Inhibition of metastasis by inhibition of tumor-derived CCL5

Potential molecular mechanisms and clinical progress in liver metastasis of breast cancer

Breast cancer is the most common malignant tumor in women and the leading cause of cancer death in women. About 30% of breast cancer patients have metastasis every year, which greatly increases the mortality rate of breast cancer. The main target organs for metastasis are bone, brain, liver and lung. The breast cancer liver metastasis (BCLM) mechanism is not fully clarified. This is a complex process involving multiple factors, which is not only related to the microenvironment of the primary tumor and liver, but also regulated by a variety of signaling pathways. Clarifying these mechanisms is of great help to guide clinical treatment. With the in-depth study of BCLM, a variety of new treatment schemes such as targeted therapy and endocrine therapy provide new ideas for the cure of BCLM. In this review, we will summarize the molecular mechanism and treatment of BCLM.

Metastatic Breast Cancer, Organotropism and Therapeutics: A Review

The final stage of breast cancer involves spreading breast cancer cells to the vital organs like the brain, liver lungs and bones in the process called metastasis. Once the target organ is overtaken by the metastatic breast cancer cells, its usual function is compromised causing organ dysfunction and death. Despite the significant research on breast cancer metastasis, it's still the main culprit of breast cancer-related deaths. Exploring the complex molecular pathways associated with the initiation and progression of breast cancer metastasis could lead to the discovery of more effective ways of treating the devastating phenomenon. The present review article highlights the recent advances to understand the complexity associated with breast cancer metastases, organotropism and therapeutic advances.

Tamoxifen suppresses brain metastasis of estrogen receptor-deficient breast cancer by skewing microglia polarization and enhancing their immune functions

Background

Brain metastasis of breast cancer exhibits exceedingly poor prognosis, and both triple negative (TN) and Her2⁺ subtypes have the highest incidence of brain metastasis. Although estrogen blockers are considered to be ineffective for their treatment, recent evidence indicates that estrogen blockade using tamoxifen showed certain efficacy. However, how estrogen affects brain metastasis of triple negative breast cancer (TNBC) remains elusive.

Methods

To examine the effect of estrogen on brain metastasis progression, nude mice were implanted with brain metastatic cells and treated with either estrogen supplement, tamoxifen, or ovariectomy for estrogen depletion. For clinical validation study, brain metastasis specimens from pre- and post-menopause breast cancer patients were examined for microglia polarization by immunohistochemistry. To examine the estrogen-induced M2 microglia polarization, microglia cells were treated with estrogen, and the M1/M2 microglia polarization was detected by qRT-PCR and FACS. The estrogen receptor-deficient brain metastatic cells, SkBrM and 231BrM, were treated with conditioned medium (CM) derived from microglia that were treated with estrogen in the presence or absence of tamoxifen. The effect of microglia-derived CM on tumor cells was examined by colony formation assay and sphere forming ability.

Results

We found that M2 microglia were abundantly infiltrated in brain metastasis of pre-menopausal breast cancer patients. A similar observation was made in vivo, when we treated mice systemically with estrogen. Blocking of estrogen signaling either by tamoxifen treatment or surgical resection of mice ovaries suppressed M2 microglial polarization and decreased the secretion of C-C motif chemokine ligand 5, resulting in suppression of brain metastasis. The estrogen modulation also suppressed stemness in TNBC cells in vitro. Importantly, estrogen enhanced the expression of signal regulatory protein α on microglia and restricted their phagocytic ability.

Conclusions

Our results indicate that estrogen promotes brain metastasis by skewing polarity of M2 microglia and inhibiting their phagocytic ability, while tamoxifen suppresses brain metastasis by blocking the M2 polarization of microglia and increasing their anti-tumor phagocytic ability. Our results also highlight a potential therapeutic utility of tamoxifen for treating brain metastasis of hormone receptor-deficient breast cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13058-021-01412-z.

Autocrine CCL5 Effect Mediates Trastuzumab Resistance by ERK Pathway Activation in HER2-Positive Breast Cancer

HER2-positive breast cancer is currently managed with chemotherapy in combination with specific anti-HER2 therapies, including trastuzumab. However, a high percentage of patients with HER2-positive tumors do not respond to trastuzumab (primary resistance) or either recur (acquired resistance), mostly due to molecular alterations in the tumor that are either unknown or undetermined in clinical practice. Those alterations may cause the tumor to be refractory to treatment with trastuzumab, promoting tumor proliferation and metastasis. Using continued exposure of a HER2-positive cell line to trastuzumab, we generated a model of acquired resistance characterized by increased expression of several cytokines. Differential gene expression analysis indicated an overexpression of 15 genes, including five different chemokines, and highlighting CCL5/RANTES as the most overexpressed one. Functional studies, either by in vitro gene silencing or by in vitro and in vivo pharmacologic inhibition of the CCL5/CCR5 interaction with maraviroc, confirmed that CCL5 overexpression was implicated in acquired resistance to trastuzumab, which was mediated by ERK activation. In patient samples, increased CCL5 expression significantly correlated with lower rates of complete response after neoadjuvant therapy, confirmed by detection of high serum CCL5 levels by ELISA. Overexpression of CCL5 correlated with ERK phosphorylation in tumor cells and was statistically associated with worse disease-free survival and overall cancer survival in patients with early HER2-positive breast cancer.

Progranulin promotes melanoma progression by inhibiting natural killer cell recruitment to the tumor microenvironment

Progranulin (PGRN) is a growth factor with significant biological effects in different types of cancer. However, its role in melanoma progression has not been explored. In this study, we first analyze clinical datasets and show that high PGRN expression levels are correlated with poor prognosis of melanoma patients. Further, we demonstrate in a transplanted murine melanoma model in which the endogenous Grn gene encoding PGRN has been deleted that tumor-derived, not host-derived PGRN, promotes melanoma growth and metastasis. Immunological analyses reveal an enhanced infiltration of natural killer cells, but not T lymphocytes, into PGRN-deficient tumors compared to the wild type control. Antibody-mediated depletion confirms the critical role of NK cells in controlling B16 tumor growth. RNA-seq analysis reveals that several chemokines including CCL5 are strongly upregulated in PGRN-deficient tumor. Silencing CCL5 expression in PGRN-deficient tumor reduces NK cell recruitment and restores tumor growth to the control level. Lastly, we show that PGRN inhibits Ccl5 gene expression at the transcriptional level. This study highlights a novel and critical role of PGRN in melanoma growth and metastasis and suggests that it may represent a potential therapeutic target.

Collagen IV-conveyed signals can regulate chemokine production and promote liver metastasis

Liver metastases remain a major cause of death from gastrointestinal tract cancers as well as from other malignancies such as breast and lung carcinomas and melanoma. Understanding the underlying biology is essential for the design of effective targeted therapies. We previously reported that collagen IV α1/α2 overexpression in non-metastatic lung carcinoma (M27^colIV) cells increased their metastatic ability, specifically to the liver and documented high collagen IV levels in surgical resections of liver metastases from diverse tumor types. Here, we aimed to elucidate the functional relevance of collagen IV to metastatic outgrowth in the liver. Gene expression profiling revealed in M27^colIVcells significant increases in the expression of chemokines CCL5 (5.7-fold) and CCL7 (2.6-fold) relative to wild-type cells, and this was validated by qPCR and western blotting. Similarly, in human colon carcinoma KM12C and KM12SM cells with divergent liver-colonizing potentials, CCL7 and CCL5 production correlated with type IV collagen expression and the metastatic phenotype. CCL7 silencing by short hairpin RNA (shRNA) reduced experimental liver metastasis in both cell types, whereas CCL5 silencing reduced metastasis of M27^colIV cells, implicating these cytokines in metastatic expansion in the liver. Subsequent functional analyses implicated both MEK/ERK and PI3K signaling upstream of CCL7 upregulation and identified CCL7 (but not CCL5) as a critical migration/invasion factor, acting via the chemokine receptor CCR3. Chemokine CCL5 was identified as a regulator of the T-cell immune response in the liver. Loss of CCL7 in KM12SM cells was also associated with altered E-cadherin and reduced vimentin and Snail expression, implicating it in epithelial-to-mesenchymal transition in these cells. Moreover, in clinical specimens of colon cancer liver metastases analyzed by immunohistochemistry, CCL5 and CCL7 levels paralleled those of collagen IV. The results identify the chemokines CCL5 and CCL7 as type IV collagen-regulated genes that promote liver metastasis by distinct and complementary mechanisms.

RANTES and IL-6 cooperate in inducing a more aggressive phenotype in breast cancer cells

Both the CC chemokine ligand 5 (CCL5/RANTES) and interleukin-6 (IL-6), released by mesenchymal stem cells (MSCs) as well as by neoplastic cells, promote breast cancer cell progression through autocrine and paracrine mechanisms. In order to assess the effects of the simultaneous overexpression of RANTES and IL-6 on the tumor cell phenotype, we overexpressed both proteins in MCF-7 and MDA-MB-231 human breast cancer cell lines. MCF-7 cells co-expressing RANTES and IL-6 had a greater ability to form colonies in soft agar, compared to cells overexpressing RANTES or IL-6. In addition, both MCF-7 and MDA-MB-231 clones co-expressing RANTES and IL-6 showed a significantly higher ability to migrate and to invade. The analysis of phosphorylated ERK1/2, AKT and STAT3 signal transduction proteins revealed that several signaling pathways are simultaneously activated in cells overexpressing both factors. Finally, the overexpression of RANTES and IL-6 in MCF-7 cells significantly increased the in vivo tumor growth. Collectively, our data suggest that the simultaneous expression of IL-6 and RANTES produces a more aggressive phenotype in breast cancer cells and provide evidence that IL-6 and RANTES might represent potential targets for novel therapeutic strategies aimed to block the tumor-stroma interaction.

High CCL5 expression is associated with osteosarcoma metastasis and poor prognosis of patients with osteosarcoma

Osteosarcoma is the most common primary malignant tumor of the skeletal system and is characterized by an aggressive clinical course and high metastatic potential. Regulated upon Activation Normal T cell Expressed and Secreted, also termed C‑C motif chemokine ligand 5 (CCL5), is associated with metastasis and poor prognosis in various types of cancer. The aim of the current study was to investigate the association between CCL5 expression and clinicopathological features and prognosis in patients with osteosarcoma. Tissue microarrays and reverse transcription‑quantitative polymerase chain reaction and immunohistochemistry were used to examine the expression of CCL5 in human osteosarcoma tissues. The prognostic value of CCL5 expression was evaluated by the Kaplan‑Meier method and Cox proportional hazards regression model. The rate of high CCL5 expression was significantly higher in metastatic osteosarcomas than in osteosarcomas without metastases. The overall survival rates (P=0.001) and the metastasis‑free survival rates (P<0.001) of the low CCL5 expression group were significantly higher than the CCL5 high expression group. Multivariate Cox regression analysis indicated that CCL5 expression had independent predictive value for the prognosis of patients with osteosarcoma. In conclusion, the data of the current study indicated that CCL5 may serve as a biomarker for prognosis of osteosarcoma, and may be a potential molecular target for osteosarcoma therapy.

Neutrophils drive accelerated tumor progression in the collagen-dense mammary tumor microenvironment

Background

High mammographic density has been correlated with a 4-fold to 6-fold increased risk of developing breast cancer, and is associated with increased stromal deposition of extracellular matrix proteins, including collagen I. The molecular and cellular mechanisms responsible for high breast tissue density are not completely understood.

Methods

We previously described accelerated tumor formation and metastases in a transgenic mouse model of collagen-dense mammary tumors (type I collagen-α1 (Col1α1)^tm1Jae and mouse mammary tumor virus - polyoma virus middle T antigen (MMTV-PyVT)) compared to wild-type mice. Using ELISA cytokine arrays and multi-color flow cytometry analysis, we studied cytokine signals and the non-malignant, immune cells in the collagen-dense tumor microenvironment that may promote accelerated tumor progression and metastasis.

Results

Collagen-dense tumors did not show any alteration in immune cell populations at late stages. The cytokine signals in the mammary tumor microenvironment were clearly different between wild-type and collagen-dense tumors. Cytokines associated with neutrophil signaling, such as granulocyte monocyte-colony stimulated factor (GM-CSF), were increased in collagen-dense tumors. Depleting neutrophils with anti-Ly6G (1A8) significantly reduced the number of tumors, and blocked metastasis in over 80 % of mice with collagen-dense tumors, but did not impact tumor growth or metastasis in wild-type mice.

Conclusion

Our study suggests that tumor progression in a collagen-dense microenvironment is mechanistically different, with pro-tumor neutrophils, compared to a non-dense microenvironment.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-016-0703-7) contains supplementary material, which is available to authorized users.

Expression of Tumor-Related Macrophages and Cytokines After Surgery of Triple-Negative Breast Cancer Patients and its Implications

Background

Triple-negative breast cancer (TNBC) has negative expression of progesterone receptor (PR) and estrogen receptor (ER), and low expression of human epithelial growth factor receptor-2 (HER-2). This study aimed to investigate the expressional profile of cytokines in TNBC patients with significant expression of macrophages.

Material/Methods

Immunohistochemical (IHC) S-P staining method was used to detect the tumor-associated macrophages (TAMs) marker CD68 expression in 48 cases of TNBC samples. The correlation between CD68 expression and prognosis was analyzed. Expressions of key cytokines – interleukin-6 (IL-6), IL-10, IL-12, IL-1β, chemokine (C-C motif) ligand-5 (CCL-5), and macrophage inflammatory protein-2 (MIP-2) – were quantified by RT-PCR and enzyme-linked immunosorbent assay (ELISA).

Results

Thirty-four out of 48 TNBC samples (71.4%) had CD68-positive expression. IL-6 and CCL-5 were up-regulated in high-infiltrated tumors when compared to low-infiltrated samples. Other cytokines had no significant difference regarding the expression level across groups.

Conclusions

TAMs were up-regulated in most TNBC patients after the surgery. Its expression suggested unfavorable prognosis, especially in the high-infiltrated group. Those tumors with more macrophage also had elevated expression of cytokine IL-6 and chemotactic factor CCL-5, both of which have potency to be clinical index and drug target for TNBC.

Role of Chemokines in Non-Small Cell Lung Cancer: Angiogenesis and Inflammation

Non-small cell lung cancer (NSCLC) is one of the most common types of aggressive cancer. The tumor tissue, which shows an active angiogenesis, is composed of neoplastic and stromal cells, and an abundant inflammatory infiltrate. Angiogenesis is important to support tumor growth, while infiltrating cells contribute to the tumor microenvironment through the secretion of growth factors, cytokines and chemokines, important molecules in the progression of the disease. Chemokines are important in development, activation of the immune response, and physiological angiogenesis. Chemokines have emerged as important regulators in the pathophysiology of cancer. These molecules are involved in the angiogenesis/angiostasis balance and in the recruitment of tumor infiltrating hematopoietic cells. In addition, chemokines promote tumor cell survival, as well as the directing and establishment of tumor cells to metastasis sites. The findings summarized here emphasize the central role of chemokines as modulators of tumor angiogenesis and their potential role as therapeutic targets in the inflammatory process of NSCLC angiogenesis.

The role of inflammation in progression of breast cancer: Friend or foe? (Review)

There is a growing interest in the role of the microenvironment in cancer, however, it has been known for over one hundred years that the immune system plays a prominent role in cancer. Recent decades have revealed more and more data on how our own host response to cancer cells can help or hinder progression of the disease. Despite all this work it is surprising how little is known about the role of the immune system in human breast cancer development, as compared to other cancers. Recent successes of PD-1 blockade in treating multiple cancers, and new developments with other immune targets such as CTLA-4 and CSF-1 inhibitors, highlight that it is becoming ever more important that we understand the complexity of the immune and inflammatory systems in the development and progression of breast cancer. With this knowledge it may be possible to not only target therapy but also more accurately predict those patients that truly need it. This review summarises some of the most significant findings for the role of the immune system and inflammatory response in breast cancer progression. Focusing on how the inflammatory microenvironment may be involved in the progression of pre-invasive ductal carcinoma in situ to invasive breast cancer. It will also discuss the use of immune markers as diagnostic and prognostic tools and summarise the state of the art of immune-therapeutics in breast cancer treatment.

Tumor-induced pressure in the bone microenvironment causes osteocytes to promote the growth of prostate cancer bone metastases

Cross-talk between tumor cells and their microenvironment is critical for malignant progression. Cross-talk mediators, including soluble factors and direct cell contact, have been identified, but roles for the interaction of physical forces between tumor cells and the bone microenvironment have not been described. Here, we report preclinical evidence that tumor-generated pressure acts to modify the bone microenvironment to promote the growth of prostate cancer bone metastases. Tumors growing in mouse tibiae increased intraosseous pressure. Application of pressure to osteocytes, the main mechanotransducing cells in bone, induced prostate cancer growth and invasion. Mechanistic investigations revealed that this process was mediated in part by upregulation of CCL5 and matrix metalloproteinases in osteocytes. Our results defined the critical contribution of physical forces to tumor cell growth in the tumor microenvironment, and they identified osteocytes as a critical mediator in the bone metastatic niche.

Mechanisms involved in breast cancer liver metastasis

Liver metastasis is a frequent occurrence in patients with breast cancer; however, the available treatments are limited and ineffective. While liver-specific homing of breast cancer cells is an important feature of metastasis, the formation of liver metastases is not random. Indeed, breast cancer cell factors contribute to the liver microenvironment. Major breakthroughs have been achieved recently in understanding breast cancer liver metastasis (BCLM). The process of liver metastasis consists of multiple steps and involves various factors from breast cancer cells and the liver microenvironment. A further understanding of the roles of breast cancer cells and the liver microenvironment is crucial to guide future work in clinical treatments. In this review we discuss the contribution of breast cancer cells and the liver microenvironment to liver metastasis, with the aim to improve therapeutic efficacy for patients with BCLM.

CCL5/CCR5 axis induces vascular endothelial growth factor-mediated tumor angiogenesis in human osteosarcoma microenvironment

Chemokines modulate angiogenesis and metastasis that dictate cancer development in tumor microenvironment. Osteosarcoma is the most frequent bone tumor and is characterized by a high metastatic potential. Chemokine CCL5 (previously called RANTES) has been reported to facilitate tumor progression and metastasis. However, the crosstalk between chemokine CCL5 and vascular endothelial growth factor (VEGF) as well as tumor angiogenesis in human osteosarcoma microenvironment has not been well explored. In this study, we found that CCL5 increased VEGF expression and production in human osteosarcoma cells. The conditioned medium (CM) from CCL5-treated osteosarcoma cells significantly induced tube formation and migration of human endothelial progenitor cells. Pretreatment of cells with CCR5 antibody or transfection with CCR5 specific siRNA blocked CCL5-induced VEGF expression and angiogenesis. CCL5/CCR5 axis demonstrably activated protein kinase Cδ (PKCδ), c-Src and hypoxia-inducible factor-1 alpha (HIF-1α) signaling cascades to induce VEGF-dependent angiogenesis. Furthermore, knockdown of CCL5 suppressed VEGF expression and attenuated osteosarcoma CM-induced angiogenesis in vitro and in vivo. CCL5 knockdown dramatically abolished tumor growth and angiogenesis in the osteosarcoma xenograft animal model. Importantly, we demonstrated that the expression of CCL5 and VEGF were correlated with tumor stage according the immunohistochemistry analysis of human osteosarcoma tissues. Taken together, our findings provide evidence that CCL5/CCR5 axis promotes VEGF-dependent tumor angiogenesis in human osteosarcoma microenvironment through PKCδ/c-Src/HIF-1α signaling pathway. CCL5 may represent a potential therapeutic target against human osteosarcoma.

Inflammation-induced hepatocellular carcinoma is dependent on CCR5 in mice

Human hepatocellular carcinoma (HCC) is an inflammation-induced cancer, which is the third-leading cause of cancer mortality worldwide. We investigated the role of the chemokine receptors, CCR5 and CCR1, in regulating inflammation and tumorigenesis in an inflammation-induced HCC model in mice. Multidrug resistance 2 gene (Mdr2)-knockout (Mdr2-KO) mice spontaneously develop chronic cholestatic hepatitis and fibrosis that is eventually followed by HCC. We generated two new strains from the Mdr2-KO mouse, the Mdr2:CCR5 and the Mdr2:CCR1 double knockouts (DKOs), and set out to compare inflammation and tumorigenesis among these strains. We found that in Mdr2-KO mice lacking the chemokine receptor, CCR5 (Mdr2:CCR5 DKO mice), but not CCR1 (Mdr2:CCR1 DKO), macrophage recruitment and trafficking to the liver was significantly reduced. Furthermore, in the absence of CCR5, reduced inflammation was also associated with reduced periductal accumulation of CD24(+) oval cells and abrogation of fibrosis. DKO mice for Mdr2 and CCR5 exhibited a significant decrease in tumor incidence and size.

CONCLUSIONS

Our results indicate that CCR5 has a critical role in both the development and progression of liver cancer. Therefore, we propose that a CCR5 antagonist can serve for HCC cancer prevention and treatment.

Inflammatory chemokines and metastasis--tracing the accessory

The tumor microenvironment consists of stromal cells and leukocytes that contribute to cancer progression. Cross-talk between tumor cells and their microenvironment is facilitated by a variety of soluble factors, including growth factors and cytokines such as chemokines. Due to a wide expression of chemokine receptors on cells in the tumor microenvironment, including tumor cells, chemokines affect various processes such as leukocyte recruitment, angiogenesis, tumor cell survival, tumor cell adhesion, proliferation, vascular permeability, immune suppression, invasion and metastasis. Inflammatory chemokines are instrumental players in cancer-related inflammation and significantly contribute to numerous steps during metastasis. Recruitment of myeloid-derived cells to metastatic sites is mainly mediated by the inflammatory chemokines CCL2 and CCL5. Tumor cell homing and extravasation from the circulation to distant organs are also regulated by inflammatory chemokines. Recent experimental evidence demonstrated that besides leukocyte recruitment, tumor cell-derived CCL2 directly activated endothelial cells and together with monocytes facilitated tumor cell extravasation, in a CCL2- and CCL5-dependent manner. Furthermore, CX3CL1 expression in the bone facilitated metastasis of CX3CR1 expressing tumor cells to this site. Current findings in preclinical models strongly suggest that inflammatory chemokines have an important role during metastasis and targeting of the chemokine axis might have a therapeutic potential.

Mesenchymal stem cell-derived CCL-9 and CCL-5 promote mammary tumor cell invasion and the activation of matrix metalloproteinases

Stromal chemokine gradients within the breast tissue microenvironment play a critical role in breast cancer cell invasion, a prerequisite to metastasis. To elucidate which chemokines and mechanisms are involved in mammary cell migration we determined whether mesenchymal D1 stem cells secreted specific chemokines that differentially promoted the invasion of mammary tumor cells in vitro. Results indicate that mesenchymal D1 cells produced concentrations of CCL5 and CCL9 4- to 5-fold higher than the concentrations secreted by 4T1 tumor cells (P < 0.01). Moreover, 4T1 tumor cell invasion toward D1 mesenchymal stem cell conditioned media (D1CM), CCL5 alone, CCL9 alone or a combination CCL5 and CCL9 was observed. The invasion of 4T1 cells toward D1 mesenchymal stem CM was dose-dependently suppressed by pre-incubation with the CCR1/CCR5 antagonist met-CCL5 (P < 0.01). Furthermore, the invasion of 4T1 cells toward these chemokines was prevented by incubation with the broad-spectrum MMP inhibitor GM6001. Additionally, the addition of specific MMP9/MMP13 and MMP14 inhibitors prevented the MMP activities of supernatants collected from 4T1 cells incubated with D1CM, CCL5 or CCL9. Taken together these data highlight the role of CCL5 and CCL9 produced by mesenchymal stem cells in mammary tumor cell invasion.

Autocrine CCL5 signaling promotes invasion and migration of CD133+ ovarian cancer stem-like cells via NF-κB-mediated MMP-9 upregulation

The concept of cancer stem cells (CSCs) proposes that solely CSCs are capable of generating tumor metastases. However, how CSCs maintain their invasion and migration abilities, the most important properties of metastatic cells, still remains elusive. Here we used CD133 to mark a specific population from human ovarian cancer cell line and ovarian cancer tissue and determined its hyperactivity in migration and invasion. Therefore, we labeled this population as cancer stem-like cells (CSLCs). In comparison to CD133- non-CSLCs, chemokine CCL5 and its receptors, CCR1, CCR3, and CCR5, were consistently upregulated in CSLCs, and most importantly, blocking of CCL5, CCR1, or CCR3 effectively inhibits the invasive capacity of CSLCs. Mechanistically, we identified that this enhanced invasiveness is mediated through nuclear factor κB (NF-κB) activation and the consequently elevated MMP9 secretion. Our results suggested that the autocrine activation of CCR1 and CCR3 by CCL5 represents one of major mechanisms underlying the metastatic property of ovarian CSLCs.

Development of a metastatic fluorescent Lewis Lung carcinoma mouse model: identification of mRNAs and microRNAs involved in tumor invasion

Cancer metastasis is the foremost cause of death in cancer patients. A series of observable pathological changes takes place during progression and metastasis of cancer, but the underlying genetic changes remain unclear. Therefore, new approaches are required, including insights from cancer mouse models. To examine the mechanisms involved in tumor metastasis, we first generated a stably transfected Lewis Lung carcinoma cell line expressing a far-red fluorescent protein, called Katushka. After in vivo growth in syngeneic mice, two fluorescent Lewis Lung cancer subpopulations were isolated from primary tumors and lung metastases. The metastasis-derived cells exhibited a significant improvement in in vitro invasive activity compared to the primary tumor-derived cells, using a quantitative invasion chamber assay. Moreover, expression levels of 84 tumor metastasis-related mRNAs, 88 cancer-related microRNAs as well as Dicer and Drosha were determined using RT-qPCR. Compared to the primary Lewis Lung carcinoma subculture, the metastasis-derived cells exhibited statistically significantly increased mRNA levels for several matrix metalloproteinases as well as hepatocyte growth factor (HGF) and spleen tyrosine kinase (SYK). A modest decrease in Drosha and Dicer mRNA levels was accompanied by significant downregulation of ten microRNAs, including miR-9 and miR-203, in the lung metastatic Lewis Lung carcinoma cell culture. Thus, a tool for cancer metastasis studies has been established and the model is well suited for the identification of novel microRNAs and mRNAs involved in malignant progression. Our results suggest that increases in metalloproteinase expression and impairment of microRNA processing are involved in the acquirement of metastatic ability.

Mechanisms regulating the secretion of the promalignancy chemokine CCL5 by breast tumor cells: CCL5's 40s loop and intracellular glycosaminoglycans

The chemokine CCL5 (RANTES) plays active promalignancy roles in breast malignancy. The secretion of CCL5 by breast tumor cells is an important step in its tumor-promoting activities; therefore, inhibition of CCL5 secretion may have antitumorigenic effects. We demonstrate that, in breast tumor cells, CCL5 secretion necessitated the trafficking of CCL5-containing vesicles on microtubules from the endoplasmic reticulum (ER) to the post-Golgi stage, and CCL5 release was regulated by the rigidity of the actin cytoskeleton. Focusing on the 40s loop of CCL5, we found that the (43)TRKN(46) sequence of CCL5 was indispensable for its inclusion in motile vesicles, and for its secretion. The TRKN-mutated chemokine reached the Golgi, but trafficked along the ER-to-post-Golgi route differently than the wild-type (WT) chemokine. Based on the studies showing that the 40s loop of CCL5 mediates its binding to glycosaminoglycans (GAG), we analyzed the roles of GAG in regulating CCL5 secretion. TRKN-mutated CCL5 had lower propensity for colocalization with GAG in the Golgi compared to the WT chemokine. Secretion of WT CCL5 was significantly reduced in CHO mutant cells deficient in GAG synthesis, and the WT chemokine acquired an ER-like distribution in these cells, similar to that of TRKN-mutated CCL5 in GAG-expressing cells. The release of WT CCL5 was also reduced after inhibition of GAG presence/synthesis by intracellular expression of heparanase, inhibition of GAG sulfation, and sulfate deprivation. The need for a (43)TRKN(46) motif and for a GAG-mediated process in CCL5 secretion may enable the future design of modalities that prevent CCL5 release by breast tumor cells.

CCR5 antagonist blocks metastasis of basal breast cancer cells

The roles of the chemokine CCL5 and its receptor CCR5 in breast cancer progression remain unclear. Here, we conducted microarray analysis on 2,254 human breast cancer specimens and found increased expression of CCL5 and its receptor CCR5, but not CCR3, in the basal and HER-2 genetic subtypes. The subpopulation of human breast cancer cell lines found to express CCR5 displayed a functional response to CCL5. In addition, oncogene transformation induced CCR5 expression, and the subpopulation of cells that expressed functional CCR5 also displayed increased invasiveness. The CCR5 antagonists maraviroc or vicriviroc, developed to block CCR5 HIV coreceptor function, reduced in vitro invasion of basal breast cancer cells without affecting cell proliferation or viability, and maraviroc decreased pulmonary metastasis in a preclinical mouse model of breast cancer. Taken together, our findings provide evidence for the key role of CCL5/CCR5 in the invasiveness of basal breast cancer cells and suggest that CCR5 antagonists may be used as an adjuvant therapy to reduce the risk of metastasis in patients with the basal breast cancer subtype.

Relationship between CCL5 and transforming growth factor-β1 (TGFβ1) in breast cancer

PURPOSE

Investigate circulating CCL5 in breast cancer patients and healthy controls, along with gene expression levels in corresponding tumour tissue and isolated primary stromal cells. Hormonal control of CCL5, and a potential relationship with TGFβ1, was also investigated.

METHODS

Circulating levels of CCL5 and TGFβ1 were measured in 102 breast cancer patients and 66 controls using ELISA. Gene expression levels (CCL5, CCR5, TGFβ1, TGFβRII) were quantified in corresponding tumour tissue (n = 43), normal tissue (n = 16), and isolated tumour (n = 22) and normal (n = 3) stromal cells using RQ-PCR. CCL5 and circulating menstrual hormones (LH, FSH, Oestradiol, Progesterone) were analysed in serum samples from healthy, premenopausal volunteers (n = 60).

RESULTS

TGFβ1 was significantly higher in breast cancer patients (Mean(SEM) 27.4(0.9)ng/ml) compared to controls (14.9(0.9)ng/ml). CCL5 levels decreased in the transition from node negative (59.6(3.7)ng/ml) to node positive disease (40.5(6.3)ng/ml) and increased again as the number of positive lymph nodes increased (⩾3 positive 50.95(9.8)ng/ml). A significant positive correlation between circulating CCL5 and TGFβ1 (r = 0.423, p<0.0001) was observed, and mirrored at the gene expression level in tumour tissue from the same patients (r = 0.44, p<0.001). CCL5, CCR5 and TGFβ1 expression was significantly higher in tumour compared to normal breast tissue (p < 0.001). A significant negative correlation was observed between circulating CCL5, Oestradiol and Progesterone (r = -0.50, r = -0.39, respectively, p < 0.05).

CONCLUSION

CCL5 expression is elevated in the tumour microenvironment. The data support a role for hormonal control of circulating CCL5 and also highlight a potentially important relationship between CCL5 and TGFβ1 in breast cancer.

Inflammatory mediators in breast cancer: coordinated expression of TNFα & IL-1β with CCL2 & CCL5 and effects on epithelial-to-mesenchymal transition

Background

The inflammatory chemokines CCL2 (MCP-1) & CCL5 (RANTES) and the inflammatory cytokines TNFα & IL-1β were shown to contribute to breast cancer development and metastasis. In this study, we wished to determine whether there are associations between these factors along stages of breast cancer progression, and to identify the possible implications of these factors to disease course.

Methods

The expression of CCL2, CCL5, TNFα and IL-1β was determined by immunohistochemistry in patients diagnosed with: (1) Benign breast disorders (=healthy individuals); (2) Ductal Carcinoma In Situ (DCIS); (3) Invasive Ducal Carcinoma without relapse (IDC-no-relapse); (4) IDC-with-relapse. Based on the results obtained, breast tumor cells were stimulated by the inflammatory cytokines, and epithelial-to-mesenchymal transition (EMT) was determined by flow cytometry, confocal analyses and adhesion, migration and invasion experiments.

Results

CCL2, CCL5, TNFα and IL-1β were expressed at very low incidence in normal breast epithelial cells, but their incidence was significantly elevated in tumor cells of the three groups of cancer patients. Significant associations were found between CCL2 & CCL5 and TNFα & IL-1β in the tumor cells in DCIS and IDC-no-relapse patients. In the IDC-with-relapse group, the expression of CCL2 & CCL5 was accompanied by further elevated incidence of TNFα & IL-1β expression. These results suggest progression-related roles for TNFα and IL-1β in breast cancer, as indeed indicated by the following: (1) Tumors of the IDC-with-relapse group had significantly higher persistence of TNFα and IL-1β compared to tumors of DCIS or IDC-no-relapse; (2) Continuous stimulation of the tumor cells by TNFα (and to some extent IL-1β) has led to EMT in the tumor cells; (3) Combined analyses with relevant clinical parameters suggested that IL-1β acts jointly with other pro-malignancy factors to promote disease relapse.

Conclusions

Our findings suggest that the coordinated expression of CCL2 & CCL5 and TNFα & IL-1β may be important for disease course, and that TNFα & IL-1β may promote disease relapse. Further in vitro and in vivo studies are needed for determination of the joint powers of the four factors in breast cancer, as well as analyses of their combined targeting in breast cancer.

Snail-mediated regulation of reactive oxygen species in ARCaP human prostate cancer cells

Reactive oxygen species increases in various diseases including cancer and has been associated with induction of epithelial-mesenchymal transition (EMT), as evidenced by decrease in cell adhesion-associated molecules like E-cadherin, and increase in mesenchymal markers like vimentin. We investigated the molecular mechanisms by which Snail transcription factor, an inducer of EMT, promotes tumor aggressiveness utilizing ARCaP prostate cancer cell line. An EMT model created by Snail overexpression in ARCaP cells was associated with decreased E-cadherin and increased vimentin. Moreover, Snail-expressing cells displayed increased concentration of reactive oxygen species (ROS), specifically, superoxide and hydrogen peroxide, in vitro and in vivo. Real Time PCR profiling demonstrated increased expression of oxidative stress-responsive genes, such as aldehyde oxidase I, in response to Snail. The ROS scavenger, N-acetyl cysteine partially reversed Snail-mediated EMT after 7 days characterized by increased E-cadherin levels and decreased ERK activity, while treatment with the MEK inhibitor, UO126, resulted in a more marked effect by 3 days, characterized by cells returning back to the epithelial morphology and increased E-cadherin. In conclusion, this study shows for the first time that Snail transcription factor can regulate oxidative stress enzymes and increase ROS-mediated EMT regulated in part by ERK activation. Therefore, Snail may be an attractive molecule for therapeutic targeting to prevent tumor progression in human prostate cancer.

CCL5 as an adjuvant for cancer immunotherapy

IMPORTANCE OF THE FIELD

To date cancer immunotherapy has only achieved limited clinical efficacy, thus more efficient immunotherapeutic approaches need to be explored. The CC chemokine CCL5 plays a role in chemoattraction and activation of immune cells implying its potential clinical application as an adjuvant for boosting anti-tumor immunity, although an effect on carcinogenesis and tumor cell invasiveness is also reported to be associated with CCL5.

AREAS COVERED IN THIS REVIEW

Recent progress in exploiting CCL5 as an adjuvant for cancer prevention and treatment, and updated understanding on how CCL5 is involved in tumor invasiveness and carcinogenesis.

WHAT THE READER WILL GAIN

CCL5 represents a natural adjuvant for enhancing anti-tumor immune responses. However, animal experiments and clinical reports suggest that CCL5 plays a role in carcinogenesis and invasiveness of tumor cells. Therefore, a CCL5-based cancer therapeutic approach needs to avoid the CCL5-associated potential detrimental effects.

TAKE HOME MESSAGE

CCL5 has a pre-eminent role in chemotaxis and activation of a wide spectrum of immune cells. CCL5 functions as an adjuvant to boost anti-tumor immunity by diverse protocols such as co-immunization of recombinant CCL5 protein with tumor-associated antigen, vaccination with CCL-5-expressing tumor cells, or viral vector delivery of CCL5 cDNA into growing tumor. CCL5 may also promote tumor cell survival, proliferation and invasion by different mechanisms.

Metastasis-inducing S100A4 and RANTES cooperate in promoting tumor progression in mice

BACKGROUND

The tumor microenvironment has been described as a critical milieu determining tumor growth and metastases. A pivotal role of metastasis-inducing S100A4 in the development of tumor stroma has been proven in animal models and verified in human breast cancer biopsies. Expression and release of S100A4 has been shown in various types of stroma composing cells, including fibroblasts and immune cells. However, the events implicated in upstream and downstream pathways regulating the activity of the extracellular S100A4 protein in the tumor milieu remain unsolved.

METHODOLOGY/PRINCIPAL FINDINGS

We studied the interplay between the tumor cell-derived cytokine regulated-upon-activation, normal T-cell expressed and secreted (RANTES; CCL5) and S100A4 which were shown to be critical factors in tumor progression. We found that RANTES stimulates the externalization of S100A4 via microparticle shedding from the plasma membrane of tumor and stroma cells. Conversely, the released S100A4 protein induces the upregulation of fibronectin (FN) in fibroblasts and a number of cytokines, including RANTES in tumor cells as well as stimulates cell motility in a wound healing assay. Importantly, using wild type and S100A4-deficient mouse models, we demonstrated a substantial influence of tumor cell-derived RANTES on S100A4 release into blood circulation which ultimately increases the metastatic burden in mice.

CONCLUSIONS/SIGNIFICANCE

Altogether, the data presented strongly validate the pro-metastatic function of S100A4 in the tumor microenvironment and define how the tumor cell-derived cytokine RANTES acts as a critical regulator of S100A4-dependent tumor cell dissemination. Additionally, for the first time we demonstrated the mechanism of S100A4 release associated with plasma membrane microparticle shedding from various cells types.

Functional and Molecular Alterations in T Cells Induced by CCL5

To delineate whether, and the extent to which, CCL5 could impact T cell function we examined cytokine production and proliferative ability following CCL5 treatment in vitro. We report a decreased ability of splenic T cells to produce IFN-? and TNF-a as well as proliferate in response to crosslinking with antibody to CD3 after 72, but not 24 hours of CCL5 exposure. To identify a mechanism by which CCL5 modulated T cell function, we examined T cell receptor translocation and lipid raft clustering. After exposure to CCL5, T cells were less efficient at translocating the TCR and clustering lipid rafts. Since TCR translocation and lipid raft clustering are required for creation of an immunological synapse, these data suggest that extended exposure to CCL5 may impact T cell effector function by modulating the ability to create a functional immunological synapse.

IL-12 can target human lung adenocarcinoma cells and normal bronchial epithelial cells surrounding tumor lesions

Background

Non small cell lung cancer (NSCLC) is a leading cause of cancer death. We have shown previously that IL-12rb2 KO mice develop spontaneously lung adenocarcinomas or bronchioalveolar carcinomas.

Aim of the study was to investigate i) IL-12Rβ2 expression in human primary lung adenocarcinomas and in their counterparts, i.e. normal bronchial epithelial cells (NBEC), ii) the direct anti-tumor activity of IL-12 on lung adenocarcinoma cells in vitro and vivo, and the mechanisms involved, and iii) IL-12 activity on NBEC.

Methodology/Principal Findings

Stage I lung adenocarcinomas showed significantly (P = 0.012) higher frequency of IL-12Rβ2 expressing samples than stage II/III tumors. IL-12 treatment of IL-12R⁺ neoplastic cells isolated from primary adenocarcinoma (n = 6) inhibited angiogenesis in vitro through down-regulation of different pro-angiogenic genes (e.g. IL-6, VEGF-C, VEGF-D, and laminin-5), as assessed by chorioallantoic membrane (CAM) assay and PCR array. In order to perform in vivo studies, the Calu6 NSCLC cell line was transfected with the IL-12RB2 containing plasmid (Calu6/β2). Similar to that observed in primary tumors, IL-12 treatment of Calu6/β2⁺ cells inhibited angiogenesis in vitro. Tumors formed by Calu6/β2 cells in SCID/NOD mice, inoculated subcutaneously or orthotopically, were significantly smaller following IL-12 vs PBS treatment due to inhibition of angiogenesis, and of IL-6 and VEGF-C production. Explanted tumors were studied by histology, immuno-histochemistry and PCR array. NBEC cells were isolated and cultured from lung specimens of non neoplastic origin. NBEC expressed IL-12R and released constitutively tumor promoting cytokines (e.g. IL-6 and CCL2). Treatment of NBEC with IL-12 down-regulated production of these cytokines.

Conclusions

This study demonstrates that IL-12 inhibits directly the growth of human lung adenocarcinoma and targets the adjacent NBEC. These novel anti-tumor activities of IL-12 add to the well known immune-modulatory properties of the cytokine and may provide a rational basis for the development of a clinical trial.

CCL5 secreted by senescent aged fibroblasts induces proliferation of prostate epithelial cells and expression of genes that modulate angiogenesis

There is increased interest in the effects of secretory products from aged cells on promoting both benign and malignant cell growth. We identified a human fibroblast line, AG04382, from an aged donor that naturally demonstrated senescence-associated features and whose conditioned media significantly induced proliferation of benign prostatic hyperplasia (BPH1) cells. Candidate cytokines mediating this effect were identified with protein arrays and validated by ELISA. We found that the AG04382 fibroblast line secreted high levels of CXCL5, CCL5, and CCL2, but relative to the other lines, its conditioned media was unique in its increased expression of CCL5. Blocking studies using specific antibodies against CXCL5, CCL5, and CCL2 in the conditioned media of AG04382 showed that only CCL5 contributed significantly to BPH1 proliferation. Stimulation of BPH1 cells with rhuCCL5 resulted in increased proliferation and migration, as well as significant changes in the expression of genes that influence angiogenesis. These data suggest that CCL5 is a candidate chemokine secreted by aged cells that promotes prostate growth and regulates angiogenesis.

Immunological investigation of the hepatic tissue from infants with biliary atresia

PURPOSE

Matrix metalloproteinases (MMPs) and their endogenous tissue inhibitors [tissue inhibitors of metalloproteinases (TIMPs)] have been implicated in tissue injury and remodeling in many organs. The objective of this study was to evaluate the expression of MMP-3 and -9, and TIMP-1, -2, and -3 and their relationship to liver fibrosis in infants with biliary atresia.

METHODS

The expression of MMP-3 and-9 and TIMP-1, -2 and -3 was investigated in liver tissue samples of nine patients with biliary atresia. In addition, the expression of CCR-4 and CCR-5 was analyzed to investigate the activation of Th1 and Th2 cells. The mRNA levels were measured by semiquantitative reverse transcriptase polymerase chain reaction.

RESULTS

The expression of MMP-3 was higher than that of MMP-9 in all samples (P < 0.01). The expression of TIMP-1 was higher than that of TIMP-2 and -3 in all samples (P < 0.01). The expression of CCR-5 was higher than that of CCR-4 (P < 0.05), which implied higher activation of Th1 cells relative to Th2 cells.

CONCLUSION

Our findings suggest that MMP-3, possibly induced by Th1 cytokines, and its balance with TIMP-1, may be one of the factors involved in the pathogenesis of biliary atresia.

Concomitant expression of the chemokines RANTES and MCP-1 in human breast cancer: a basis for tumor-promoting interactions

The chemokines RANTES (CCL5) and MCP-1 (CCL2) were suggested to contribute, independently, to breast malignancy. In the present study, we asked if the two chemokines are jointly expressed in clinical samples of breast cancer patients, and do they interact in breast tumor cells. We found that RANTES and MCP-1 were expressed by breast tumor cells in primary tumors of Ductal Carcinoma In Situ and of Invasive Ductal Carcinoma, but minimally in normal breast epithelial duct cells. The chemokines were also detected in metastases and pleural effusions. Novel findings showed that co-expression of RANTES and MCP-1 in the same tumor was associated with more advanced stages of disease, suggesting that breast tumors "benefit" from interactions between the two chemokines. Accordingly, MCP-1 significantly promoted the release of RANTES from endogenous pre-made vesicles, in an active process that depended on calcium from intracellular and extracellular sources, and on intracellular transport of RANTES towards exocytosis. Our findings show a chemokine-triggered release of stored pro-malignancy chemokine from breast tumor cells. These observations support a major tumor-promoting role for co-expression of the chemokines in breast malignancy, and agree with the significant association of joint RANTES and MCP-1 expression with advanced stages of breast cancer.

Chemokine decoy receptor d6 plays a negative role in human breast cancer

Chemokine binding protein D6 is a promiscuous decoy receptor that can inhibit inflammation in vivo; however, the role it plays in cancer is not well known yet. In this study, we showed for the first time that human breast cancer differentially expressed D6 and the expression could be regulated by some cytokines. More importantly, overexpression of D6 in human breast cancer cells inhibits proliferation and invasion in vitro and tumorigenesis and lung metastasis in vivo. This inhibition is associated with decreased chemokines (e.g., CCL2 and CCL5), vessel density, and tumor-associated macrophage infiltration. Furthermore, D6 expression is inversely correlated to lymph node metastasis as well as clinical stages, but positively correlated to disease-free survival rate in cancer patients. Therefore, D6 plays a negative role in the growth and metastasis of breast cancer.

The inflammatory chemokines CCL2 and CCL5 in breast cancer

A causal role was recently attributed to inflammation in many malignant diseases, including breast cancer. The different inflammatory mediators that are involved in this disease include cells, cytokines and chemokines. Of these, many studies have addressed the involvement and roles of the inflammatory chemokines CCL2 (MCP-1) and CCL5 (RANTES) in breast malignancy. While minimally expressed by normal breast epithelial duct cells, both chemokines are highly expressed by breast tumor cells at primary tumor sites, indicating that CCL2 and CCL5 expression is acquired in the course of malignant transformation, and suggesting that the two chemokines play a role in breast cancer development and/or progression. Supporting this possibility are findings showing significant associations between CCL2 and CCL5 and more advanced disease course and progression. Furthermore, studies in animal model systems have shown active and causative roles for the two chemokines in this disease. In line with the tumor-promoting roles of CCL2 and CCL5 in breast cancer, the two chemokines were shown to mediate many types of tumor-promoting cross-talks between the tumor cells and cells of the tumor microenvironment: (1) they shift the balance at the tumor site between different leukocyte cell types by increasing the presence of deleterious tumor-associated macrophages (TAM) and inhibiting potential anti-tumor T cell activities; (2) of the two chemokines, mainly CCL2 promotes angiogenesis; (3) CCL2 and CCL5 which are expressed by cells of the tumor microenvironment osteoblasts and mesenchymal stem cells play a role in breast metastatic processes. In addition, both chemokines act directly on the tumor cells to promote their pro-malignancy phenotype, by increasing their migratory and invasion-related properties. Together, the overall current information suggests that CCL2 and CCL5 are inflammatory mediators with pro-malignancy activities in breast cancer, and that they should be considered as potential therapeutic targets for the limitation of this disease.

The chemokine CCL5 as a potential prognostic factor predicting disease progression in stage II breast cancer patients

PURPOSE

The aim of this study was to determine the prognostic value of the chemokine CCL5, considered as a promalignancy factor in breast cancer, in predicting breast cancer progression and to evaluate its ability to strengthen the prognostic significance of other biomarkers.

EXPERIMENTAL DESIGN

The expression of CCL5, alone and in conjunction with estrogen receptor (ER)-alpha, ER-beta, progesterone receptor (PR), and HER-2/neu (ErbB2), was determined in breast tumor cells by immunohistochemistry. The study included 142 breast cancer patients, including individuals in whom disease has progressed.

RESULTS

Using Cox proportional hazard models, univariate analysis suggested that, in stage I breast cancer patients, CCL5 was not a significant predictor of disease progression. In contrast, in stage II patients, the expression of CCL5 (CCL5(+)), the absence of ER-alpha (ER-alpha(-)), and the lack of PR expression (PR(-)) increased significantly the risk for disease progression (P = 0.0045, 0.0041, and 0.0107, respectively). The prognostic strength of CCL5, as well as of ER-alpha(-), improved by combining them together (CCL5(+)/ER-alpha(-): P = 0.0001), being highly evident in the stage IIA subgroup [CCL5(+)/ER-alpha(-) (P = 0.0003); ER-alpha(-) (P = 0.0315)]. In the stage II group as a whole, the combinations of CCL5(-)/ER-alpha(+) and CCL5(-)/PR(+) were highly correlated with an improved prognosis. Multivariate analysis indicated that, in stage II patients, ER-alpha and CCL5 were independent predictors of disease progression.

CONCLUSIONS

CCL5 could be considered as a biomarker for disease progression in stage II breast cancer patients, with the CCL5(+)/ER-alpha(-) combination providing improved prediction of disease progression, primarily in the stage IIA subgroup.

Tumor-derived CCL5 does not contribute to breast cancer progression

Besides functioning as a chemotactic factor, CCL5 has been associated with progression of disease in women with breast cancer, immune modulation and metastasis. Here we asked whether CCL5 produced by tumor cells contributed to growth or metastasis of breast cancer. For this purpose, we used two murine mammary carcinomas, the 4T1 tumor which is metastatic and constitutively expresses CCL5, and the 168 tumor which is not metastatic and does not constitutively express CCL5. RNA interference was used to inhibit CCL5 expression from the 4T1 tumor, and a CCL5 transgene was used to express CCL5 by the 168 tumor. Six different clones of 4T1 that exhibited stable reduction in CCL5 expression, and three different clones of 168 that exhibited stable CCL5 expression were compared to the parental tumors and vector transfected controls. Significantly, in both models, tumor-derived CCL5 expression did not correlate with MHC expression, growth rate, or metastatic ability of the tumors. These results show that tumor-derived CCL5 expression alone does not make a significant contribution to breast cancer progression.

The multifaceted roles of chemokines in malignancy

Tumor development and progression are multifactorial processes, regulated by a large variety of intrinsic and microenvironmental factors. A key role in cancer is played by members of the chemokine superfamily. Chemokines and their receptors are expressed by tumor cells and by host cells, in primary tumors and in specific metastatic loci. The effects of chemokines on tumorigenesis are diverse: While some members of the superfamily significantly support this process, others inhibit fundamental events required for tumor establishment and metastasis. The current review describes the multifaceted roles of chemokines in malignancy, addressing four major aspects of their activities: (1) inducing leukocyte infiltration to tumors and regulating immune functions, with emphasis on tumor-associated macrophages (and the chemokines CCL2, CCL5), T cells (and the chemokines CXCL9, CXCL10) and dendritic cells (and the chemokines CCL19, CCL20, CCL21); (2) directing the homing of tumor cells to specific metastatic sites (the CXCL12-CXCR4 axis); (3) regulating angiogenic processes (mainly the ELR(+)-CXC and non-ELR-CXC chemokines); (4) acting directly on the tumor cells to control their malignancy-related functions. Together, these different chemokine functions establish a net of interactions between the tumor cells and their microenvironment, and partly dictate the fate of the malignancy cascade.