Differential CXC receptor expression in colorectal carcinomas

Colorectal Cancer: The Contribution of CXCL12 and Its Receptors CXCR4 and CXCR7

Simple Summary

Many signaling pathways are involved in cancer progression, and among these pathways, the CXCL12 axis and its two receptors CXCR4 and CXCR7 are well described for many cancers. This review presents the current knowledge on the role played by each of the actors of this axis in colorectal cancer and on its consideration in the development of new therapeutic strategies.

Abstract

Colorectal cancer is one of the most common cancers, and diagnosis at late metastatic stages is the main cause of death related to this cancer. This progression to metastasis is complex and involves different molecules such as the chemokine CXCL12 and its two receptors CXCR4 and CXCR7. The high expression of receptors in CRC is often associated with a poor prognosis and aggressiveness of the tumor. The interaction of CXCL12 and its receptors activates signaling pathways that induce chemotaxis, proliferation, migration, and cell invasion. To this end, receptor inhibitors were developed, and their use in preclinical and clinical studies is ongoing. This review provides an overview of studies involving CXCR4 and CXCR7 in CRC with an update on their targeting in anti-cancer therapies.

Fluorescence Molecular Targeting of Colon Cancer to Visualize the Invisible

Colorectal cancer (CRC) is a common cause of cancer and cancer-related death. Surgery is the only curative modality. Fluorescence-enhanced visualization of CRC with targeted fluorescent probes that can delineate boundaries and target tumor-specific biomarkers can increase rates of curative resection. Approaches to enhancing visualization of the tumor-to-normal tissue interface are active areas of investigation. Nonspecific dyes are the most-used approach, but tumor-specific targeting agents are progressing in clinical trials. The present narrative review describes the principles of fluorescence targeting of CRC for diagnosis and fluorescence-guided surgery with molecular biomarkers for preclinical or clinical evaluation.

A Pilot Study Investigating the Expression Levels of Pluripotency-Associated Genes in Rectal Swab Samples for Colorectal Polyp and Cancer Diagnosis and Prognosis

Change in gene expression is inevitable in cancer development. With more studies demonstrating the contributions of cancer stem cells (CSCs) in colorectal cancer (CRC) development, this study is aimed at investigating whether rectal swab specimen serves as a tool for detection of dysregulation of CSC or stem cell (SC) markers and at evaluating its potential as a new promising screening method for high-risk patients. Expression levels of 15 pluripotency-associated genes were assessed by quantitative PCR in 53 rectal swab specimens referred for endoscopic screening. Dysregulated genes and joint panels based on such genes were examined for their diagnostic potentials for both polyp and CRC. Out of 15 genes, Oct4, CD26, c-MYC, and CXCR4 showed significantly differential expression among normal, polyp, and CRC patients. A panel of Oct4 and CD26 showed an AUC value of 0.80 (p = 0.003) in identifying CRC patients from polyp/normal subjects, with sensitivity and specificity of 84.6% and 69.2%. A panel of c-MYC and CXCR4 achieved CRC/polyp identification with an AUC value of 0.79 (p = 0.002), with a sensitivity of 82.8% and specificity of 80.0%. The sensitivity for polyp and CRC was 80.0% and 85.7%, respectively. Further analysis showed that higher c-MYC and CXCR4 level was detected in normal subjects who developed polyps after 5-6 years, in comparison with subjects with no lesion developed, and the AUC of the c-MYC and CXCR4 panel increased to 0.88 (p < 0.001), with sensitivity and specificity of 84.4% and 92.3%, respectively, when these patients were included in the polyp group. This study suggests that the Oct4 and CD26 panel is a promising biomarker for distinguishing CRC from normal and polyp patients, whereas the c-MYC and CXCR4 panel may identify polyp and CRC from normal individuals.

Fibroblast activation protein α-positive pancreatic stellate cells promote the migration and invasion of pancreatic cancer by CXCL1-mediated Akt phosphorylation

Background

Pancreatic stellate cells (PSCs) is a highly heterogeneic stroma cell population in pancreatic cancer tissue. Interaction between PSCs and pancreatic cancer cells has not been well elucidated. This research was aimed to study the relationship between fibroblast activation protein α (FAPα)-positive (FAPα+) PSCs and the pathological features and prognosis of pancreatic cancer. The effects and mechanisms of FAPα + PSCs in pancreatic cancer were also explored.

Methods

Tissue microarray analysis was used to detect FAPα expression in tumor and adjacent tissues. The relationship between FAPα expression and pancreatic pathological features and prognosis were analyzed. The effects of FAPα+ PSCs on the proliferation, migration and invasion of pancreatic cancer were detected in vitro and in vivo. A cytokine chip was used to detect the differential expression of cytokines in FAPα-positive (FAPα+) and FAPα-negative (FAPα-) PSCs. Phosphorylated tyrosine kinase receptors were detected by a human phosphotyrosine kinase receptor protein chip. The interaction between differential cytokine and tyrosine kinase receptors was detected by immunoprecipitation.

Results

Compared with the adjacent tissues, pancreatic cancer stromal tissues showed high FAPα expression. FAPα was mainly expressed in the PSCs. FAPα+ PSCs were associated with lymph node metastasis. Higher numbers of FAPα+ PSCs predicted shorter survival. Pancreatic cancer cells released TGFβ1 and induced PSCs to express FAPα. FAPα+ PSCs released the chemokine CXCL1 and promoted the phosphorylation of the tyrosine kinase receptors EphB1 and EphB3 in pancreatic cancer cells. CXCL1, EphrinB1, and EphrinB3 worked together to promote the migration and invasion of pancreatic cancer cells by Akt phosphorylation. Talabostat (PT100), an FAPα inhibitor, inhibited the roles of FAPα+ PSCs.

Conclusions

FAPα+ PSCs can promote the migration, invasion, and metastasis of pancreatic cancer by the Akt signaling pathway. This interaction of FAPα+ PSCs with pancreatic cancer cells may become a new strategy for the comprehensive treatment of pancreatic cancer.

The Role of CXCL12 Axis in Lung Metastasis of Colorectal Cancer

This study aimed to explore the mechanism of lung metastases of colorectal cancer. The expression of CXCR4, CXCR7, and CXCL12 in colorectal cancer and lung metastases was analyzed by the immunohistochemical (IHC) method. Further, the study aimed at getting new insights into the role of CXCL12 in lung metastasis. A total of 41 patients who underwent surgical resections for both colorectal cancer and lung metastasis were retrospectively selected for this study. Also, 41 patients who underwent lung resection for benign lung disease were selected as the control group. In the in vivo experiment, the mice were injected with exosomes isolated from CT26. The mice with and without injection were sacrificed 3 weeks later. The lung tissue was analyzed by the IHC method and quantitative real-time PCR. The expression of CXCR7 and CXCL12 was significantly higher in lung metastases than in paired primary lesions. The expression of CXCL12 was significantly higher in the noncancerous lung tissue of patients with CRC than in patients with benign lung disease. Also, the expression of CXCL12 in the lung was higher in mice with exosome education. The results inferred that the expression of CXCR7 and CXCL12 was significantly higher in lung metastases than in primary tumors. Their combination could promote colorectal cancer lung metastasis. The expression of CXCL12 was elevated before metastasis. And this effect was induced by exosomes.

Molecular fluorescence-guided surgery of peritoneal carcinomatosis of colorectal origin: A narrative review

Patients with peritoneal carcinomatosis (PC) from colorectal origin may undergo cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC) as a curative approach. One major prognostic factor that affects survival is completeness of cytoreduction. Molecular Fluorescence Guided Surgery (MFGS) is a novel intraoperative imaging technique that may improve tumor identification in the future, potentially preventing over- and under-treatment in these patients. This narrative review outlines a chronological overview of MFGS development in patients with PC of colorectal origin.

Clinicopathologic Significance of CXCL12 and CXCR4 Expressions in Patients with Colorectal Cancer

Background

Colorectal cancer (CRC) is both a global and national burden, being the third most common malignancy in men and the second in women, worldwide. The prognosis of CRC is affected by various factors like the histological grade, angiolymphatic invasion, and distant metastases. Metastasis is an intricate process; one of the possible mechanisms is through the interaction of the chemokines CXCL12 and CXCR4. This study aims to reveal the expression patterns of CXCL12 and CXCR4 in CRC.

Methods

The quantitative expressions of CXCL12 and CXCR4 messenger RNA (mRNA) were evaluated in 32 patients with adenocarcinoma-type CRC. Real-time polymerase chain reaction (qRT-PCR) was performed on formalin-fixed tissues. CXCL12 and CXCR4's expressions, clinicopathologic features, and the treatment response to the CRC were analysed.

Results

All tumour tissues showed higher levels of both chemokines compared to normal colonic tissue. The expression of CXCL12 mRNA was higher in rectal location (p = 0.04) with a tendency to be higher in later stages (p = 0.15), while the expression of CXCR4 was lower in tumours with a lymphatic invasion (p = 0.02), compared to their counterparts. There was no difference in the expression of CXCL12 and CXCR4 according to the patients' ages, gender, tumour differentiation, or response to chemotherapy.

Conclusion

Our study demonstrated that the mRNA expression of CXCL12 was significantly correlated with rectal location. CXCR4 mRNA expression was inversely correlated in tumours with a lymphatic invasion.

CXCR3 is a prognostic marker and a potential target for patients with solid tumors: a meta-analysis

OBJECTIVE

To deeply verify the clinical significance of CXCR3 in prediction of cancer patients' prognosis.

DATA SOURCES

We performed a meta-analysis including 12 studies searched from PubMed, Web of Science, Embase, and Cochrane databases. A total of 1,751 patients were used to analyze the association between CXCR3 and patients' prognosis, based on either overall survival or time to tumor progression.

STUDY SELECTION

Studies evaluating CXCR3 expression for predicting prognosis in human solid tumors were included.

RESULTS

It showed that patients with higher expression of CXCR3 had significantly shorter OS (pooled hazard ratio =2.315, 95% CI: 1.162-4.611, P=0.017). In addition, higher CXCR3 expression was associated with distant metastasis (yes vs no: pooled relative ratio [RR] =1.828, 95% CI: 1.140-2.931, P=0.012) in solid tumors and indicated advanced tumor stage (III/IV vs I/II, RR =2.656, 95% CI: 1.809-3.900, P<0.001) and lymph node metastasis (yes vs no: RR =2.28, 95% CI: 1.61-3.25, P<0.001) in colorectal cancer.

CONCLUSION

Our study highlights the role of CXCR3 as a potential prognostic marker and a promising therapeutic target in solid tumors.

The role of vitamin D in hepatic metastases from colorectal cancer

Colorectal cancer (CRC) represents a significant health burden worldwide, comprising approximately 10% of annual cancer cases globally. Hepatic metastases are the most common site of CRC metastasis, and are the leading cause of death in CRC patients. There is strong epidemiologic evidence for an inverse association between vitamin D status and risk of CRC; however, the role of vitamin D in the natural history of liver metastases has not yet been investigated. Several researchers have proposed hallmarks of metastases; crucially, metastases can be blocked by interrupting just one rate-limiting step. Vitamin D status has been implicated in each proposed hallmark of metastasis. The aim of this review is to examine the potential role for vitamin D in reducing the development of hepatic metastases from CRC and outline the candidate mechanisms by which vitamin D may mediate these effects. The results of ongoing randomised intervention trials are eagerly awaited to determine whether addressing vitamin D insufficiency in CRC patients could reduce the occurrence of liver metastases, and the consequent morbidity and mortality.

NF-κB signaling regulates cell-autonomous regulation of CXCL10 in breast cancer 4T1 cells

The chemokine CXCL10 and its receptor CXCR3 play a role in breast cancer metastasis to bone and osteoclast activation. However, the mechanism of CXCL10/CXCR3-induced intracellular signaling has not been fully investigated. To evaluate CXCL10-induced cellular events in the mouse breast cancer cell line 4T1, we developed a new synthetic CXCR3 antagonist JN-2. In this study, we observed that secretion of CXCL10 in the supernatant of 4T1 cells was gradually increased during cell growth. JN-2 inhibited basal and CXCL10-induced CXCL10 expression and cell motility in 4T1 cells. Treatment of 4T1 cells with CXCL10 increased the expression of P65, a subunit of the NF-κB pathway, via activation of the NF-κB transcriptional activity. Ectopic overexpression of P65 increased CXCL10 secretion and blunted JN-2-induced suppression of CXCL10 secretion, whereas overexpression of IκBα suppressed CXCL10 secretion. These results indicate that the CXCL10/CXCR3 axis creates a positive feedback loop through the canonical NF-κB signaling pathway in 4T1 cells. In addition, treatment of osteoblasts with conditioned medium from JN-2-treated 4T1 cells inhibited the expression of RANKL, a crucial cytokine for osteoclast differentiation, which resulted in an inhibitory effect on osteoclast differentiation in the co-culture system of bone marrow-derived macrophages and osteoblasts. Direct intrafemoral injection of 4T1 cells induced severe bone destruction; however, this effect was suppressed by the CXCR3 antagonist via downregulation of P65 expression in an animal model. Collectively, these results suggest that the CXCL10/CXCR3-mediated NF-κB signaling pathway plays a role in the control of autonomous regulation of CXCL10 and malignant tumor properties in breast cancer 4T1 cells.

CXCR3 in carcinoma progression

CXCR3 is a G-protein coupled receptor which binds to ELR-negative CXC chemokines that have been found to impact immune responses, vascular develop, and wound repair. More recently, CXCR3 has been examined in the context of cancer and increased expression in many human tumors has been correlated with poor prognosis in breast, melanoma, colon and renal cancer patients. Three variants of CXCR3 are identified so far (CXCR3-A, CXCR3-B and CXCR3-alt) with the two primary ones, CXCR3-A and CXCR3-B, considered to induce opposite physiological functions. Generally, CXCR3-A, the predominant form in hematopoietic cells, appears to mediate tumor "go" signaling via promoting cell proliferation, survival, chemotaxis, invasion and metastasis; while CXCR3-B, the main form on formed elements including epithelial cells, appears to mediate tumor "stop" signaling via promoting growth suppression, apoptosis and vascular involution. Thus, aberrant expression of the isoforms CXCR3-A and CXCR3-B could affect tumor progression. In this review, we have discussed the profiles of CXCR3 variants and related signaling, as well as the role of CXCR3 variants in cancer.

The role of toll-like receptors in colorectal cancer progression: evidence for epithelial to leucocytic transition

Toll-like receptors (TLRs) are expressed by immune cells, intestinal epithelium, and tumor cells. In the homeostatic setting, they help to regulate control over invading pathogens and maintain the epithelial lining of the large and small intestines. Aberrant expression of certain TLRs by tumor cells can induce growth inhibition while others contribute to tumorigenesis and progression. Activation of these TLRs can induce inflammation, tumor cell proliferation, immune evasion, local invasion, and distant metastasis. These TLR-influenced behaviors have similarities with properties observed in leukocytes, suggesting that tumors may be hijacking immune programs to become more aggressive. The concept of epithelial to leucocytic-transition (ELT) is proposed, akin to epithelial to mesenchymal transition, in which tumors develop the ability to activate leucocytic traits otherwise inaccessible to epithelial cells. Understanding the mechanisms of ELT could lead to novel therapeutic strategies for inhibiting tumor metastasis.

Chemokine receptor CCR6 expression is regulated by miR-518a-5p in colorectal cancer cells

Background

Recently, involvement of the chemokine/receptor system CCL20/CCR6 in colorectal cancer (CRC) progression was shown. Here, we analyzed the functional interaction of miRNA-518-5p (miR-518a-5p) with CCR6 and its impact on CCR6 expression in CRC cells.

Methods

MiR-518a-5p was identified by computer software to potentially interact with CCR6. Hence, functional implications of miR-518a-5p with the 3′UTR of CCR6 were analyzed using the Dual Luciferase Reporter assay system. Confirmation of the predicted target site for miR-518a-5p was achieved by site-directed mutagenesis of the seed sequence in the 3′UTR of CCR6 and subsequent application of the mutated seed sequence in a luciferase assay with miR-518a-5p mimics. Accordingly, two CRC cell lines (Caco-2 and HT-29) were transfected with miR-518a-5p miRNA mimics and gene and protein expression of CCR6 was monitored using qRT PCR and immunocytochemistry, respectively.

Results

Addition of miR-518a-5p led to significant down-regulation of luciferase activity (P < 0.05), which was significantly reversed in a reporter test system containing the mutated seed sequences in the 3′UTR of CCR6. Following transfection of CRC cell lines with miR-518a-5p mimics and subsequent monitoring of CCR6 expression showed significant down-regulation of CCR6 mRNA and CCR6 protein expression in both CRC cell lines under investigation (P < 0.05).

Conclusions

We have shown that miR-518a-5p functionally interacts with CCR6 and that transfection of CRC cells with miR-518a-5p leads to significant CCR6 down-regulation. Consequently, CCR6 expression is regulated by miR-518a-5p in CRC cells indicating that regulation of CCR6 expression by miR-518a-5p might be a regulatory mechanism involved in CRC pathogenesis.

Critical appraisal of quantitative PCR results in colorectal cancer research: can we rely on published qPCR results?

The use of real-time quantitative polymerase chain reaction (qPCR) in cancer research has become ubiquitous. The relative simplicity of qPCR experiments, which deliver fast and cost-effective results, means that each year an increasing number of papers utilizing this technique are being published. But how reliable are the published results? Since the validity of gene expression data is greatly dependent on appropriate normalisation to compensate for sample-to-sample and run-to-run variation, we have evaluated the adequacy of normalisation procedures in qPCR-based experiments. Consequently, we assessed all colorectal cancer publications that made use of qPCR from 2006 until August 2013 for the number of reference genes used and whether they had been validated. Using even these minimal evaluation criteria, the validity of only three percent (6/179) of the publications can be adequately assessed. We describe common errors, and conclude that the current state of reporting on qPCR in colorectal cancer research is disquieting. Extrapolated to the study of cancer in general, it is clear that the majority of studies using qPCR cannot be reliably assessed and that at best, the results of these studies may or may not be valid and at worst, pervasive incorrect normalisation is resulting in the wholesale publication of incorrect conclusions. This survey demonstrates that the existence of guidelines, such as MIQE, is necessary but not sufficient to address this problem and suggests that the scientific community should examine its responsibility and be aware of the implications of these findings for current and future research.

Altered CXCR3 isoform expression regulates prostate cancer cell migration and invasion

BACKGROUND

Carcinoma cells must circumvent the normally suppressive signals to disseminate. While often considered 'stop' signals for adherent cells, CXCR3-binding chemokines have recently been correlated positively with cancer progression though the molecular basis remains unclear.

RESULTS

Here, we examined the expression and function of two CXCR3 variants in human prostate cancer biopsies and cell lines. Globally, both CXCR3 mRNA and protein were elevated in localized and metastatic human cancer biopsies compared to normal. Additionally, CXCR3A mRNA level was upregulated while CXCR3B mRNA was downregulated in these prostate cancer specimens. In contrast to normal prostate epithelial cells (RWPE-1), CXCR3A was up to half the receptor in the invasive and metastatic DU-145 and PC-3 prostate cancer cells, but not in the localized LNCaP cells. Instead of inhibiting cell migration as in RWPE-1 cells, the CXCR3 ligands CXCL4/PF4 and CXCL10/IP10 promoted cell motility and invasiveness in both DU-145 and PC-3 cells via PLCβ3 and μ-calpain activation. CXCR3-mediated diminution of cell motility in RWPE-1 cells is likely a result of cAMP upregulation and m-calpain inhibition via CXCR3B signal transduction. Interestingly, overexpression of CXCR3B in DU-145 cells decreased cell movement and invasion.

CONCLUSION

These data suggest that the aberrant expression of CXCR3A and down-regulation of CXCR3B may switch a progression "stop" to a "go" signal to promote prostate tumor metastasis via stimulating cell migration and invasion.

Molecular mechanisms of liver metastasis

Colorectal cancer is the second most common cancer, and is the third leading cause of cancer-related death in Japan. The majority of these deaths is attributable to liver metastasis. Recent studies have provided increasing evidence that the chemokine-chemokine receptor system is a potential mechanism of tumor metastasis via multiple complementary actions: (a) by promoting cancer cell migration, invasion, survival and angiogenesis; and (b) by recruiting distal stromal cells (i.e., myeloid bone marrow-derived cells) to indirectly facilitate tumor invasion and metastasis. Here, we discuss recent preclinical and clinical data supporting the view that chemokine pathways are potential therapeutic targets for liver metastasis of colorectal cancer.

Selecting Potential Targetable Biomarkers for Imaging Purposes in Colorectal Cancer Using TArget Selection Criteria (TASC): A Novel Target Identification Tool

Peritoneal carcinomatosis (PC) of colorectal origin is associated with a poor prognosis. However, cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy is available for a selected group of PC patients, which significantly increases overall survival rates up to 30%. As a consequence, there is substantial room for improvement. Tumor targeting is expected to improve the treatment efficacy of colorectal cancer (CRC) further through 1) more sensitive preoperative tumor detection, thus reducing overtreatment; 2) better intraoperative detection and surgical elimination of residual disease using tumor-specific intraoperative imaging; and 3) tumor-specific targeted therapeutics. This review focuses, in particular, on the development of tumor-targeted imaging agents. A large number of biomarkers are known to be upregulated in CRC. However, to date, no validated criteria have been described for the selection of the most promising biomarkers for tumor targeting. Such a scoring system might improve the selection of the correct biomarker for imaging purposes. In this review, we present the TArget Selection Criteria (TASC) scoring system for selection of potential biomarkers for tumor-targeted imaging. By applying TASC to biomarkers for CRC, we identified seven biomarkers (carcinoembryonic antigen, CXC chemokine receptor 4, epidermal growth factor receptor, epithelial cell adhesion molecule, matrix metalloproteinases, mucin 1, and vascular endothelial growth factor A) that seem most suitable for tumor-targeted imaging applications in colorectal cancer. Further cross-validation studies in CRC and other tumor types are necessary to establish its definitive value.

CXC receptor-4 mRNA silencing abrogates CXCL12-induced migration of colorectal cancer cells

BACKGROUND

Interactions between CXCR4 and its ligand CXCL12 have been shown to be involved in cancer progression in colorectal cancer (CRC). We performed a comparative CXCL12/CXCR4 expression analysis and assessed the effect of external CXCL12 stimulation on migration of CRC cells without and with CXCR4 inhibition.

METHODS

Expression of CXCL12/CXCR4 was assessed by quantitative real-time PCR, ELISA and immunohistochemistry in resection specimens of 50 CRC patients as well as in the corresponding normal tissues and in three human CRC cell lines with different metastatic potential (Caco-2, SW480 and HT-29). Migration assays were performed after stimulation with CXCL12 and CXCR4 was inhibited by siRNA and neutralizing antibodies.

RESULTS

In CRC tissues CXCL12 was significantly down-regulated and CXCR4 was significantly up-regulated compared to the corresponding normal tissues. In cell lines CXCR4 was predominantly expressed in SW480 and less pronounced in HT-29 cells. CXCL12 was only detectable in Caco-2 cells. CXCL12 stimulation had no impact on Caco-2 cells but significantly increased migration of CXCR4 bearing SW480 and HT-29 cells. This effect was significantly abrogated by neutralizing anti-CXCR4 antibody as well as by CXCR4 siRNAs (P < 0.05).

CONCLUSIONS

CXCR4 expression was up-regulated in CRC and CXCL12 stimulation increased migration in CXCR4 bearing cell lines. Migration was inhibited by both neutralizing CXCR4 antibodies and CXCR4 siRNAs. Thus, the expression and functionality of CXCR4 might be associated with the metastatic potential of CRC cells and CXCL12/CXCR4 interactions might therefore constitute a promising target for specific treatment interventions.

Epithelial and mesenchymal phenotypic switchings modulate cell motility in metastasis

The most ominous stage of cancer progression is metastasis, or the dissemination of carcinoma cells from the primary site into distant organs. Metastases are often resistant to current extirpative therapies and even the newest biological agents cure only a small subset of patients. Therefore a greater understanding of tumor biology that integrates properties intrinsic to carcinomas with tissue environmental modulators of behavior is needed. In no aspect of tumor progression is this more evident than the acquisition of cell motility that is critical for both escape from the primary tumor and colonization. In this overview, we discuss how this behavior is modified by carcinoma cell phenotypic plasticity that is evidenced by reversible switching between epithelial and mesenchymal phenotypes. The presence or absence of intercellular adhesions mediate these switches and dictate the receptivity towards signals from the extracellular milieu. These signals, which include soluble growth factors, cytokines, and extracellular matrix embedded with matrikines and matricryptines will be discussed in depth. Finally, we will describe a new mode of discerning the balance between epithelioid and mesenchymal movement.