Oncoprotein signaling mediates tumor-specific inflammation and enhances tumor progression

Rethinking the chemokine cascade in brain metastasis: Preventive and therapeutic implications

Brain metastasis (BrM) is one of the major causes of death in cancer patients and is associated with an estimated 10-40 % of total cancer cases. The survival rate of brain metastatic patients has not improved due to intratumor heterogeneity, the survival adaptations of brain homing metastatic cells, and the lack of understanding of underlying molecular mechanisms that limit the availability of effective therapies. The heterogeneous population of immune cells and tumor-initiating cells or cancer stem cells in the tumor microenvironment (TME) release various factors, such as chemokines that upon binding to their cognate receptors enhance tumor growth at primary sites and help tumor cells metastasize to the brain. Furthermore, brain metastatic sites have unique heterogeneous microenvironment that fuels cancer cells in establishing BrM. This review explores the crosstalk of chemokines with the heterogeneous TME during the progression of BrM and recognizes potential therapeutic approaches. We also discuss and summarize different targeted, immunotherapeutic, chemotherapeutic, and combinatorial strategies (with chemo-/immune- or targeted-therapies) to attenuate chemokines mediated BrM.

CCL2/CCR2 signaling in cancer pathogenesis

Chemokines are a family of small cytokines, which guide a variety of immune/inflammatory cells to the site of tumor in tumorigenesis. A dysregulated expression of chemokines is implicated in different types of cancer including prostate cancer. The progression and metastasis of prostate cancer involve a complex network of chemokines that regulate the recruitment and trafficking of immune cells. The chemokine CCL2 and its main receptor CCR2 have been receiving particular interest on their roles in cancer pathogenesis. The up-regulation of CCL2/CCR2 and varied immune conditions in prostate cancer, are associated with cancer advancement, metastasis, and relapse. Here we reviewed recent findings, which link CCL2/CCR2 to the inflammation and cancer pathogenesis, and discussed the therapeutic potential of CCL2/CCR2 axis in cancer treatment based on results from our group and other investigators, with a major focus on prostate cancer. Video Abstract.

Neutrophil-to-lymphocyte and platelet-to-lymphocyte ratios as predictors of tumor response in hepatocellular carcinoma after DEB-TACE

OBJECTIVES

To investigate the predictive value of quantifiable imaging and inflammatory biomarkers in patients with hepatocellular carcinoma (HCC) for the clinical outcome after drug-eluting bead transarterial chemoembolization (DEB-TACE) measured as volumetric tumor response and progression-free survival (PFS).

METHODS

This retrospective study included 46 patients with treatment-naïve HCC who received DEB-TACE. Laboratory work-up prior to treatment included complete and differential blood count, liver function, and alpha-fetoprotein levels. Neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) were correlated with radiomic features extracted from pretreatment contrast-enhanced magnetic resonance imaging (MRI) and with tumor response according to quantitative European Association for the Study of the Liver (qEASL) criteria and progression-free survival (PFS) after DEB-TACE. Radiomic features included single nodular tumor growth measured as sphericity, dynamic contrast uptake behavior, arterial hyperenhancement, and homogeneity of contrast uptake. Statistics included univariate and multivariate linear regression, Cox regression, and Kaplan-Meier analysis.

RESULTS

Accounting for laboratory and clinical parameters, high baseline NLR and PLR were predictive of poorer tumor response (p = 0.014 and p = 0.004) and shorter PFS (p = 0.002 and p < 0.001). When compared to baseline imaging, high NLR and PLR correlated with non-spherical tumor growth (p = 0.001 and p < 0.001).

CONCLUSIONS

This study establishes the prognostic value of quantitative inflammatory biomarkers associated with aggressive non-spherical tumor growth and predictive of poorer tumor response and shorter PFS after DEB-TACE.

KEY POINTS

• In treatment-naïve hepatocellular carcinoma (HCC), high baseline platelet-to-lymphocyte ratio (PLR) and neutrophil-to-lymphocyte ratio (NLR) are associated with non-nodular tumor growth measured as low tumor sphericity. • High PLR and NLR are predictive of poorer volumetric enhancement-based tumor response and PFS after DEB-TACE in HCC. • This set of readily available, quantitative immunologic biomarkers can easily be implemented in clinical guidelines providing a paradigm to guide and monitor the personalized application of loco-regional therapies in HCC.

RET-mediated modulation of tumor microenvironment and immune response in multiple endocrine neoplasia type 2 (MEN2)

Medullary thyroid carcinomas (MTC) arise from thyroid parafollicular, calcitonin-producing C-cells and can occur either as sporadic or as hereditary diseases in the context of familial syndromes, including multiple endocrine neoplasia 2A (MEN2A), multiple endocrine neoplasia 2B (MEN2B) and familial MTC (FMTC). In a large fraction of sporadic cases, and virtually in all inherited cases of MTC, activating point mutations of the RET proto-oncogene are found. RET encodes for a receptor tyrosine kinase protein endowed with transforming potential on thyroid parafollicular cells. As in other cancer types, microenvironmental factors play a critical role in MTC. Tumor-associated extracellular matrix, stromal cells and immune cells interact and influence the behavior of cancer cells both in a tumor-promoting and in a tumor-suppressing manner. Several studies have shown that, besides the neoplastic transformation of thyroid C-cells, a profound modification of tumor microenvironment has been associated to the RET FMTC/MEN2-associated oncoproteins. They influence the surrounding stroma, activating cancer-associated fibroblasts (CAFs), promoting cancer-associated inflammation and suppressing anti-cancer immune response. These mechanisms might be exploited to develop innovative anti-cancer therapies and novel prognostic tools in the context of familial, RET-associated MTC.

HLA-G is differentially expressed in thyroid tissues

BACKGROUND

HLA-G is a nonclassical major histocompatibility complex molecule that has well-recognized immunomodulatory properties. The expression of HLA-G in tumor cells has been considered to be detrimental, permitting tumor spreading and decreased survival. We evaluated the expression of HLA-G in histologically normal thyroid tissue, goiter, and benign and malignant thyroid tumors, and studied the relationship between HLA-G expression and patient clinical variables.

PATIENTS AND METHODS

The immunohistochemistry expression of HLA-G was performed on 72 specimens of papillary thyroid carcinoma (PTC), 19 follicular thyroid carcinomas (FTC), 22 follicular adenomas (FA), 22 colloid goiters (CG), and 14 histologically normal thyroid glands (NT). The percentage of HLA-G staining was graded from absent (-) to intense (+++).

RESULTS

HLA-G was faintly expressed in areas of hyperplasia in NT and CG. In PTC, FTC, and FA, the percentage of cell staining was significantly higher than in NT and CG (p<0.001 for each comparison). The tumor area with HLA-G expression was greater in FTC (p=0.0059) and PTC (p=0.0330) compared to FA. According to the magnitude of HLA-G staining, PTC tumors >1 cm exhibited increased HLA-G staining when compared to smaller tumors (p=0.03). Aggressive histologic subtypes of PTC have a higher median stained tumor area. No association was found between HLA-G expression and tumoral staging or patient disease-free survival.

CONCLUSIONS

The gradual increase of HLA-G expression from hyperplasia to carcinomas, and the association of strong HLA staining with some variables implicated in poor prognosis corroborate the unfavorable role of HLA-G in tumor thyroid cells, inhibiting cytotoxic immune system cells and facilitating tumor evasion and progression.

Innate and adaptive immune cells in the tumor microenvironment

Most tumor cells express antigens that can mediate recognition by host CD8(+) T cells. Cancers that are detected clinically must have evaded antitumor immune responses to grow progressively. Recent work has suggested two broad categories of tumor escape based on cellular and molecular characteristics of the tumor microenvironment. One major subset shows a T cell-inflamed phenotype consisting of infiltrating T cells, a broad chemokine profile and a type I interferon signature indicative of innate immune activation. These tumors appear to resist immune attack through the dominant inhibitory effects of immune system-suppressive pathways. The other major phenotype lacks this T cell-inflamed phenotype and appears to resist immune attack through immune system exclusion or ignorance. These two major phenotypes of tumor microenvironment may require distinct immunotherapeutic interventions for maximal therapeutic effect.

Innate and adaptive immune cells in the tumor microenvironment

Most tumor cells express antigens that can mediate recognition by host CD8(+) T cells. Cancers that are detected clinically must have evaded antitumor immune responses to grow progressively. Recent work has suggested two broad categories of tumor escape based on cellular and molecular characteristics of the tumor microenvironment. One major subset shows a T cell-inflamed phenotype consisting of infiltrating T cells, a broad chemokine profile and a type I interferon signature indicative of innate immune activation. These tumors appear to resist immune attack through the dominant inhibitory effects of immune system-suppressive pathways. The other major phenotype lacks this T cell-inflamed phenotype and appears to resist immune attack through immune system exclusion or ignorance. These two major phenotypes of tumor microenvironment may require distinct immunotherapeutic interventions for maximal therapeutic effect.

The nuclear factor kappa-B signaling pathway as a therapeutic target against thyroid cancers

BACKGROUND

The nuclear factor kappa-B (NF-κB) proteins, a family of transcription factors found virtually in all cells, are known to play crucial roles in the growth of a number of human malignancies. The ability of NF-κB to target a large number of genes that regulate cell proliferation, differentiation, survival, and apoptosis, provides clues toward its deregulation during the process of tumorigenesis, metastatic progression, and therapeutic resistance of tumors.

SUMMARY

In addition to the signaling pathways known to be involved in thyroid tumorigenesis, such as the mitogen-activated protein kinase and janus kinase cascades, studies implicate the NF-κB pathway in the development of both less aggressive thyroid cancers, papillary and follicular adenocarcinomas, and progression to aggressive thyroid cancers, such as anaplastic adenocarcinomas. A constitutively activated NF-κB pathway also closely links Hashimoto's thyroiditis with increased incidence of thyroid cancers. The NF-κB pathway is becoming one of the major targets for drug development, and a number of compounds have been developed to inhibit this pathway at different levels in cancer cells. Some of these targets have shown promising outcomes in both in vitro and in vivo investigations and a handful of them have shown efficacy in the clinical setting.

CONCLUSIONS

This review discusses the recent findings that demonstrate that the inhibition of NF-κB, alone or with other signaling pathway inhibitors may be of significant therapeutic benefits against aggressive thyroid cancers.

Emerging avenues linking inflammation and cancer

The role of inflammation in carcinogenesis has been extensively investigated and well documented. Many biochemical processes that are altered during chronic inflammation have been implicated in tumorigenesis. These include shifting cellular redox balance toward oxidative stress; induction of genomic instability; increased DNA damage; stimulation of cell proliferation, metastasis, and angiogenesis; deregulation of cellular epigenetic control of gene expression; and inappropriate epithelial-to-mesenchymal transition. A wide array of proinflammatory cytokines, prostaglandins, nitric oxide, and matricellular proteins are closely involved in premalignant and malignant conversion of cells in a background of chronic inflammation. Inappropriate transcription of genes encoding inflammatory mediators, survival factors, and angiogenic and metastatic proteins is the key molecular event in linking inflammation and cancer. Aberrant cell signaling pathways comprising various kinases and their downstream transcription factors have been identified as the major contributors in abnormal gene expression associated with inflammation-driven carcinogenesis. The posttranscriptional regulation of gene expression by microRNAs also provides the molecular basis for linking inflammation to cancer. This review highlights the multifaceted role of inflammation in carcinogenesis in the context of altered cellular redox signaling.

Coordinated regulation of myeloid cells by tumours

Myeloid cells are the most abundant nucleated haematopoietic cells in the human body and are a collection of distinct cell populations with many diverse functions. The three groups of terminally differentiated myeloid cells - macrophages, dendritic cells and granulocytes - are essential for the normal function of both the innate and adaptive immune systems. Mounting evidence indicates that the tumour microenvironment alters myeloid cells and can convert them into potent immunosuppressive cells. Here, we consider myeloid cells as an intricately connected, complex, single system and we focus on how tumours manipulate the myeloid system to evade the host immune response.

Intracellular signal transduction and modification of the tumor microenvironment induced by RET/PTCs in papillary thyroid carcinoma

RET gene rearrangements (RET/PTCs) represent together with BRAF point mutations the two major groups of mutations involved in papillary thyroid carcinoma (PTC) initiation and progression. In this review, we will examine the mechanisms involved in RET/PTC-induced thyroid cell transformation. In detail, we will summarize the data on the molecular mechanisms involved in RET/PTC formation and in its function as a dominant oncogene, on the activated signal transduction pathways and on the induced gene expression modifications. Moreover, we will report on the effects of RET/PTCs on the tumor microenvironment. Finally, a short review of the literature on RET/PTC prognostic significance will be presented.

Targeting stroma to treat cancers

All cancers depend on stroma for support of growth. Leukemias, solid tumors, cancer cells causing effusions, metastases as well as micro-disseminated cancer cells release factors that stimulate stromal cells, which in turn produce ligands that stimulate cancer cells. Therefore, elimination of stromal support by destroying the stromal cells or by inhibiting feedback stimulation of cancer growth is in the focus of many evolving therapies. A stringent evaluation of the efficacy of stromal targeting requires testing in animal models. Most current studies emphasize the successes of stromal targeting rather than deciphering its limitations. Here we show that many of the stromal targeting approaches, while often reducing tumor growth rates, are rarely curative. Therefore, we will also discuss conditions where stromal targeting can eradicate large established tumors. Finally, we will examine still unanswered questions of this promising and exciting area of cancer research.

Metastatic dormancy and progression in thyroid cancer: targeting cells in the metastatic frontier

BACKGROUND

Metastatic dormancy, or the ability of cancer cells to survive but not progress in metastatic environments, is now recognized to be a common occurrence in cancer.

SUMMARY

From a clinical perspective, this phenomenon is common in metastatic well-differentiated thyroid cancer, whereby patients often present with distant metastases that remain stable for years after removal of the primary tumor and subsequent treatment. Experimental data suggest that metastases can develop throughout the life of a cancer and that progression in the distant environment depends on the biology of the cancer cells that metastasize as well as that of the various microenvironments they encounter. A firm understanding of how thyroid cancer cell progression is regulated in different metastatic environments is necessary to devise effective therapies targeting progressive metastatic thyroid cancer.

CONCLUSION

In this review, current models of metastatic progression and factors that regulate late-stage metastatic progression that are particularly relevant for thyroid cancer are discussed.

The RET/PTC3 oncogene activates classical NF-κB by stabilizing NIK

The oncogenic fusion protein RET/PTC3 (RP3) that is expressed in papillary thyroid carcinoma (PTC) and thyroid epithelia in Hashimoto's thyroiditis activates nuclear factor-kappa B (NF-κB) and induces pro-inflammatory gene expression; however, the mechanism of this activation is unknown. To address this, we expressed RP3 in murine embryonic fibroblasts (MEFs) lacking key classical and noncanonical NF-κB signaling components. In wild-type MEFs, RP3 upregulated CCL2, CXCL1, granulocyte-macrophage colony-stimulating factor and tumor necrosis factor expression and activated classical but not noncanonical NF-κB. RP3-activated NF-κB in IκB kinase (IKK)β(-/-) MEFs but not IKKα- or NF-κB essential modulator (NEMO)-deficient cells and activation was inhibited by a peptide that blocks NEMO binding to the IKKs. RP3 increased the levels of NF-κB-inducing kinase (NIK) and did not activate NF-κB in NIK-deficient MEFs. Notably, NIK stabilization was not accompanied by TRAF3 degradation demonstrating that RP3 disrupts normal basal NIK regulation. Dominant-negative NIK blocked RP3-induced NF-κB activation and an RP3 signaling mutant (RP3(Y588F)) did not stabilize NIK. Finally, examination of PTC specimens revealed strong positive staining for NIK. We therefore conclude that RP3 activates classical NF-κB via NIK, NEMO and IKKα. Importantly, our findings reveal a novel mechanism for oncogene-induced NF-κB activation via stabilization of NIK.

Mast cells have a protumorigenic role in human thyroid cancer

In different human carcinoma types, mast cell infiltrate increases with respect to normal tissue and mast cell density correlates with a bad prognosis. To assess the role of mast cells in human thyroid cancer, we compared the density of tryptase-positive mast cells in 96 papillary thyroid carcinomas (PTCs) versus normal thyroid tissue from 14 healthy individuals. Mast cell density was higher in 95% of PTCs (n=91) than in control tissue. Mast cell infiltrate correlated with extrathyroidal extension (P=0.0005) of PTCs. We show that thyroid cancer cell-line-derived soluble factors induce mast cell activation and chemoattraction in vitro. Different mast cell lines (HMC-1 and LAD2) and primary human lung mast cells induced thyroid cancer cell invasive ability, survival and DNA synthesis in vitro. The latter effect was mainly mediated by three mast-cell-derived mediators: histamine, and chemokines CXCL1/GROα and CXCL10/IP10. We show that xenografts of thyroid carcinoma cells (8505-C) could recruit mast cells injected into the tail vein of mice. Co-injection of human mast cells accelerated the growth of thyroid cancer cell (8505-C) xenografts in athymic mice. This effect was mediated by increased tumor vascularization and proliferation, and was reverted by treating mice with sodium cromoglycate (Cromolyn), a specific mast cell inhibitor. In conclusion, our study data suggest that mast cells are recruited into thyroid carcinomas and promote proliferation, survival and invasive ability of cancer cells, thereby contributing to thyroid carcinoma growth and invasiveness.

Thyroid cancer and inflammation

Some cancer types are strongly associated with chronic inflammatory or infectious diseases whereas others are not, but an inflammatory component is present in most human neoplastic lesions. This review focuses on various aspects of thyroid cancer and inflammation. The incidence of thyroid cancer, in particular of well-differentiated papillary thyroid carcinomas (PTCs), is increased in autoimmune thyroid diseases such as Hashimoto's thyroiditis. Thyroid cancer often has an inflammatory cell infiltrate, which includes lymphocytes, macrophages, dendritic cells and mast cells, whose role in thyroid cancer is still not completely understood. However, most experimental evidence suggests these cells exert a protumorigenic function. Moreover, oncoproteins typically expressed in human PTCs, such as RET/PTC, RAS, and BRAF, trigger a proinflammatory programme in thyreocytes. These data suggest that inflammatory molecules are promising targets for thyroid cancer therapy.

Role of NF-kappaB in thyroid cancer

Thyroid cancer is the most common neoplasia of the endocrine system and accounts for approximately 1% of all newly diagnosed cancer cases. Its incidence has rapidly grown over the past few decades. Although most thyroid carcinomas are of the well-differentiated papillary histology, and respond well to treatment with surgical resection followed by radioactive iodine ablation, tumors with more aggressive phenotype, such as follicular, poorly differentiated, anaplastic, and medullary cancers, lead to almost 1500 patient deaths annually. Therefore, understanding molecular mechanisms that regulate the biology of these carcinomas could be helpful to identify new molecules acting as novel targets for therapeutic intervention. NF-kappaB has been recently shown to play an important role in thyroid cancer for its ability to control the proliferative and the anti-apoptotic signaling pathways of thyroid neoplastic cells. Oncogenic proteins RET/PTC, RAS and BRAF, that are involved in many aspects of thyroid carcinogenesis, can induce NF-kappaB activation in papillary, follicular, and medullary thyroid carcinomas, while constitutive de-regulated NF-kappaB activity has been found in anaplastic thyroid carcinomas. A number of NF-kappaB inhibitors have been demonstrated to induce anti-proliferative effects and/or massive apoptosis, especially in combination with radio- or chemo-therapy. The results obtained suggest that targeting NF-kappaB could be a promising strategy for advanced thyroid cancer treatment.