Induction of CD44 variant 9-expressing cancer stem cells might attenuate the efficacy of chemoradioselection and Worsens the prognosis of patients with advanced head and neck cancer

The CD44std and CD44v9 subpopulations in non-tumorigenic invasive SNU-423 cells present different features of cancer stem cells

Hepatocellular carcinoma (HCC) is a type of liver cancer, in which CD44 isoforms have been proposed as markers to identify cancer stem cells (CSCs). However, it is unclear what characteristics are associated with CSCs that exclusively express CD44 isoforms. The objective of the present study was to determine the expression of CD44 isoforms and their properties in CSCs. Analysis of transcriptomic data from HCC patient samples identified CD44v8-10 as a potential marker in HCC. In SNU-423 cells, CD44 expression was detected in over 99% of cells, and two CD44 isoforms, namely, CD44std and CD44v9, were identified in this cell line. CD44 subpopulations, including both CD44v9+ (CD44v9) and CD44v9- (CD44std) cells, were obtained by purification using a magnetic cell separation kit for human CD44v9+ cancer stem cells. CD44v9 cells showed greater potential for colony and spheroid formation, whereas CD44std cells demonstrated significant migration and invasion capabilities. These findings suggested that CD44std and CD44v9 may be used to identify features in CSC populations and provide insights into their roles in HCC.

Expression of CD44 variant 9 induces chemoresistance of gastric cancer by controlling intracellular reactive oxygen spices accumulation

BACKGROUND

CD44 variant 9 (CD44v9) has been reported to suppress reactive oxygen spices (ROS) in association with antioxidant factors such as glutathione (GSH) and glutathione peroxidase 2 (GPx2), resulting in promoted tumor growth.

METHODS

CD44v9 and GPx2 expression were investigated by immunohistochemistry in resected specimens from 193 gastric cancer (GC) patients without preoperative chemotherapy and in pretreatment biopsy specimens from 29 GC patients with preoperative chemotherapy. We analyzed the relationship between CD44v9 expression and clinicopathological factors, prognosis, and pathological response to chemotherapy. In GC cell lines, we examined the relationship between CD44v9 expression and chemotherapeutic sensitivity.

RESULTS

In patients without preoperative chemotherapy, CD44v9 expression was significantly associated with depth of invasion, lymphatic permeation, vascular invasion, distant metastasis and GPx2 expression. In multivariate analysis, CD44v9 expression was an independent poor prognosis factor for overall survival and recurrence-free survival. In patients with preoperative chemotherapy, CD44v9 expression was significantly associated with worse pathological response and GPx2 expression. In GC cell lines, downregulation of CD44v9 expression enhanced chemotherapeutic sensitivity to 5-fluorouracil with changing GSH and ROS levels.

CONCLUSIONS

CD44v9-positive expression was associated with chemotherapeutic resistance by controlling intracellular accumulated ROS, suggesting that CD44v9 may be a predictive biomarker for chemotherapy in GC.

Prognostic value of CD44v9 expression in human cancers: A systematic review and meta-analysis

BACKGROUND

The prognostic significance of CD44 variant-9 (CD44v9) expression in human cancers has been investigated in several studies, however, definite conclusion has not be reached. The aim of this systematic review and meta-analysis was to evaluate the prognostic significance of CD44v9 expression in various cancers.

METHODS

Three common databases were searched and retrieved studies were assessed using the inclusion and exclusion criteria. The further analyses for overall survival (OS), recurrence-free survival (RFS), and clinicopathological parameters were performed.

RESULTS

Fifteen studies containing 1633 cancer patients were included into this research. Patients with positive CD44v9 expression tended to have shorter OS (hazard ratio [HR] = 1.93, 95% confidence interval [CI] = 1.48-2.52, P < .01) and RFS (HR = 3.60, 95% CI = 1.52-8.53, P < .01) when compared with patients with negative CD44v9 expression. Positive CD44v9 expression was associated with larger tumor size (P = .04), deeper tumor invasion (P < .01), earlier lymph node metastasis (P < .01), and more advanced clinical stage (P < .01) when compared with negative CD44v9 expression.

CONCLUSION

Positive CD44v9 expression predicted worse prognosis in human cancers compared with negative CD44v9 expression. CD44v9 expression could serve as a prognostic factor of human cancers.

Stress-triggered YAP1/SOX2 activation transcriptionally reprograms head and neck squamous cell carcinoma for the acquisition of stemness

PURPOSE

The clinical importance of cancer stem cells (CSCs) in head and neck squamous cell carcinoma (HNSCC) is well recognized. However, a reliable method for the detection of functioning CSC has not yet been established. We hypothesized that YAP1, a transcriptional coactivator, and SOX2, a master transcription factor of SCC, may cooperatively induce stemness through transcriptional reprogramming.

METHODS

We immunohistochemically examined the expression of SOX2 and YAP1 in the CD44 variant 9 (CD44v9)-positive invasion front. A CSC-inducible module was identified through a combination of siRNAs and sphere formation assays. YAP1 and SOX2 interactions were analyzed in vitro.

RESULTS

The triple overexpression of SOX2, YAP1, and CD44v9 was significantly associated with poor prognosis. TCGA data revealed that the CSC-inducible module, which was related to EMT and angiogenesis, was significantly correlated with poor prognosis. The KLF7 expression, representatively chosen from the module, also correlated with poor prognosis and was essential for sphere formation and CSC propagation. Sphere stress-activated YAP1 enhanced SOX2 activity.

CONCLUSIONS

The stress-triggered activation of YAP1/SOX2 transcriptionally reprograms HNSCC for the acquisition of stemness. Triple SOX2, YAP1, and CD44v9 immunostaining assays may be useful for the selection of high-risk patients with functioning CSCs, and YAP1 targeting may lead to the development of a CSC-targeting therapy.

Hyaluronan-CD44 axis orchestrates cancer stem cell functions

The prominent role of CD44 in tumor cell signaling together with its establishment as a cancer stem cell (CSC) marker for various tumor entities imply a key role for CD44 in CSC functional properties. Hyaluronan, the main ligand of CD44, is a major constituent of CSC niche and, therefore, the hyaluronan-CD44 signaling axis is of functional importance in this special microenvironment. This review aims to provide recent advances in the importance of hyaluronan-CD44 interactions in the acquisition and maintenance of a CSC phenotype. Hyaluronan-CD44 axis has a substantial impact on stemness properties of CSCs and drug resistance through induction of EMT program, oxidative stress resistance, secretion of extracellular vesicles/exosomes and epigenetic control. Potential therapeutic approaches targeting CSCs based on the hyaluronan-CD44 axis are also presented.

A Reporter System Evaluates Tumorigenesis, Metastasis, β-catenin/MMP Regulation, and Druggability

Cancer invasion, metastasis, and therapy resistance are the crucial phenomena in cancer malignancy. The high expression of matrix metalloproteinase 9 (MMP9) is a biomarker as well as a causal factor of cancer invasiveness and metastatic activity. However, a regulatory mechanism underlying MMP9 expression in cancer is not clarified yet. In addition, a new strategy for anticancer drug discovery is becoming an important clue. In the present study, we aimed (i) to develop a novel reporter system evaluating tumorigenesis, invasiveness, metastasis, and druggability with a combination of three-dimensional tumoroid model and Mmp9 promoter and (ii) to examine pharmacological actions of anticancer medications using this reporter system. High expression and genetic amplification of MMP9 were found in colon cancer cases. We found that proximal promoter sequences of MMP9 in murine and human contained conserved binding sites for transcription factors β-catenin/TCF/LEF, glucocorticoid receptor (GR), and nuclear factor kappa-B (NF-κB). The murine Mmp9 promoter (-569 to +19) was markedly activated in metastatic colon cancer cells and additionally activated by tumoroid formation and by β-catenin signaling stimulator lithium chloride. The Mmp9 promoter-driven fluorescent reporter cells enabled the monitoring of activities of MMP9/gelatinase, tumorigenesis, invasion, and metastasis in syngeneic transplantation experiments. We also demonstrated pharmacological actions as follows: dexamethasone and hydrocortisone, steroidal medications binding to GR, inhibited the Mmp9 promoter but did not inhibit tumorigenesis. On the contrary, antimetabolite 5-fluorouracil, a gold standard for colon cancer chemotherapy, inhibited tumoroid formation but did not inhibit Mmp9 promoter activity. Notably, antimalaria medication artesunate inhibited both tumorigenesis and the Mmp9 promoter in vitro, potentially through inhibition of β-catenin/TCF/LEF signaling. Thus, this novel reporter system enabled monitoring tumorigenesis, invasiveness, metastasis, key regulatory signalings such as β-catenin/MMP9 axis, and druggability. Impact Statement Cancer invasion and metastasis have been shown to be driven by matrix metalloproteinase 9 (MMP9), whose expression mechanism is not clarified yet. In addition, a new strategy for anticancer drug discovery is becoming important. We established a novel reporter system evaluating tumorigenesis, invasiveness, metastasis, and druggability with a combination of three-dimensional (3D) tumoroid model and Mmp9 promoter. Using this reporter system, we demonstrated pharmacological actions of anticancer medications such as antimetabolite 5-fluorouracil (5-FU) and antimalaria medication artesunate (ART), which inhibited both tumorigenesis and β-catenin/MMP regulatory signaling. Our study impacts the translational fields of oncology, drug discovery, and organoid model.

Head and neck cancer management and cancer stem cells implication

Head and neck squamous cell carcinomas (HNSCCs) arise in the mucosal linings of the upper aerodigestive tract and are heterogeneous in nature. Risk factors for HNSCCs are smoking, excessive alcohol consumption, and the human papilloma virus. Conventional treatments are surgery, radiotherapy, chemotherapy, or a combined modality; however, no international standard mode of therapy exists. In contrast to the conventional model of clonal evolution in tumor development, there is a newly proposed theory based on the activity of cancer stem cells (CSCs) as the model for carcinogenesis. This “CSC hypothesis” may explain the high mortality rate, low response to treatments, and tendency to develop multiple tumors for HNSCC patients. We review current knowledge on HNSCC etiology and treatment, with a focus on CSCs, including their origins, identifications, and effects on therapeutic options.

Sulfasalazine could modulate the CD44v9-xCT system and enhance cisplatin-induced cytotoxic effects in metastatic bladder cancer

The prognostic role of CD44v9, a variant isoform of CD44 and a new cell surface marker of cancer stem cells, remains unclear in bladder cancer (BC) patients. Furthermore, limited information is available on the functional role of sulfasalazine (SSZ), which could modulate the CD44v9‐xCT system in order to enhance cisplatin (CDDP)‐induced cytotoxicity and inhibit the metastatic potential of BC. CD44v9 protein expression was examined immunohistochemically in 63 muscle invasive BC (MIBC) patients who underwent radical cystectomy. CD44v9 expression was independently associated with disease recurrence and cancer‐specific death in MIBC. Cytotoxic effects, glutathione levels, and reactive oxygen species production by SSZ and CD44v9 and phospho‐p38^MAPK protein expression by SSZ with or without CDDP were assessed in MBT‐2V cells with highly metastatic potential. Sulfasalazine exerted cytotoxic effects against MBT‐2V cells by inhibiting glutathione levels and inducing the production of reactive oxygen species. Sulfasalazine in combination with CDDP appeared to exert strong cytotoxic effects against MBT‐2V cells by inhibiting CD44v9 expression and upregulating phospho‐p38^MAPK expression. The inhibitory effects of SSZ with or without CDDP were also investigated using an MBT‐2V lung metastatic model. In the murine lung metastatic BC model, SSZ significantly prolonged animal survival. Furthermore, the combination of SSZ with CDDP exerted stronger inhibitory effects on the establishment of lung tumor nodules than SSZ or CDDP alone. CD44v9 expression could be a clinical biomarker for predicting poor outcomes in MIBC patients. Sulfasalazine in combination with CDDP has potential as a novel therapy against metastatic BC.

Prognostic Value of CD44 and Its Isoforms in Advanced Cancer: A Systematic Meta-Analysis With Trial Sequential Analysis

Objective: Cancer stem cell marker CD44 and its variant isoforms (CD44v) may be correlated with tumor growth, metastasis, and chemo-radiotherapy resistance. However, the prognostic power of CD44 and CD44v in advanced cancer remains controversial. Therefore, the purpose of our study was to generalize the prognostic significance of these cancer stem cell markers in advanced cancer patients.

Methods: Hazard ratios (HRs) with 95% confidence intervals (95% CIs) were calculated from multivariable analysis to assess the associations among CD44, CD44v6, and CD44v9 positivity and overall survival (OS), disease-free survival (DFS), progression-free survival (PFS), cancer-specific survival (CSS), and recurrence-free survival (RFS). Trial sequential analysis (TSA) was also conducted.

Results: We included 15 articles that reported on 1,201 patients with advanced cancer (CD44: nine studies with 796 cases, CD44v6: three studies with 143 cases, and CD44v9: three studies with 262 cases). CD44 expression was slightly linked to worse OS (HR = 2.03, P = 0.027), but there was no correlation between CD44 expression and DFS, RFS, or PFS. Stratified analysis showed that CD44 expression was not correlated with OS at ≥5 years or OS in patients receiving adjuvant therapy. CD44v6 expression was not associated with OS. CD44v9 expression was closely associated with poor 5-years CSS in patients treated with chemo/radiotherapy (HR = 3.62, P < 0.001). However, TSA suggested that additional trials were needed to confirm these conclusions.

Conclusions: CD44 or CD44v9 might be novel therapeutic targets for improving the treatment of advanced cancer patients. Additional prospective clinical trials are strongly needed across different cancer types.

High expression level of CD44v8-10 in cancer stem-like cells is associated with poor prognosis in esophageal squamous cell carcinoma patients treated with chemoradiotherapy

Background

Strong reactive oxygen species (ROS) suppression in cancer stem-like cell components in various solid tumors is associated with therapeutic resistance. In this study, we investigated the influence of CD44v8-10 expression on the overall survival of esophageal squamous cell carcinoma (E-SCC) patients after definitive chemoradiotherapy (dCRT) and on radio-sensitivities of E-SCC cell lines treated with or without sulfasalazine, a CD44v8-10-xCT-GSH axis inhibitor.

Methods

Seventy-three patients with E-SCC who received dCRT were examined retrospectively. CD44v8-10 expression was analyzed immunohistochemically using paraffin-blocked pre-dCRT biopsy specimens obtained by esophagoscopy and was expressed as a histo-score (H-score). The relationship between the H-score and overall survival was analyzed. From human E-SCC cell lines (T.T, T.Tn, or Kyse-3650), we collected CD44v8-10^High and CD44v8-10^Low subpopulations using a cell sorter. Water-soluble tetrazolium salt-8 (WST), glutathione-SH (GSH) and ROS assays were performed to compare the effect of sulfasalazine on the radio-sensitivities of these subpopulations in T.Tn and Kyse-3650.

Results

High CD44v8-10 expression was independently associated with poor prognosis in E-SCC patients treated with dCRT (hazard ratio = 2.906, 95% CI = 1.277–6.611, p = 0.011). In CD44v8-10^High cells of each cell line, sulfasalazine decreased cellular GSH levels, resulting in increased radiation-induced ROS and reduced cell viability. In contrast, sulfasalazine had no significant effects in CD44v8-10^Low cells.

Conclusion

High CD44v8-10 expression was an independent prognostic factor in E-SCC patients treated with dCRT. CD44v8-10-xCT-GSH axis inhibition sensitized CD44v8-10^High E-SCC cells to ROS-inducing treatments such as radiotherapy. Targeting CD44v8-10-xCT-GSH axis may improve the prognosis of post-dCRT E-SCC patients.

CD44v9 as a poor prognostic factor of triple-negative breast cancer treated with neoadjuvant chemotherapy

Background

Neoadjuvant chemotherapy (NAC) is the standard therapeutic strategy for triple-negative breast cancer (TNBC). TNBC patients with residual disease after NAC have a significantly worse survival than those with pathological complete response (pCR); however, there is no apparent prognostic factor for non-pCR patients. Cancer stemness or epithelial–mesenchymal transition (EMT) might influence the sensitivity to chemotherapy.

Patients and methods

Forty-eight patients with TNBC who were treated with NAC were available were included in this study. The expressions of stemness marker CD44v9, EMT marker vimentin and BRCA1, and basal phenotype were evaluated with immunohistochemistry. The relationships between the expression of these proteins and the pCR rate and the prognosis, especially in the patients with residual tumors, were investigated.

Results

Among the 48 patients, pCR was achieved in 14 cases. High nuclear grade and basal phenotype in the pre-NAC samples were significantly correlated with pCR (p = 0.0458 and 0.0343). There were no significant relationships between the pCR rate and the expression of CD44v9, vimentin, or BRCA1. Achieving pCR was significantly correlated with longer distant metastasis-free survival (DMFS) (p = 0.0206). High CD44v9 expression was significantly associated with shorter DMFS (p = 0.0291). Among the patients in whom pCR was not achieved, high grade in the residual tumor cells, poor pathological response and high CD44v9 expression in the pre-treatment CNB samples were significantly correlated with a poor DMFS (p = 0.0433, 0.0406 and p = 0.0333). In addition, high grade in the residual tumor cells was significantly associated with high CD44v9 expression in the pre-treatment CNB (p = 0.0389).

Conclusions

High CD44v9 expression in pre-NAC samples was associated with poor prognosis in TNBC patients treated with NAC, especially for those in whom pCR was not achieved.

Electronic supplementary material

The online version of this article (10.1007/s12282-018-0888-y) contains supplementary material, which is available to authorized users.

CD44 promotes cell proliferation in non-small cell lung cancer

Cluster of differentiation 44 (CD44), a marker for cancer stem cells, has been reported to be associated with poor prognosis in non-small cell lung cancer (NSCLC), but its involvement in tumor growth has not fully been elucidated. The present study explored the associations between CD44 expression and clinicopathological features using immunohistochemistry in 94 NSCLC cases, as well as proliferation in cells with aberrant expression of this protein. Overexpression of CD44 was achieved by transfecting H1299 cells with CD44 expression vectors, and inhibition of CD44 expression was performed by transfecting small interfering RNAs into A549 cells. Cell proliferation was measured using Cell Counting Kit-8 assays and flat plate colony formation assay was performed to confirm the cellular anchorage growth in vitro. In total, 64 (68.1%) of the 94 NSCLC cases stained positive for CD44 expression. High expression of CD44 was associated with advanced T stage in NSCLC. Overexpression of CD44 in H1299 cells promoted cell proliferation and colony formation in vitro. Meanwhile, knockdown of CD44 expression in A549 cells suppressed cell proliferation and colony formation in vitro. High expression of CD44 may promote NSCLC progression by increasing cancer cell proliferation; therefore, it may serve as a potential biomarker for diagnosis or target therapy.

Utility of chemoradioselection for the optimization of treatment intensity in advanced hypopharyngeal and laryngeal carcinoma

Definitive concomitant chemoradiotherapy (CRT) with high-dose cis-platinum (CDDP) is a current standard protocol for advanced laryngeal and hypopharyngeal cancer sparing surgery for salvage. However, this modality is associated with limited feasibility and frequent sever toxicities. In the present study, a ‘chemoradioselection’ protocol with minimal toxicity was developed using initial response to CRT as a biomarker for patient selection. Between 2000, March and 2012, September 123 patients with stage III (44), IV (79) laryngeal (64) and hypopharyngeal carcinoma (59) excluding T4 cases were enrolled to this protocol. Two cycles of split (15 mg/m² ×5 days, 2000–2008) or bolus (80 mg/m², 2009-present) CDDP was concurrently administered. Tumor responses were evaluated after 40 Gy of CRT and 64 responders (chemoradioselected, CRS) received further CRT up to 70 Gy, while radical surgery was recommended for the 59 non-responders (N-CRS), and 34 underwent surgery (N-CRS-ope). The remaining 25 patients who refused surgery (N-CRS-refu) were treated with continuous CRT. The 5-year overall survival (OS) and disease-specific survival (DSS) were 67, and 77%, respectively. The CRS demonstrated favorable 5-year OS (73%) and laryngo-esophageal dysfunction-free survival (LEDFS, 69%) rates. In contrast, the N-CRS-refu showed significantly lower 5-year OS (47%) compared with CRS (73%) and N-CRS-ope (70%) (P=0.0193), and significantly lower 5-year LEDFS (20%) compared with the CRS (69%) (P<0.0001). On multivariate analyses, including T, N, primary site and planned treatment (CRS + N-CRS-ope) or not (N-CRS-refu), unplanned treatment alone showed a significant correlation with poor OS [hazard ratio (HR), 2.584; 95% confidence interval (CI), 1.313–4.354; P=0.007). Chemoradioselection reflects the biological aggressiveness of each tumor, and is able to segregate patients for functional laryngeal preservation with moderate intensity CRT (150–160 mg/m² of CDDP) from those who would be better treated with surgery. This strategy may be useful for the optimization of the therapeutic intensity.

Variant CD44 expression is enriching for a cell population with cancer stem cell-like characteristics in human lung adenocarcinoma

Background: Preliminary studies have identified cancer stem cells (CSCs) in various cancers and there are several ongoing clinical studies targeting these cells. CD44 (standard or variant isoforms) and/or aldehyde dehydrogenase (ALDH) expression is the most commonly used markers for the identification of CSCs. The goal of the current study was to examine the ability of CD44v, either alone or in combination with ALDH, to identify CSCs within human lung cancer cells lines.

Methods: We examined several lung adenocarcinoma cell lines for the ability of CD44v and/or ALDH expression to enrich for cells with CSC characteristics such as in vitro differential proliferation rate, chemotherapeutic-resistance, tumorsphere formation, and in vivo tumorigenicity. We also compared their in vivo secondary tumor formation, and histological characteristics of their xenograft tumors, and examined their expression of PD-L1, EGFR, xCT, and reactive oxygen species (ROS).

Results: Both CD44v^high/ALDH^high and CD44v^high/ALDH^low cells were enriched in cells with CSC characteristics, with the CD44v^high/ALDH^low cells being more proliferative and more resistant to chemotherapeutics, whereas CD44v^high/ALDH^high cells were more efficient in forming tumorspheres in vitro, in making primary xenograft tumors, and in propagating secondary tumors in vivo. Applying stricter sorting gates to select for cells with the highest CD44v/ALDH expression caused the CD44v^high/ALDH^low cells to lose their high proliferation rates and chemotherapeutic resistance ability, but enriched for the tumorsphere-forming cells among the CD44v^high/ALDH^high and CD44v^high/ALDH^low cells. CD44v^high expression was associated with PD-L1 and xCT expression in both H1650 and HCC827 cells. This association was not modified by ALDH expression in the H1650 cell line. However, in the HCC827 cell line, ALDH expression was negatively associated with PD-L1 and positively associated with xCT expression.

Conclusion: Lung adenocarcinoma cells with high CD44v expression are enriched for CSCs. Addition of ALDH as an enrichment marker bestowed some CSCs characteristics to CD44v^high/ALDH^low cells and others to CD44v^high/ALDH^high cells. We propose that lung adenocarcinoma contains different CSCs, each of them endowed with different CSC characteristics.

CD44 variant 9 expression as a predictor for gastric cancer recurrence: immunohistochemical and metabolomic analysis of surgically resected tissues

CD44 variant 9 (CD44v9) and the heavy chain of 4F2 cell-surface antigen (CD98hc) appear important for regulation of reactive oxygen species defence and tumor growth in gastric cancer. This study examined the roles of CD44v9 and CD98hc as markers of gastric cancer recurrence, and investigated associations with energy metabolism. We applied capillary electrophoresis time-of-flight mass spectrometry to metabolome profiling of gastric cancer specimens from 103 patients who underwent resection with no residual tumor or microscopic residual tumor, and compared metabolite levels to immunohistochemical staining for CD44v9 and CD98hc. Positive expression rates were 40.7% for CD44v9 and 42.7% for CD98hc. Various tumor characteristics were significantly associated with CD44v9 expression. Five-year recurrence-free survival rate was significantly lower for CD44v9-positive tumors (39.1%) than for CD44v9-negative tumors (73.5%; P < 0.0001), but no significant differences in recurrence-free survival were seen according to CD98hc expression. Uni- and multivariate analyses identified positive CD44v9 expression as an independent predictor of poorer recurrence-free survival. Metabolome analysis of 110 metabolites found that levels of glutathione disulfide were significantly lower and reduced glutathione (GSH)/ glutathione disulfide (GSSG) ratio was significantly higher in CD44v9-positive tumors than in CD44v9-negative tumors, suggesting that CD44v9 may enhance pentose phosphate pathway flux and maintain GSH levels in cancer cells.

Roles and targeting of the HAS/hyaluronan/CD44 molecular system in cancer

Synthesis, deposition, and interactions of hyaluronan (HA) with its cellular receptor CD44 are crucial events that regulate the onset and progression of tumors. The intracellular signaling pathways initiated by HA interactions with CD44 leading to tumorigenic responses are complex. Moreover, HA molecules may perform dual functions depending on their concentration and size. Overexpression of variant isoforms of CD44 (CD44v) is most commonly linked to cancer progression, whereas their loss is associated with inhibition of tumor growth. In this review, we highlight that the regulation of HA synthases (HASes) by post-translational modifications, such as O-GlcNAcylation and ubiquitination, environmental factors and the action of microRNAs is important for HA synthesis and secretion in the tumor microenvironment. Moreover, we focus on the roles and interactions of CD44 with various proteins that reside extra- and intracellularly, as well as on cellular membranes with particular reference to the CD44-HA axis in cancer stem cell functions, and the importance of CD44/CD44v6 targeting to inhibit tumorigenesis.

Stress-triggered atavistic reprogramming (STAR) addiction: driving force behind head and neck cancer?

Recent results of the Cancer Genome Atlas on head and neck squamous cell carcinoma (HNSCC) revealed that HNSCC lacked predominant gain-of-function mutations in oncogenes, whereas an essential role for epigenetics in oncogenesis has become apparent. In parallel, it has gained general acceptance that cancer is considered as complex adaptive system, which evolves responding environmental selective pressures. This somatic evolution appears to proceed concurrently with the acquisition of an atavistic pluripotent state (i.e., "stemness"), which is inducible by intrinsic epigenetic reprogramming program as demonstrated by induced pluripotent stem (iPS) cells. This Nobel prize-winning discovery has markedly accelerated and expanded cancer stem cell research from the point of epigenetic reprogramming. Taken together, we hypothesize that stress-triggered atavistic reprogramming (STAR) may be the major driving force of HNSCC evolution. In this perspective, we discuss the possible mechanisms of STAR in HNSCC, focusing on recent topics of epigenetic reprogramming in developmental and cancer cell biology.

Variant isoforms of CD44 expression in upper tract urothelial cancer as a predictive marker for recurrence and mortality

PURPOSE

The variant isoforms of CD44 (CD44v), which has been associated with treatment resistance and tumor recurrence, are contributed to the feature of some of the new cell surface markers for cancer stem cells. The aim of this study is to address the prognostic significant of CD44v expression in upper tract urothelial cancer (UTUC).

MATERIALS AND METHODS

We retrospectively analyzed the medical records of 110 patients treated surgically for≥pT2 UTUC. To determine the biological significance of CD44v in UTUC, we examined the immunohistochemical expression of CD44v9 and its association with clinical features and oncological outcomes.

RESULTS

During the mean follow-up of 4.8 years, tumor recurrence, including local and distant metastasis, was observed in 57 patients (51.8%), and 42 patients (38.2%) died of the disease. The incidence of ureter cancers was significantly higher in patients expressing CD44v9. In this series, 37 patients in the CD44v9-positive group (45.1%) and 5 (17.9%) in the CD44v9-negative group died of the disease. Kaplan-Meier curves revealed that cancer-specific survival and recurrence-free survival rates were significantly lower in the CD44v9-positive group than in the CD44v9-negative group (P = 0.032 and P = 0.038, respectively). A multivariate analysis identified the expression of CD44v9 as one of the independent risk factors for cancer-specific survival (P = 0.040, hazard ratio = 2.67) in addition to tumor grade G3, and also for recurrence-free survival (P = 0.028, hazard ratio = 2.33), in addition to tumor grade G3 and lymphovascular invasion.

CONCLUSIONS

The expression of CD44v9 may be a new biomarker of malignant potential in muscle invasive UTUC and provide additional prognostic information in patients with UTUC.

The Importance of CD44 as a Stem Cell Biomarker and Therapeutic Target in Cancer

CD44 is a cell surface HA-binding glycoprotein that is overexpressed to some extent by almost all tumors of epithelial origin and plays an important role in tumor initiation and metastasis. CD44 is a compelling marker for cancer stem cells of many solid malignancies. In addition, interaction of HA and CD44 promotes EGFR-mediated pathways, consequently leading to tumor cell growth, tumor cell migration, and chemotherapy resistance in solid cancers. Accumulating evidence indicates that major HA-CD44 signaling pathways involve a specific variant of CD44 isoforms; however, the particular variant almost certainly depends on the type of tumor cell and the stage of the cancer progression. Research to date suggests use of monoclonal antibodies against different CD44 variant isoforms and targeted inhibition of HA/CD44-mediated signaling combined with conventional radio/chemotherapy may be the most favorable therapeutic strategy for future treatments of advanced stage malignancies. Thus, this paper briefly focuses on the association of the major CD44 variant isoforms in cancer progression, the role of HA-CD44 interaction in oncogenic pathways, and strategies to target CD44-overexpressed tumor cells.