Cell cycle‐related and expression‐elevated protein in tumor overexpression is associated with proliferation behaviors and poor prognosis in non‐small‐cell lung cancer

The cell cycle‐related and expression‐elevated protein in tumor (CREPT) is overexpressed in several human malignancies. However, the clinical relevance of CREPT expression and its biological role in non‐small‐cell lung cancer (NSCLC) remains unclear. In this study, we detected the expression of CREPT in both NSCLC tissues and cell lines by immunohistochemistry, Western blot analysis, and RT‐PCR. The correlation between CREPT expression and clinicopathologic features was analyzed in 271 NSCLC patients. The prognostic value of CREPT expression was evaluated by Kaplan–Meier analysis and Cox regression analysis. CREPT was overexpressed in Calu‐1 cell lines by using plasmid vector and its biological function was explored both in vitro and in vivo. We found that CREPT was significantly overexpressed in NSCLC compared with paired adjacent non‐tumor tissues, and the expression level of CREPT was correlated with tumor differentiation, lymph node metastasis, and clinical stage. Kaplan–Meier analysis showed that the recurrence‐free survival and overall survival of high CREPT expression groups were significantly shorter than those of the low CREPT expression group. Multivariate analysis identified that CREPT might be an independent biomarker for the prediction of NSCLC prognosis. Overexpression of CREPT increased cell proliferation and enhanced the migration and invasion ability of Calu‐1 cells (a human NSCLC cell line with relative low CRPET expression) in vitro. Moreover, CREPT overexpression promoted tumor growth in a nude mice model. These results suggest that CREPT is closely relevant to the proliferation of NSCLC cells and it might be a potential prognostic marker in NSCLC patients.     

miR‐203 inhibits cell proliferation,invasion, and migration of non‐small‐cell lung cancer by downregulating RGS17

Involvement of the RGS17 oncogene in the promotion of non‐small‐cell lung cancer (NSCLC) has been reported, but the regulation mechanism in NSCLC remains unclear. MicroRNAs (miRNAs) negatively regulate gene expression, and their dysregulation has been implicated in tumorigenesis. To understand the role of miRNAs in Regulator of G Protein Signaling 17 (RGS17)‐induced NSCLC, we showed that miR‐203 was downregulated during tumorigenesis, and inhibited the proliferation and invasion of lung cancer cells. We then determined whether miR‐203 regulated NSCLC by targeting RGS17. To characterize the regulatory effect of miR‐203 on RGS17, we used lung cancer cell lines, A549 and Calu‐1, and the constructed miR‐203 and RGS17 overexpression vectors. The CCK8 kit was used to determine cell proliferation, and the Transwell® assay was used to measure cell invasion and migration. RT‐PCR, western blots, and immunofluorescence were used to analyze expression of miR‐203 and RGS17, and the luciferase reporter assay was used to examine the interaction between miR‐203 and RGS17. Nude mice were used to characterize in vivo tumor growth regulation. Expression of miR‐203 inhibited proliferation, invasion, and migration of lung cancer cell lines A549 and Calu‐1 by targeting RGS17. The regulatory effect of miR‐203 was inhibited after overexpression of RGS17. The luciferase reporter assay showed that miR‐203 downregulated RGS17 by direct integration into the 3′‐UTR of RGS17 mRNA. In vivo studies showed that expression of miR‐203 significantly inhibited growth of tumors. Taken together, the results suggested that expression of miR‐203 inhibited tumor growth and metastasis by targeting RGS17.     

High G2 and S‐phase expressed 1 expression promotes acral melanoma progression and correlates with poor clinical prognosis

G2 and S‐phase expressed 1 (GTSE1) regulates cell cycle progression in human cancers. However, its significance and mechanism of action in acral melanoma (AM) remain unknown. In the present study, we found that GTSE1 expression was upregulated in advanced stage/metastatic AM tissues and metastatic cell lines, and correlated with higher stage (P = .028) and poor disease‐free survival (DFS) in patients with AM (P = .003). Cox regression assays validated GTSE1 expression to be an independent prognostic factor of DFS for patients with AM (P = .004). Ectopic expression of GTSE1 enhanced primary AM cell proliferation, invasion, and migration. Loss‐of‐function in GTSE1 attenuated metastatic AM cell proliferation and metastatic ability in vitro and in vivo. We additionally observed that inhibition of migration and invasion occurred concomitantly with a GTSE1 knockdown‐mediated increase in E‐cadherin and decreases in N‐cadherin and Slug. We further showed that integrin subunit alpha 2 (ITGA2) interacts with GTSE1 and is a downstream effector of GTSE1. Further, ITGA2 levels were positively correlated with GTSE1 expression in human AM tissues. Ectopic ITGA2 expression rescued siGTSE1‐mediated inhibition of migration and invasion, thereby restoring epithelial‐to‐mesenchymal transition (EMT). In conclusion, GTSE1 expression promotes AM progression and correlates with clinical outcomes of patients with AM, and may represent a promising therapeutic target to suppress AM progression.     

Cancer‐associated fibroblast migration in non‐small cell lung cancers is modulated by increased integrin α11 expression

Cancer‐associated fibroblasts (CAFs) regulate cancer progression through the modulation of extracellular matrix (ECM) and cancer cell adhesion. While undergoing a series of phenotypic changes, CAFs control cancer–stroma interactions through integrin receptor signaling. Here, we isolated CAFs from patients with non‐small‐cell lung cancer (NSCLC) and examined their gene expression profiles. We identified collagen type XI α1 (COL11A1), integrin α11 (ITGA11), and the ITGA11 major ligand collagen type I α1 (COL1A1) among the 390 genes that were significantly enriched in NSCLC‐associated CAFs. Increased ITGA11 expression in cancer stroma was correlated with a poor clinical outcome in patients with NSCLC. Increased expression of fibronectin and collagen type I induced ITGA11 expression in CAFs. The cellular migration of CAFs toward collagen type I and fibronectin was promoted via ERK1/2 signaling, independently of the fibronectin receptor integrin α5β1. Additionally, ERK1/2 signaling induced ITGA11 and COL11A1 expression in cancer stroma. We, therefore, propose that targeting ITGA11 and COL11A1 expressing CAFs to block cancer–stroma interactions may serve as a novel, promising anti‐tumor strategy.     

Overexpression of TRIM44 contributes to malignant outcome in gastric carcinoma

Recent studies have shown that some members of the tripartite motif‐containing protein (TRIM) family, which is characterized by a conserved RING finger, B‐box, and coiled‐coil domains, function as important regulators for carcinogenesis. In this study, we tested whether TRIM44 (11p13) acts as a cancer‐promoting gene through overexpression in gastric cancer. We analyzed seven gastric cancer cell lines and 112 primary tumors, which were curatively resected in our hospital between 2001 and 2003. Expression of the TRIM44 protein was detected in gastric cancer cell lines (2/7 cell lines; 29%) and primary tumor samples of gastric cancer (29/112 cases; 25%). Knockdown of TRIM44 expression using several specific siRNAs inhibited the proliferation, migration, and invasion of TRIM44‐overexpressing cells. Overexpression of the TRIM44 protein was significantly correlated with an advanced type of macroscopic appearance, lymphatic invasion, and higher recurrence rate. TRIM44‐overexpressing tumors had a worse overall rate of survival than those with non‐expressing tumors (P = 0.0038, log–rank test) in both intensity and proportion expression‐dependent manner. TRIM44 positivity was independently associated with worse outcome in multivariate analysis (P = 0.0233, hazard ratio 3.37 [1.18–9.64]). These findings suggest that TRIM44 plays a crucial role in tumor cell proliferation through its overexpression, and highlight its usefulness as a predictor and potential therapeutic target in gastric cancer.     

KIAA0247 inhibits growth,migration, invasion of non‐small‐cell lung cancer through regulating the Notch pathway

Lung cancer remains the leading cause of cancer‐related death worldwide. Previous studies have shown that the novel KIAA0247 gene potentially targeted by the tumor suppressor p53 may inhibit the development of several cancers. However, the exact function of KIAA0247 in non‐small‐cell lung cancer (NSCLC) is unknown. The purpose of the present study was to clarify the role of KIAA0247 in NSCLC. KIAA0247 expression was evaluated in tumors and adjacent normal tissues of 197 NSCLC patients by immunohistochemistry and real‐time PCR and analyzed for association with clinicopathological parameters. Results indicated that KIAA0247 levels positively correlated with cell differentiation (P < .001) and patient survival (P < .0001) and negatively correlated with lymph node metastasis (P < .001) and advanced p‐TNM stage (P < .001). In cultured NSCLC cell lines, KIAA0247 overexpression inhibited cell migration, invasion, and proliferation and downregulated the expression of Jagged1, Notch1 intracellular domain (NICD), Snail, cyclin D1, RhoA, RhoC, and MMP9, while upregulating that of E‐cadherin and p21. The Notch inhibitor DAPT reduced the biological effects of KIAA0247 knockdown, suggesting that KIAA0247 decreased the carcinogenic activity of NSCLC cells through downregulation of Notch signaling. Our results indicate that KIAA0247 inhibits NSCLC progression by reducing the metastatic potential of cancer cells through downregulation of the Notch pathway, which may underlie the association of KIAA0247 expression with favorable clinicopathological characteristics of NSCLC patients. These findings suggest that KIAA0247 is a candidate prognostic biomarker and potential therapeutic target in NSCLC.     

Tumor‐suppressive microRNA‐223 inhibits cancer cell migration and invasion by targeting ITGA3/ITGB1 signaling in prostate cancer

Analysis of microRNA (miRNA) expression signatures in prostate cancer (PCa) and castration‐resistant PCa has revealed that miRNA‐223 is significantly downregulated in cancer tissues, suggesting that miR‐223 acts as a tumor‐suppressive miRNA by targeting oncogenes. The aim of this study was to investigate the functional roles of miR‐223 and identify downstream oncogenic targets regulated by miR‐223 in PCa cells. Functional studies of miR‐223 were carried out to investigate cell proliferation, migration, and invasion using PC3 and PC3M PCa cell lines. Restoration of miR‐223 significantly inhibited cancer cell migration and invasion in PCa cells. In silico database and genome‐wide gene expression analyses revealed that ITGA3 and ITGB1 were direct targets of miR‐223 regulation. Knockdown of ITGA3 and ITGB1 significantly inhibited cancer cell migration and invasion in PCa cells by regulating downstream signaling. Moreover, overexpression of ITGA3 and ITGB1 was observed in PCa clinical specimens. Thus, our data indicated that downregulation of miR‐223 enhanced ITGA3/ITGB1 signaling and contributed to cancer cell migration and invasion in PCa cells. Elucidation of the molecular pathways modulated by tumor‐suppressive miRNAs provides insights into the mechanisms of PCa progression and metastasis.     

shRNA抑制非小细胞肺癌H460SM细胞锚定非依赖生长和侵袭

目的:探讨慢病毒介导α6整合素(integrinα6,ITGA6)shRNA对人非小细胞肺癌(non-small cell lung cancer,NSCLC)H460SM细胞生长和侵袭的影响。方法:实时定量PCR和Western blotting检测ITGA6在9种NSCLC细胞中的表达。慢病毒介导ITGA6 shRNA感染H460SM细胞后,实时定量PCR和Wesern blotting检测H460SM中ITGA6的表达,显微镜下观察H460SM细胞形态的变化,MTS法检测细胞增殖,软琼脂实验检测H460SM细胞锚定非依赖性生长,流式细胞术检测细胞凋亡和细胞周期,迁移和侵袭实验检测H460SM细胞体外迁移和侵袭能力。结果:ITGA6在7种人NSCLC细胞中均有表达,H460SM细胞中ITGA6表达水平明显高于亲本H460细胞[(8.75±0.09)vs(5.78±0.26),P<0.01]。慢病毒介导ITGA6shRNA稳定感染H460SM细胞后的H460SM-75、H460SM-76细胞中,ITGA6表达水平明显低于阴性对照组H460SM-NS细胞[(0.11±0.04)、(0.22±0.04)vs(1.00±0.01),P<0.01]。H460SM-75、H460SM-76细胞增殖活性与H460SM-NS细胞无差异(P>0.05),且凋亡率、细胞增殖指数、G0/G1期细胞的比例也无差异(P>0.05)。H460SM-75、H460SM-76细胞的克隆形成率明显低于H460SM-NS细胞[(18.87±1.47)%、(18.85±1.11)%vs(20.81±1.38)%,P<0.05],迁移率[(43.92±0.41)%、(24.10±0.33)%vs(100.00±0.50)%,P<0.01]和侵袭率[(7.04±2.96)%、(4.68±0.27)%vs(100.00±6.74)%,P<0.01]也明显低于H460SM-NS细胞。结论:抑制ITGA6的表达可以抑制NSCLC细胞锚定非依赖性生长、迁移和侵袭,但不影响NSCLC细胞增殖和凋亡。     

Significant role of Psf3 expression in non‐small‐cell lung cancer

The GINS complex associates with cell division cycle (Cdc) protein 45 and mini‐chromosome maintenance (Mcm) proteins 2–7 to form the Cdc45–Mcm–GINS (CMG) complex, which is essential for DNA duplication. One member of the GINS complex is Psf3. We previously found that increased Psf3 expression was strongly associated with poor survival in lung adenocarcinoma. Here, we investigated the role of Psf3 expression in non‐small‐cell lung cancer (NSCLC). We verified Psf3 expression in human NSCLC tissues (180 patients) and cell lines. Immunohistochemical analysis revealed that the overexpression of Psf3 was significantly associated with vessel invasion (P = 0.016), lymphatic invasion (P = 0.002), and pleural invasion (P = 0.036). The overall survival rate in patients with Psf3 overexpression was significantly lower than that in patients without Psf3 overexpression (P = 0.006). Multivariate survival analysis revealed Psf3 expression to be an independent risk factor for an unfavorable outcome (P = 0.049). A proximal ligation assay showed interactions between Psf3 and other CMG components (such as Mcm2 and Cdc45) in both NSCLC specimens and cell lines, indicating that Psf3 acted as the CMG complex, which could lead to excessive proliferation. Knockdown of Psf3 inhibited the proliferation of both cell lines by delaying the S phase, which revealed that Psf3 played an important role in cancer proliferation. Thus, Psf3 acted as the CMG complex, promoting excessive proliferation. These results suggest that Psf3 inhibition might be a therapeutic target for NSCLC with Psf3 overexpression.     

p0071 interacts with E‐cadherin in the cytoplasm so as to promote the invasion and metastasis of non‐small cell lung cancer

As a member of the p120‐catenin (p120ctn) subfamily, the p0071 study in tumor is very limited. We demonstrated the clinicopathological significance of p0071 in non‐small cell lung cancer (NSCLC), as well as E‐cadherin. Co‐immunoprecipitation was used to detect the interaction of p0071 with E‐cadherin in A549 and SPC cells (E‐cadherin is mainly expressed in the cytoplasm of these cells). p0071 cytoplasmic expression was knocked down by siRNA in these cells and this effect on the RhoA activity and cell invasion and migration ability were measured. p0071 overexpression in the cytoplasm of tumor cell was correlated with lymphatic metastase and poor prognosis of NSCLC. The patients with both abnormal expression of p0071 and E‐cadherin (cytoplasmic expression) had a statistically significant shorter survival than the patients without both abnormal expression (P < 0.05). There is a significant correlation between cytoplasmic overexpression of p0071 and E‐cadherin in NSCLC tissues. p0071 interacted with E‐cadherin in the cytoplasm of A549 and SPC cell lines. Treatment with siRNA‐p0071 inhibited the invasion and migration ability of NSCLC cells. Above results confirmed that p0071 interacted with E‐cadherin in the cytoplasm so as to promote the invasion and metastasis of NSCLC.     

miR-374a对肺腺癌细胞增殖与侵袭迁移的影响

目的探究分析miR-374a对非小细胞肺癌细胞增殖、侵袭、迁移等生物学行为能力的影响。方法采用RT-PCR检测miR-374a在正常肺上皮细胞CCD-8L及非小细胞肺癌细胞A549、H1975中的表达情况。采用miR-374a mimic和miR-374a inhibitor转染非小细胞肺癌细胞A549、H1975,采用RT-PCR检测各组细胞转染效率。分别采用CCK8细胞增殖实验、平板克隆实验、Transwell迁移实验和Transwell侵袭实验检测转染前后非小细胞肺癌细胞株增殖、迁移及侵袭能力变化情况。结果与正常肺上皮细胞CCD-8L比较,非小细胞肺癌细胞A549、H1975中miR-374a呈稳定高表达(P<0.05)。miR-374a mimic、miR-374a inhibitor可分别瞬时过表达、低表达非小细胞肺癌细胞A549、H1975中miR-374a表达情况(P<0.05)。过表达miR-374a可促进非小细胞肺癌细胞A549、H1975的增殖、迁移和侵袭(P<0.05);靶向抑制miR-374a表达可抑制非小细胞肺癌细胞A549、H1975的增殖、迁移和侵袭(P<0.05),组间差异显著,具有统计学意义。结论miR-374a在非小细胞肺癌细胞A549、H1975中呈稳定高表达,过表达miR-374a可明显促进非小细胞肺癌细胞A549、H1975的增殖、迁移和侵袭。     

Copy number variation,increased gene expression,and molecular mechanisms of neurofascin in lung cancer

Metastasis and cell adhesion are key aspects of cancer progression. Neurofascin (NFASC) is a member of the immunoglobulin superfamily of adhesion molecules and, while studies on NFASC are inadequate, other members have been indicated pivotal roles in cancer progression and metastasis. This study aimed at increasing the knowledge on the involvement of adhesion molecules in lung cancer progression by studying the regulation and role of NFASC in non‐small cell lung cancer (NSCLC). Here, copy number variations in the NFASC gene were analyzed in tumor and non‐tumorous lung tissues of 204 NSCLC patients. Frequent gene amplifications (OR = 4.50, 95%CI: 2.27‐8.92, P ≤ 0.001) and increased expression of NFASC (P = 0.034) were identified in tumors of NSCLC patients. Furthermore, molecular mechanisms of NFASC in lung cancer progression were evaluated by investigating the effects of NFASC silencing on cell proliferation, viability, migration, and invasion using siRNA technology in four NSCLC cell lines. Silencing of NFASC did not affect cell proliferation or viability but rather decreased NSCLC cell migration (P ≤ 0.001) and led to morphological changes, rearrangements in the actin cytoskeleton and changes in F‐actin networks in migrating NSCLC cell lines. This study is the first to report frequent copy number gain and increased expression of NFASC in NSCLC. Moreover, these data suggest that NFASC is a novel regulator of NSCLC cell motility and support a role of NFASC in the regulation of NSCLC progression.     

The chemokine receptor CCR4 promotes tumor growth and lung metastasis in breast cancer

Increasing evidence has shown that chemokines and chemokine receptors are associated with tumor growth and metastasis. CCR4, an important chemokine receptor for regulating immune homeostasis, is thought to be involved in hematologic malignancies and has also recently implicated in some solid tumors, such as gastric cancer. The possible role of CCR4 in breast cancer has not been well elucidated. In this study, we show that CCR4 is differentially expressed in human breast cancer cell lines. Specifically, we find that CCR4 is overexpressed in breast cancer cell lines with high metastatic potential. More importantly, we used a combination of overexpression and RNA interference to demonstrate that CCR4 promotes breast tumor growth and lung metastasis in mice. Furthermore, we find that microvessel density is significantly increased in tumors formed by CCR4-overexpressing cells and decreased in those formed by CCR4-knockdown cells. We find that overexpression of CCR4 can enhance the chemotactic response of breast cancer cells to CCL17. However, the expression of CCR4 does not affect the proliferation of breast cancer cells in vitro. Furthermore, we show that CCR4 expression is positively correlated with HER2 expression, tumor recurrence and lymph node, lung and bone metastasis (P < 0.05). Multivariate analysis showed that CCR4 expression is a significant independent prognostic factor for overall survival (P = 0.036) but not for disease-free survival in patients with breast cancer (P = 0.071). Survival analysis indicated a strong association between CCR4 expression and lower overall survival (P = 0.0001) and disease-free survival (P = 0.016) in breast cancer.     

Low miR-145 silenced by DNA methylation promotes NSCLC cell proliferation,migration and invasion by targeting mucin 1

MiR-145 has been implicated in the progression of non-small cell lung cancer (NSCLC); however, its exact mechanism is not well established. Here, we report that miR-145 expression is decreased in NSCLC cell lines and tumor tissues and that this low level of expression is associated with DNA methylation. MiR-145 methylation in NSCLC was correlated with a more aggressive tumor phenotype and was associated with poor survival time, as shown by Kaplan-Meier analysis. Additional multivariate Cox regression analysis indicated that miR-145 methylation was an independent prognostic factor for poor survival in patients with NSCLC. Furthermore, we found that restoration of miR-145 expression inhibited proliferation, migration and invasion of NSCLC by the direct targeting of mucin 1 by miR-145. Our results indicate that low miR-145 expression, due to methylation, promotes NSCLC cell proliferation, migration and invasion by targeting mucin 1. Therefore, miR-145 may be a valuable therapeutic target for NSCLC.     

Long noncoding RNA actin filament‐associated protein 1 antisense RNA 1 promotes malignant phenotype through binding with lysine‐specific demethylase 1 and repressing HMG box‐containing protein 1 in non‐small‐cell lung cancer

The number of documented long noncoding RNAs (lncRNAs) has dramatically increased, and their biological functions and underlying mechanisms in pathological processes, especially cancer, remain to be elucidated. Actin filament‐associated protein 1 antisense RNA 1 (AFAP1‐AS1) is a 6810‐nt lncRNA located on chromosome 4p16.1 that was first reported to be upregulated in esophageal adenocarcinoma tissues and cell lines. Here we reported that AFAP1‐AS1, recruiting and binding to lysine‐specific demethylase 1 (LSD1), was generally overexpressed in human non‐small‐cell lung cancer (NSCLC) tissues using quantitative real‐time PCR. Higher AFAP1‐AS1 expression was significantly correlated with larger tumor size (P = .008), lymph node metastasis (P = .025), higher TNM stage (P = .024), and worse overall survival in NSCLC patients. In vitro experiments revealed that AFAP1‐AS1 downregulation inhibited cell migration and induced apoptosis; AFAP1‐AS1 knockdown also hindered tumorigenesis in vivo. Moreover, mechanistic investigations including RNA immunoprecipitation and ChIP assays validated that AFAP1‐AS1 repressed HMG box‐containing protein 1 (HBP1) expression by recruiting LSD1 to the HBP1 promoter regions in PC‐9 and H1975 cells. Furthermore, HBP1 functions as a tumor suppressor, and its ectopic expression hindered cell proliferation. Rescue assays determined that the oncogenic effect of AFAP1‐AS1 is partially dependent on the epigenetic silencing of HBP1. In conclusion, our results indicate that AFAP1‐AS1 is carcinogenic and that the AFAP1‐AS1/LSD1/HBP1 axis could constitute a new therapeutic direction for NSCLC.     

Regulation of ITGA3 by the anti‐tumor miR‐199 family inhibits cancer cell migration and invasion in head and neck cancer

For patients with head and neck squamous cell carcinoma (HNSCC), survival rates have not improved due to local recurrence and distant metastasis. Current targeted molecular therapies do not substantially benefit HNSCC patients. Therefore, it is necessary to use advanced genomic approaches to elucidate the molecular mechanisms underlying the aggressiveness of HNSCC cells. Analysis of our microRNA (miRNA) expression signature by RNA sequencing showed that the miR‐199 family (miR‐199a‐5p, miR‐199a‐3p, miR‐199b‐5p and miR‐199b‐3p) was significantly reduced in cancer tissues. Ectopic expression of mature miRNA demonstrated that all members of the miR‐199 family inhibited cancer cell migration and invasion by HNSCC cell lines (SAS and HSC3). These findings suggested that both passenger strands and guide strands of miRNA are involved in cancer pathogenesis. In silico database and genome‐wide gene expression analyses revealed that the gene coding for integrin α3 (ITGA3) was regulated by all members of the miR‐199 family in HNSCC cells. Knockdown of ITGA3 significantly inhibited cancer cell migration and invasion by HNSCC cells. Moreover, overexpression of ITGA3 was confirmed in HNSCC specimens, and high expression of ITGA3 predicted poorer survival of the patients (P = 0.0048). Our data revealed that both strands of pre‐miR‐199a (miR‐199a‐5p and miR‐199a‐3p) and pre‐miR‐199b (miR‐199b‐5p and miR‐199b‐3p) acted as anti‐tumor miRNA in HNSCC cells. Importantly, the involvement of passenger strand miRNA in the regulation of cellular processes is a novel concept in RNA research. Novel miRNA‐based approaches for HNSCC can be used to identify potential targets for the development of new therapeutic strategies.     

Significance of P‐cadherin overexpression and possible mechanism of its regulation in intrahepatic cholangiocarcinoma and pancreatic cancer

It has become evident that P‐cadherin, one of the classical cadherins, contributes to the malignant behavior of several types of cancer. In this study, we analyzed the expression of P‐cadherin and its clinicopathological and prognostic values in intrahepatic cholangiocarcinoma (ICC) and pancreatic cancer. Furthermore, we investigated the functional role of P‐cadherin in these cancer cells by knockdown and overexpression in vitro and by analyzing the correlation between the P‐cadherin expression and its promoter methylation status. Thirty of 59 ICC cases (51%) and 36 of 73 pancreatic cancer cases (49%) stained positive for P‐cadherin with mainly membranous distribution in tumor cells by immunohistochemistry. P‐cadherin expression was significantly correlated with several clinicopathological factors, which reflect tumor behavior, and was identified as an independent adverse prognostic factor for disease‐free survival in patients with ICC (relative risk [RR] 2.93, P = 0.04) and pancreatic cancer (RR 2.68, P = 0.005) via multivariate analyses. P‐cadherin downregulation by siRNA suppressed migration and invasion, and P‐cadherin overexpression induced the opposite effects in both ICC and pancreatic cancer cells, without any effects on cell proliferation. P‐cadherin expression was related to its promoter methylation status in both cell lines and cancer tissues. In summary, P‐cadherin overexpression may serve as a useful biomarker of invasive phenotype and poor prognosis; P‐cadherin expression was found to be regulated by its promoter methylation. These results suggest that P‐cadherin represents a novel therapeutic target for the treatment of ICC and pancreatic cancer.