Immunosurveillance encounters cancer metabolism.

Tumor cells reprogram nutrient acquisition and metabolic pathways to meet their energetic, biosynthetic, and redox demands. Similarly, metabolic processes in immune cells support host immunity against cancer and determine differentiation and fate of leukocytes. Thus, metabolic deregulation and imbalance in immune cells within the tumor microenvironment have been reported to drive immune evasion and to compromise therapeutic outcomes. Interestingly, emerging evidence indicates that anti-tumor immunity could modulate tumor heterogeneity, aggressiveness, and metabolic reprogramming, suggesting that immunosurveillance can instruct cancer progression in multiple dimensions. This review summarizes our current understanding of how metabolic crosstalk within tumors affects immunogenicity of tumor cells and promotes cancer progression. Furthermore, we explain how defects in the metabolic cascade can contribute to developing dysfunctional immune responses against cancers and discuss the contribution of immunosurveillance to these defects as a feedback mechanism. Finally, we highlight ongoing clinical trials and new therapeutic strategies targeting cellular metabolism in cancer.

Regulatory circuits of mitophagy restrict distinct modes of cell death during memory CD8+ T cell formation.

Mitophagy, a central process guarding mitochondrial quality, is commonly impaired in human diseases such as Parkinson's disease, but its impact in adaptive immunity remains unclear. The differentiation and survival of memory CD8+ T cells rely on oxidative metabolism, a process that requires robust mitochondrial quality control. Here, we found that Parkinson's disease patients have a reduced frequency of CD8+ memory T cells compared with healthy donors and failed to form memory T cells upon vaccination against COVID-19, highlighting the importance of mitochondrial quality control for memory CD8+ T cell formation. We further uncovered that regulators of mitophagy, including Parkin and NIX, were up-regulated in response to interleukin-15 (IL-15) for supporting memory T cell formation. Mechanistically, Parkin suppressed VDAC1-dependent apoptosis in memory T cells. In contrast, NIX expression in T cells counteracted ferroptosis by preventing metabolic dysfunction resulting from impaired mitophagy. Together, our results indicate that the mitophagy machinery orchestrates survival and metabolic dynamics required for memory T cell formation, as well as highlight a deficit in T cell-mediated antiviral responses in Parkinson's disease patients.

Prenatal DEHP exposure predicts neurological disorders via transgenerational epigenetics.

Recent experimental and observational research has suggested that childhood allergic asthma and other conditions may be the result of prenatal exposure to environmental contaminants, such as di-(2-ethylhexyl) phthalate (DEHP). In a previous epidemiological study, we found that ancestral exposure (F0 generation) to endocrine disruptors or the common plasticizer DEHP promoted allergic airway inflammation via transgenerational transmission in mice from generation F1 to F4. In the current study, we employed a MethylationEPIC Beadchip microarray to examine global DNA methylation in the human placenta as a function of maternal exposure to DEHP during pregnancy. Interestingly, global DNA hypomethylation was observed in placental DNA following exposure to DEHP at high concentrations. Bioinformatic analysis confirmed that DNA methylation affected genes related to neurological disorders, such as autism and dementia. These results suggest that maternal exposure to DEHP may predispose offspring to neurological diseases. Given the small sample size in this study, the potential role of DNA methylation as a biomarker to assess the risk of these diseases deserves further investigation.

Immunoediting instructs tumor metabolic reprogramming to support immune evasion.

Immunoediting sculpts immunogenicity and thwarts host anti-tumor responses in tumor cells during tumorigenesis; however, it remains unknown whether metabolic programming of tumor cells can be guided by immunosurveillance. Here, we report that T cell-mediated immunosurveillance in early-stage tumorigenesis instructs c-Myc upregulation and metabolic reprogramming in tumor cells. This previously unexplored tumor-immune interaction is controlled by non-canonical interferon gamma (IFNγ)-STAT3 signaling and supports tumor immune evasion. Our findings uncover that immunoediting instructs deregulated bioenergetic programs in tumor cells to empower them to disarm the T cell-mediated immunosurveillance by imposing metabolic tug-of-war between tumor and infiltrating T cells and forming the suppressive tumor microenvironment.

PCDHB15 as a potential tumor suppressor and epigenetic biomarker for breast cancer.

Breast cancer is among the most frequently diagnosed cancer types and the leading cause of cancer-related death in women. The mortality rate of patients with breast cancer is currently increasing, perhaps due to a lack of early screening tools. In the present study, using The Cancer Genome Atlas (TCGA) breast cancer dataset (n=883), it was determined that methylation of the protocadherin ß15 (PCDHB15) promoter was higher in breast cancer samples than that in normal tissues. A negative association between promoter methylation and expression of PCDHB15 was observed in the TCGA dataset and breast cancer cell lines. In TCGA cohort, lower PCDHB15 expression was associated with shorter relapse-free survival times. Treatment with the DNA methyltransferase inhibitor restored PCDHB15 expression in a breast cancer cell line; however, overexpression of PCDHB15 was shown to suppress colony formation. PCDHB15 methylation detected in circulating cell-free DNA (cfDNA) isolated from serum samples was higher in patients with breast cancer (40.8%) compared with that in patients with benign tumors (22.4%). PCDHB15 methylation was not correlated with any clinical parameters. Taken together, PCDHB15 is a potential tumor suppressor in cases of breast cancer, which can be epigenetically silenced via promoter methylation. PCDHB15 methylation using cfDNA is a novel minimally invasive epigenetic biomarker for the diagnosis and prognosis of breast cancer.

Interplay between ceRNA and Epigenetic Control of microRNA: Modelling Approaches with Application to the Role of Estrogen in Ovarian Cancer.

MicroRNAs (miRNAs) play an important role in gene regulation by degradation or translational inhibition of the targeted mRNAs. It has been experimentally shown that the way miRNAs interact with their targets can be used to explain the indirect interactions among their targets, i.e., competing endogenous RNA (ceRNA). However, whether the protein translated from the targeted mRNAs can play any role in this ceRNA network has not been explored. Here we propose a deterministic model to demonstrate that in a network of one miRNA interacting with multiple-targeted mRNAs, the competition between miRNA-targeted mRNAs is not sufficient for the significant change of those targeted mRNA levels, while dramatic changes of these miRNA-targeted mRNAs require transcriptional inhibition of miRNA by its target proteins. When applied to estrogen receptor signaling pathways, the miR-193a targets E2F6 (a target of estrogen receptor), c-KIT (a marker for cancer stemness), and PBX1 (a transcriptional activator for immunosuppressive cytokine, IL-10) in ovarian cancer, such that epigenetic silencing of miR-193a by E2F6 protein is required for the significant change of c-KIT and PBX1 mRNA level for cancer stemness and immunoevasion, respectively, in ovarian cancer carcinogenesis.

Cyproheptadine, an epigenetic modifier, exhibits anti-tumor activity by reversing the epigenetic silencing of IRF6 in urothelial carcinoma.

BACKGROUND: Urothelial carcinoma (UC) is the second most common malignancy of the urinary system with high rate of recurrence, UC patients therefore needed to be treated with surgery followed by chemotherapy. Development of novel therapeutics with minimal side-effect is an urgent issue. Our previous study showed that cyproheptadine (CPH), an anti-histamine, exhibited antitumor activity in UC in vitro and in an xenograft model. However, the molecular mechanism of how CPH inhibits tumor progression is not fully understood. METHODS: Genes that were upregulated after treatment with CPH in UC cells, were examined by RNA-Seq. Real-time quantitative PCR (RT-qPCR) was employed to detect IRF6 expression while COBRA assay and bisulphite pyrosequencing were used to examine promoter methylation of IRF6. Enrichment of total H3K27 acetylation and H3K4 mono-methylation were detected by western blotting. Colony formation and flow cytometry were used to examine proliferation and apoptosis in UC cells overexpressed or depleted with IRF6. Nude mice xenograft model was used to examine the effect of IRF6 in UC. RESULTS: Our result showed that several genes, including IRF6 were upregulated after treatment with CPH in BFTC905 UC cells. Further experiments found that treatment of CPH could restore the expression of IRF6 in several other UC cell lines, probably due to promoter hypomethylation and enrichment of H3K27 acetylation and H3K4 mono-methylation. These results may be due to the fact that CPH could alter the activity, but not the expression of epigenetic modifiers. Finally, re-expression of IRF6 in UC inhibited tumor growth in vitro and in an xenograft mouse model, by inducing apoptosis. CONCLUSION: In conclusion, our results suggested that CPH may be an epigenetic modifier, modulating the expression of the potential tumor suppressor IRF6, in inhibiting tumor growth in UC.

Methylomic analysis identifies C11orf87 as a novel epigenetic biomarker for GI cancers.

Gastric cancer is one of the leading causes of cancer death worldwide. Previous studies demonstrated that activation of STAT3 is crucial for the development and progression of gastric cancer. However, the role of STAT3 in neuronal related gene methylation in gastric cancer has never been explored. In this study, by using DNA methylation microarray, we identified a potential STAT3 target, C11orf87, showing promoter hypomethylation in gastric cancer patients with lower STAT3 activation and AGS gastric cancer cell lines depleted with STAT3 activation. Although C11orf87 methylation is independent of its expression, ectopic expression of a constitutive activated STAT3 mutant upregulated its expression in gastric cancer cell line. Further bisulfite pyrosequencing demonstrated a progressive increase in DNA methylation of this target in patient tissues from gastritis, intestinal metaplasia, to gastric cancer. Intriguingly, patients with higher C11orf87 methylation was associated with better survival. Furthermore, hypermethylation of C11orf87 was also frequently observed in other GI cancers, as compared to their adjacent normal tissues. These results suggested that C11orf87 methylation may serve as a biomarker for diagnosis and prognosis of GI cancers, including gastric cancer. We further postulated that constitutive activation of STAT3 might be able to epigenetically silence C11orf87 as a possible negative feedback mechanism to protect the cells from the overactivation of STAT3. Targeted inhibition of STAT3 may not be appropriate in gastric cancer patients with promoter hypermethylation of C11orf87.

Epigenetic Silencing of STAT3-Targeted miR-193a, by Constitutive Activation of JAK/STAT Signaling, Leads to Tumor Progression Through Overexpression of YWHAZ in Gastric Cancer.

PURPOSE: The purpose of this study was to identify genes that were epigenetically silenced by STAT3 in gastric cancer. METHODS: MBDcap-Seq and expression microarray were performed to identify genes that were epigenetically silenced in AGS gastric cancer cell lines depleted of STAT3. Cell lines and animal experiments were performed to investigate proliferation and metastasis of miR-193a and YWHAZ in gastric cancer cell lines. Bisulfite pyrosequencing and tissue microarray were performed to investigate the promoter methylation of miR-193a and expression of STAT3, YWHAZ in patients with gastritis (n = 8) and gastric cancer (n = 71). Quantitative methylation-specific PCR was performed to examine miR-193a promoter methylation in cell-free DNA of serum samples in gastric cancer patients (n = 19). RESULTS: As compared with parental cells, depletion of STAT3 resulted in demethylation of a putative STAT3 target, miR-193a, in AGS gastric cancer cells. Although bisulfite pyrosequencing and epigenetic treatment confirmed that miR-193a was epigenetically silenced in gastric cancer cell lines, ChIP-PCR found that it may be indirectly affected by STAT3. Ectopic expression of miR-193a in AGS cells inhibited proliferation and migration of gastric cancer cells. Further expression microarray and bioinformatics analysis identified YWHAZ as one of the target of miR-193a in AGS gastric cancer cells, such that depletion of YWHAZ reduced migration in AGS cells, while its overexpression increased invasion in MKN45 cells in vitro and in vivo. Clinically, bisulfite pyrosequencing revealed that promoter methylation of miR-193a was significantly higher in human gastric cancer tissues (n = 11) as compared to gastritis (n = 8, p < 0.05). Patients infected with H. pylori showed a significantly higher miR-193a methylation than those without H. pylori infection (p < 0.05). Tissue microarray also showed a positive trend between STAT3 and YWHAZ expression in gastric cancer patients (n = 60). Patients with serum miR-193a methylation was associated with shorter overall survival than those without methylation (p < 0.05). CONCLUSIONS: Constitutive activation of JAK/STAT signaling may confer epigenetic silencing of the STAT3 indirect target and tumor suppressor microRNA, miR-193a in gastric cancer. Transcriptional suppression of miR-193a may led to overexpression of YWHAZ resulting in tumor progression. Targeted inhibition of STAT3 may be a novel therapeutic strategy against gastric cancer.

Bacteria pathogens drive host colonic epithelial cell promoter hypermethylation of tumor suppressor genes in colorectal cancer.

BACKGROUND: Altered microbiome composition and aberrant promoter hypermethylation of tumor suppressor genes (TSGs) are two important hallmarks of colorectal cancer (CRC). Here we performed concurrent 16S rRNA gene sequencing and methyl-CpG binding domain-based capture sequencing in 33 tissue biopsies (5 normal colonic mucosa tissues, 4 pairs of adenoma and adenoma-adjacent tissues, and 10 pairs of CRC and CRC-adjacent tissues) to identify significant associations between TSG promoter hypermethylation and CRC-associated bacteria, followed by functional validation of the methylation-associated bacteria. RESULTS: Fusobacterium nucleatum and Hungatella hathewayi were identified as the top two methylation-regulating bacteria. Targeted analysis on bona fide TSGs revealed that H. hathewayi and Streptococcus spp. significantly correlated with CDX2 and MLH1 promoter hypermethylation, respectively. Mechanistic validation with cell-line and animal models revealed that F. nucleatum and H. hathewayi upregulated DNA methyltransferase. H. hathewayi inoculation also promoted colonic epithelial cell proliferation in germ-free and conventional mice. CONCLUSION: Our integrative analysis revealed previously unknown epigenetic regulation of TSGs in host cells through inducing DNA methyltransferase by F. nucleatum and H. hathewayi, and established the latter as CRC-promoting bacteria. Video abstract.

Combinatorial Epigenetic and Immunotherapy in Breast Cancer Management: A Literature Review.

Breast cancer is one of the leading causes of death among cancer patients worldwide. To date, there are several drugs that have been developed for breast cancer therapy. In the 21st century, immunotherapy is considered a pioneering method for improving the management of malignancies; however, breast cancer is an exception. According to the immunoediting model, many immunosuppressive cells contribute to immunological quiescence. Therefore, there is an urgent need to enhance the therapeutic efficacy of breast cancer treatments. In the last few years, numerous combinatorial therapies involving immune checkpoint blockade have been demonstrated that effectively improve clinical outcomes in breast cancer and combining these with methods of targeting epigenetic regulators is also an innovative strategy. Nevertheless, few studies have discussed the benefits of epi-drugs in non-cancerous cells. In this review, we give a brief overview of ongoing clinical trials involving combinatorial immunotherapy with epi-drugs in breast cancer and discuss the role of epi-drugs in the tumor microenvironment, including the results of recent research.

c-Myc Acts as a Competing Endogenous RNA to Sponge miR-34a, in the Upregulation of CD44, in Urothelial Carcinoma.

MicroRNAs (miRNAs) have been shown to play a crucial role in the progression of human cancers, including urothelial carcinoma (UC), the sixth-most common cancer in the world. Among them, miR-34a has been implicated in the regulation of cancer stem cells (CSCs); however, its role in UC has yet to be fully elucidated. In this study, bioinformatics and experimental analysis confirmed that miR-34a targets CD44 (a CSC surface marker) and c-Myc (a well-known cell cycle regulator) in UC. We found that, surprisingly, most UC cell lines and patient samples did express miR-34a, although epigenetic silencing by promoter hypermethylation of miR-34a expression was observed only in UMUC3 cells, and a subset of patient samples. Importantly, overexpression of c-Myc, a frequently amplified oncogene in UC, was shown to upregulate CD44 expression through a competing endogenous RNA (ceRNA) mechanism, such that overexpression of the c-Myc 3'UTR upregulated CD44, and vice versa. Importantly, we observed a positive correlation between the expression of c-Myc and CD44 in clinical samples obtained from UC patients. Moreover, overexpression of a dominant-negative p53 mutant downregulated miR-34a, but upregulated c-Myc and CD44, in UC cell lines. Functionally, the ectopic expression of miR-34a was shown to significantly suppress CD44 expression, and subsequently, suppression of cell growth and invasion capability, while also reducing chemoresistance. In conclusion, it appears that aberrant promoter methylation, and c-Myc-mediated ceRNA mechanisms, may attenuate the function of miR-34a, in UC. The tumor suppressive role of miR-34a in controlling CSC phenotypes in UC deserves further investigation.

E2F6 functions as a competing endogenous RNA, and transcriptional repressor, to promote ovarian cancer stemness.

Ovarian cancer is the most lethal cancer of the female reproductive system. In that regard, several epidemiological studies suggest that long-term exposure to estrogen could increase ovarian cancer risk, although its precise role remains controversial. To decipher a mechanism for this, we previously generated a mathematical model of how estrogen-mediated upregulation of the transcription factor, E2F6, upregulates the ovarian cancer stem/initiating cell marker, c-Kit, by epigenetic silencing the tumor suppressor miR-193a, and a competing endogenous (ceRNA) mechanism. In this study, we tested that previous mathematical model, showing that estrogen treatment of immortalized ovarian surface epithelial cells upregulated both E2F6 and c-KIT, but downregulated miR-193a. Luciferase assays further confirmed that microRNA-193a targets both E2F6 and c-Kit. Interestingly, ChIP-PCR and bisulphite pyrosequencing showed that E2F6 also epigenetically suppresses miR-193a, through recruitment of EZH2, and by a complex ceRNA mechanism in ovarian cancer cell lines. Importantly, cell line and animal experiments both confirmed that E2F6 promotes ovarian cancer stemness, whereas E2F6 or EZH2 depletion derepressed miR-193a, which opposes cancer stemness, by alleviating DNA methylation and repressive chromatin. Finally, 118 ovarian cancer patients with miR-193a promoter hypermethylation had poorer survival than those without hypermethylation. These results suggest that an estrogen-mediated E2F6 ceRNA network epigenetically and competitively inhibits microRNA-193a activity, promoting ovarian cancer stemness and tumorigenesis.

Configuration of the circle of Willis is associated with less symptomatic intracerebral hemorrhage in ischemic stroke patients treated with intravenous thrombolysis.

BACKGROUNDS: The circle of Willis (CoW) is a primary collateral pathway that compensates quickly for a drop in cerebral blood flow. Using the complete CoW as a surrogate marker for good collateral circulation, its prognostic value after intravenous thrombolysis was examined. METHODS: We prospectively studied 64 consecutive patients with acute ischemic stroke treated with tissue plasminogen activator within 3 hours of stroke onset between October 2005 and June 2012 in our hospital. The study protocol was based on standard guidelines for intravenous thrombolysis. On computed tomographic angiography 24 hours after thrombolysis, the CoW was complete in 21 (32.8%) cases and incomplete in 43 (67.2%). RESULTS: Patients with complete CoW were more likely to have early improvement in National Institute of Health Stroke Scale (NIHSS) score (median improvement 2 vs 0 at 2 hours; 4 vs 1 at 24 hours), be independent at 3 months (42% vs 19%). In the incomplete CoW group, the rate of symptomatic intracerebral haemorrhage (SICH) according to the Safe Implementation of Thrombolysis in Stroke-Monitoring Study (SITS-MOST) definition was almost 3 times higher. Complete CoW was one of the strongest predictors of good functional outcome at 3 months (odds ratio 2.32; P = .01). CONCLUSIONS: Complete CoW independently predicted functional independence and survival.

Tic douloureux as a presenting feature of facial leprosy: diagnostic enigma in Taiwan.

PURPOSE: Leprosy is rarely seen in Taiwan. We herein report a foreign worker concomitantly with facial borderline tuberculoid leprosy presenting with trigeminal neuralgia. CASE REPORT: A 26-year-old male foreign labor from Indonesia, presented with 1 year history of a hypoanaesthetic erythematous plaque of right face and subsequent 6 months constant, severe pain in the right side of his face over the nasolabial groove. Biopsies and histopathological examination confirmed the diagnosis of leprosy. We treated the patient with a multidrug regimen including dapsone, clofazimine, and rifampine since April of 2012 with a good response. CONCLUSIONS: We report a rare case of new-onset leprosy presenting with trigeminal neuralgia in Taiwan and suggest leprosy should be listed in the differential diagnosis of unusual skin manifestations and neuralgia.

The clinical relevance of vertebral artery hypoplasia.

Congenital vertebral artery (VA) hypoplasia is an uncommon embryonic variation of posterior circulation. The frequency of this congenital variation was reported to be 2-6% from autopsy and angiograms. Is it a congenital risk factor of ischemic stroke? In this review, we gave an overview of the literature concerning vertebral artery hypoplasia. VA hypoplasia served as an independent factor of a reduction of the posterior circulation blood flow velocity. VA hypoplasia can play a negative role in cases of occlusion of a major brain vessel since it limits the potential of compensatory blood circulation. VA hypoplasia may also lead to regional hypoperfusion and complex neurovascular consequences which correspond to vestibular neuronitis and migraine pathogenesis.

Immediate regression of leukoaraiosis after carotid artery revascularization.

BACKGROUND: Leukoaraiosis (LA) affects cognition after stroke and reversal of LA may improve cognitive performance. We aimed to determine the impact of cerebral perfusion and circle of Willis (CoW) flow patterns on the extent of LA after carotid artery revascularization. METHODS: LA was scored on fluid-attenuated inversion recovery magnetic resonance (MR) images at the levels of the centrum semiovale and frontal horns in both cerebral hemispheres of 62 contiguous patients (men/women = 38/24, mean age = 63.2 ± 8.4 years, range 44-82) before and after unilateral carotid artery revascularization. The pre- and poststenting differences in LA scores, CoW flow pattern on MR angiography, and MR perfusion parameters were analyzed. RESULTS: The total LA score decreased from 9.87 ± 0.65 to 8.33 ± 0.72 after stenting (p = 0.03). The CoW was complete in 21 subjects and incomplete in 41 subjects. The incomplete CoW group had a higher preoperative LA load and higher cerebral interhemispheric asymmetry index, both of which decreased significantly postoperatively. CONCLUSIONS: CoW anomalies may contribute to LA in patients with carotid artery stenosis, and restoration of cerebral perfusion by carotid artery revascularization can reduce LA severity.

Associations between Circle of Willis morphology and white matter lesion load in subjects with carotid artery stenosis.

BACKGROUND: Various cerebral pathological changes have been reported to cause leukoaraiosis (LA). We hypothesized that circle of Willis (CoW) anomalies may contribute to LA in severe carotid artery stenosis victims through impaired cerebral autoregulation. We conducted a retrospective review on cerebral magnetic resonance (MR) patterns in patients with severe symptomatic carotid artery stenosis and compared white matter lesion (WML) load between subjects with and without complete CoW. METHODS: LA on fluid attenuation inversion recovery (FLAIR) MR images at the levels of the centrum semiovale and frontal horns in both cerebral hemispheres were scored in 106 patients with unilateral carotid artery stenosis (64 men and 42 women; mean age 68.7 ± 9.2 years, range 44-82). Subjects were divided into groups of complete and incomplete CoW according to cerebral MR angiography. Differences in the LA scores between the groups of complete and incomplete CoW were further analyzed. RESULTS: Compared with those with incomplete configuration of the CoW, subjects with a complete CoW demonstrated a decreased WML load at the level of the centrum semiovale (2.78 ± 1.17 vs. 5.62 ± 2.12, p = 0.02) and frontal horns (2.21 ± 0.79 vs. 4.22 ± 1.83, p = 0.01). CONCLUSION: Our results support the importance of a complete CoW since it may protect from WML in case of carotid stenosis.

Comorbid intracranial vertebral artery asymmetry as a risk factor for severe vestibular neuronitis.

BACKGROUND: Our previous study had demonstrated that verterbral artery hypoplasia (VAH) contribute to ipsilateral vestibular dysfunction. The aim of this study was to test if VAH contributes to prognosis of vestibular neuronitis (VN) through presumed regional malperfusion. METHODS: We performed a prospective magnetic resonance angiographic registry in patients with acute vestibular neuritis in which were then assigned to VAH (n=29) and control group (n=40). Vestibular function was determined by caloric irrigation, with the use of the vestibular paresis formula (to measure the extent of unilateral caloric paresis) within 3 days after the onset of symptoms and 12 months afterward. RESULTS: The baseline vestibular paresis was higher (56.8 ± 15.9%) in the VAH VN subjects (n=29), than in VN subjects without VAH (n=40) (37.4 ± 17.7%) (p=0.01). Analysis of variance showed a less percentage of the VAH group return to normal at 4th and 12th week visit. CONCLUSION: Our results suggested that comorbid VAH may predispose to severe VN at acute stage.

The clinical relevance of fetal variant of the circle of Willis and its influence on the cerebral collateral circulation.

In a fetal variation of circle of Willis (CoW) there is an embryological defect of the primary collateral circulation. Besides the fact that collateral flow cannot develop between anterior and posterior circulation, the tentorium namely prevents cerebellar vessels from connecting to the supra-tentorium territory. Therefore patients with a fetal variation of circle of Willis could be more prone to develop vascular insufficiency. An association between the regional cerebral blood volume (rCBV) inter-hemispheric asymmetry and CoW collateralization was observed with a topographic significance of corona radiate rather than centrum semiovale. An overview of the literature is given. We propose a fetal variation of circle of Willis as a risk factor for stroke should be subject of further investigation.