LKB1 loss at transcriptional level promotes tumor malignancy and poor patient outcomes in colorectal cancer

Hotspots and trends in liver kinase B1 research: A bibliometric analysis

Introduction

In the past 22 years, a large number of publications have reported that liver kinase B1 (LKB1) can regulate a variety of cellular processes and play an important role in many diseases. However, there is no systematic bibliometric analysis on the publications of LKB1 to reveal the research hotspots and future direction.

Methods

Publications were retrieved from the Web of Science Core Collection (WoSCC), Scopus, and PubMed databases. CiteSpace and VOSviewer were used to analysis the top countries, institutions, authors, source journals, discipline categories, references, and keywords.

Results

In the past 22 years, the number of LKB1 publications has increased gradually by year. The country, institution, author, journals that have published the most articles and cited the most frequently were the United States, Harvard University, Prof. Benoit Viollet, Journal of Biochemistry and Plos One. The focused research hotspot was the molecular functions of LKB1. The emerging hotspots and future trends are the clinical studies about LKB1 and co-mutated genes as biomarkers in tumors, especially in lung adenocarcinoma.

Conclusions

Our research could provide knowledge base, frontiers, emerging hotspots and future trends associated with LKB1 for researchers in this field, and contribute to finding potential cooperation possibilities.

No Tumor Suppressor Role for LKB1 in Prostate Cancer

To elucidate the pathogenesis of prostate diseases, following in silico analysis, the LKB1 gene was selected for further investigation. The LKB1 gene has been associated with poor prognosis and is frequently mutated in different types of cancers. In this study, 50 benign prostatic hyperplasia (BPH) and 57 prostate cancer (PCa) tissues, including matched normal tissue for the patients, were analyzed by qRT-PCR and DNA sequencing for LKB1 expression and the mutation profile, respectively. Expression of LKB1 was increased in 60.7% of the PCa tissues compared with noncancerous tissue samples (p ≤ 0.001). However, LKB1 expression was lower when compared with normal tissues in BPH (p = 0.920). Four coding sequence alterations were detected in BPH. Three silent mutations were located in codons 9, 32, and 275 and a missense mutation was observed in codon 384. Six alterations were identified in the intronic regions of the LKB1 gene in both PCa and BPH. Five mutations were observed in both patient groups. A new alteration in intron 6 was observed in a patient with PCa. The LKB1 gene may be associated with benign transformations rather than the tumors in prostate pathogenesis when its expression and mutation status are considered. However, the mechanism of LKB1 in PCa needs further studies.

Cigarette smoke-induced LKB1/AMPK pathway deficiency reduces EGFR TKI sensitivity in NSCLC

Smoker patients with non-small cell lung cancer (NSCLC) have poorer prognosis and survival than those without smoking history. However, the mechanisms underlying the low response rate of those patients to EGFR tyrosine kinase inhibitors (TKIs) are not well understood. Here we report that exposure to cigarette smoke extract enhances glycolysis and attenuates AMP-activated protein kinase (AMPK)-dependent inhibition of mTOR; this in turn reduces the sensitivity of NSCLC cells with wild-type EGFR (EGFR^WT) to EGFR TKI by repressing expression of liver kinase B1 (LKB1), a master kinase of the AMPK subfamily, via CpG island methylation. In addition, LKB1 expression is correlated positively with sensitivity to TKI in patients with NSCLC. Moreover, combined treatment of EGFR TKI with AMPK activators synergistically increases EGFR TKI sensitivity. Collectively, the current study suggests that LKB1 may serve as a marker to predict EGFR TKI sensitivity in smokers with NSCLC carrying EGFR^WT and that the combination of EGFR TKI and AMPK activator may be a potentially effective therapeutic strategy against NSCLC with EGFR^WT.

LKB1/STK11 Expression in Lung Adenocarcinoma and Associations With Patterns of Recurrence

BACKGROUND

Mutations in the serine/threonine kinase 11 (STK11)/liver kinase B1 (LKB1) have been implicated in mediating resistance to checkpoint blockade among patients with advanced lung adenocarcinoma. We sought to examine the associations between clinicopathologic characteristics, tumor LKB1 expression, features of the immune microenvironment, and postoperative prognosis among patients with early stage lung adenocarcinoma undergoing surgical therapy.

METHODS

Formalin-fixed, paraffin-embedded specimens of patients undergoing resection of stage I to III, chemotherapy-naïve adenocarcinomas (1997 to 2008) were analyzed using tissue microarray sectioning. Sublobar resections were excluded. Intratumoral LKB1/STK11 expression was quantified as H-score. In a subset, tumor-associated immune cell populations were quantified using whole tumor sections in peritumoral and intratumoral compartments.

RESULTS

In all, 104 patients met inclusion criteria. Expression of LKB1/STK11 (median H-score 102.9) was higher in women (median 123.3) than in men (100, P = .004) and in never-smokers (median 145) than in former/current smokers (100, P = .002). Expression of LKB1/STK11 was positively correlated with intratumoral infiltration of cluster of differentiation (CD) 3⁺ (r = 0.351, P = .005), CD4⁺ (r = 0.436, P < .001), and CD8⁺ (r = 0.263, P = .049) cells. Patients with extrathoracic recurrence had lower tumor expression of LKB1/STK11 than did other patients with recurrent disease. On multivariate analysis, low LKB1/STK11 expression remained independently associated with poor disease-free survival and distant disease-free survival.

CONCLUSIONS

Low LKB1/STK11 expression is associated with specific patient characteristics and poor postoperative prognosis in chemotherapy-naïve lung adenocarcinoma. Further investigation is warranted to delineate its clinical significance in the context of evaluating novel therapeutic agents in patients with resectable disease.

LKB1/AMPK Pathway and Drug Response in Cancer: A Therapeutic Perspective

Inactivating mutations of the tumor suppressor gene Liver Kinase B1 (LKB1) are frequently detected in non-small-cell lung cancer (NSCLC) and cervical carcinoma. Moreover, LKB1 expression is epigenetically regulated in several tumor types. LKB1 has an established function in the control of cell metabolism and oxidative stress. Clinical and preclinical studies support a role of LKB1 as a central modifier of cellular response to different stress-inducing drugs, suggesting LKB1 pathway as a highly promising therapeutic target. Loss of LKB1-AMPK signaling confers sensitivity to energy depletion and to redox homeostasis impairment and has been associated with an improved outcome in advanced NSCLC patients treated with chemotherapy. In this review, we provide an overview of the interplay between LKB1 and its downstream targets in cancer and focus on potential therapeutic strategies whose outcome could depend from LKB1.

LKB1 suppresses androgen synthesis in a mouse model of hyperandrogenism via IGF-1 signaling

Polycystic ovary syndrome (PCOS) is a major cause of anovulatory sterility in women, and most PCOS patients exhibit hyperandrogenism (HA). Liver kinase b1 (LKB1) is a tumor suppressor that has recently been reported to be involved in PCOS. However, the mechanism by which LKB1 affects HA has not previously been elucidated. We report here that ovarian LKB1 levels are significantly decreased in a female mouse model of HA. Moreover, we report that LKB1 expression is inhibited by elevated androgens via activation of androgen receptors. In addition, LKB1 treatment was observed to suppress androgen synthesis in theca cells and promote estrogen production in granulosa cells by regulating steroidogenic enzyme expression. As expected, LKB1 knockdown inhibited estrogen levels and enhanced androgen levels, and LKB1‐transgenic mice were protected against HA. The effect of LKB1 appears to be mediated via IGF‐1 signaling. In summary, we describe here a key role for LKB1 in controlling sex hormone levels.

Association between LKB1 expression and prognosis of patients with solid tumours: an updated systematic review and meta-analysis

OBJECTIVES

Liver kinase B1 (LKB1) is considered a tumour suppressor that can control cell growth and metabolism. Whether LKB1 expression levels are related to clinicopathology and prognosis is controversial. This review aimed to quantitatively examine the latest evidence on this question.

DESIGN

An updated systematic review and meta-analysis on the association between LKB1 expression and prognosis of patients with solid tumours were performed.

DATA SOURCES

Eligible studies were identified through literature searches from database establishment until 15 June 2018 in the following databases: Embase, PubMed, Web of Science, Cochrane Library, China National Knowledge Infrastructure and Wan Fang databases.

ELIGIBILITY CRITERIA

The association between LKB1 expression and clinicopathological characteristics, overall survival (OS), disease-free survival (DFS) and relapse-free survival (RFS) of patients with solid tumours were reported. Sufficient data were available to calculate the OR or HR and 95% CI.

DATA EXTRACTION AND SYNTHESIS

Relevant data were meta-analysed for OS, DFS, RFS and various clinical parameters.

RESULTS

The systematic review included 25 studies containing 6012 patients with solid tumours. Compared with patients with high LKB1 expression, patients with low expression showed significantly shorter OS in univariate analysis (HR=1.63, 95% CI 1.35 to 1.97, p<0.01) and multivariate analysis (HR=1.61, 95% CI 1.26 to 2.06, p<0.01). In contrast, the two groups showed similar DFS in univariate analysis (HR=1.49, 95% CI 0.73 to 3.01, p=0.27) as well as similar RFS in univariate analysis (HR=1.44, 95% CI 0.65 to 3.17, p=0.37) and multivariate analysis (HR=1.02, 95% CI 0.42 to 2.47, p=0.97). Patients with low LKB1 expression showed significantly worse tumour differentiation (OR=1.71, 95% CI 1.14 to 2.55, p<0.01), larger tumours (OR=1.68, 95% CI 1.24 to 2.27, p<0.01), earlier lymph node metastasis (OR=1.43, 95% CI 1.26 to 1.62, p<0.01) and more advanced tumour, node, metastases (TNM) stage (OR=1.80, 95% CI 1.56 to 2.07, p<0.01).

CONCLUSION

Low LKB1 expression predicts shorter OS, worse tumour differentiation, larger tumours, earlier lymph node metastasis and more advanced TNM stage. Low LKB1 expression may be a useful biomarker of poor clinicopathology and prognosis.

Loss of LKB1 Protein Expression Correlates with Increased Risk of Recurrence and Death in Patients with Resected, Stage II or III Colon Cancer

PURPOSE

The purpose of this study was to investigate the prognostic significance of liver kinase b1 (LKB1) loss in patients with operable colon cancer (CC).

Materials and Methods

Two hundred sixty-two specimens from consecutive patients with stage III or high-risk stage II CC, who underwent surgical resection with curative intent and received adjuvant chemotherapy with fluoropyrimidine and oxaliplatin, were analyzed for LKB1 protein expression loss, by immunohistochemistry as well as for KRAS exon 2 and BRAFV600E mutations by Sanger sequencing and TS, ERCC1, MYC, and NEDD9 mRNA expression by real-time quantitative reverse transcription polymerase chain reaction.

RESULTS

LKB1 expression loss was observed in 117 patients (44.7%) patients and correlated with right-sided located primaries (p=0.032), and pericolic lymph nodes involvement (p=0.003), BRAFV600E mutations (p=0.024), and TS mRNA expression (p=0.041). Patients with LKB1 expression loss experienced significantly lower disease-free survival (DFS) (hazard ratio [HR], 1.287; 95% confidence interval [CI], 1.093 to 1.654; p=0.021) and overall survival (OS) (HR, 1.541; 95% CI, 1.197 to 1.932; p=0.002), compared to patients with LKB1 expressing expressing tumors. Multivariate analysis revealed LKB1 expression loss as independent prognostic factor for both decreased DFS (HR, 1.217; 95% CI, 1.074 to 1.812; p=0.034) and decreased OS (HR, 1.467; 95% CI, 1.226 to 2.122; p=0.019).

CONCLUSION

Loss of tumoral LKB1 protein expression, constitutes an adverse prognostic factor in patients with operable CC.

Decreased expression of LKB1 predicts poor prognosis in pancreatic neuroendocrine tumor patients undergoing curative resection

Background

Liver kinase B1 (LKB1) is a key regulatory protein of cellular metabolism, proliferation, and polarity. The present study aimed to characterize the expression pattern of LKB1 in pancreatic neuroendocrine tumors (pNETs) and evaluate the relationship between LKB1 expression and prognosis in pNETs.

Patients and methods

We retrospectively analyzed the pathologic and clinical data of 71 pNET patients who underwent curative surgical resection in Guangdong General Hospital. LKB1 mRNA and protein levels in tumor tissues and paired nontumor tissues were evaluated in 24 patients by quantitative real-time reverse-transcription polymerase chain reaction and Western blot, respectively. Immunohistochemical expression of LKB1 in tumor tissues was detected in all of the 71 patients, and the immunohistochemical expression level was re-coded in two classes (high versus low/negative) and correlated with clinicopathological parameters and survival outcomes. The association between LKB1 expression and clinicopathological characters was evaluated by chi-square test and Student’s t-test. Kaplan–Meier curves and log-rank test were used to analyze the survival outcomes, including overall survival (OS) and disease-free survival (DFS).

Results

Compared to adjacent normal tissues, LKB1 mRNA level and protein expression level in tumor tissues were both increased. The immunostaining of LKB1 was mainly found within the cytoplasm. Overall, 52 of 71 (73.2%) cases were positive for LKB1 protein, which showed either a diffuse staining pattern or a partial staining pattern. Decreased LKB1 expression was correlated with older age (P=0.042), increased Ki-67 index (P=0.004), increased mitotic count (P=0.001), and advanced histologic grade (P=0.001). Moreover, patients with low/negative LKB1 expression had shorter OS and DFS than those with high expression.

Conclusion

Our results suggested that LKB1 expression could be a useful prognostic marker for recurrence and survival in pNET patients who had received curative resection.

Effects of mammalian target of rapamycin inhibitors on cytokine production and differentiation in keratinocytes

Risk factors for the development of cutaneous squamous cell carcinoma (cSCC) include ultraviolet radiation and immunosuppression. In particular, solid organ transplant recipients show a high incidence of cSCC, depending on the immunosuppressive regimen. While azathioprine or calcineurin inhibitors increase the risk of cSCC development, mammalian target of rapamycin (mTOR) inhibitors decreases this risk. At the moment, the mechanisms behind this protective effect of mTOR inhibitors are not fully understood. We evaluated effects of the mTOR inhibitors sirolimus and everolimus on keratinocytes, cSCC cell lines and an organotypic skin model in vitro in regard to proliferation, cytokine secretion and differentiation. We show that mTOR inhibitors block keratinocyte proliferation and alter cytokine and cytokeratin production: in particular, mTOR inhibition leads to upregulation of interleukin-6 and downregulation of cytokeratin 10. Therefore, mTOR inhibitors have effects on keratinocytes, which could play a role in the pathogenesis of cSCC.

Loss of LKB1 Expression Decreases the Survival and Promotes Laryngeal Cancer Metastasis

Background: Given recent results indicating that diminished LKB1 expression in laryngeal cancer correlates with shorter survival. We aim to perform an analysis estimate the role of decreased liver kinase B1(LKB1) and in the prognostication of human laryngeal squamous cell carcinoma (LSCC). Methods: We conducted a retrospective study and evaluate the expression of LKB1 and p16INK4a (p16) in 208 clinical advanced-stage LSCC tissue samples by using immunohistochemistry. The specimens were received at Sun Yat-sen University Cancer Center (Guangzhou, China). To evaluate the independent prognostic relevance of LKB1, univariate and multivariate Cox regression models were used, overall survival (OS) and distant metastasis-free survival (DMFS) were compared using the Kaplan-Meier method. Results: Immunohistochemical analyses revealed that 80/208 (38.5%) of the LSCC tissue samples expressed high LKB1. Low LKB1 expression was associated with a significantly shorter OS and DMFS than high LKB1 expression (P = 0.041 and 0.028, respectively; log-rank test), and there was a poorer OS in the p16-positive than p16-negative group. In the subgroup stratified by p16 status, the shorter OS were also seen with low LKB1 expression. Multivariate survival analysis indicated that high LKB1 expression was an independent prognostic factor for OS (hazard ratio [HR]: 1.628, 95% confidence interval [CI]: 1.060-2.500, P = 0.026) and DMFS (HR: 2.182, 95% CI: 1.069-4.456, P = 0.032). Conclusions: Our data indicated that low expression of LKB1 was significantly associated with poor prognosis and it may represent a marker of tumor metastasis in patients with LSCC. When combined with p16, LKB1 was also of prognostic value.

Prognostic significance of LKB1 promoter methylation in cutaneous malignant melanoma

Liver kinase B1 (LKB1) loss is a common occurrence in various types of human cancer, and promoter methylation has been hypothesized to be a major mechanism of LKB1 inactivation. The association between LKB1 gene promoter methylation status and tumor progression in cutaneous malignant melanoma (CMM) remains unknown. In the present study, the methylation status of the LKB1 promoter region was examined in 57 human cutaneous malignant melanomas and 50 benign skin lesion controls by methylation-specific polymerase chain reaction. Consequently, 12 (12/57) melanoma tissues exhibited LKB1 promoter methylation, while only 2 (2/50) benign lesions presented with LKB1 hypermethylation. The frequency of LKB1 promoter methylation in melanoma was significantly increased compared with the benign controls (P<0.05). Additional statistical analysis demonstrated that hypermethylation of the LKB1 gene was correlated with Breslow's thickness, presence of ulceration and American Joint Committee on Cancer stage (P<0.05). Additionally, Kaplan-Meier analysis revealed that LKB1 hypermethylation was significantly associated with poorer survival (P<0.01). Multivariate COX regression analysis indicated that LKB1 promoter methylation was an independent prognostic factor for overall survival in patients with melanoma.

High expression of partitioning defective 3-like protein is associated with malignancy in colorectal cancer

Partitioning defective 3-like protein is a novel cell polarity protein. Recently, partitioning defective 3-like protein has been demonstrated with tumor-promoting function by disrupting tight junction, inhibiting tumor suppressor liver kinase B1, and maintaining mammary stem cells. For the first time, we studied partitioning defective 3-like protein expression in malignant colorectal cancer. We used immunohistochemistry scoring system to evaluate partitioning defective 3-like protein expression in 196 colorectal cancer tissues and 33 adjacent normal tissues. We found that colorectal cancer tissues had much stronger partitioning defective 3-like protein immunoreactivity than normal tissues, and colorectal cancer patients with positive partitioning defective 3-like protein expression were characterized with higher cancer stages, metastasis, poor tumor differentiation, larger tumor size, as well as high levels of colorectal cancer markers carcinoembryonic antigen and cancer antigen 19-9. Besides, partitioning defective 3-like protein overexpression was independently predictive of lower survival rate in colorectal cancer patients, even after adjusting the influence of cofactors. Moreover, we also found that partitioning defective 3-like protein was associated with rapid growing colorectal cancer, while knockdown of partitioning defective 3-like protein expression largely inhibited cancer cell proliferation. Our study provided the first evidence that partitioning defective 3-like protein was overexpressed in colorectal cancer and associated with disease malignancy. Also, partitioning defective 3-like protein may serve as a promising prognostic marker and a potential therapeutic target for colorectal cancer treatment. Further study is necessary to understand the regulatory mechanism of partitioning defective 3-like protein in colorectal cancer and the feasibility of its application in clinic.

Downregulation of LKB1 promotes tumor progression and predicts unfavorable prognosis in patients with glioma

The liver kinase B1 (LKB1)/5′-adenosine monophosphate-activated protein kinase pathway has been reported to facilitate glioma cell growth by improving growth conditions. To investigate the clinical significance of LKB1 in human gliomas western blot analysis and quantitative polymerase chain reaction experiments were performed. The present study demonstrated that LKB1 expression was markedly decreased at the messenger RNA and protein levels in 30 freshly prepared glioma tissues, compared with non-neoplastic brain tissues (P<0.001). Subsequently, immunohistochemical analysis demonstrated that LKB1 immunostaining in 180 glioma tissues was significantly decreased compared with that in the corresponding non-neoplastic brain tissues (P<0.001). Notably, this downregulation frequently occurred in high-grade gliomas, and statistical analysis revealed that low LKB1 expression was significantly associated with large tumor size (P=0.02), advanced World Health Organization grade (P=0.006) and low Karnofsky performance scale (P=0.01). The prognostic value of LKB1 expression in patients with glioma was additionally evaluated using Kaplan-Meier survival curves and Cox proportional hazards regression models. As a result, the overall survival time of patients with glioma with low LKB1 expression was shorter compared with that of patients with high LKB1 expression (P<0.001), and low LKB1 expression also indicated decreased survival time in patients with high-grade glioma (P<0.001). Collectively, the present data indicated that the downregulation of LKB1 was closely associated with the malignant degree of human gliomas, exhibiting lower expression at a higher grade. Notably, LKB1 may serve as a potential prognostic biomarker for patients with glioma following surgery.

The Prognostic Value of Decreased LKB1 in Solid Tumors: A Meta-Analysis

Background

Liver kinase B1 (LKB1) is a protein kinase that regulates the growth, integrity and polarity of mammalian cells. Recent studies have reported the prognostic value of decreased LKB1 expression in different tumors. However, the results of these studies remain controversial. Therefore, this meta-analysis was performed to more accurately estimate the role of decreased LKB1 in the prognostication of human solid tumors.

Methods

A systematic literature search in the electronic databases PubMed, Embase, Web of Science and CNKI (updated to October 15, 2015) was performed to identify eligible studies. The overall survival (OS), relapse-free survival (RFS), disease-free survival (DFS) and clinicopathological features data were collected from these studies. The hazard ratios (HRs), odds ratios (ORs) and 95% confidence intervals (CIs) were calculated and pooled with a random-effects models using Stata12.0 software.

Results

A total of 14 studies covering 1915 patients with solid tumors were included in this meta-analysis. Decreased LKB1 was associated with poorer OS in both the univariate (HR: 1.86, 95%CI: 1.42–2.42, P<0.001) and multivariate (HR: 1.55, 95%CI: 1.09–2.21, P = 0.015) analyses. A subgroup analysis revealed that the associations between decreased LKB1 and poor OS were significant within the Asian region (HR 2.18, 95%CI: 1.66–2.86, P<0.001) and obvious for lung cancer (HR: 2.16, 95%CI: 1.47–3.18, P<0.001). However, the articles that involved analyses of both RFS and DFS numbered only 3, and no statistically significant correlations of decreased LKB1 with RFS or DFS were observed in this study. Additionally, the pooled odds ratios (ORs) indicated that decreased LKB1 was associated with larger tumor size (OR: 1.60, 95%CI: 1.09–2.36, P = 0.017), lymph node metastasis (OR: 2.41, 95%CI: 1.53–3.78, P<0.001) and a higher TNM stage (OR: 3.35, 95%CI: 2.20–5.09, P<0.001).

Conclusion

These results suggest that decreased LKB1 expression in patients with solid tumors might be related to poor prognosis and serve as a potential predictive marker of poor clinicopathological prognostic factors. Additional studies are required to verify the clinical utility of decreased LKB1 in solid tumors.

Energy sensing and cancer: LKB1 function and lessons learnt from Peutz-Jeghers syndrome

We describe in this review increasing evidence that loss of LKB1 kinase in Peutz-Jeghers syndrome (PJS) derails the existing natural balance between cell survival and tumour growth suppression. LKB1 deletion can plunge cells into an energy/oxidative stress-induced crisis which leads to the activation of alternative and often carcinogenic pathways to maintain cellular energy levels. It therefore appears that although LKB1 deficiency can suppress oncogenic transformation in the short term, it can ultimately lead to more progressed and malignant phenotypes by driving abnormal cell differentiation, genomic instability and increased tumour heterogeneity.

LKB1 loss promotes endometrial cancer progression via CCL2-dependent macrophage recruitment

Endometrial cancer is the most common gynecologic malignancy and the fourth most common malignancy in women. For most patients in whom the disease is confined to the uterus, treatment results in successful remission; however, there are no curative treatments for tumors that have progressed beyond the uterus. The serine/threonine kinase LKB1 has been identified as a potent suppressor of uterine cancer, but the biological modes of action of LKB1 in this context remain incompletely understood. Here, we have shown that LKB1 suppresses tumor progression by altering gene expression in the tumor microenvironment. We determined that LKB1 inactivation results in abnormal, cell-autonomous production of the inflammatory cytokine chemokine (C-C motif) ligand 2 (CCL2) within tumors, which leads to increased recruitment of macrophages with prominent tumor-promoting activities. Inactivation of Ccl2 in an Lkb1-driven mouse model of endometrial cancer slowed tumor progression and increased survival. In human primary endometrial cancers, loss of LKB1 protein was strongly associated with increased CCL2 expression by tumor cells as well as increased macrophage density in the tumor microenvironment. These data demonstrate that CCL2 is a potent effector of LKB1 loss in endometrial cancer, creating potential avenues for therapeutic opportunities.

Update on the roles of liver kinase B1 in pancreatic cancer

Germline mutations of the liver kinase B1 (STK11/LKB1) gene which encodes a serine/threonine kinase is responsible for Peutz-Jeghers syndrome. There are 14 AMP-activated protein kinase (AMPK)-related kinases in pathways downstream of LKB1, which are involved in many physiological and pathological processes such as regulation of energy metabolism, cell polarity and apoptosis in cells. LKB1 gene mutation has been investigated extensively in a variety of cancers, including pancreatic cancer. Pancreatic cancer is commonly recognized as a disease with extremely poor prognosis. Therefore, a full understanding of its molecular pathology is critical. This review aims to elucidate the structure, distribution, and function of LKB1, and the relationship with pancreatic cancer. In addition, we also point out that in some scenarios, LKB1 may play a role as a tumor protector.

Decreased LKB1 predicts poor prognosis in Pancreatic Ductal Adenocarcinoma

Liver kinase B1 (LKB1) has been identified as a critical modulator involved in cell proliferation and polarity. The purpose of the current study was to characterize the expression pattern of LKB1 and assess the clinical significance of LKB1 expression in pancreatic ductal adenocarcinoma (PDAC) patients. LKB1 mRNA expression which was analyzed in 32 PDAC lesions and matched non-tumor tissues, was downregulated in 50% (16/32) of PDAC lesions. Similar results were also obtained by analyzing three independent datasets from Oncomine. Protein expression of LKB1 was significantly reduced in 6 PDAC cell lines and downregulated in 31.3% (10/32) of PDAC lesions compared to matched non-tumorous tissues, as determined by Western blot analysis. Additionally, tissue microarray containing 205 PDAC specimens was evaluated for LKB1 expression by IHC and demonstrated that reduced expression of LKB1 in 17.6% (36/205) of PDAC tissues was significantly correlated with clinical stage, T classification, N classification, liver metastasis and vascular invasion. Importantly, Kaplan-Meier survival and Cox regression analyses were executed to evaluate the prognosis of PDAC and found that LKB1 protein expression was one of the independent prognostic factors for overall survival of PDAC patients.