The M2 phenotype of tumor-associated macrophages in the stroma confers a poor prognosis in pancreatic cancer. Tumour Biol. 2016;37:8657-8664. [PMID: 26738860 DOI: 10.1007/s13277-015-4741-z]

Targeting the tumor microenvironment in pancreatic ductal adenocarcinoma

Introduction: The dismally slow improvement in patient survival over the years for pancreatic cancer patients is mainly due to two factors: the late diagnosis, at which point the disease is spread to distant organs; and the fact that tumor cells are surrounded by a dense, highly immunosuppressive microenvironment. The tumor microenvironment not only shields pancreatic cancer cells from chemotherapy but also leaves it unsusceptible to various immunotherapeutic strategies that have been proven successful in other types of cancer. Areas covered: This review highlights the main components of the pancreatic tumor microenvironment, how they cross-talk with each other to generate stroma and promote tumor growth. Additionally, we discuss the most promising treatment targets in the microenvironment whose modulation can be robustly tested in combination with standard of care chemotherapy. Currently, active clinical trials for pancreatic cancer involving components of the microenvironment are also listed. Expert opinion: Although immunotherapeutic approaches involving checkpoint inhibition are being pursued enthusiastically, there is still more work to be done with several other emerging immune targets that could provide therapeutic benefit.

Outcome of head compared to body and tail pancreatic cancer: a systematic review and meta-analysis of 93 studies

Background

Even when resectable pancreatic cancer (PC) is associated with a dismal prognosis. Initial presentation varies according with primary tumor location. Aim of this systematic review and meta-analysis was to evaluate the prognosis associated with site (head versus body/tail) in patients with PC.

Methods

We searched PubMed, Cochrane Library, SCOPUS, Web of Science, EMBASE, Google Scholar, LILACS, and CINAHL databases from inception to March 2018. Studies reporting information on the independent prognostic role of site in PC and comparing overall survival (OS) in head versus body/tail tumors were selected. Data were aggregated using hazard ratios (HRs) for OS of head versus body/tail PC according to fixed- or random-effect model.

Results

A total of 93 studies including 254,429 patients were identified. Long-term prognosis of head was better than body/tail cancers (HR =0.96, 95% CI: 0.92-0.99; P=0.02). A pooled HR of 0.95 (95% CI: 0.92-0.99, P=0.02) from multivariate analysis only (n=77 publications) showed that head site was an independent prognostic factor for survival.

Conclusions

Primary tumor location in the head of the pancreas at the time of diagnosis is a predictor of better survival. Such indicator should be acknowledged when designing future studies, in particular in the operable and neoadjuvant setting.

Tumor-associated macrophage-secreted 14-3-3ζ signals via AXL to promote pancreatic cancer chemoresistance

Pancreatic ductal adenocarcinoma (PDAC) is an inherently chemoresistant tumor. Chemotherapy leads to apoptosis of cancer cells, and in previous studies we have shown that tumor-associated macrophage (TAM) infiltration increases following chemotherapy in PDAC. Since one of the main functions of macrophages is to eliminate apoptotic cells, we hypothesized that TAMs phagocytose chemotherapy-induced apoptotic cells and secrete factors, which favor PDAC chemoresistance. To test this hypothesis, primary human PDAC cultures were treated with conditioned media (CM) from monocyte-derived macrophage cultures incubated with apoptotic PDAC cells (MØ^ApopCM). MØ^ApopCM pretreatment rendered naïve PDAC cells resistant to Gemcitabine- or Abraxane-induced apoptosis. Proteomic analysis of MØ^ApopCM identified YWHAZ/14-3-3 protein zeta/delta (14-3-3ζ), a major regulator of apoptotic cellular pathways, as a potential mediator of chemoresistance, which was subsequently validated in patient transcriptional datasets, serum samples from PDAC patients and using recombinant 14-3-3ζ and inhibitors thereof. Moreover, in mice bearing orthotopic PDAC tumors, the antitumor potential of Gemcitabine was significantly enhanced by elimination of TAMs using clodronate liposomes or by pharmacological inhibition of the Axl receptor tyrosine kinase, a 14-3-3ζ interacting partner. These data highlight a unique regulatory mechanism by which chemotherapy-induced apoptosis acts as a switch to initiate a protumor/antiapoptotic mechanism in PDAC via 14-3-3ζ/Axl signaling, leading to phosphorylation of Akt and activation of cellular prosurvival mechanisms. The data presented therefore challenge the idea that apoptosis of tumor cells is therapeutically beneficial, at least when immune sensor cells, such as macrophages, are present.

TAMing pancreatic cancer: combat with a double edged sword

Among all the deadly cancers, pancreatic cancer ranks seventh in mortality. The absence of any grave symptoms coupled with the unavailability of early prognostic and diagnostic markers make the disease incurable in most of the cases. This leads to a late diagnosis, where the disease would have aggravated and thus, incurable. Only around 20% of the cases present the early disease diagnosis. Surgical resection is the prime option available for curative local disease but in the case of advanced cancer, chemotherapy is the standard treatment modality although the patients end up with drug resistance and severe side effects. Desmoplasia plays a very important role in chemoresistance associated with pancreatic cancer and consists of a thick scar tissue around the tumor comprised of different cell populations. The interplay between this heterogenous population in the tumor microenvironment results in sustained tumor growth and metastasis. Accumulating evidences expose the crucial role played by the tumor-associated macrophages in pancreatic cancer and this review briefly presents the origin from their parent lineage and the importance in maintaining tumor hallmarks. Finally we have tried to address their role in imparting chemoresistance and the therapeutic interventions leading to reduced tumor burden.

Exosomes and the Future of Immunotherapy in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease, associated with a late diagnosis and a five-year survival rate of 8%. Currently available treatments fall short in improving the survival and quality of life of PDAC patients. The only possible curative option is still the surgical resection of the tumor. Exosomes are extracellular vesicles secreted by cells that transport proteins, lipids, and nucleic acids to other cells, triggering phenotypic changes in the recipient cells. Tumor cells often secrete increased amounts of exosomes. Tumor exosomes are now accepted as important players in the remodeling of PDAC tumor stroma, particularly in the establishment of an immunosuppressive microenvironment. This has sparked the interest in their usefulness as mediators of immunomodulatory effects for the treatment of PDAC. In fact, exosomes are now under study to understand their potential as nanocarriers to stimulate an immune response against cancer. This review highlights the latest findings regarding the function of exosomes in tumor-driven immunomodulation, and the challenges and advantages associated with the use of these vesicles to potentiate immunotherapy in PDAC.

Prognostic value of tumor-associated macrophages in pancreatic cancer: a meta-analysis

Objective: Tumor-associated macrophages (TAMs) deserve more focus because of its pivotal role in the development of solid tumors and they are related to poor outcomes of several tumors. However, the prognostic value of tumor-infiltrating TAMs in pancreatic cancer is still controversial. Experimental design: We conduct a meta-analysis of 1699 patients in 13 studies by reviewing the studies in which the authors evaluated the prognostic value of TAMs density in pancreatic cancer. These studies were searched from inception to November 2018. Hazard ratios (HR) with their corresponding 95% confidence intervals (95% CIs) were assessed to explore the prognostic significance of TAMs in pancreatic cancer. Besides, we also conducted a subgroup analysis and sensitivity analysis. Two reviewers independently abstracted data. Results: A total of 13 studies with 1699 patients were pooled in the analysis to evaluate prognostic value of TAMs in pancreatic cancer. The pooled HRs demonstrated CD68+ TAMs correlated with worse overall survival (OS) in pancreatic cancer patients (HR =1.41, 95% CI =1.05-1.90, random effects model, I²=82.5%, P=0.021). And high generalized M2-TAMs density was significantly associated with poor OS (HR =1.95, 95% CI =1.63-2.33, random effects model, I²=59.2%, P=0.000) and disease-free survival (HR =1.83, 95% CI =1.43-2.36, fixed effects model, I²=0.00%, P=0.000). Pooled analysis showed no significant correlation between elevated TAMs infiltration and lymph node metastasis, tumor stage, histological grade, sex, or tumor location. Conclusion: The density of TAMs has an impact on the overall survival of pancreatic cancer patients. M2-TAMs can be recognized as a prognostic indicator in pancreatic cancer, which may serve as a potential therapeutic target in the treatment of pancreatic cancer.

Crosstalk between the Tumor Microenvironment and Immune System in Pancreatic Ductal Adenocarcinoma: Potential Targets for New Therapeutic Approaches

Pancreatic ductal adenocarcinoma is a lethal disease for which radical surgery and chemotherapy represent the only curative options for a small proportion of patients. Recently, FOLFIRINOX and nab-paclitaxel plus gemcitabine have improved the survival of metastatic patients but prognosis remains poor. A pancreatic tumor microenvironment is a dynamic milieu of cellular and acellular elements, and it represents one of the major limitations to chemotherapy efficacy. The continued crosstalk between cancer cells and the surrounding microenvironment causes immunosuppression within pancreatic immune infiltrate increasing tumor aggressiveness. Several potential targets have been identified among tumor microenvironment components, and different therapeutic approaches are under investigation. In this article, we provide a qualitative literature review about the crosstalk between the tumor microenvironment components and immune system in pancreatic cancer. Finally, we discuss potential therapeutic strategies targeting the tumor microenvironment and we show the ongoing trials.

PD-L1 expression enhancement by infiltrating macrophage-derived tumor necrosis factor-α leads to poor pancreatic cancer prognosis

Immunotherapy using anti‐PD‐1/PD‐L1 antibodies for several types of cancer has received considerable attention in recent decades. However, the molecular mechanism underlying PD‐L1 expression in pancreatic ductal adenocarcinoma (PDAC) cells has not been clearly elucidated. We investigated the clinical significance and regulatory mechanism of PD‐L1 expression in PDAC cells. Among the various cytokines tested, tumor necrosis factor (TNF)‐α upregulated PD‐L1 expression in PDAC cells through NF‐κB signaling. The induction of PD‐L1 expression was also caused by co‐culture with activated macrophages, and the upregulation was inhibited by neutralization with anti‐TNF‐α antibody after co‐culture with activated macrophages. PD‐L1 expression in PDAC cells was positively correlated with macrophage infiltration in tumor stroma of human PDAC tissues. In addition, survival analysis revealed that high PD‐L1 expression was significantly associated with poor prognosis in 235 PDAC patients and especially in patients harboring high CD8‐positive T‐cell infiltration. These findings indicate that tumor‐infiltrating macrophage‐derived TNF‐α could be a potential therapeutic target for PDAC.

Tumor-promoting effects of pancreatic cancer cell exosomes on THP-1-derived macrophages

Pancreatic ductal adenocarcinoma (PDAC) tumor growth is enhanced by tumor-associated macrophages (TAMs), yet the mechanisms by which tumor cells and TAMs communicate are not fully understood. Here we show that exosomes secreted by PDAC cell lines differed in their surface proteins, lipid composition, and efficiency of fusing with THP-1-derived macrophages in vitro. Exosomes from AsPC-1, an ascites-derived human PDAC cell line, were enriched in ICAM-1, which mediated their docking to macrophages through interactions with surface-exposed CD11c on macrophages. AsPC-1 exosomes also contained much higher levels of arachidonic acid (AA), and they fused at a higher rate with THP-1-derived macrophages than did exosomes from other PDAC cell lines or from an immortalized normal pancreatic ductal epithelial cell line (HPDE) H6c7. Phospholipase A2 enzymatic cleavage of arachidonic acid from AsPC-1 exosomes reduced fusion efficiency. PGE2 secretion was elevated in macrophages treated with AsPC-1 exosomes but not in macrophages treated with exosomes from other cell lines, suggesting a functional role for the AsPC-1 exosome-delivered arachidonic acid in macrophages. Non-polarized (M0) macrophages treated with AsPC-1 exosomes had increased levels of surface markers indicative of polarization to an immunosuppressive M2-like phenotype (CD14hi CD163hi CD206hi). Furthermore, macrophages treated with AsPC-1 exosomes had significantly increased secretion of pro-tumoral, bioactive molecules including VEGF, MCP-1, IL-6, IL-1β, MMP-9, and TNFα. Together, these results demonstrate that compared to exosomes from other primary tumor-derived PDAC cell lines, AsPC-1 exosomes alter THP-1-derived macrophage phenotype and function. AsPC-1 exosomes mediate communication between tumor cells and TAMs that contributes to tumor progression.

PD-1, PD-L1, and CD163 in pancreatic undifferentiated carcinoma with osteoclast-like giant cells: expression patterns and clinical implications

Undifferentiated carcinoma with osteoclast-like giant cells (UCOGC), a variant of pancreatic ductal adenocarcinoma (PDAC), has a striking genetic similarity to PDAC but a significantly improved overall survival. We hypothesize that this difference could be due to the immune response to the tumor, and as such, we investigated the expression of PD-1, PD-L1, and CD163 in a series of UCOGC. To this aim, 27 pancreatic UCOGCs (11 pure and 16 PDAC-associated), 5 extrapancreatic tumors with osteoclast-like giant cells and 10 pancreatic anaplastic carcinomas were immunostained using antibodies against PD-1, PD-L1, and CD163. In pancreatic UCOGCs, PD-L1 was expressed in neoplastic cells of 17 (63%) of 27 cases, more often in cases with an associated PDAC (P = .04). Expression of PD-L1 was associated with poor prognosis, confirmed by multivariate analysis: patients with PD-L1-positive UCOGCs had a risk of all-cause mortality that was 3 times higher than did patients with PD-L1-negative UCOGCs (hazard ratio, 3.397; 95% confidence interval, 1.023-18.375; P = .034). PD-L1 expression on tumor cells was also associated with aberrant P53 expression (P = .035). PD-1 was expressed on rare lymphocytes in 12 UCOGCs (44.4%), mainly located at the tumor periphery. CD163 was expressed on histiocytes, with a diffuse and strong staining pattern in all UCOGCs. Extrapancreatic tumors with osteoclast-like giant cells showed very similar staining patterns for the same proteins. Anaplastic carcinomas have some similarities to UCOGCs, but PD-L1 has no prognostic roles. Our results may have important implications for immunotherapeutic strategies in UCOGCs; these tumors may also represent a model for future therapeutic approaches against PDAC.

Why is immunotherapy effective (or not) in patients with MSI/MMRD tumors?

In the last few years, immunotherapy has revolutionized the oncology landscape by targeting the host immune system. Blocking immune checkpoints such as cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), programmed cell death-1 (PD-1) and its ligand (PD-L1 or B7-H1), has proven its efficacy in several solid cancers. Recently, several clinical studies have demonstrated a significant improvement in clinical response to the anti-PD-1-based immunotherapy in a subset of patients with microsatellite instability-high (MSI-H)/mismatch repair (MMR)-deficient tumors that accumulate short insertion/deletion mutations notably in coding microsatellites regions of the genome. Thus, the responsiveness of MSI cancers to immune checkpoint inhibitors can be explained by the increased rate of putative frameshift peptide neoantigens and the immunogenic tumor microenvironment. However, not all MSI tumors respond to immunotherapy. The current review will summarize how and why MMR deficiency has emerged as an important predictor of sensitivity for immunotherapy-based strategies. We will also discuss tumor-cell intrinsic genetic and immune-related features of MSI tumors that can modulate immune checkpoint blockade response and explain primary and/or acquired resistance to anti-PD-1 therapy. Finally, we will also discuss about emerging scores which can define more precisely the immune context of the tumor microenvironment and thus better evaluate prognosis and predict response to Immune Checkpoint Blockade.

Diverse Functions of Macrophages in Different Tumor Microenvironments

Tumor-associated macrophages are a major constituent of malignant tumors and are known to stimulate key steps in tumor progression. In our review in this journal in 2006, we postulated that functionally distinct subsets of these cells exist in different areas within solid tumors. Here, we review the many experimental and clinical studies conducted since then to investigate the function(s), regulation, and clinical significance of macrophages in these sites. The latter include three sites of cancer cell invasion, tumor nests, the tumor stroma, and areas close to, or distant from, the tumor vasculature. A more complete understanding of macrophage diversity in tumors could lead to the development of more selective therapies to restore the formidable, anticancer functions of these cells. Cancer Res; 78(19); 5492-503. ©2018 AACR.

Nrf2 activation drive macrophages polarization and cancer cell epithelial-mesenchymal transition during interaction

Background

The M2 phenotype of tumor-associated macrophages (TAM) inhibits the anti-tumor inflammation, increases angiogenesis and promotes tumor progression. The transcription factor Nuclear Factor (erythroid-derived 2)-Like 2 (Nrf2) not only modulates the angiogenesis but also plays the anti-inflammatory role through inhibiting pro-inflammatory cytokines expression; however, the role of Nrf2 in the cancer cell and macrophages interaction is not clear.

Methods

Hepatocellular carcinoma cells (Hep G2 and Huh 7) and pancreatic cancer cells (SUIT2 and Panc-1) were co-cultured with monocytes cells (THP-1) or peripheral blood monocytes derived macrophages, then the phenotype changes of macrophages and epithelial-mesenchymal transition of cancer cells were detected. Also, the role of Nrf2 in cancer cells and macrophages interaction were investigated.

Results

In this study, we found that cancer cells could induce an M2-like macrophage characterized by up-regulation of CD163 and Arg1, and down-regulation of IL-1b and IL-6 through Nrf2 activation. Also, Nrf2 activation of macrophages promoted VEGF expression. The Nrf2 activation of macrophages correlated with the reactive oxygen species induced by cancer cells derived lactate. Cancer cells educated macrophages could activate Nrf2 of the cancer cells, in turn, to increase cancer cells epithelial-mesenchymal transition (EMT) through paracrine VEGF. These findings suggested that Nrf2 played the important role in the cancer cells and macrophages interaction.

Conclusions

Macrophage Nrf2 activation by cancer cell-derived lactate skews macrophages polarization towards an M2-like phenotype and educated macrophages activate Nrf2 of the cancer cells to promote EMT of cancer cells. This study provides a new understanding of the role of Nrf2 in the cancer cell and TAM interaction and suggests a potential therapeutic target.

Electronic supplementary material

The online version of this article (10.1186/s12964-018-0262-x) contains supplementary material, which is available to authorized users.

Tumor microenvironment participates in metastasis of pancreatic cancer

Pancreatic cancer is a deadly disease with high mortality due to difficulties in its early diagnosis and metastasis. The tumor microenvironment induced by interactions between pancreatic epithelial/cancer cells and stromal cells is critical for pancreatic cancer progression and has been implicated in the failure of chemotherapy, radiation therapy and immunotherapy. Microenvironment formation requires interactions between pancreatic cancer cells and stromal cells. Components of the pancreatic cancer microenvironment that contribute to desmoplasia and immunosuppression are associated with poor patient prognosis. These components can facilitate desmoplasia and immunosuppression in primary and metastatic sites or can promote metastasis by stimulating angiogenesis/lymphangiogenesis, epithelial-mesenchymal transition, invasion/migration, and pre-metastatic niche formation. Some molecules participate in both microenvironment formation and metastasis. In this review, we focus on the mechanisms of pancreatic cancer microenvironment formation and discuss how the pancreatic cancer microenvironment participates in metastasis, representing a potential target for combination therapy to enhance overall survival.

Transfer of miRNA in Macrophage-Derived Exosomes Induces Drug Resistance in Pancreatic Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is known for its resistance to gemcitabine, which acts to inhibit cell growth by termination of DNA replication. Tumor-associated macrophages (TAM) were recently shown to contribute to gemcitabine resistance; however, the exact mechanism of this process is still unclear. Using a genetic mouse model of PDAC and electron microscopy analysis, we show that TAM communicate with the tumor microenvironment via secretion of approximately 90 nm vesicles, which are selectively internalized by cancer cells. Transfection of artificial dsDNA (barcode fragment) to murine peritoneal macrophages and injection to mice bearing PDAC tumors revealed a 4-log higher concentration of the barcode fragment in primary tumors and in liver metastasis than in normal tissue. These macrophage-derived exosomes (MDE) significantly decreased the sensitivity of PDAC cells to gemcitabine, in vitro and in vivo This effect was mediated by the transfer of miR-365 in MDE. miR-365 impaired activation of gemcitabine by upregulation of the triphospho-nucleotide pool in cancer cells and the induction of the enzyme cytidine deaminase; the latter inactivates gemcitabine. Adoptive transfer of miR-365 in TAM induced gemcitabine resistance in PDAC-bearing mice, whereas immune transfer of the miR-365 antagonist recovered the sensitivity to gemcitabine. Mice deficient of Rab27 a/b genes, which lack exosomal secretion, responded significantly better to gemcitabine than did wildtype. These results identify MDE as key regulators of gemcitabine resistance in PDAC and demonstrate that blocking miR-365 can potentiate gemcitabine response.Significance: Harnessing macrophage-derived exosomes as conveyers of antagomiRs augments the effect of chemotherapy against cancer, opening new therapeutic options against malignancies where resistance to nucleotide analogs remains an obstacle to overcome. Cancer Res; 78(18); 5287-99. ©2018 AACR.

Prognostic value of tumor infiltrating NK cells and macrophages in stage II+III esophageal cancer patients

The detailed understanding of the immunobiology of tumor microenvironment has recently translated into new therapeutic approach against human cancers. Besides the role of immune cells mediating adaptive immune responses, the tumor infiltrating components of the innate immune system including, neutrophils, mast cells, NK cells, and macrophages, also role importantly in anti-tumor immunity. In our present study, we retrospectively analyzed the prognostic value of the densities of tumor infiltrating NK cells and macrophages in esophageal cancer tissues derived from stage II+III patients. Our results showed that the density of the infiltrating NK cells in tumor stroma was significantly associated with nodal status. In addition, the densities of the infiltrating NK cells in tumor nest, and the infiltrating macrophages in tumor nest as well as in tumor stroma, were significantly associated with patients' postoperative prognoses. Furthermore, the combination of infiltrating NK cells in tumor nest and stroma, or the combination of infiltrating macrophages in tumor nest and stroma, could also be used as important prognostic tool in predicting the survival of the stage II+III esophageal cancer patients.

MFHAS1 promotes colorectal cancer progress by regulating polarization of tumor-associated macrophages via STAT6 signaling pathway

Malignant fibrous histiocytoma amplified sequence 1 (MFHAS1) is a predicted oncoprotein that demonstrates tumorigenic activity in vivo; however, the mechanisms involved are unknown. Macrophages are divided into the pro-inflammatory M1 and anti-inflammatory/protumoral M2 subtypes. Tumor cells can induce M2 polarization of tumor-associated macrophages (TAMs) to promote metastasis; but the underlying pathways require to be elucidated. In this study, we detected a positive association between MFHAS1 expression in TAMs and human colorectal cancer (CRC) TNM stage. Supernatant of CT26 murine CRC cells induced MFHAS1 expression in RAW264.7 murine macrophages. Additionally, CT26 supernatant induced the M2 marker CD206 and activated the pro-M2 STAT6 and KLF4 signaling in control but not MFHAS1-silenced RAW264.7 macrophages. Moreover, supernatant of control, but not MFHAS1-silenced macrophages promoted CT26 cell proliferation, migration and epithelial-mesenchymal transition. Compared with control macrophages, MFHAS1-silenced macrophages showed significantly reduced protumoral effects in vivo. Together, these results suggested that CRC cells induce M2 polarization of TAMs through MFHAS1 induction and subsequent STAT6 and KLF4 activation to promote CRC progress. Finally, similar to CT26 supernatant stimulation, peroxisome proliferator-activated receptor-γ (PPARγ) activation by rosiglitazone induced M2 polarization of RAW264.7 macrophages through MFHAS1-dependent pathway. Our results highlight the role of MFHAS1 as a regulator of macrophages polarization and CRC progress.

Targeting tumor-associated macrophages to combat pancreatic cancer

The tumor microenvironment is replete with cells that evolve with and provide support to tumor cells during the transition to malignancy. The hijacking of the immune system in the pancreatic tumor microenvironment is suggested to contribute to the failure to date to produce significant improvements in pancreatic cancer survival by various chemotherapeutics. Regulatory T cells, myeloid derived suppressor cells, and fibroblasts, all of which constitute a complex ecology microenvironment, can suppress CD8+ T cells and NK cells, thus inhibiting effector immune responses. Tumor-associated macrophages (TAM) are versatile immune cells that can express different functional programs in response to stimuli in tumor microenvironment at different stages of pancreatic cancer development. TAM have been implicated in suppression of anti-tumorigenic immune responses, promotion of cancer cell proliferation, stimulation of tumor angiogenesis and extracellular matrix breakdown, and subsequent enhancement of tumor invasion and metastasis. Many emerging agents that have demonstrated efficacy in combating other types of tumors via modulation of macrophages in tumor microenvironments are, however, only marginally studied for pancreatic cancer prevention and treatment. A better understanding of the paradoxical roles of TAM in pancreatic cancer may pave the way to novel preventive and therapeutic approaches. Here we give an overview of the recruitment and differentiation of macrophages, TAM and pancreatic cancer progression and prognosis, as well as the potential preventive and therapeutic targets that interact with TAM for pancreatic cancer prevention and treatment.

Intratumoural leukocyte infiltration is a prognostic indicator among pancreatic cancer patients with type 2 diabetes

BACKGROUND

The life expectancy of pancreatic cancer patients remains minimal. The disease progression may be influenced by type 2 diabetes (T2D) and inflammatory status, although important gaps persist around their joint effects on disease outcome. The aim of this study was to investigate the clinical significance of the tumour immune microenvironment on pancreatic cancer prognosis in relation to T2D status.

METHOD

Tumour-infiltrating macrophages, neutrophils and eosinophils were studied in primary pancreatic tumours and paired lymph node metastases in relation to patient and tumour characteristics, T2D status and overall survival in a retrospective cohort of patients with resectable pancreatic cancer in Sweden.

RESULTS

Of the 80 included pancreatic cancer patients, 22 (27.2%) had T2D. The diabetic pancreatic cancer patients had significantly higher systemic high white blood cell count than those without diabetes (P = 0.028). Macrophage infiltration levels were higher in lymph node metastases compared with primary tumours (P = 0.040) among pancreatic cancer patients with diabetes. Type 2 diabetes or intra-tumoural leukocyte (macrophage, neutrophil or eosinophil) infiltration alone did not significantly influence pancreatic cancer prognosis. However, among cancer patients with T2D high macrophage or neutrophil tumour-infiltration was associated with a significant reduction in overall survival (adjusted hazard ratio [HR] 7.2; 95% CI 1.5-35.0 and HR 5.4; 95% CI 1.1-26.3, respectively).

CONCLUSION

These results demonstrate associations between T2D and enhanced inflammatory processes with significant implications on survival among pancreatic cancer patients with T2D. Validation in larger independent patient cohorts may identify additional prognostic tools and improved treatment strategies for specific patient subsets.

Interleukin 6 induces M2 macrophage differentiation by STAT3 activation that correlates with gastric cancer progression

Interleukin 6 (IL-6) was abundant in the tumor microenvironment and played potential roles in tumor progression. In our study, the expression of IL-6 in tumor tissues from 36 gastric cancer (GC) patients was significantly higher than in non-tumor tissues. Moreover, the number of CD163+CD206+ M2 macrophages that infiltrated in tumor tissues was significantly greater than those infiltrated in non-tumor tissues. The frequencies of M2 macrophages were positively correlated with the IL-6 expression in GC tumors. We also found that IL-6 could induce normal macrophages to differentiate into M2 macrophages with higher IL-10 and TGF-β expression, and lower IL-12 expression, via activating STAT3 phosphorylation. Accordingly, knocking down STAT3 using small interfering RNA decreased the expression of M2 macrophages-related cytokines (IL-10 and TGF-β). Furthermore, supernatants from IL-6-induced M2 macrophages promote GC cell proliferation and migration. Moreover, IL-6 production and CD163+CD206+ M2 macrophage infiltration in tumors were associated with disease progression and reduced GC patient survival. In conclusion, our data indicate that IL-6 induces M2 macrophage differentiation (IL-10highTGF-βhighIL-12 p35low ) by activating STAT3 phosphorylation, and the IL-6-induced M2 macrophages exert a pro-tumor function by promoting GC cell proliferation and migration.

CXCL8 derived from tumor-associated macrophages and esophageal squamous cell carcinomas contributes to tumor progression by promoting migration and invasion of cancer cells

Tumor-associated macrophages (TAMs) are involved in tumor progression and poor prognosis in several malignancies. We previously demonstrated the interaction between high numbers of infiltrating TAMs and poor prognosis in esophageal squamous cell carcinomas (ESCCs). To investigate the significance of TAMs in ESCC, we conducted a cDNA microarray analysis of peripheral blood monocytes (PBMo)-derived macrophages and PBMo-derived macrophages stimulated with conditioned media of TE-series ESCC cell lines (TAM-like PBMo-derived macrophages). C-X-C motif chemokine ligand 8 (CXCL8) was up-regulated in the TAM-like PBMo-derived macrophages. Here we confirmed a high expression level of CXCL8 in TAM-like PBMo-derived macrophages and the expression of CXCR1/2, known as CXCL8 receptors, in TE-series ESCC cell lines. Recombinant human CXCL8 induced the ESCC cell lines’ migration and invasion by the phosphorylation of Akt and Erk1/2. In indirect co-cultures, not only signal pathway inhibitors but also neutralizing antibodies against CXCL8, CXCR1 and CXCR2 suppressed these phenotypes induced by TAM-like PBMo-derived macrophages. Immunohistochemical analysis of 70 resected ESCC samples showed that high expression levels of CXCL8 in ESCC tissues were significantly associated with lymph node metastasis and poor prognosis. These results suggest that CXCL8 up-regulated in the microenvironment may contribute to ESCC progression by promoting cancer cells’ migration and invasion.

The humanized anti-human AMHRII mAb 3C23K exerts an anti-tumor activity against human ovarian cancer through tumor-associated macrophages

Müllerian inhibiting substance, also called anti-Müllerian hormone (AMH), inhibits proliferation and induces apoptosis of AMH type II receptor-positive tumor cells, such as human ovarian cancers (OCs). On this basis, a humanized glyco-engineered monoclonal antibody (3C23K) has been developed. The aim of this study was therefore to experimentally confirm the therapeutic potential of 3C23K in human OCs. We first determined by immunofluorescence, immunohistochemistry and cytofluorometry analyses the expression of AMHRII in patient’s tumors and found that a majority (60 to 80% depending on the detection technique) of OCs were positive for this marker. We then provided evidence that the tumor stroma of OC is enriched in tumor-associated macrophages and that these cells are responsible for 3C23K-induced killing of tumor cells through ADCP and ADCC mechanisms. In addition, we showed that 3C23K reduced macrophages induced-T cells immunosuppression. Finally, we evaluated the therapeutic efficacy of 3C23K alone and in combination with a carboplatin-paclitaxel chemotherapy in a panel of OC Patient-Derived Xenografts. In those experiments, we showed that 3C23K significantly increased the proportion and the quality of chemotherapy-based in vivo responses. Altogether, our data support the potential interest of AMHRII targeting in human ovarian cancers and the evaluation of 3C23K in further clinical trials.

Apolipoprotein A-I mimetic peptide 4F suppresses tumor-associated macrophages and pancreatic cancer progression

Pancreatic cancer is an aggressive malignancy that is unresponsive to conventional radiation and chemotherapy. Therefore, development of novel immune therapeutic strategies is urgently needed. L-4F, an Apolipoprotein A-I (ApoA-I) mimetic peptide, is engineered to mimic the anti-inflammatory and anti-oxidative functionalities of ApoA-I. In this work, H7 cells were orthotopically implanted in C57BL/6 mice and treated with L-4F. Then, pancreatic cancer progression and the inflammatory microenvironment were investigated in vivo. The cytotoxicity of L-4F toward H7 cells was assessed in vitro. Furthermore, we investigated the effects of L-4F on macrophage polarization by analyzing the polarization and genes of mouse bone marrow-derived macrophages in vitro. The results show that L-4F substantially reduced the tumorigenicity of H7 cells. L-4F inhibited inflammation by reducing the accumulation of inflammatory cells, such as IL-17A-, IL-4-, GM-CSF-, IL-1β-, and IL-6-producing cells and Th1 and Th17. Notably, L-4F also decreased the percentage of macrophages in tumor tissues, especially M2 macrophages (CD11b⁺F4/80⁺CD206⁺), which was also confirmed in vitro. Additionally, the expression of the M2 marker genes Arg1, MRC1, and CCL22 and the inflammatory genes IL-6, iNOS, and IL-12 was decreased by L-4F, indicating that L-4F prevents M2 type macrophage polarization. However, L-4F could not directly attenuate H7 cell invasion or proliferation and did not induce apoptosis. In addition, L-4F potently down-regulated STAT3, JNK and ERK signaling pathways but not affects the phosphorylation of p38 in RAW 264.7 cells. These results suggest that L-4F exhibits an effective therapeutic effect on pancreatic cancer progression by inhibiting tumor-associated macrophages and inflammation.

A 25-gene classifier predicts overall survival in resectable pancreatic cancer

BACKGROUND

Pancreatic carcinoma is one of the most lethal human cancers. In patients with resectable tumors, surgery followed by adjuvant chemotherapy is the only curative treatment. However, the 5-year survival is 20%. Because of a strong metastatic propensity, neoadjuvant chemotherapy is being tested in randomized clinical trials. In this context, improving the selection of patients for immediate surgery or neoadjuvant chemotherapy is crucial, and high-throughput molecular analyses may help; the present study aims to address this.

METHODS

Clinicopathological and gene expression data of 695 pancreatic carcinoma samples were collected from nine datasets and supervised analysis was applied to search for a gene expression signature predictive for overall survival (OS) in the 601 informative operated patients. The signature was identified in a learning set of patients and tested for its robustness in a large independent validation set.

RESULTS

Supervised analysis identified 1400 genes differentially expressed between two selected patient groups in the learning set, namely 17 long-term survivors (LTS; ≥ 36 months after surgery) and 22 short-term survivors (STS; dead of disease between 2 and 6 months after surgery). From these, a 25-gene prognostic classifier was developed, which identified two classes ("STS-like" and "LTS-like") in the independent validation set (n = 562), with a 25% (95% CI 18-33) and 48% (95% CI 42-54) 2-year OS (P = 4.33 × 10-9), respectively. Importantly, the prognostic value of this classifier was independent from both clinicopathological prognostic features and molecular subtypes in multivariate analysis, and existed in each of the nine datasets separately. The generation of 100,000 random gene signatures by a resampling scheme showed the non-random nature of our prognostic classifier.

CONCLUSION

This study, the largest prognostic study of gene expression profiles in pancreatic carcinoma, reports a 25-gene signature associated with post-operative OS independently of classical factors and molecular subtypes. This classifier may help select patients with resectable disease for either immediate surgery (the LTS-like class) or neoadjuvant chemotherapy (the STS-like class). Its assessment in the current prospective trials of adjuvant and neoadjuvant chemotherapy trials is warranted, as well as the functional analysis of the classifier genes, which may provide new therapeutic targets.

Validation of Lymphocyte-to-Monocyte Ratio as a Prognostic Factor in Advanced Pancreatic Cancer: An East Asian Cohort Study of 2 Countries

OBJECTIVES

Although the prognostic value of lymphocyte-to-monocyte ratio (LMR) has been recently demonstrated in solid tumors, little is known of its impact on advanced pancreatic cancer (APC). This study evaluates and validates the cutoff value of LMR for predicting palliative chemotherapy outcome using a transnational cohort of APC patients.

METHODS

A total of 405 APC patients receiving first-line palliative chemotherapy were retrospectively reviewed. Of these, 153 patients were from Shanghai General Hospital (training set) and 252 patients were from Kyoto University Hospital (validation set). The optimal cutoff value of LMR was determined by a generating receiver operating characteristic curve for the training set. The association between LMR and survival was evaluated using log-rank tests, and a Cox regression model was used to validate the independent prognostic significance of LMR in APC patients.

RESULTS

The optimal cutoff value of LMR was 2.8. Overall survival was significantly longer in patients with LMR of 2.8 or greater than those with LMR of less than 2.8 (P < 0.001). Cox regression analysis showed that LMR was an independent prognostic factor. The impact of LMR was widely observed in all subgroups except the performance status 2 subgroup.

CONCLUSIONS

Lymphocyte-to-monocyte ratio may be considered as a promising prognostic marker for APC patients receiving palliative chemotherapy.

M2-polarized tumour-associated macrophages in stroma correlate with poor prognosis and Epstein-Barr viral infection in nasopharyngeal carcinoma

OBJECTIVES

To assess the relationships between CD163 expression, localization of CD163⁺ macrophages, clinicopathological features and prognosis of NPC.

METHODS

A total of 110 cases of NPC specimens and 80 cases of nasopharyngitis specimens were analysed for CD163 expression by immunohistochemistry and EBERs expression in situ hybridization.

RESULTS

CD163 + macrophages in the tumour stroma were positively correlated with the tumour and nodal stage. Higher expression of Epstein-Barr virus-encoded RNAs (EBERs) in the nuclei of tumour cells was associated with higher density of CD163 + macrophages in the tumour stroma. More importantly, greater infiltration of CD163 + macrophages in the tumour stroma was associated with poor overall survival (OS) and poor progression-free survival (PFS). Multivariate analysis revealed that the density of CD163⁺ macrophages in the tumour stroma may be an independent risk factor for NPC prognosis.

CONCLUSIONS

Increased infiltration of CD163⁺ macrophages in the tumour stroma correlates with worse outcomes and with Epstein-Barr virus (EBV) infection status of tumour cells in nasopharyngeal carcinoma (NPC).

PLD1 overexpression promotes invasion and migration and function as a risk factor for Chinese glioma patients

Glioma is a lethal disease with few effective therapeutic options. Recently, insights into cancer biology had suggested that abnormal lipid metabolism was a risk factor for various human malignancies, including glioma. As a key enzyme implicated in lipid metabolism, PLD1 was overexpression in multiple human cancers, and it was stated to be responsible for aggressive phenotypes, such as angiogenesis and chemoresistance. However, there was still much to know about its expression and function in glioma. In the present study, we showed that PLD1 was overexpression in clinical samples of glioma. In addition, the correlation assay revealed that PLD1 overexpression was correlated with poor differentiation (p = 0.04), and it was responsible for a poor prognosis for the patients (p = 0.009). Furthermore, we showed in COX regression assay that PLD1 was a risk factor for glioma (p = 0.018, HR = 0.461, 95% CI = 0.243–0.887). Consistently, we found that PLD1 was overexpression in glioma cell lines, and it could facilitate the proliferation and migration. Taken together, our study suggested that PLD1 was pro-tumoral in glioma, and that further studies were urgently needed so as to define whether it was a novel therapeutic target for the disease.

Targeting iron metabolism in drug discovery and delivery

Iron fulfils a central role in many essential biochemical processes in human physiology; thus, proper processing of iron is crucial. Although iron metabolism is subject to relatively strict physiological control, numerous disorders, such as cancer and neurodegenerative diseases, have recently been linked to deregulated iron homeostasis. Consequently, iron metabolism constitutes a promising and largely unexploited therapeutic target for the development of new pharmacological treatments for these diseases. Several iron metabolism-targeted therapies are already under clinical evaluation for haematological disorders, and these and newly developed therapeutic agents are likely to have substantial benefit in the clinical management of iron metabolism-associated diseases, for which few efficacious treatments are currently available.

M2 macrophage is the predominant phenotype in airways inflammatory lesions in patients with granulomatosis with polyangiitis

Background

Macrophages may present two distinct phenotypes indicated as M1 and M2 under different stimuli. M1 and M2 macrophages have divergent functions that range from enhancement of inflammation for M1 to tissue repair and remodeling for M2 macrophages. The objective of this study was to evaluate the distribution of M1 and M2 macrophage phenotypes in biopsies from the airways of patients with active granulomatosis with polyangiitis (GPA) and to analyze their associations with T and B cells in those biopsies, and with nasal carriage of Staphylococcus aureus, disease parameters and therapy.

Methods

Consecutive GPA patients (n = 35) with active airway disease, who underwent respiratory tract biopsy were included. Immunohistochemical evaluation was performed to assess the distribution of macrophages and T and B cells using the markers CD68, CD3 and CD20, respectively. CD86 was used as the M1 marker and CD163 as the M2 marker while Tbet and GATA-3 were used as Th1 and Th2 markers, respectively. At the time of the biopsy patients were assessed for nasal carriage of Staphylococcus aureus and treatment.

Results

Percentages of macrophages and T cells were significantly higher than those of B cells in lesional tissue from the respiratory tract in GPA. M2 macrophages and Th2 cells were more frequent than M1 macrophages (p = 0.0007) and Th1 cells (p < 0.0001), respectively. Percentages of T cells were higher in nose biopsies than in biopsies from other sites (p = 0.021); macrophages and CD163⁺ macrophages were more predominant in biopsy sites other than the nose (p = 0.039 and p = 0.012, respectively). Carriage of Staphylococcus aureus was associated with higher T cell scores (p = 0.014). The frequency of macrophages, especially M2 macrophages, was higher in GPA patients treated with immunosuppressive agents (p = 0.010); daily prednisolone dose was positively correlated with all macrophage markers. However, in multivariate analysis no independent associations were found between disease parameters and therapy with macrophage markers or T cells.

Conclusion

In GPA, M2 is the predominant macrophage phenotype in the respiratory tract. Although some associations were observed between macrophages and T cells with therapy and nasal carriage of Staphylococcus aureus, they were not independently significant in multivariate analysis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1310-4) contains supplementary material, which is available to authorized users.

PEDF increases the tumoricidal activity of macrophages towards prostate cancer cells in vitro

Background

Although inflammation and prostate cancer (PCa) have been linked, the molecular interactions between macrophages and PCa cells are poorly explored. Pigment Epithelium-Derived Factor (PEDF) is an anti-angiogenic and anti-tumor factor. We previously showed that PEDF induces macrophages recruitment in vitro, correlates with macrophages density in human prostate, and stimulates macrophages polarization towards the classically activated pathway. Here, we demonstrate that PEDF modulates the interaction between macrophages and PCa cells through a bidirectional signalling leading to tumor cell apoptosis and phagocytosis.

Methods

RAW 264.7 and THP-1 cells, and BMDMs were grown in vitro as mono- or co-cultures with PC3 or CL1 tumor cells. The effects of PEDF and its derived P18 peptide were measured on macrophages differentiation, migration, and superoxide production, and tumor cell apoptosis and phagocytosis. PEDF receptors (ATP5B, PNPLA2, and LRP6) and CD47 mRNA and protein expression were quantified in macrophages and tumor cells by quantitative RT-PCR, western blot, immunofluorescence and flow cytometry.

Results

We found that PEDF induced the migration of macrophages towards tumor 3D spheroids and 2D cultures. In co-culture, PEDF increased PCa cells phagocytosis through an indirect apoptosis-dependent mechanism. Moreover, PEDF stimulated the production of superoxide by macrophages. Conditioned media from macrophages exposed to PEDF induced tumor cells apoptosis in contrast to control conditioned media suggesting that ROS may be involved in tumor cells apoptosis. ATP5B and PNPLA2 PEDF receptors on macrophages and CD47 on tumor cells were respectively up- and down-regulated by PEDF. As PEDF, blocking CD47 induced phagocytosis. Inhibiting ATP5B reduced phagocytosis. Inversely, PNPLA2 inhibition blocks differentiation but maintains phagocytosis. CD47-induced phagocytosis was partially reverted by ATP5B inhibition suggesting a complementary action. Similar effects were observed with P18 PEDF-derived peptide.

Conclusions

These data established that modulating the molecular interactions between macrophages and PCa cells using PEDF may be a promising strategy for PCa treatment.

Stratification of Pancreatic Ductal Adenocarcinoma: Combinatorial Genetic, Stromal, and Immunologic Markers

Purpose: Pancreatic ductal adenocarcinoma (PDAC) is associated with an immunosuppressive milieu that supports immune system evasion and disease progression. Here, we interrogated genetic, stromal, and immunologic features of PDAC to delineate impact on prognosis and means to more effectively employ immunotherapy.Experimental Design: A cohort of 109 PDAC cases annotated for overall survival was utilized as a primary discovery cohort. Gene expression analysis defined immunologic subtypes of PDAC that were confirmed in the Cancer Genome Atlas dataset. Stromal and metabolic characteristics of PDAC cases were evaluated by histologic analysis and immunostaining. Enumeration of lymphocytes, as well as staining for CD8, FOXP3, CD68, CD163, PDL1, and CTLA4 characterized immune infiltrate. Neoantigens were determined by analysis of whole-exome sequencing data. Random-forest clustering was employed to define multimarker subtypes, with univariate and multivariate analyses interrogating prognostic significance.Results: PDAC cases exhibited distinct stromal phenotypes that were associated with prognosis, glycolytic and hypoxic biomarkers, and immune infiltrate composition. Immune infiltrate was diverse among PDAC cases and enrichment for M2 macrophages and select immune checkpoints regulators were specifically associated with survival. Composite analysis with neoantigen burden, immunologic, and stromal features defined novel subtypes of PDAC that could have bearing on sensitivity to immunologic therapy approaches. In addition, a subtype with low levels of neoantigens and minimal lymphocyte infiltrate was associated with improved overall survival.Conclusions: The mutational burden of PDAC is associated with distinct immunosuppressive mechanisms that are conditioned by the tumor stromal environment. The defined subtypes have significance for utilizing immunotherapy in the treatment of PDAC. Clin Cancer Res; 23(15); 4429-40. ©2017 AACR.

Human Tumor-Infiltrating Myeloid Cells: Phenotypic and Functional Diversity

Our current understanding of human tumor-resident myeloid cells is, for the most part, based on a large body of work in murine models or studies enumerating myeloid cells in patient tumor samples using immunohistochemistry (IHC). This has led to the establishment of the theory that, by and large, tumor-resident myeloid cells are either “protumor” M2 macrophages or myeloid-derived suppressor cells (MDSC). This concept has accelerated our understanding of myeloid cells in tumor progression and enabled the elucidation of many key regulatory mechanisms involved in cell recruitment, polarization, and activation. On the other hand, this paradigm does not embrace the complexity of the tumor-resident myeloid cell phenotype (IHC can only measure 1 or 2 markers per sample) and their possible divergent function in the hostile tumor microenvironment. Here, we examine the criteria that define human tumor-infiltrating myeloid cell subsets and provide a comprehensive and critical review of human myeloid cell nomenclature in cancer. We also highlight new evidence characterizing their contribution to cancer pathogenesis based on evidence derived from clinical studies drawing comparisons with murine studies where necessary. We then review the mechanisms in which myeloid cells are regulated by tumors in humans and how these are being targeted therapeutically.

Intraepithelial Attack Rather than Intratumorally Infiltration of CD8+T Lymphocytes is a Favorable Prognostic Indicator in Pancreatic Ductal Adenocarcinoma

BACKGROUND

Tumor-infiltrating lymphocytes (TILs) are one of the major participants in the tumor microenvironment of pancreatic ductal adenocarcinoma (PDAC). However, the mechanism of interaction between TILs and tumors is complex and remains unclear.

OBJECTIVE

To evaluate the state of immunoreactions in PDAC tissues, and explore the prognostic value of these markers in a large sample, to provide a new theoretical basis for PDAC immunotherapy.

METHOD

Immunohistochemical staining of CD4+ and CD8+T cells was performed in a tissue microarray (TMA) of 143 cases of PDAC. Two major variables for the spatial distributions of CD4+T and CD8+T cells in PDAC tissues, intraepithelial attack and intratumoral infiltration, were used to evaluate the state of immunoreactions, and the interrelationships with the clinicopathological variables were analyzed.

RESULTS

Our data showed that both the intraepithelial CD4+T and CD8+T attack were less frequent than the intratumoral infiltration. CD8+T intraepithelial attack and intratumoral infiltration were more intense than CD4+T. CD8+T intraepithelial attack was an independent favorable prognostic factor for overall survival, correlating negatively with vascular invasion and positively with CD4+T and CD8+T high intratumoral infiltration. CD8+T high intratumoral infiltration without CD8+T intraepithelial attack was a poor prognostic factor. CD8+T high intratumoral infiltration was accompanied by T stage progression. Conclusively, in PDAC progression, imbalances of T cells occurred in CD4+ and CD8+ immunoreactions. The CD8+T intraepithelial attack was an independent favorable prognostic indicator, however the intraepithelial attack of CD4+T and the both intratumoral infiltration of CD8+T and CD4+T played an ambiguous role.

CONCLUSION

Our data suggested that it is a potential approach to increasing the number of intraepithelial attacking CD8+T cells for tumor immunotherapy, and exploring a new mechanism for immunosuppression in a tumor microenvironment with high T cell infiltration without attack.

Simultaneous high expression of PLD1 and Sp1 predicts a poor prognosis for pancreatic ductal adenocarcinoma patients

Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease with few therapeutic options. Recently, insight into cancer biology suggested abnormal lipid metabolism to be a risk factor for human malignancies. As a key enzyme implicated in lipid metabolism, PLD1 was elevated in various human cancer associating with malignant phenotypes. However, little was known about its expression and function in PDAC. We showed that PLD1 was elevated in both the cell lines and clinical samples of PDAC, and it positively correlated with vascular invasion (p = 0.041) and responsible for a poor prognosis (p = 0.009). Meanwhile, we also found Sp1 to be elevated in the disease, correlating with vascular invasion (p = 0.007). Moreover, the correlation assay suggested that PLD1 positively correlated with Sp1 in the clinical sample (r = 0.390; p < 0.001) and the cell lines. Finally, we showed that co-high expression of both the factors confers the poorest prognosis for the patients, and that their simultaneous high expression might be an independent prognostic factor (p = 0.001; HR = 3.427; 95% CI 1.629-7.211).

The role of integrins in TGFβ activation in the tumour stroma

TGFβ1 is the most pleiotropic of all known cytokines and thus, to avoid uncontrolled TGFβ-activated processes, its activity is tightly regulated. Studies in fibrosis have led to the discovery that αv integrins are the major regulators of the local activation of latent TGFβ in our tissues. Since all cells can express one or more types of αv integrins, this raises the possibility that, in the complex milieu of a developing cancer, multiple cell types including both cancer cells and stromal cells activate TGFβ. In normal tissues, TGFβ1 is a tumour suppressor through its ability to suppress epithelial cell division, whereas in cancer, in which tumour cells develop genetic escape mechanisms to become resistant to TGFβ growth suppression, TGFβ signalling creates a tumour-permissive environment by activating fibroblast-to-myofibroblast transition, by promoting angiogenesis, by suppressing immune cell populations and by promoting the secretion of both matrix proteins and proteases. In addition, TGFβ drives epithelial-to-mesenchymal transition (EMT) increasing the potential for metastasis. Since αv integrins activate TGFβ, they almost certainly drive TGFβ-dependent cancer progression. In this review, we discuss the data that are helping to develop this hypothesis and describe the evidence that αv integrins regulate the TGFβ promotion of cancer. Graphical Abstract Mechanisms of integrin-mediated transforming growth factor beta (TGFβ) activation and its effect on stromal processes. 1 Matrix-bound latent LAP-TGFβ1 binds αv integrins expressed by epithelial cells or fibroblasts (LAP latency-associated peptide). TGFβ1 becomes exposed. 2 Active TGFβ1 binds the TGFβ receptor in an autocrine or paracrine fashion. 3 TGFβ1 signalling increases integrin expression, LAP-TGFβ1 secretion and trans-differentiation of fibroblasts into contractile cells that secrete collagens and collagen cross-linking proteins. By contracting the matrix, latent TGFβ1 is stretched making the activation of latent TGFβ1 easier and creating a continuous cycle of TGFβ1 signalling. TGFβ1 promotes cancer progression by promoting angiogenesis, immune suppression and epithelial-to-mesenchymal transition (EMT).

Macrophages induce resistance to 5-fluorouracil chemotherapy in colorectal cancer through the release of putrescine

The development of chemoresistance to 5-fluorouracil (5-FU) is a major obstacle for sustained effective treatment of colorectal cancer (CRC), with the mechanisms being not fully understood. Here we demonstrated that tumor associated macrophages (TAMs) became activated during treatment with 5-FU and secreted factors that protected the CRC cells against chemotherapy with 5-FU. By performing metabolomics analysis, we identified putrescine, a member of polyamines, inducing resistance to 5-FU-triggered CRC apoptosis and tumor suppression via JNK-caspase-3 pathway. Noteworthily, either pharmacological or genetic blockage of ornithine decarboxylase (ODC) prevented TAMs-induced chemoresistance to 5-FU in vitro and in vivo. Our findings show that TAMs are potent mediators of resistance to 5-FU chemotherapy and uncover potential targets to enhance chemotherapy sensitivity in patients with CRC.