rechallenge. These studies indicate that the ability of HDACi to mediate subtherapeutic levels of tumor cell apoptosis can be exploited by combining with antibodies that augment host antitumor immune responses to mediate robust and prolonged eradication of solid tumors.