Autocrine CSF-1 and CSF-1 receptor coexpression promotes renal cell carcinoma growth

Colony stimulating factor-1 receptor drives glomerular parietal epithelial cell activation in focal segmental glomerulosclerosis

Parietal epithelial cells (PECs) are kidney progenitor cells with similarities to a bone marrow stem cell niche. In focal segmental glomerulosclerosis (FSGS) PECs become activated and contribute to extracellular matrix deposition. Colony stimulating factor-1 (CSF-1), a hematopoietic growth factor, acts via its specific receptor, CSF-1R, and has been implicated in several glomerular diseases, although its role on PEC activation is unknown. Here, we found that CSF-1R was upregulated in PECs and podocytes in biopsies from patients with FSGS. Through in vitro studies, PECs were found to constitutively express CSF-1R. Incubation with CSF-1 induced CSF-1R upregulation and significant transcriptional regulation of genes involved in pathways associated with PEC activation. Specifically, CSF-1/CSF-1R activated the ERK1/2 signaling pathway and upregulated CD44 in PECs, while both ERK and CSF-1R inhibitors reduced CD44 expression. Functional studies showed that CSF-1 induced PEC proliferation and migration, while reducing the differentiation of PECs into podocytes. These results were validated in the Adriamycin-induced FSGS experimental mouse model. Importantly, treatment with either the CSF-1R-specific inhibitor GW2580 or Ki20227 provided a robust therapeutic effect. Thus, we provide evidence of the role of the CSF-1/CSF-1R pathway in PEC activation in FSGS, paving the way for future clinical studies investigating the therapeutic effect of CSF-1R inhibitors on patients with FSGS.

Single-cell analysis reveals ADGRL4+ renal tubule cells as a highly aggressive cell type in clear cell renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) is a highly heterogeneous cancer that poses great challenge to clinical treatment and prognostic prediction. Characterizing the cellular landscape of ccRCC in a single-cell dimension can help better understand the tumor heterogeneity and molecular mechanisms of ccRCC. This study analyzed single-cell profiles in ccRCC samples and para-tumor samples from Gene Expression Omnibus and identified a highly heterogeneous subcluster of renal tubule cells. Single-cell regulatory network inference and clustering analyses and cell communication analysis were performed to develop transcription factor-target gene regulatory networks and cell-cell interactions. Additionally, the distribution and prognostic risk of renal tubule cells from spatial transcriptome data (GSM6415706) and The Cancer Genome Atlas-Kidney Clear Cell Carcinoma data were analyzed. A total of 10 cell types were identified in ccRCC and para-tumor samples. The ccRCC renal tubule cells showed a high expression of the oncogene nicotinamide N-methyltransferase and a significantly high degree of tumor heterogeneity. We further identified 6 cell subclusters with specific expression of BEX2, PTHLH, SFRP2, KLRB1, ADGRL4, and HGF from the ccRCC renal tubule cells. ADGRL4+ renal tubule cells had highly metastatic and angiogenesis-inducing characteristics, with more ADGRL4+ renal tubule cells indicating a worse survival. ADGRL4+ renal tubule cells regulated the metastasis of other renal tubule cells through metastasis-related receptor-ligand communication. We also found that ADGRL4+ renal tubule cells clustered around the glomeruli but the rest of the renal tubule cell subclusters rarely localized in ccRCC tissues. ETS1 and ELK3 -dominant GRNs were remarkably activated in ADGRL4+ renal tubule cells, functionally, knockdown of ELK3 in A498 significantly disturbedaffected the cell migration and invasion. ADGRL4+ renal tubule cells, which were highly metastatic and invasive, might be an essential cell subcluster for ccRCC, and ADGRL4 could be used a novel therapeutic target.

p53 Gain-of-Function Mutation Induces Metastasis via BRD4-Dependent CSF-1 Expression

TP53 mutations are frequent in esophageal squamous cell carcinoma (ESCC) and other SCCs and are associated with a proclivity for metastasis. Here, we report that colony-stimulating factor-1 (CSF-1) expression is upregulated significantly in a p53-R172H-dependent manner in metastatic lung lesions of ESCC. The p53-R172H-dependent CSF-1 signaling, through its cognate receptor CSF-1R, increases tumor cell invasion and lung metastasis, which in turn is mediated in part through Stat3 phosphorylation and epithelial-to-mesenchymal transition (EMT). In Trp53R172H tumor cells, p53 occupies the Csf-1 promoter. The Csf-1 locus is enriched with histone 3 lysine 27 acetylation (H3K27ac), which is likely permissive for fostering an interaction between bromodomain-containing domain 4 (BRD4) and p53-R172H to regulate Csf-1 transcription. Inhibition of BRD4 not only reduces tumor invasion and lung metastasis but also reduces circulating CSF-1 levels. Overall, our results establish a novel p53-R172H-dependent BRD4-CSF-1 axis that promotes ESCC lung metastasis and suggest avenues for therapeutic strategies for this difficult-to-treat disease.

SIGNIFICANCE

The invasion-metastasis cascade is a recalcitrant barrier to effective cancer therapy. We establish that the p53-R172H-dependent BRD4-CSF-1 axis is a mediator of prometastatic properties, correlates with patient survival and tumor stages, and its inhibition significantly reduces tumor cell invasion and lung metastasis. This axis can be exploited for therapeutic advantage. This article is featured in Selected Articles from This Issue, p. 2489.

Antitumor activity of a pexidartinib bioisostere inhibiting CSF1 production and CSF1R kinase activity in human hepatocellular carcinoma

Macrophage colony-stimulating factor (M-CSF, also known as CSF1) in tumor tissues stimulates tumor growth and tumor-induced angiogenesis through an autocrine and paracrine action on CSF1 receptor (CSF1R). In the present study, novel bioisosteres of pexidartinib (1) were synthesized and evaluated their inhibitory activities against CSF1R kinase and tumor growth. Among newly synthesized bioisosteres, compound 3 showed the highest inhibition (95.1%) against CSF1R tyrosine kinase at a fixed concentration (1 μM). The half maximal inhibitory concentration (IC₅₀) of pexidartinib (1) and compound 3 was 2.7 and 57.8 nM, respectively. Unlike pexidartinib (1), which cross-reacts to three targets with structural homology, such as CSF1R, c-KIT, and FLT3, compound 3 inhibited CSF1R, c-KIT, but not FLT3, indicating compound 3 may be a more selective CSF1R inhibitor than pexidartinib (1). The inhibitory effect of compound 3 on the proliferation of various cancer cell lines was the strongest in U937 cells followed by THP-1 cells. In the case of cancer cell lines derived from solid tumors, the anti-proliferative activity of compound 3 was weaker than pexidartinib (1), except for Hep3B. However, compound 3 was safer than pexidartinib (1) in terminally differentiated normal cells such as macrophages. Pexidartinib (1) and compound 3 suppressed the production of CSF1 in Hep3B liver cancer cells as well as in the co-culture of Hep3B cells and macrophages. Also, pexidartinib (1) and compound 3 decreased the population ratio of the M2/M1 phenotype and inhibited their migration. Importantly, compound 3 preferentially inhibited M2 phenotype over M1, and the effect was about 4 times greater than that of pexidartinib (1). In addition, compound 3 inhibited maintenance of cancer stem cell population. In a chick chorioallantoic membrane (CAM) tumor model implanted with Hep3B cells, tumor growth and tumor-induced angiogenesis were significantly blocked by compound 3 to a similar extent as pexidartinib (1). Overall, compound 3, a bioisostere of pexidartinib, is an effective dual inhibitor to block CSF1R kinase and CSF1 production, resulting in significant inhibition of tumor growth.

Macrophage-Colony-Stimulating Factor Receptor Enhances Prostate Cancer Cell Growth and Aggressiveness In Vitro and In Vivo and Increases Osteopontin Expression

Prostate cancer is a major public health concern and one of the most prevalent forms of cancer worldwide. The definition of altered signaling pathways implicated in this complex disease is thus essential. In this context, abnormal expression of the receptor of Macrophage Colony-Stimulating Factor-1 (M-CSF or CSF-1) has been described in prostate cancer cells. Yet, outcomes of this expression remain unknown. Using mouse and human prostate cancer cell lines, this study has investigated the functionality of the wild-type CSF-1 receptor in prostate tumor cells and identified molecular mechanisms underlying its ligand-induced activation. Here, we showed that upon CSF-1 binding, the receptor autophosphorylates and activates multiple signaling pathways in prostate tumor cells. Biological experiments demonstrated that the CSF-1R/CSF-1 axis conferred significant advantages in cell growth and cell invasion in vitro. Mouse xenograft experiments showed that CSF-1R expression promoted the aggressiveness of prostate tumor cells. In particular, we demonstrated that the ligand-activated CSF-1R increased the expression of spp1 transcript encoding for osteopontin, a key player in cancer development and metastasis. Therefore, this study highlights that the CSF-1 receptor is fully functional in a prostate cancer cell and may be a potential therapeutic target for the treatment of prostate cancer.

Differential responses to immune checkpoint inhibitor dictated by pre-existing differential immune profiles in squamous cell carcinomas caused by same initial oncogenic drivers

BACKGROUND

While immune checkpoint inhibitors (ICI) were approved for head and neck squamous cell carcinomas (HNSCCs), the response rate remains relatively low. Mechanisms underlying ICI unresponsiveness versus sensitivity are not fully understood.

METHOD

To better delineate differential responses to ICI treatment, we employed mouse SCC models, termed KPPA tumors that were caused by deleting p53 and hyperactivating PIK3CA, two most frequently mutated genes in human HNSCCs. We transplanted two KPPA tumor lines (TAb2 versus TCh3) into C57BL/6 recipients and examined the immune tumor microenvironment using flow cytometry. Furthermore, we employed single-cell RNA sequencing to identify the difference in tumor infiltrating lymphocytes (TILs).

RESULTS

We found that different KPPA tumors exhibited heterogeneous immune profiles pre-existing treatment that dictated their sensitivity or unresponsiveness to anti-PD-L1. Unresponsive TAb2 tumors were highly enriched with functional tumor-associated macrophages (TAMs), especially M2-TAMs. In contrast, sensitive TCh3 tumors contained more CD8 TILs with better effector functions. TAb2 tumor cells drastically expanded F4/80⁺ TAMs from bone marrow precursors, requiring CSF1 and VEGF. Consistently, a higher combined expression of VEGF-C and CSF1 predicts worse survival in PIK3CA^Amp/TP53^Mutated HNSCC patients. Unresponsive TAb2 tumors upregulated distinct signaling pathways that correlate with aggressive tumor phenotypes. While anti-PD-L1 did not affect the TME of TAb2 tumors, it significantly increased the number of CD8 TILs in TCh3 tumors.

CONCLUSIONS

We uncovered tumor-intrinsic differences that may underlie the differential responses to ICI by establishing and employing two SCC tumor lines, TAb2 vs. TCh3, both of which harbor TP53 deletion and PIK3CA hyperactivation. Our study indicates the limitation of stratifying cancers according to their genetic alterations and suggests that evaluating HNSCC tumor-intrinsic cues along with immune profiles in the TME may help better predict ICI responses. Our experimental models may provide a platform for pinpointing tumor-intrinsic differences underlying an immunosuppressive TME in HNSCCs and for testing combined immunotherapies targeting either tumor-specific or TAM-specific players to improve ICI efficacy.

LncRNA GAPLINC Promotes Renal Cell Cancer Tumorigenesis by Targeting the miR-135b-5p/CSF1 Axis

Background

Long noncoding RNAs (lncRNAs) are closely related to the occurrence and development of cancer. Gastric adenocarcinoma-associated, positive CD44 regulator, long intergenic noncoding RNA (GAPLINC) is a recently identified lncRNA that can actively participate in the tumorigenesis of various cancers. Here, we investigated the functional roles and mechanism of GAPLINC in renal cell carcinoma (RCC) development.

Methods

Differentially expressed lncRNAs between RCC tissues and normal kidney tissues were detected by using a microarray technique. RNA sequencing was applied to explore the mRNA expression profile changes after GAPLINC silencing. After gain- and loss-of-function approaches were implemented, the effect of GAPLINC on RCC in vitro and in vivo was assessed by cell proliferation and migration assays. Moreover, rescue experiments and luciferase reporter assays were used to study the interactions between GAPLINC, miR-135b-5p and CSF1.

Results

GAPLINC was significantly upregulated in RCC tissues and cell lines and was associated with a poor prognosis in RCC patients. Knockdown of GAPLINC repressed RCC growth in vitro and in vivo, while overexpression of GAPLINC exhibited the opposite effect. Mechanistically, we found that GAPLINC upregulates oncogene CSF1 expression by acting as a sponge of miR-135b-5p.

Conclusion

Taken together, our results suggest that GAPLINC is a novel prognostic marker and molecular therapeutic target for RCC.

Next frontier in tumor immunotherapy: macrophage-mediated immune evasion

Tumor-associated macrophages (TAMs), at the core of immunosuppressive cells and cytokines networks, play a crucial role in tumor immune evasion. Increasing evidences suggest that potential mechanisms of macrophage-mediated tumor immune escape imply interpretation and breakthrough to bottleneck of current tumor immunotherapy. Therefore, it is pivotal to understand the interactions between macrophages and other immune cells and factors for enhancing existing anti-cancer treatments. In this review, we focus on the specific signaling pathways through which TAMs involve in tumor antigen recognition disorders, recruitment and function of immunosuppressive cells, secretion of immunosuppressive cytokines, crosstalk with immune checkpoints and formation of immune privileged sites. Furthermore, we summarize correlative pre-clinical and clinical studies to provide new ideas for immunotherapy. From our perspective, macrophage-targeted therapy is expected to be the next frontier of cancer immunotherapy.

Overexpression of macrophage-colony stimulating factor-1 receptor as a prognostic factor for survival in cancer: A systematic review and meta-analysis

BACKGROUND

The relation between the expression of macrophage-colony stimulating factor-1 receptor (CSF-1R) and prognosis of cancer patients has been evaluated in multiple studies, but the results remain controversial. We, therefore, performed a meta-analysis and systematic review to figure out the role of CSF-1R in the prognosis of patients with cancer.

METHODS

Several databases were searched, including Web of Science, PubMed, and EMBASE. All human studies were published as full text. The Newcastle-Ottawa risk of bias scale was applied to evaluate the research. We extracted hazard ratios (HRs) with 95% confidence interval (95% CI) which assessed progression-free survival (PFS) and overall survival (OS) in order to assess the impacts of CSF-1R on the prognosis of cancer patients.

RESULTS

A total of 12 citations were identified, with studies including 2260 patients in different cancer types that met the eligibility criteria. It was suggested in a pooled analysis that the over-expression of CSF-1R was significantly related to worse PFS (HR: 1.68; P < .001, 1.25-2.10, 95% CI) and also poorer OS (HR=1.28; P < .001, 1.03-1.54, 95% CI). Analysis in subgroups indicated over-expressed CSF-1R was significantly associated with worse OS in hematological malignancy (HR = 2.29; P < .001, 1.49-3.09, 95% CI; model of fixed-effects; I2 = 0.0%, P < .001). Sensitivity analysis suggested that there was no study influencing the stability of the results.

CONCLUSIONS

The overexpression of CSF-1R was significantly predictive of worse prognosis in those who suffer from different kinds of malignancies, particularly in hematological malignancy, which indicates that it might be a potential biomarker of prognosis in cancer survival and a potential molecular target in the treatment of malignant tumors.

Reno-protective effect of IL-34 inhibition on cisplatin-induced nephrotoxicity in mice

INTRODUCTION

Interleukin-34 (IL-34) shares a receptor (cFMS) with colony stimulating factor-1 (CSF-1), and these two ligands mediate macrophage proliferation. However, in contrast to CSF-1, the influence of IL-34 on tubular epithelial cells (TECs) injury remains unclear. We investigated the physiological effects of IL-34 on TEC damage caused by cisplatin nephrotoxicity (CP-N).

METHODS

Mice were administered anti-mouse IL-34 antibody (anti-IL-34 Ab; 400 ng/kg) or vehicle from 1 day before and up to 2 days after CP-N induction. In vitro, mouse renal proximal TECs (MRPTEpiC) were cultured to analyze the inhibitory effects of IL-34 on CP-induced TEC apoptosis.

RESULTS

Compared to vehicle treatment, anti-IL-34 Ab treatment significantly suppressed the intra-renal expression of IL-34 and its two receptors, cFMS and PTP-ζ, and significantly improved renal function, ameliorated tubulointerstitial injury, suppressed macrophage infiltration, and reduced apoptotic cell numbers in CP-N mice. It also significantly reduced the renal transcript levels of Kim-1, MIP-1/CCL3, TNF-α, and Bax in CP-N mice. Furthermore, anti-IL-34 Ab-treated CP-N mice showed less renal infiltration of F4/80+TNF-α+ cells. In vitro, stimulation with CP induced the expression of IL-34 and its two receptors in MRPTEpiC. Anti-IL-34 Ab treatment significantly suppressed CP-induced Bax expression with the degradation of ERK1/2 phosphorylation in damaged MRPTEpiC.

CONCLUSIONS

IL-34 secreted from damaged TECs appeared to be involved in the progression of CP-N. Inhibition of IL-34 with neutralizing antibody directly prevented CP-induced TEC apoptosis by inhibiting the phosphorylation of ERK 1/2. Blocking of IL-34 appears to suppress the proliferation of cytotoxic macrophages, which indirectly attenuates CP-N. Thus, IL-34 represents a potential therapeutic target for TEC injury, and the inhibition of IL-34 might have a reno-protective effect.

The Roles of Stroma-Derived Chemokine in Different Stages of Cancer Metastases

The intricate interplay between malignant cells and host cellular and non-cellular components play crucial role in different stages of tumor development, progression, and metastases. Tumor and stromal cells communicate to each other through receptors such as integrins and secretion of signaling molecules like growth factors, cytokines, chemokines and inflammatory mediators. Chemokines mediated signaling pathways have emerged as major mechanisms underlying multifaceted roles played by host cells during tumor progression. In response to tumor stimuli, host cells-derived chemokines further activates signaling cascades that support the ability of tumor cells to invade surrounding basement membrane and extra-cellular matrix. The host-derived chemokines act on endothelial cells to increase their permeability and facilitate tumor cells intravasation and extravasation. The tumor cells-host neutrophils interaction within the vasculature initiates chemokines driven recruitment of inflammatory cells that protects circulatory tumor cells from immune attack. Chemokines secreted by tumor cells and stromal immune and non-immune cells within the tumor microenvironment enter the circulation and are responsible for formation of a "pre-metastatic niche" like a "soil" in distant organs whereby circulating tumor cells "seed' and colonize, leading to formation of metastatic foci. Given the importance of host derived chemokines in cancer progression and metastases several drugs like Mogamulizumab, Plerixafor, Repertaxin among others are part of ongoing clinical trial which target chemokines and their receptors against cancer pathogenesis. In this review, we focus on recent advances in understanding the complexity of chemokines network in tumor microenvironment, with an emphasis on chemokines secreted from host cells. We especially summarize the role of host-derived chemokines in different stages of metastases, including invasion, dissemination, migration into the vasculature, and seeding into the pre-metastatic niche. We finally provide a brief description of prospective drugs that target chemokines in different clinical trials against cancer.

Impact of inflammation and immunotherapy in renal cell carcinoma

Substantial research attention has been directed at exploring the mechanisms and treatment of renal cell carcinoma (RCC). Indeed, the association between inflammation and tumor phenotypes has been at the center of cancer research. Concomitant with research on the inflammation response and inflammatory molecules involved in RCC, new breakthroughs have emerged. A large body of knowledge now shows that treatments targeting inflammation and immunity in RCC provide substantial clinical benefits. Adequate analysis and a better understanding of the mechanisms of inflammatory factors in the occurrence and progression of RCC are highly desirable. Currently, numerous RCC treatments targeted at inflammation and immunotherapy are available. The current review describes in detail the link between inflammation and RCC.

Characterization of a p53/miR-34a/CSF1R/STAT3 Feedback Loop in Colorectal Cancer

BACKGROUND & AIMS

The miR-34a gene is a direct target of p53 and is commonly silenced in colorectal cancer (CRC). Here we identified the receptor tyrosine kinase CSF1R as a direct miR-34a target and characterized CSF1R as an effector of p53/miR-34a-mediated CRC suppression.

METHODS

Analyses of TCGA-COAD and three other CRC cohorts for association of mRNA expression and signatures with patient survival and molecular subtypes. Bioinformatics identification and experimental validation of miRNA and transcription factor targets. Functional analysis of factors/pathways in the regulation of epithelial-mesenchymal transition (EMT), invasion, migration, acquired chemo-resistance and metastasis. Analyses of protein expression and CpG methylation within primary human colon cancer samples.

RESULTS

In primary CRCs increased CSF1R, CSF1 and IL34 expression was associated with poor patient survival and a mesenchymal-like subtype. CSF1R displayed an inverse correlation with miR-34a expression. This was explained by direct inhibition of CSF1R by miR-34a. Furthermore, p53 repressed CSF1R via inducing miR-34a, whereas SNAIL induced CSF1R both directly and indirectly via repressing miR-34a in a coherent feed-forward loop. Activation of CSF1R induced EMT, migration, invasion and metastasis of CRC cells via STAT3-mediated down-regulation of miR-34a. 5-FU resistance of CRC cells was mediated by CpG-methylation of miR-34a and the resulting elevated expression of CSF1R. In primary CRCs elevated expression of CSF1R was detected at the tumor invasion front and was associated with CpG methylation of the miR-34a promoter as well as distant metastasis.

CONCLUSIONS

The reciprocal inhibition between miR-34a and CSF1R and its loss in tumor cells may be relevant for therapeutic and prognostic approaches towards CRC management.

The combination of bevacizumab/Avastin and erlotinib/Tarceva is relevant for the treatment of metastatic renal cell carcinoma: the role of a synonymous mutation of the EGFR receptor

Metastatic clear cell renal cell carcinomas (mRCC) over-express the vascular endothelial growth factor (VEGF). Hence, the anti-VEGF antibody bevacizumab/Avastin (BVZ) combined with interferon alpha (IFN) was approved for the treatment of mRCC. However, approval was lost in July 2016 due to the absence of sustained efficacy. We previously showed that BVZ accelerates tumor growth in experimental models of mRCC in mice, results in part explained by down-regulation of the phospho tyrosine phosphatase receptor kappa (PTPRκ) in tumor cells. The epidermal growth factor receptor (EGFR) is a direct target of PTPRκ. Its down-regulation leads to constitutive activation of EGFR, an observation which prompted us to test the effect of the EGFR inhibitor erlotinib/Tarceva (ERLO) in addition to BVZ/IFN. The influence of the long non-coding RNA, EGFR-AS1, on ERLO efficacy was also addressed.

Methods: The effect of BVZ/IFN/ERLO was tested on the growth of experimental tumors in nude mice. The presence of germline mutation in the EGFR was evaluated on cell lines and primary RCC cells. In vitro translation and transfections of expression vectors coding the wild-type or the EGFR mutated gene in HEK-293 cells were used to test the role of EGFR mutation of the ERLO efficacy. Correlation between EGFR/EGFR-AS1 expression and survival was analyzed with an online available data base (TCGA).

Results: Tumor growth was strongly reduced by the triple combination BVZ/IFN/ERLO and linked to reduced levels of pro-angiogenic/pro-inflammatory cytokines of the ELR+CXCL family and to subsequent inhibition of vascularization, a decreased number of lymphatic vessels and polarization of macrophages towards the M1 phenotype. Cells isolated from surgical resection of human tumors presented a range of sensitivity to ERLO depending on the presence of a newly detected mutation in the EGFR and to the presence of EGFR-AS1.

Conclusions: Our results point-out that the BVZ/IFN/ERLO combination deserves testing for the treatment of mRCC that have a specific mutation in the EGFR.

Phase Ib study of the combination of pexidartinib (PLX3397), a CSF-1R inhibitor, and paclitaxel in patients with advanced solid tumors

Purpose:

To evaluate the safety, recommended phase II dose (RP2D) and efficacy of pexidartinib, a colony stimulating factor receptor 1 (CSF-1R) inhibitor, in combination with weekly paclitaxel in patients with advanced solid tumors.

Patients and Methods:

In part 1 of this phase Ib study, 24 patients with advanced solid tumors received escalating doses of pexidartinib with weekly paclitaxel (80 mg/m²). Pexidartinib was administered at 600 mg/day in cohort 1. For subsequent cohorts, the dose was increased by ⩽50% using a standard 3+3 design. In part 2, 30 patients with metastatic solid tumors were enrolled to examine safety, tolerability and efficacy of the RP2D. Pharmacokinetics and biomarkers were also assessed.

Results:

A total of 51 patients reported ≥1 adverse event(s) (AEs) that were at least possibly related to either study drug. Grade 3–4 AEs, including anemia (26%), neutropenia (22%), lymphopenia (19%), fatigue (15%), and hypertension (11%), were recorded in 38 patients (70%). In part 1, no maximum tolerated dose was achieved and 1600 mg/day was determined to be the RP2D. Of 38 patients evaluable for efficacy, 1 (3%) had complete response, 5 (13%) partial response, 13 (34%) stable disease, and 17 (45%) progressive disease. No drug–drug interactions were found. Plasma CSF-1 levels increased 1.6- to 53-fold, and CD14dim/CD16+ monocyte levels decreased by 57–100%.

Conclusions:

The combination of pexidartinib and paclitaxel was generally well tolerated. RP2D for pexidartinib was 1600 mg/day. Pexidartinib blocked CSF-1R signaling, indicating potential for mitigating macrophage tumor infiltration.

Modeling the Hematopoietic Landscape

Some time ago, we proposed a continuum-like view of the lineages open to hematopoietic stem cells (HSCs); each HSC self-renews or chooses from the spectrum of all end-cell options and can then "merely" differentiate. Having selected a cell lineage, an individual HSC may still "step sideways" to an alternative, albeit closely related, fate: HSC and their progeny therefore remain versatile. The hematopoietic cytokines erythropoietin, granulocyte colony-stimulating factor, macrophage colony-stimulating factor, granulocyte/macrophage colony-stimulating factor and ligand for the fms-like tyrosine kinase 3 instruct cell lineage. Sub-populations of HSCs express each of the cytokine receptors that are positively auto-regulated upon cytokine binding. Many years ago, Waddington proposed that the epigenetic landscape played an important role in cell lineage choice. This landscape is dynamic and unstable especially regarding DNA methylation patterns across genomic DNA. This may underlie the receptor diversity of HSC and their decision-making.

Pan-Cancer analysis of the expression and regulation of matrisome genes across 32 tumor types

The microenvironment plays a central role in cancer, and neoplastic cells actively shape it to their needs by complex arrays of extracellular matrix (ECM) proteins, enzymes, cytokines and growth factors collectively referred to as the matrisome. Studies on the cancer matrisome have been performed for single or few neoplasms, but a more systematic analysis is still missing. Here we present a Pan-Cancer study of matrisome gene expression in 10,487 patients across 32 tumor types, supplemented with transcription factors (TFs) and driver genes/pathways regulating each tumor's matrisome. We report on 919 TF-target pairs, either used specifically or shared across tumor types, and their prognostic significance, 40 master regulators, 31 overarching regulatory pathways and the potential for druggability with FDA-approved cancer drugs. These results provide a comprehensive transcriptional architecture of the cancer matrisome and suggest the need for development of specific matrisome-targeting approaches for future therapies.

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In-depth characterization of matrisome gene expression and regulation in 10,487 patients across 32 human tumor types.

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Identification of transcription factor (TF) and “master regulators” governing each cancer’s matrisome.

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Analysis unveils therapeutic possibilities and suggests new treatments by repurposing of FDA-approved cancer drugs.

IL-34-Dependent Intrarenal and Systemic Mechanisms Promote Lupus Nephritis in MRL-Faslpr Mice

BACKGROUND

In people with SLE and in the MRL-Fas^lpr lupus mouse model, macrophages and autoantibodies are central to lupus nephritis. IL-34 mediates macrophage survival and proliferation, is expressed by tubular epithelial cells (TECs), and binds to the cFMS receptor on macrophages and to a newly identified second receptor, PTPRZ.

METHODS

To investigate whether IL-34-dependent intrarenal and systemic mechanisms promote lupus nephritis, we compared lupus nephritis and systemic illness in MRL-Fas^lpr mice expressing IL-34 and IL-34 knockout (KO) MRL-Fas^lpr mice. We also assessed expression of IL-34 and the cFMS and PTPRZ receptors in patients with lupus nephritis.

RESULTS

Intrarenal IL-34 and its two receptors increase during lupus nephritis in MRL-Fas^lpr mice. In knockout mice lacking IL-34, nephritis and systemic illness are suppressed. IL-34 fosters intrarenal macrophage accumulation via monocyte proliferation in bone marrow (which increases circulating monocytes that are recruited by chemokines into the kidney) and via intrarenal macrophage proliferation. This accumulation leads to macrophage-mediated TEC apoptosis. We also found suppression of circulating autoantibodies and glomerular antibody deposits in the knockout mice. This is consistent with fewer activated and proliferating intrarenal and splenic B cells in mice lacking IL-34, and with our novel discovery that PTPRZ is expressed by macrophages, B and T cells. These findings appear translatable to human patients with lupus nephritis, whose expression of IL-34, cFMS, and PTPRZ is similar to that seen in the MRL-Fas^lpr lupus mouse model. Moreover, expression of IL-34 in TECs correlates with disease activity.

CONCLUSIONS

IL-34 is a promising novel therapeutic target for patients with lupus nephritis.

Colony-stimulating factor-1 receptor provides a growth advantage in epithelial cancer cell line A431 in the presence of epidermal growth factor receptor inhibitor gefitinib

Although epidermal growth factor receptor (EGFR) has been identified as a potent "oncogenic driver" in various tumors of epithelial origin, EGFR-targeted therapies are often of limited success. One of the challenges of improving targeted therapies is to overcome bypassing signaling pathways. Analysis of RNA-seq data of 1006 cell lines from the Cancer Cell Line Encyclopedia (CCLE) revealed that more than 12% of carcinoma cell lines expressed markedly elevated mRNA levels of colony-stimulating factor (CSF)-1 receptor (CSF-1R). Since epithelial cells also express CSF-1, elevated levels of CSF-1R may participate in providing alternative growth and survival signals under targeted therapies. To address this question, we ectopically expressed CSF-1R in A431 cells that express EGFR at high levels, but no biologically relevant level of CSF-1R. In the presence of EGFR inhibitor gefitinib, CSF-1R provided a significant growth advantage in A431 cells. As expected, activation of both receptors, EGFR or CSF-1R, induced phosphorylation of extracellular signal-regulated kinase (Erk)1/2, Akt, protein kinase C (PKC) and signal transducer and activator of transcription (STAT)3. However, EGFR, but not CSF-1R, also induced STAT5 phosphorylation. Inhibitor of phosphatidylinositol 3-kinase (PI3K) (AZD8186), MAPK/ERK kinase (MEK)1/2 (U0126), PKCs (Bisindolylmaleimide I or Gö6976) or STAT3 (Stattic) partially reduced proliferation of CSF-1R expressing A431 cells in the presence of gefitinib. Moreover, multi-kinase inhibitor, cabozantinib, suppressed CSF-1R activation and drastically reduced cell growth when combined with gefitinib. These data suggest that CSF-1R has the potential to reduce sensitivity to gefitinib and may be involved in resistance development.

The RUNX1/IL-34/CSF-1R axis is an autocrinally regulated modulator of resistance to BRAF-V600E inhibition in melanoma

Resistance to current therapies still impacts a significant number of melanoma patients and can be regulated by epigenetic alterations. Analysis of global cytosine methylation in a cohort of primary melanomas revealed a pattern of early demethylation associated with overexpression of oncogenic transcripts. Loss of methylation and associated overexpression of the CSF 1 receptor (CSF1R) was seen in a majority of tumors and was driven by an alternative, endogenous viral promoter in a subset of samples. CSF1R was particularly elevated in melanomas with BRAF and other MAPK activating mutations. Furthermore, rebound ERK activation after BRAF inhibition was associated with RUNX1-mediated further upregulation of CSF-1R and its ligand IL-34. Importantly, increased CSF-1R and IL-34 overexpression were detected in an independent cohort of resistant melanomas. Inhibition of CSF-1R kinase or decreased CSF-1R expression by RNAi reduced 3-D growth and invasiveness of melanoma cells. Coinhibition of CSF-1R and BRAF resulted in synergistic efficacy in vivo. To our knowledge, our data unveil a previously unknown role for the autocrine-regulated CSF-1R in BRAF V600E resistance and provide a preclinical rationale for targeting this pathway in melanoma.

Colony-stimulating factor-1 and colony-stimulating factor-1 receptor co-expression is associated with disease progression in gastric cancer

Colony‑stimulating‑factor‑1 (CSF‑1) is a hematopoietic growth factor that exerts its effects through the c‑fms/CSF‑1 receptor (CSF‑1R). The CSF‑1/CSF‑1R axis is thought to be involved in the development of several types of cancer. This study aimed to clarify the clinical and biological significance of the CSF‑1/CSF‑1R axis in gastric cancer (GC). For this purpose, we evaluated CSF‑1 and CSF‑1R expression in GC tissues from 148 patients by RT‑qPCR and immunohistochemistry. The biological roles of the CSF‑1/CSF‑1R axis were investigated by measuring the cell proliferation and migration, and anoikis resistance in a human GC cell line following treatment with recombinant human CSF‑1 and/or CSF‑1R inhibitor. The results revealed that an elevated expression of CSF‑1 or CSF‑1R significantly correlated with disease progression and with a poor overall survival (OS, P=0.037 and 0.016, respectively) and disease‑free survival (DFS, P<0.001 and <0.001, respectively) of patients with GC. Furthermore, a high co‑expression of CSF‑1 and CSF‑1R was an independent prognostic factor for OS (HR, 1.38; 95% CI, 1.02‑1.88; P=0.038) and DFS (HR, 1.79; 95% CI, 1.21‑2.67; P=0.004), and an independent risk factor for lymph node and peritoneal metastasis. Immunohistochemical analysis revealed an intense CSF‑1/CSF‑1R expression in the cytoplasm of cancer cells in primary GC tissues. CSF‑1 or CSF‑1R expression positively correlated with vascular endothelial growth factor A (VEGFA) or Fms related tyrosine kinase 1 (FLT1) expression in GC tissues. Treatment with recombinant human CSF‑1 promoted proliferation, migration and anoikis resistance in a GC cell line. These effects were generally blocked by CSF‑1R inhibition. On the whole, the findings of this study indicate that the CSF‑1/CSF‑1R axis may be a clinically useful prognostic and predictive biomarker for lymph node and peritoneal metastasis and a potential therapeutic target in GC.

A General Framework for Interrogation of mRNA Stability Programs Identifies RNA-Binding Proteins that Govern Cancer Transcriptomes

Widespread remodeling of the transcriptome is a signature of cancer; however, little is known about the post-transcriptional regulatory factors, including RNA-binding proteins (RBPs) that regulate mRNA stability, and the extent to which RBPs contribute to cancer-associated pathways. Here, by modeling the global change in gene expression based on the effect of sequence-specific RBPs on mRNA stability, we show that RBP-mediated stability programs are recurrently deregulated in cancerous tissues. Particularly, we uncovered several RBPs that contribute to the abnormal transcriptome of renal cell carcinoma (RCC), including PCBP2, ESRP2, and MBNL2. Modulation of these proteins in cancer cell lines alters the expression of pathways that are central to the disease and highlights RBPs as driving master regulators of RCC transcriptome. This study presents a framework for the screening of RBP activities based on computational modeling of mRNA stability programs in cancer and highlights the role of post-transcriptional gene dysregulation in RCC.

Recent Advances of Colony-Stimulating Factor-1 Receptor (CSF-1R) Kinase and Its Inhibitors

Colony stimulation factor-1 receptor (CSF-1R), which is also known as FMS kinase, plays an important role in initiating inflammatory, cancer, and bone disorders when it is overstimulated by its ligand, CSF-1. Innate immunity, as well as macrophage differentiation and survival, are regulated by the stimulation of the CSF-1R. Another ligand, interlukin-34 (IL-34), was recently reported to activate the CSF-1R receptor in a different manner. The relationship between CSF-1R and microglia has been reviewed. Both CSF-1 antibodies and small molecule CSF-1R kinase inhibitors have now been tested in animal models and in humans. In this Perspective, we discuss the role of CSF-1 and IL-34 in producing cancer, bone disorders, and inflammation. We also review the newly discovered and improved small molecule kinase inhibitors and monoclonal antibodies that have shown potent activity toward CSF-1R, reported from 2012 until 2017.

Inhibition of the colony-stimulating-factor-1 receptor affects the resistance of lung cancer cells to cisplatin

In the present work we show that multiple lung cancer cell lines contain cisplatin resistant cell subpopulations expressing the Colony-Stimulating-Factor-Receptor-1 (CSF-1R) and surviving chemotherapy-induced stress. By exploiting siRNA-mediated knock down in vitro and the use of an investigational CSF-1R TKI (JNJ-40346527) in vitro and in vivo, we show that expression and function of the receptor are required for the clonogenicity and chemoresistance of the cell lines. Thus, inhibition of the kinase activity of the receptor reduced the levels of EMT-associated genes, stem cell markers and chemoresistance genes. Additionally, the number of high aldehyde dehydrogenase (ALDH) expressing cells was reduced, consequent to the lack of cisplatin-induced increase of ALDH isoforms. This affected the collective chemoresistance of the treated cultures. Treatment of tumor bearing mice with JNJ-40346527, at pharmacologically relevant doses, produced strong chemo-sensitizing effects in vivo. These anticancer effects correlated with a reduced number of CSF-1Rpos cells, in tumors excised from the treated mice. Depletion of the CD45pos cells within the treated tumors did not, apparently, play a major role in mediating the therapeutic response to the TKI. Thus, lung cancer cells express a functional CSF-1 and CSF-1R duo which mediates pro-tumorigenic effects in vivo and in vitro and can be targeted in a therapeutically relevant way. These observations complement the already known role for the CSF-1R at mediating the pro-tumorigenic properties of tumor-infiltrating immune components.

The role of C1QBP in CSF-1-dependent PKCζ activation and macrophage migration

Macrophages view as double agents in tumor progression. Trafficking of macrophages to the proximity of tumors is mediated by colony-stimulating factor-1 (CSF-1), a growth factor. In this study, we investigated the role of complement1q-binding protein (C1QBP)/ atypical protein kinase C ζ (PKCζ) in CSF-1-induced macrophage migration. Disruption of C1QBP expression impaired chemotaxis and adhesion of macrophage. Phosphorylation of PKCζ is an essential component in macrophage chemotaxis signaling pathway. C1QBP could interact with PKCζ in macrophage. C1QBP knockdown inhibited CSF-1 induced phosphorylation of PKCζ and integrin-β1. However, C1QBP knockdown didn't affect the phosphorylation of PKCζ induced by MCP-1. Furthermore, CSF-1 from RCC cell condition medium promoted macrophage chemotaxis and adhesion. Taken together, our results demonstrated that C1QBP plays an essential role in CSF-1 induced migration of macrophages.

TSC-22 inhibits CSF-1R function and induces apoptosis in cervical cancer

Colony stimulating factor 1 receptor (CSF-1R) regulates the monocyte/macrophage system, which is an essential component of cancer development. Therefore, CSF-1R might be an effective target for anti-cancer therapy. The overexpression of transforming growth factor (TGF)-β stimulated clone-22 (TSC-22) inhibits cancer cell proliferation and induces apoptosis, and TSC-22 is emerging as a key factor in tumorigenesis. In this study, we discovered CSF-1R as a new interacting partner of TSC-22 and identified its elevated expression in cervical cancer cells. In particular, we found that TSC-22 interacted with the intracellular tyrosine kinase insert domain (539–749) of CSF-1R, which activates the AKT and ERK signaling pathways. This binding blocked AKT and ERK signaling, thereby suppressing the transcriptional activity of NF-κB. The overexpression of TSC-22 significantly decreased CSF-1R protein levels, affecting their autocrine loop. TSC-22 injected into a xenograft mouse model of human cervical cancer markedly inhibited tumor growth. The reduction of CSF-1R protein significantly suppresses cervical cancer cell proliferation and motility and induces apoptotic cell death. This association between TSC-22 and CSF-1R could be used as a novel therapeutic target and prognostic marker for cervical cancer.

Engineering a monomeric variant of macrophage colony-stimulating factor (M-CSF) that antagonizes the c-FMS receptor

Enhanced activation of the signaling pathways that mediate the differentiation of mononuclear monocytes into osteoclasts is an underlying cause of several bone diseases and bone metastasis. In particular, dysregulation and overexpression of macrophage colony-stimulating factor (M-CSF) and its c-FMS tyrosine kinase receptor, proteins that are essential for osteoclast differentiation, are known to promote bone metastasis and osteoporosis, making both the ligand and its receptor attractive targets for therapeutic intervention. With this aim in mind, our starting point was the previously held concept that the potential of the M-CSF_C31S mutant as a therapeutic is derived from its inability to dimerize and hence to act as an agonist. The current study showed, however, that dimerization is not abolished in M-CSF_C31S and that the protein retains agonistic activity toward osteoclasts. To design an M-CSF mutant with diminished dimerization capabilities, we solved the crystal structure of the M-CSF_C31S dimer complex and used structure-based energy calculations to identify the residues responsible for its dimeric form. We then used that analysis to develop M-CSF_C31S,M27R, a ligand-based, high-affinity antagonist for c-FMS that retained its binding ability but prevented the ligand dimerization that leads to receptor dimerization and activation. The monomeric properties of M-CSF_C31S,M27R were validated using dynamic light scattering and small-angle X-ray scattering analyses. It was shown that this mutant is a functional inhibitor of M-CSF-dependent c-FMS activation and osteoclast differentiation in vitro Our study, therefore, provided insights into the sequence-structure-function relationships of the M-CSF/c-FMS interaction and of ligand/receptor tyrosine kinase interactions in general.

Sunitinib Stimulates Expression of VEGFC by Tumor Cells and Promotes Lymphangiogenesis in Clear Cell Renal Cell Carcinomas

Sunitinib is an antiangiogenic therapy given as a first-line treatment for renal cell carcinoma (RCC). While treatment improves progression-free survival, most patients relapse. We hypothesized that patient relapse can stem from the development of a lymphatic network driven by the production of the main growth factor for lymphatic endothelial cells, VEGFC. In this study, we found that sunitinib can stimulate vegfc gene transcription and increase VEGFC mRNA half-life. In addition, sunitinib activated p38 MAPK, which resulted in the upregulation/activity of HuR and inactivation of tristetraprolin, two AU-rich element-binding proteins. Sunitinib stimulated a VEGFC-dependent development of lymphatic vessels in experimental tumors. This may explain our findings of increased lymph node invasion and new metastatic sites in 30% of sunitinib-treated patients and increased lymphatic vessels found in 70% of neoadjuvant treated patients. In summary, a therapy dedicated to destroying tumor blood vessels induced the development of lymphatic vessels, which may have contributed to the treatment failure. Cancer Res; 77(5); 1212-26. ©2017 AACR.

High Expression of Colony-Stimulating Factor 1 Receptor Associates with Unfavorable Cancer-Specific Survival of Patients with Clear Cell Renal Cell Carcinoma

BACKGROUND

Colony-stimulating factor 1 receptor (CSF-1R), a single-pass type III transmembrane tyrosine-protein kinase, is mainly involved in inflammation and immune regulation to facilitate the progression of solid tumors. This study aimed to evaluate the impact of CSF-1R expression on clinical outcome of patients with clear cell renal cell carcinoma (ccRCC) after surgery.

METHODS

We retrospectively enrolled 268 patients with ccRCC undergoing nephrectomy between 2001 and 2004. Clinicopathologic features and cancer-specific survival (CSS) were collected. Western blot analysis was performed in the pairwise comparisons of CSF-1R expression in peritumor and tumor tissues of patients with ccRCC. Immunohistochemistry was conducted to determine CSF-1R expression level in tumor specimens. Survival analysis was performed by the Kaplan-Meier method. Cox regression models were used to evaluate the impact of prognostic factors on CSS. A concordance index was calculated to measure prognostic accuracy. A prognostic nomogram was constructed on the basis of the identified independent prognostic factors.

RESULTS

CSF-1R expression in tumor tissues was higher than in peritumor tissues in 71.4% (5 of 7) patients. CSF-1R expression of tumor tissues was positively associated with metastasis, tumor, node, metastasis classification system (TNM) stage, Eastern Cooperative Oncology Group performance status score and poor CSS. CSF-1R expression was determined as an independent prognostic factor for CSS in patients with ccRCC. Furthermore, extension of the well-established prognostic models with CSF-1R expression presented significantly improved prognostic accuracy. An efficient prognostic nomogram was constructed on the basis of the independent prognostic factors.

CONCLUSIONS

High CSF-1R expression is a potential independent adverse prognostic factor for CSS in patients with ccRCC.

Glioblastoma-derived Macrophage Colony-stimulating Factor (MCSF) Induces Microglial Release of Insulin-like Growth Factor-binding Protein 1 (IGFBP1) to Promote Angiogenesis

Glioblastoma (grade IV glioma/GBM) is the most common primary adult malignant brain tumor with poor prognosis. To characterize molecular determinants of tumor-stroma interaction in GBM, we profiled 48 serum cytokines and identified macrophage colony-stimulating factor (MCSF) as one of the elevated cytokines in sera from GBM patients. Both MCSF transcript and protein were up-regulated in GBM tissue samples through a spleen tyrosine kinase (SYK)-dependent activation of the PI3K-NFκB pathway. Ectopic overexpression and silencing experiments revealed that glioma-secreted MCSF has no role in autocrine functions and M2 polarization of macrophages. In contrast, silencing expression of MCSF in glioma cells prevented tube formation of human umbilical vein endothelial cells elicited by the supernatant from monocytes/microglial cells treated with conditioned medium from glioma cells. Quantitative proteomics based on stable isotope labeling by amino acids in cell culture showed that glioma-derived MCSF induces changes in microglial secretome and identified insulin-like growth factor-binding protein 1 (IGFBP1) as one of the MCSF-regulated proteins secreted by microglia. Silencing IGFBP1 expression in microglial cells or its neutralization by an antibody reduced the ability of supernatants derived from microglial cells treated with glioma cell-conditioned medium to induce angiogenesis. In conclusion, this study shows up-regulation of MCSF in GBM via a SYK-PI3K-NFκB-dependent mechanism and identifies IGFBP1 released by microglial cells as a novel mediator of MCSF-induced angiogenesis, of potential interest for developing targeted therapy to prevent GBM progression.

Tumour and patient factors in renal cell carcinoma-towards personalized therapy

Renal cell carcinoma (RCC) comprises a heterogeneous group of histologically and molecularly distinct tumour subtypes. Current targeted therapies have improved survival in patients with advanced disease but complete response occurs rarely, if at all. The genomic characterization of RCC is central to the development of novel targeted therapies. Large-scale studies employing multiple 'omics' platforms have led to the identification of key driver genes and commonly altered pathways. Specific molecular alterations and signatures that correlate with tumour phenotype and clinical outcome have been identified and can be harnessed for patient management and counselling. RCC seems to be a remarkably diverse malignancy with significant intratumour and intertumour genetic heterogeneity. The tumour microenvironment is increasingly recognized as a vital regulator of RCC tumour biology. Patient factors, including immune response and drug metabolism, vary widely, which can lead to widely divergent responses to drug therapy. Intratumour heterogeneity poses a significant challenge to the development of personalized therapies in RCC as a single biopsy might not accurately represent the clonal population ultimately responsible for aggressive biologic behaviour. On the other hand, the diversity of genomic alterations in RCC could also afford opportunities for targeting unique pathways based on analysis of an individual tumour's molecular composition.

Increased expression of colony stimulating factor-1 is a predictor of poor prognosis in patients with clear-cell renal cell carcinoma

Background

This study aims to evaluate the impact of colony stimulating factor-1 (CSF-1) expression on recurrence and survival of patients with clear-cell renal cell carcinoma (ccRCC) following surgery.

Methods

We retrospectively enrolled 267 patients (195 in the training cohort and 72 in the validation cohort) with ccRCC undergoing nephrectomy at a single institution. Clinicopathologic features, cancer-specific survival (CSS) and recurrence-free survival (RFS) were recorded. CSF-1 levels were assessed by immunohistochemistry in tumor tissues. Kaplan-Meier method was applied to compare survival curves. Cox regression models were used to analyze the impact of prognostic factors on CSS and RFS. Concordance index (C-index) was calculated to assess predictive accuracy.

Results

In both cohorts, CSF-1 expression positively correlated with advanced Fuhrman grade and necrosis. High CSF-1 expression indicated poor survival and early recurrence of ccRCC patients after surgery, especially those with advanced TNM stage disease. Multivariate Cox regression analysis showed CSF-1 expression was an independent unfavorable prognostic factor for recurrence and survival. The predictive accuracy of the University of California Los Angeles Integrated Staging System (UISS) was significantly improved when CSF-1 expression was incorporated.

Conclusions

High CSF-1 expression is a potential adverse prognostic biomarker for recurrence and survival of ccRCC patients after nephrectomy.

Cross-resistance to clinically used tyrosine kinase inhibitors sunitinib, sorafenib and pazopanib

PURPOSE

When during cancer treatment resistance to a tyrosine kinase inhibitor (TKI) occurs, switching to another TKI is often considered as a reasonable option. Previously, we reported that resistance to sunitinib may be caused by increased lysosomal sequestration, leading to increased intracellular lysosomal storage and, thereby, inactivity. Here, we studied the effect of several other TKIs on the development of (cross-) resistance.

METHODS

TKI resistance was induced by continuous exposure of cancer cell lines to increasing TKI concentrations for 3-4 months. (Cross-) resistance was evaluated using MTT cell proliferation assays. Intracellular TKI concentrations were measured using LC-MS/MS. Western blotting was used to detect lysosome-associated membrane protein-1 and -2 (LAMP1/2) expression.

RESULTS

The previously generated sunitinib-resistant (SUN) renal cancer cells (786-O) and colorectal cancer cells (HT-29) were found to be cross-resistant to pazopanib, erlotinib and lapatinib, but not sorafenib. Exposure of 786-O and HT-29 cells to sorafenib, pazopanib or erlotinib for 3-4 months induced drug resistance to pazopanib and erlotinib, but not sorafenib. Intracellular drug accumulation was found to be increased in pazopanib- and erlotinib-, but not in sorafenib-exposed cells. Lysosomal capacity, reflected by LAMP1/2 expression, was found to be increased in resistant cells and, in addition, to be transient. No cross-resistance to the mTOR inhibitor everolimus was detected.

CONCLUSIONS

Our data indicate that tumor cells can develop (cross-) resistance to TKIs, and that such resistance includes increased intracellular drug accumulation accompanied by increased lysosomal storage. Transient (cross-) resistance was found to occur for several of the TKIs tested, but not for everolimus, indicating that switching from a TKI to a mTOR inhibitor may be an attractive therapeutic option.

Molecular analysis of sunitinib resistant renal cell carcinoma cells after sequential treatment with RAD001 (everolimus) or sorafenib

Sequential application of target drugs is standard procedure after renal cell carcinoma (RCC) patients develop resistance. To optimize the sequence, antitumour effects of the mTOR inhibitor RAD001 or the tyrosine kinase inhibitor (TKI) sorafenib on RCC cells with acquired resistance to the TKI sunitinib was evaluated. RCC cells were exposed to 1 μM sunitinib for 24 hrs (as control) and for 8 weeks (to induce resistance) and then switched to RAD001 (5 nM) or sorafenib (5 μM) for a further 8 weeks. Tumour cell growth, cell cycle progression, cell cycle regulating proteins and intracellular signalling were then investigated. Short-term application of sunitinib (24 hrs) induced cell growth blockade with accumulation in the G2/M phase. RCC cells became resistant to sunitinib after 8 weeks, demonstrated by accelerated cell growth along with enhanced cdk1, cdk2, loss of p27, activation of Akt, Rictor and Raptor. Switching to sorafenib only slightly reduced growth of the sunitinib resistant RCC cells and molecular analysis indicated distinct cross-resistance. In contrast, full response was achieved when the cancer cells were treated with RAD001. p19 and p27 strongly increased, phosphorylated Akt, Rictor and Raptor decreased and the tumour cells accumulated in G0/G1. It is concluded that an mTOR-inhibitor for second-line therapy could be the strategy of choice after first-line sunitinib failure.

Macrophage density and macrophage colony-stimulating factor expression predict the postoperative prognosis in patients with intrahepatic cholangiocarcinoma

PURPOSES

Macrophages are included in the stromal compartments in various neoplasms, and their behavior against tumors is diverse. The aim of this study was to examine the role of tumor-infiltrating macrophages and their main regulator, macrophage colony-stimulating factor (M-CSF), in intrahepatic cholangiocarcinoma (ICC).

METHODS

Macrophage density and M-CSF expression in 39 resected ICC specimens were immunohistochemically evaluated in the central and peripheral areas of tumors, which were defined as fields more than and within 500 μm from the invasive front, respectively. The number of CD68-positive macrophages was counted using an image-analyzing software program. The relationship between these results and other clinicopathological factors and the postoperative prognosis were evaluated.

RESULTS

Sporadic M-CSF expression in cancer cells around the peripheral area was observed in fourteen patients. M-CSF-positive ICCs showed a higher macrophage density in the tumor-peripheral area than did M-CSF-negative ICCs. M-CSF expression and higher macrophage density in the tumor-peripheral area were related to a better postoperative prognosis, whereas a higher macrophage density in the central area was one of the significant risk factors for a poor prognosis in a univariate analysis.

CONCLUSION

Tumor-peripheral macrophage infiltration, presumably dependent on M-CSF, and M-CSF-independent tumor-central macrophage infiltration are predictive factors for better and worse postoperative prognosis in ICC patients, respectively. The tumor microenvironment, such as the presence of hypoxia, may affect the behavior of infiltrating macrophages in ICC.

Autocrine CSF-1R signaling drives mesothelioma chemoresistance via AKT activation

Clinical management of malignant pleural mesothelioma (MPM) is very challenging because of the uncommon resistance of this tumor to chemotherapy. We report here increased expression of macrophage colony-stimulating-factor-1-receptor (M-CSF/CSF-1R) mRNA in mesothelioma versus normal tissue specimens and demonstrate that CSF-1R expression identifies chemoresistant cells of mesothelial nature in both primary cultures and mesothelioma cell lines. By using RNAi or ligand trapping, we demonstrate that the chemoresistance properties of those cells depend on autocrine CSF-1R signaling. At the single-cell level, the isolated CSF-1R^pos cells exhibit a complex repertoire of pluripotency, epithelial–mesenchymal transition and detoxifying factors, which define a clonogenic, chemoresistant, precursor-like cell sub-population. The simple activation of CSF-1R in untransformed mesothelial cells is sufficient to confer clonogenicity and resistance to pemetrexed, hallmarks of mesothelioma. In addition, this induced a gene expression profile highly mimicking that observed in the MPM cells endogenously expressing the receptor and the ligands, suggesting that CSF-1R expression is mainly responsible for the phenotype of the identified cell sub-populations. The survival of CSF1R^pos cells requires active AKT (v-akt murine thymoma viral oncogene homolog 1) signaling, which contributed to increased levels of nuclear, transcriptionally competent β-catenin. Inhibition of AKT reduced the transcriptional activity of β-catenin-dependent reporters and sensitized the cells to senescence-induced clonogenic death after pemetrexed treatment. This work expands what is known on the non-macrophage functions of CSF-1R and its role in solid tumors, and suggests that CSF-1R signaling may have a critical pathogenic role in a prototypical, inflammation-related cancer such as MPM and therefore may represent a promising target for therapeutic intervention.

Modification of the tumor microenvironment as a novel target of renal cell carcinoma therapeutics

To move forward with immunotherapy, it is important to understand how the tumor microenvironment generates systemic immunosuppression in patients with renal cell carcinoma (RCC) as well as in patients with other types of solid tumors. Even though antigen discovery in RCC has lagged behind melanoma, recent clinical trials have finally authenticated that RCC is susceptible to vaccine-based therapy. Furthermore, judicious coadministration of cytokines and chemotherapy can potentiate therapeutic responses to vaccine in RCC and prolong survival, as has already proved possible for melanoma. Although high-dose interleukin 2 immunotherapy has been superseded as first-line therapy for RCC by promiscuous receptor tyrosine kinase inhibitors (rTKIs) such as sunitinib, sunitinib itself is a potent immunoadjunct in animal tumor models. A reasonable therapeutic goal is to unite antiangiogenic strategies with immunotherapy as first-line therapy for RCC. This strategy is equally appropriate for testing in all solid tumors in which the microenvironment generates immunosuppression. A common element of RCC and pancreatic, colon, breast, and other solid tumors is large numbers of circulating myeloid-derived suppressor cells (MDSCs), and because MDSCs elicit regulatory T cells rather than vice versa, gaining control over MDSCs is an important initial step in any immunotherapy. Although rTKIs like sunitinib have a remarkable capacity to deplete MDSCs and restore normal T-cell function in peripheral body compartments such as the bloodstream and the spleen, such rTKIs are effective only against MDSCs, which are engaged in phospho-STAT3-dependent programming (pSTAT3+). Unfortunately, rTKI-resistant pSTAT3- MDSCs are especially apt to arise within the tumor microenvironment itself, necessitating strategies that do not rely exclusively on STAT3 disruption. The most utilitarian strategy to gain control of both pSTAT3+ and pSTAT3- MDSCs may be to exploit the natural differentiation pathway, which permits MDSCs to mature into tumoricidal macrophages (TM1) via such stimuli as Toll-like receptor agonists, interferon γ, and CD40 ligation. Overall, this review highlights the mechanisms of immune suppression used by the different regulatory cell types operative in RCC as well as other tumors. It also describes the different therapeutic strategies to overcome the suppressive nature of the tumor microenvironment.

Sex differences in the human peripheral blood transcriptome

BACKGROUND

Genomes of men and women differ in only a limited number of genes located on the sex chromosomes, whereas the transcriptome is far more sex-specific. Identification of sex-biased gene expression will contribute to understanding the molecular basis of sex-differences in complex traits and common diseases.

RESULTS

Sex differences in the human peripheral blood transcriptome were characterized using microarrays in 5,241 subjects, accounting for menopause status and hormonal contraceptive use. Sex-specific expression was observed for 582 autosomal genes, of which 57.7% was upregulated in women (female-biased genes). Female-biased genes were enriched for several immune system GO categories, genes linked to rheumatoid arthritis (16%) and genes regulated by estrogen (18%). Male-biased genes were enriched for genes linked to renal cancer (9%). Sex-differences in gene expression were smaller in postmenopausal women, larger in women using hormonal contraceptives and not caused by sex-specific eQTLs, confirming the role of estrogen in regulating sex-biased genes.

CONCLUSIONS

This study indicates that sex-bias in gene expression is extensive and may underlie sex-differences in the prevalence of common diseases.

Emerging role of tumor-associated macrophages as therapeutic targets in patients with metastatic renal cell carcinoma

Tumor-associated macrophages (TAMs) derived from peripheral blood monocytes recruited into the renal cell carcinoma (RCC) microenvironment. In response to inflammatory stimuli, macrophages undergo M1 (classical) or M2 (alternative) activation. M1 cells produce high levels of inflammatory cytokines, such as tumor necrosis factor-α, interleukin (IL)-12, IL-23 and IL-6, while M2 cells produce anti-inflammatory cytokines, such as IL-10, thus contributing to RCC-related immune dysfunction. The presence of extensive TAM infiltration in RCC microenvironment contributes to cancer progression and metastasis by stimulating angiogenesis, tumor growth, and cellular migration and invasion. Moreover, TAMs are involved in epithelial-mesenchymal transition of RCC cancer cells and in the development of tumor resistance to targeted agents. Interestingly, macrophage autophagy seems to play an important role in RCC. Based on this scenario, TAMs represent a promising and effective target for cancer therapy in RCC. Several strategies have been proposed to suppress TAM recruitment, to deplete their number, to switch M2 TAMs into antitumor M1 phenotype and to inhibit TAM-associated molecules. In this review, we summarize current data on the essential role of TAMs in RCC angiogenesis, invasion, impaired anti-tumor immune response and development of drug resistance, thus describing the emerging TAM-centered therapies for RCC patients.

Failed renoprotection by alternatively activated bone marrow macrophages is due to a proliferation-dependent phenotype switch in vivo

Alternatively activated macrophages (M2) regulate immune responses and ex vivo polarized splenic M2 are able to ameliorate renal injury including models of renal disease, such as adriamycin nephropathy. Whether M2 derived from other organs have similar protective efficacy is unknown. Here, we report adoptively transferred bone marrow M2 macrophages did not improve renal function or reduce renal injury in adriamycin nephropathy, whereas splenic M2 macrophages were protective. Bone marrow and splenic M2 macrophages showed similar regulatory phenotypes and suppressive functions in vitro. Within the inflamed kidney, suppressive phenotypes in bone marrow but not in splenic M2 macrophages, were dramatically reduced. Loss of the suppressive phenotype in bone marrow M2 was related to strong proliferation of bone marrow M2. Bone marrow M2 proliferation in vivo correlated with M-CSF expression by tubular cells in the inflamed kidney. Inhibition of M-CSF in vitro limited bone marrow M2 proliferation and prevented switch of phenotype. Proliferating cells derived from transfused bone marrow M2 were inflammatory rather than regulatory in their phenotype and function. Thus bone marrow in contrast to splenic M2 macrophages do not protect against renal structural and functional injury in murine adriamycin nephropathy. The failed renoprotection of bone marrow M2 is due to the switch of transfused M2 macrophages from a regulatory to an inflammatory phenotype.

Mononuclear phagocyte system in kidney disease and repair

The mononuclear phagocyte system is comprised of circulating monocytes, tissue macrophages and dendritic cells (DCs) that play key roles in tissue homeostasis, immune surveillance, and immune and non-immune-mediated tissue injury and repair. This review summarizes the various subsets within this system that exhibit significant functional and phenotypic diversity that can adapt to their surrounding microenvironments during inflammation and in response to colony-stimulating factor (CSF)-1. The current understanding of the co-ordination of monocyte infiltration into the homeostatic and diseased kidney through adhesion molecules, chemokines and chemokine receptors, and cytokines are described. Furthermore, the significant confusion and controversy associated with monocyte differentiation into renal macrophages and DCs following infiltration into the kidney, the considerable functional and phenotypic overlap between both tissue populations and their respective roles in immune and non-immune-mediated renal is also discussed. Understanding the factors that control the activation and recruitment of cells from the mononuclear phagocyte system during renal injury may offer an avenue for the development of new cellular and growth factor-based therapies in combination with existing therapies as an alternative treatment option for patients with renal disease.

Extracellular assembly and activation principles of oncogenic class III receptor tyrosine kinases

Intracellular signalling cascades initiated by class III receptor tyrosine kinases (RTK-IIIs) and their cytokine ligands contribute to haematopoiesis and mesenchymal tissue development. They are also implicated in a wide range of inflammatory disorders and cancers. Recent snapshots of RTK-III ectodomains in complex with cognate cytokines have revealed timely insights into the structural determinants of RTK-III activation, evolution and pathology. Importantly, candidate 'driver' and 'passenger' mutations that have been identified in RTK-IIIs can now be collectively mapped for the first time to structural scaffolds of the corresponding RTK-III ectodomains. Such insights will generate a renewed interest in dissecting the mechanistic effects of such mutations and their therapeutic relevance.

Immunological heterogeneity of the RCC microenvironment: do targeted therapies influence immune response?

The introduction of targeted agents has substantially improved treatment of metastatic clear-cell renal cell carcinoma (RCC). However, complete responses are rare and therapy is not curative. Moreover, information on the latest generation of potent and selective vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitors (TKI) suggests that a plateau has been reached in terms of efficacy. Recent data reveal that targeted agents are involved in modulating immune responses in RCC. In addition, current research adds to our understanding of how RCC escapes an effective anti-tumor response with the potential to modulate these processes by drug development. This review provides specific insight into targeted therapy induced changes in the immunological microenvironment of RCC, summarizes the available evidence, and discusses potential therapeutic implications.