Roles of MiR-101 and its target gene Cox-2 in early diagnosis of cervical cancer in Uygur women

miRNAs role in cervical cancer pathogenesis and targeted therapy: Signaling pathways interplay

Cervical cancer (CC) is the primary cause of cancer deaths in underdeveloped countries. The persistence of infection with high-risk human papillomavirus (HPV) is a significant contributor to the development of CC. However, few women with morphologic HPV infection develop invasive illnesses, suggesting other mechanisms contribute to cervical carcinogenesis. MicroRNAs (miRNAs, miRs) are small chain nucleic acids that can regulate wide networks of cellular events. They can inhibit or degrade their target protein-encoding genes. They had the power to regulate CC's invasion, pathophysiology, angiogenesis, apoptosis, proliferation, and cell cycle phases. Further research is required, even though novel methods have been developed for employing miRNAs in the diagnosis, and treatment of CC. We'll go through some of the new findings about miRNAs and their function in CC below. The function of miRNAs in the development of CC and its treatment is one of these. Clinical uses of miRNAs in the analysis, prediction, and management of CC are also covered.

Circulating MicroRNAs in Relation to Esophageal Adenocarcinoma Diagnosis and Survival

BACKGROUND AND AIMS

Tissue miRNA can discriminate between esophageal adenocarcinoma (EA) and normal epithelium. However, no studies have examined a comprehensive panel of circulating miRNAs in relation to EA diagnosis and survival.

METHODS

We used all 62 EA cases from the US Multi-Center case-control study with available serum matched 1:1 to controls. Cases were followed for vital status. MiRNAs (n = 2064) were assessed using the HTG EdgeSeq miRNA Whole Transcriptome Assay. Differential expression analysis of miRNAs in relation to case-control status was conducted. In cases, Cox regression models were fit to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause mortality. P values were adjusted using the Benjamini-Hochberg (BH) procedure for false discovery rate control. Predictive performance was assessed using cross-validation.

RESULTS

Sixty-eight distinct miRNAs were significantly upregulated between cases and controls (e.g., miR-1255b-2-3p fold change = 1.74, BH-adjusted P = 0.01). Assessing the predictive performance of these significantly upregulated miRNAs yielded 60% sensitivity, 65% specificity, and 0.62 AUC. miR-4253 and miR-1238-5p were associated with risk of mortality after EA diagnosis (HR = 4.85, 95% CI: 2.30-10.23, BH-adjusted P = 0.04 and HR = 3.81, 95% CI: 2.02-7.19, BH-adjusted P = 0.04, respectively).

CONCLUSIONS

While they require replication, these findings suggest that circulating miRNAs may be associated with EA diagnosis and survival.

Long non-coding RNA HAND2-AS1 delays cervical cancer progression via its regulation on the microRNA-21-5p/TIMP3/VEGFA axis

Cervical cancer is a common cause of cancer-related mortality in women. Mounting evidence suggests that long non-coding RNAs (lncRNAs) function vitally in many cancers. In this study, we discovered that the regulation of the heart and neural crest derivatives expressed 2-antisense RNA 1 (HAND2-AS1) in cervical cancer. RT-qPCR was conducted to detect the expression of HAND2-AS1 and microRNA-21-5p (miR-21-5p). The relationship of HAND2-AS1 and miR-21-5p was identified by dual-luciferase reporter gene assay. The roles of HAND2-AS1, miR-21-5p and tissue inhibitor of metalloproteinases-3 (TIMP3) in cervical cancer were accessed via gain- and loss-of-function approaches. The expression of related proteins in the vascular endothelial growth factor A (VEGFA) signaling pathway was detected through Western blot analysis. Finally, xenografts of cervical cancer in nude mice were established to assess the effect of HAND2-AS1 on tumorigenesis in vivo. HAND2-AS1 and TIMP3 were downregulated in cervical cancer, which were identified to be associated with a poor prognosis of patients with cervical cancer. Moreover, HAND2-AS1 was upregulated the expression of TIMP3 through competitively binding to miR-21-5p. Overexpressed HAND2-AS1 or downregulated miR-21-5p inhibited cell proliferation, migration, and invasion while promoting cell apoptosis, in association with increased expression of proteins in VEGFA signaling pathway. These changes were reversed by silencing of TIMP3. Overexpressed HAND2-AS1 reduced the tumor formation ability in nude mice. In summary, HAND2-AS1 may exert inhibitory effects on cervical cancer cell growth and cervical cancer development through its regulation on the miR-21-5p/TIMP3/VEGFA axis. This highlights that HAND2-AS1 may serve as a potential target for cervical cancer diagnosis and treatment.

MicroRNA-101 inhibits cadmium-induced angiogenesis by targeting cyclooxygenase-2 in primary human umbilical vein endothelial cells

Exposure to toxic metal contaminants, such as cadmium compounds (Cd²⁺), has been shown to induce adverse effects on various organs and tissues. In particular, blood vessels are severely impacted by Cd²⁺ exposure, which may lead to cardiovascular diseases (CVDs). According to previous studies, CVDs are associated with increased cyclooxygenase 2 (COX-2) levels. However, the mechanisms by which CdCl₂-induced COX-2 overexpression leads to cardiovascular dysfunction remain unclear. Herein, we show that the relative gene expressions of VEGF and PTGS2 (COX-2 encoding gene) are positively correlated in CVDs patients. Moreover, we demonstrate that the in vitro administration of CdCl₂ induces cytotoxicity and endoplasmic reticulum (ER) stress in primary human umbilical vein endothelial cells (HUVECs). The induction of ER stress and the overexpression of COX-2 in CdCl₂-treated cells alters the protein level of vascular endothelial growth factor (VEGF), resulting in abnormal angiogenesis and increased cytotoxicity. At the pre-transcription level, the inhibition of ER stress by siGRP78 (a key mediator of ER stress) can restore normal angiogenesis in the CdCl₂-exposed cells. Meanwhile, at the transcription level, the adverse effects of CdCl₂ exposure may be reversed via genetic modification with siRNA (siPTGS2) or by using phytochemical inhibitors (parthenolide, PN) of COX-2. Finally, at the post-transcription level, COX-2 expression may be restricted by the binding of microRNA-101 (miR-101) to the 3'-UTR of PTGS2 mRNA. The use of mimic miR-101 (mi101) to induce the expression of miR-101 eventually leads to reduced COX-2 protein levels, relieved ER stress, and less abnormal angiogenesis and cytotoxicity of CdCl₂-exposed primary HUVECs. Overall, our results suggest that CdCl₂-induced abnormal angiogenesis is mediated by miR-101/COX-2/VEGF-axis-dependent ER stress, and that cardiovascular dysfunction may be controlled by manipulating COX-2 at the pre-transcription, transcription, and post-transcription levels.

Knockdown of circHomer1 ameliorates METH-induced neuronal injury through inhibiting Bbc3 expression

Current studies have illustrated that circular RNAs (circRNAs) are a vital part of non-coding RNA (ncRNAs) species and highly abundant and dynamically expressed in brain. However, the exact mechanisms by which circRNAs modulate methamphetamine (METH)-induced neuronal damage still remain largely unexplored. Consistent with our previous study, the expression of circHomer1 was significantly up-regulated after METH treatment in HT-22 cells. We confirmed its loop structure by detection of its back-splice junction with qRT-PCR product via sequence. Moreover, circHomer1 was resistant against RNase R digestion compared with its linear mRNA Homer1. Inhibition of circHomer1 expression indeed alleviated METH-induced neurotoxicity, with lower apoptosis rate via flow cytometry and cleaved Caspase3 protein level. Furthermore, we speculated that Bbc3 functioned as a target of circHomer1 based on computational algorithm, and knockdown of circHomer1 actually reduced Bbc3 expression at the mRNA and protein level. Besides, suppression of Bbc3 decreased the reactive oxygen species (ROS) level and radio of PI-positive cells. Furthermore, we analyzed the correlation in pairs among circHomer1, Bbc3 and behaviors in well-developed METH-addicted models using Pearson's correlation coefficient, which implied an important role of circHomer1 and Bbc3 in addictive behaviors. In all, we for the first time identified a novel circRNA, circHomer1 and our results suggested that circHomer1 regulated METH-induced lethal process by suppressing the Bbc3 expression.

The roles of microRNA in human cervical cancer

Although a potentially preventable disease, cervical cancer (CC) is the second most commonly diagnosed gynaecological cancer with at least 530,000 new cases annually, and the prognosis with CC is still poor. Studies suggest that aberrant expression of microRNA (miRNA) contributes to the progression of CC. As a group of small non-coding RNA with 18-25 nucleotides, miRNA regulate about one-third of all human genes. They function by repressing translation or inducing mRNA cleavage or degradation, including genes involved in diverse and important cellular processes, including cell cycling, proliferation, differentiation, and apoptosis. Results showed that misexpression of miRNA is closely related to the onset and progression of CC. This review will provide an overview of the function of miRNA in CC and the mechanisms involved in cervical carcinogenesis.

Human Papillomavirus Infections, Cervical Cancer and MicroRNAs: An Overview and Implications for Public Health

Human Papillomavirus (HPV) is among the most common sexually transmitted infections in both females and males across the world that generally do not cause symptoms and are characterized by high rates of clearance. Persistent infections due at least to twelve well-recognized High-Risk (HR) or oncogenic genotypes, although less frequent, can occur, leading to diseases and malignancies, principally cervical cancer. Three vaccination strategies are currently available for preventing certain HR HPVs-associated diseases, infections due to HPV6 and HPV11 low-risk types, as well as for providing cross-protection against non-vaccine genotypes. Nevertheless, the limited vaccine coverage hampers reducing the burden of HPV-related diseases globally. For HR HPV types, especially HPV16 and HPV18, the E6 and E7 oncoproteins are needed for cancer development. As for other tumors, even in cervical cancer, non-coding microRNAs (miRNAs) are involved in posttranscriptional regulation, resulting in aberrant expression profiles. In this study, we provide a summary of the epidemiological background for HPV occurrence and available immunization programs. In addition, we present an overview of the most relevant evidence of miRNAs deregulation in cervical cancer, underlining that targeting these biomolecules could lead to wide translational perspectives, allowing better diagnosis, prognosis and therapeutics, and with valuable applications in the field of prevention. The literature on this topic is rapidly growing, but advanced investigations are required to achieve more consistent findings on the up-regulated and down-regulated miRNAs in cervical carcinogenesis. Because the expression of miRNAs is heterogeneously reported, it may be valuable to assess factors and risks related to individual susceptibility.

MiR-101 acts as a novel bio-marker in the diagnosis of bladder carcinoma

MiR-101 plays an important role in tumorigenesis. The aim of this study was to estimate diagnostic potential of serum miR-101 in bladder cancer.Serum level of miR-101 in 122 bladder cancer patients and 110 healthy volunteers was detected using quantitative real-time polymerase chain reaction method. The association between miR-101 expression and clinicopathological characteristic was analyzed via χ test. Then receiver operating characteristic (ROC) curve was plotted to evaluate diagnostic value of serum miR-101 in bladder cancer.MiR-101 expression was statistically down-regulated in bladder cancer patients compared to healthy controls. MiR-101 expression was significantly associated with TNM stage (P = .019), pathological grade (P = .006) and lymph node metastasis (P = .010). ROC analysis suggested that miR-101 had high value in discriminating between bladder cancer patients and healthy individuals with an AUC value of 0.884. The cut-off value for serum miR-101 in bladder cancer diagnosis was 1.645, with a sensitivity of 82.0% and a specificity of 80.9%.MiR-101 is decreased in bladder cancer patients, and shows negative association with aggressive clinical characteristics. MiR-101 may serve as a bio-marker in diagnosing bladder cancer.

Low Serum Levels of miR-101 Are Associated with Poor Prognosis of Colorectal Cancer Patients After Curative Resection

BACKGROUND Recent studies showed low expression of microRNA (miR)-101 in various malignancies. However, the association of serum miR-101 and colorectal cancer (CRC) remains unknown. We investigated diagnostic and prognostic significance of serum miR-101 in CRC. MATERIAL AND METHODS A total of 263 consecutive CRC patients and 126 healthy controls were enrolled in this study. Serum miR-101 levels were measured using real-time quantitative reverse transcription polymerase chain reactions. The association between serum miR-101 level and survival outcome was analyzed. RESULTS Serum miR-101 in CRC patients was significantly lower than in healthy volunteers (P<0.001). Low serum miR-101 level was significantly associated with advanced cancer stage. Moreover, survival analysis demonstrated that patients with a low serum miR-101 had poorer 5-year overall survival than patients with a high serum miR-101 level (p=0.041). Serum miR-101 level also were confirmed as an independent risk factor for CRC in multivariate analysis (hazard ratio, 1.468; 95%CI, 0.981-1.976; p<0.001). CONCLUSIONS Serum miR-101 level was significantly downregulated in CRC patients and was closely correlated with poor clinical outcome, suggesting that serum miR-101 might be a useful diagnostic and prognostic marker for CRC.

miR-1238 inhibits cell proliferation by targeting LHX2 in non-small cell lung cancer

In human cancers, dysregulated expression of LIM-homeobox gene 2 (LHX2) and downregulation of miR-1238 has been reported separately. However, the relationship between them remains unclear. We investigated the functional contribution of miR-1238 to the regulation of LHX2 in non-small cell lung cancer (NSCLC). Here, computational algorithms predicted that the 3′-untranslated region (3′-UTR) of LHX2 is a target of miR-1238. Luciferase assays validated that miR-1238 directly bound to 3′-UTR of LHX2. qRT-PCR and western blot analyses further confirmed that overexpression of miR-1238 mimic in NSCLC A549 and LTEP-α-2 cells inhibited endogenous expression of LHX2 mRNA and protein. Moreover, ectopic expression of miR-1238 in NSCLC A549 and LTEP-α-2 cells suppressed cellular viability and proliferation. siRNA-induced knockdown of LHX2 copied the phenotype of miR-1238 overexpression in NSCLC A549 and LTEP-α-2 cells and LHX2 knockdown inhibited cell cycle. In addition, miR-1238 expression was frequently decreased in human NSCLC tissues and reversely correlated with LHX2 expression, which was increased in NSCLC tissues. Collectively, our findings demonstrate that miR-1238 inhibit the proliferation of NSCLC cells at least partly via repression of LHX2, shedding light on the mechanistic interaction of miR-1238 and LHX2 in NSCLC carcinogenesis. Furthermore, our data suggest that expression of miR-1238 could be a promising therapeutic strategy for NSCLC treatment.

Cyclooxygenase-2, a Potential Therapeutic Target, Is Regulated by miR-101 in Esophageal Squamous Cell Carcinoma

BACKGROUND & AIMS

Cyclooxygenase-2 (COX-2) is known to promote the carcinogenesis of esophageal squamous cell carcinoma (ESCC). There are no reports on whether microRNAs (miRNAs) regulate COX-2 expression in ESCC. This study investigated the effect of miR-101 on ESCC through modulating COX-2 expression in ESCC.

METHODS

Real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) was used to quantify miR-101 expression in ESCC clinical tissues and cell lines. The effects of miR-101 on ESCC progression were evaluated by cell counting kit-8 (CCK8), transwell migration and invasion assays, as well as by flow cytometry. The COX-2 and PEG2 levels were determined by western blot and enzyme-linked immunosorbent assays (ELISA). The luciferase reporter assay was used to verify COX-2 as a direct target of miR-101. The anti-tumor activity of miR-101 in vivo was investigated in a xenograft nude mouse model of ESCC.

RESULTS

Downregulation of miR-101 was confirmed through comparison of 30 pairs of ESCC tumor and adjacent normal tissues (P < 0.001), as well as in 11 ESCC cell lines and a human immortalized esophageal cell line (P < 0.001). Transfection of miR-101 in ESCC cell lines significantly suppressed cell proliferation, migration, and invasion (all P < 0.001). The antitumor effect of miR-101 was verified in a xenograft model. Furthermore, COX-2 was shown to be a target of miR-101.

CONCLUSIONS

Overexpression of miR-101 in ESCC inhibits proliferation and metastasis. Therefore, the miR-101/COX-2 pathway might be a therapeutic target in ESCC.

MicroRNA-101 inhibits the migration and invasion of intrahepatic cholangiocarcinoma cells via direct suppression of vascular endothelial growth factor-C

MicroRNAs (miRs) have important roles in the pathogenesis of human malignancy. It has previously been suggested that deregulation of miR‑101 is associated with the progression of intrahepatic cholangiocarcinoma (ICC); however, the exact role of miR‑101 in the regulation of ICC metastasis remains largely unknown. The present study demonstrated that the expression levels of miR‑101 were significantly decreased in ICC tissue, as compared with matched adjacent normal tissue. Furthermore, miR‑101 was downregulated in the ICC‑9810 human ICC cell line, as compared with in the normal human intrahepatic biliary epithelial cell (HIBEC) line. Vascular endothelial growth factor (VEGF)‑C was identified as a target gene of miR‑101 in ICC‑9810 cells. The expression of VEGF‑C was negatively regulated by miR‑101 at the post‑transcriptional level in ICC‑9810 cells. Further investigation demonstrated that overexpression of miR‑101 markedly suppressed the migration and invasion of ICC‑9810 cells, and these effects were similar to those observed following VEGF‑C knockdown. Conversely, restoration of VEGF‑C reversed the inhibitory effects of miR‑101 overexpression on ICC‑9810 cell migration and invasion, thus suggesting that miR‑101 may suppress ICC‑9810 cell migration and invasion, at least partly via inhibition of VEGF‑C. It was also demonstrated that the mRNA and protein expression levels of VEGF‑C were frequently upregulated in ICC tissue and cells, and its expression level was inversely correlated with that of miR‑101 in ICC tissue. In conclusion, the present study identified important roles for miR‑101 and VEGF‑C in ICC, suggesting that miR‑101/VEGF‑C signaling may be a promising diagnostic and/or therapeutic target for ICC.

MicroRNA-146a enhances Helicobacter pylori induced cell apoptosis in human gastric cancer epithelial cells

Helicobacter pylori (H. pylori) infection induces apoptosis in gastric epithelial cells, and this occurrence may link to gastric carcinogenesis. However, the regulatory mechanism of H. pylori-induced apoptosis is not clear. MicroRNA-146a has been implicated as a key regulator of the immune system. This report describes our discovery of molecular mechanisms of microRNA-146a regulation of apoptosis in human gastric cancer cells. We found that overexpression of microRNA-146a by transfecting microRNA-146a mimics could significantly enhance apoptosis, and this up-regulation was triggered by COX-2 inhibition. Furthermore, we found that microRNA-146a density was positively correlated with apoptosis rates in H. pylori-positive gastric cancer tissues and intratumoral microRNA-146a density was negatively correlated with lymph node metastasis among H. pylori-positive gastric cancer patients. Understanding the important roles of microRNA-146a in regulating cell apoptosis in H. pylori infected human gastric cancer cells will contribute to the development of microRNA targeted therapy in the future.

MicroRNAs: biogenesis, roles for carcinogenesis and as potential biomarkers for cancer diagnosis and prognosis

MicroRNAs (miRNAs) are short non-coding RNAs of 20-24 nucleotides that play important roles in carcinogenesis. Accordingly, miRNAs control numerous cancer-relevant biological events such as cell proliferation, cell cycle control, metabolism and apoptosis. In this review, we summarize the current knowledge and concepts concerning the biogenesis of miRNAs, miRNA roles in cancer and their potential as biomarkers for cancer diagnosis and prognosis including the regulation of key cancer-related pathways, such as cell cycle control and miRNA dysregulation. Moreover, microRNA molecules are already receiving the attention of world researchers as therapeutic targets and agents. Therefore, in-depth knowledge of microRNAs has the potential not only to identify their roles in cancer, but also to exploit them as potential biomarkers for cancer diagnosis and identify therapeutic targets for new drug discovery.

Micro ribonucleic acid (RNA)-101 inhibits cell proliferation and invasion of lung cancer by regulating cyclooxygenase-2

Background

Micro ribonucleic acid (miR-101) can regulate the expression of cyclooxygenase-2 (COX-2) and participate in the pathogenesis of malignant tumors. This study investigates the effects of miRNA-101 and COX-2 in lung cancer and the impact of miR-101 on the proliferation and invasion of human lung cancer A549 cell line.

Methods

The expression of miR-101 in 20 separate lung cancer tissues was detected by real time polymerase chain reaction; COX-2 expression was also detected. A549 cells were transfected with miR-101 or negative control oligonucleotide duplex mimic (miR-NC). In vivo tumorigenesis abilities were detected in localized human lung cancer xeno-transplant models in BALB/c nude mice.

Results

MiR-101 expression was significantly lower and the level of COX-2 significantly higher in lung cancer tissues than in adjacent parenchyma (2.918 ± 1.006 vs. 5.953 ± 1.976, P = 0.001; 0.887 ± 0.260 vs. 0.355 ± 0.156, P = 0.001, respectively). Correlation analysis revealed that miR-101 negatively correlated with COX-2 in lung cancer tissues (R = −0.596, P = 0.002). Compared with A549-miR-NC cells, the expression of COX-2 was significantly decreased in A549 cells transfected with miR-101 (P < 0.001). The proliferation of A549 cells was markedly inhibited after transfection of miR-101. The in vivo tumor growth of A549 cells transfected with miR-101 was significantly slower than wide type A549 cells.

Conclusion

MiR-101 expression is decreased in lung cancer, inducing an increase in COX-2 level. Enforced expression of miR-101 can remarkably reduce the cell proliferation and invasion ability of lung cancer cells.

Meta-analysis of microRNA expression profiling studies in human cervical cancer

Cervical cancer is one of the most common malignant tumors in women, and numerous studies have associated the disease with changes in microRNA (miRNA) expression. This meta-analysis aimed to consolidate and assess the results of these studies in order to identify potential miRNA biomarkers of cervical cancer. We systematically searched the literature for studies comparing miRNA expression between cervical cancer tissues and normal cervical tissues, and we meta-analyzed the result of 27 studies comprising 1,132 cancer samples and 943 normal samples. We used a vote-counting strategy that took into account total sample and mean fold-change, in order to comprehensively assess associations between certain miRNAs and cervical cancer occurrence and progression. The studies described 195 miRNAs that were significantly up-regulated and 96 microRNAs that were down-regulated in cervical cancer tissues (stage I-IV) relative to normal cervical tissues. Vote-counting analysis showed that up-regulation was most consistently reported for miR-20a and miR-21 (four studies), followed by miR-10a, miR-15b, miR-20b, miR-141, miR-200a, and miR-224 (three studies). Down-regulation was reported most consistently for miR-143 (seven studies), followed by miR-203 and miR-145 (six studies). Fourteen miRNA, respectively, showed a significantly correlated lymphatic node metastasis in eight studies. This meta-analysis has identified several miRNAs whose expression correlates reliably with cervical cancer. These should be probed in further studies to explore their potential as diagnostic biomarkers.

Dependence of intracellular and exosomal microRNAs on viral E6/E7 oncogene expression in HPV-positive tumor cells

Specific types of human papillomaviruses (HPVs) cause cervical cancer. Cervical cancers exhibit aberrant cellular microRNA (miRNA) expression patterns. By genome-wide analyses, we investigate whether the intracellular and exosomal miRNA compositions of HPV-positive cancer cells are dependent on endogenous E6/E7 oncogene expression. Deep sequencing studies combined with qRT-PCR analyses show that E6/E7 silencing significantly affects ten of the 52 most abundant intracellular miRNAs in HPV18-positive HeLa cells, downregulating miR-17-5p, miR-186-5p, miR-378a-3p, miR-378f, miR-629-5p and miR-7-5p, and upregulating miR-143-3p, miR-23a-3p, miR-23b-3p and miR-27b-3p. The effects of E6/E7 silencing on miRNA levels are mainly not dependent on p53 and similarly observed in HPV16-positive SiHa cells. The E6/E7-regulated miRNAs are enriched for species involved in the control of cell proliferation, senescence and apoptosis, suggesting that they contribute to the growth of HPV-positive cancer cells. Consistently, we show that sustained E6/E7 expression is required to maintain the intracellular levels of members of the miR-17~92 cluster, which reduce expression of the anti-proliferative p21 gene in HPV-positive cancer cells. In exosomes secreted by HeLa cells, a distinct seven-miRNA-signature was identified among the most abundant miRNAs, with significant downregulation of let-7d-5p, miR-20a-5p, miR-378a-3p, miR-423-3p, miR-7-5p, miR-92a-3p and upregulation of miR-21-5p, upon E6/E7 silencing. Several of the E6/E7-dependent exosomal miRNAs have also been linked to the control of cell proliferation and apoptosis. This study represents the first global analysis of intracellular and exosomal miRNAs and shows that viral oncogene expression affects the abundance of multiple miRNAs likely contributing to the E6/E7-dependent growth of HPV-positive cancer cells.