Forcet C, Etienne-Manneville S, Gaude H, Fournier L, Debilly S, Salmi M et al.. Functional analysis of Peutz-Jeghers mutations reveals that the LKB1 C-terminal region exerts a crucial role in regulating both the AMPK pathway and the cell polarity. Hum Mol Genet 14: 1283-1292
Germline mutations of the LKB1 gene are responsible for the cancer-prone Peutz-Jeghers syndrome (PJS). LKB1 encodes a serine-threonine kinase that acts as a regulator of cell cycle, metabolism and cell polarity. The majority of PJS missense mutations abolish LKB1 enzymatic activity and thereby impair all functions assigned to LKB1. Here, we have investigated the functional consequences of recurrent missense mutations identified in PJS and in sporadic tumors which map in the LKB1 C-terminal non-catalytic region. We report that these C-terminal mutations neither disrupt LKB1 kinase activity nor interfere with LKB1-induced growth arrest. However, these naturally occuring mutations lessened LKB1-mediated activation of the AMP-activated protein kinase (AMPK) and impaired downstream signaling. Furthermore, C-terminal mutations compromise LKB1 ability to establish and maintain polarity of both intestinal epithelial cells and migrating astrocytes. Consistent with these findings, mutational analysis reveals that the LKB1 tail exerts an essential function in the control of cell polarity. Overall, our results ascribe a crucial regulatory role to the LKB1 C-terminal region. Our findings further indicate that LKB1 tumor suppressor activity is likely to depend on the regulation of AMPK signaling and cell polarization.
[Show abstract] [Hide abstract] ABSTRACT: Ewing sarcoma (ES) is the second most common malignant bone and soft tissue tumor in children and adolescents. Despite advances in comprehensive treatment, patients with ES metastases still suffer poor outcomes, thus, emphasizing the need for detailed genetic profiles of ES patients to identify suitable molecular biomarkers for improved prognosis and development of effective and targeted therapies. In this study, the next generation sequencing Ion AmpliSeq™ Cancer Hotspot Panel v2 was used to identify cancer-related gene mutations in the tissue samples from 20 ES patients. This platform targeted 207 amplicons of 2800 loci in 50 cancer-related genes. Among the 20 tissue specimens, 62 nonsynonymous hotspot mutations were identified in 26 cancer-related genes, revealing the molecular heterogeneity of ES. Among these, five novel mutations in cancer-related genes (KDR, STK11, MLH1, KRAS, and PTPN11) were detected in ES, and these mutations were confirmed with traditional Sanger sequencing. ES patients with KDR, STK11, and MLH1 mutations had higher Ki-67 proliferation indices than the ES patients lacking such mutations. Notably, more than half of the ES patients harbored one or two possible 'druggable' mutations that have been previously linked to a clinical cancer treatment option. Our results provided the foundation to not only elucidate possible mechanisms involved in ES pathogenesis but also indicated the utility of Ion Torrent sequencing as a sensitive and cost-effective tool to screen key oncogenes and tumor suppressors in order to develop personalized therapy for ES patients.0Comments 0Citations
- "In our study, one D350N and three F354L amino acid changes due to missense mutations of STK11 were firstly discovered in our ES cohort. The latter F354L mutation is thought to be deleterious in PJS patients, mainly by impairing STK11 polarizing activity and interfering with the activation of AMPK and subsequent downstream pathways . Apart from it, this mutation has been described in colon cancer and serous ovarian carcinoma. "
[Show abstract] [Hide abstract] ABSTRACT: Background: Peutz-Jeghers syndrome (PJS) is a rare autosomal dominant inherited disease characterized by gastrointestinal hamartomatous polyps and mucocutaneous melanin spots. Germline mutation of the serine/threonine kinase 11 (STK11) gene are responsible for PJS. In this study, we investigated the clinical characteristics and molecular basis of the disease in Chinese children with PJS. Methods: Thirteen children diagnosed with PJS in our hospital were enrolled in this study from 2011 to 2015, and their clinical data on polyp characteristics, intussusceptions events, family histories, etc. were described. Genomic DNA was extracted from whole-blood samples from each subject, and the entire coding sequence of the STK11 gene was amplified by polymerase chain reaction and analyzed by direct sequencing. Results: The median age at the onset of symptoms was 2 years and 4 months. To date, these children have undergone 40 endoscopy screenings, 17 laparotomies and 9 intussusceptions. Polyps were found in the stomach, duodenum, small bowel, colon and rectum, with large polyps found in 7 children. Mutations were found in eleven children, including seven novel mutations (c.481het_dupA, c.943_944het_delCCinsG, c.397het_delG, c.862 + 1G > G/A, c.348_349het_delGT, and c.803_804het_delGGinsC and c.121_139de l19insTT) and four previously reported mutations (c.658C > C/T, c.890G > G/A, c.1062 C > C/G, and c.290 + 1G > G/A). One PJS patient did not have any STK11 mutations. Conclusions: The polyps caused significant clinical consequences in children with PJS, and mutations of the STK11 gene are generally the cause of PJS in Chinese children. This study expands the spectrum of known STK11 gene mutations.0Comments 0Citations
- "Loss of the C-terminal domain of STK11 leads to the loss of cell polarity and hamartoma formation as a result of inappropriate overgrowth of differentiated cells. These mutations lead to impairments in both AMPK signaling and LKB1 polarity function . Case 8 carried a de novo STK11 gene mutation that was previously unreported in Chinese populations, although it had been reported in a French population . "
[Show abstract] [Hide abstract] ABSTRACT: Medullary thyroid carcinoma (MTC) is a rare malignancy originating from the calcitonin-secreting parafollicular thyroid C cells. Approximately 75% of cases are sporadic. Rearranged during transfection (RET) proto-oncogene plays a crucial role in MTC development. Besides RET, other oncogenes commonly involved in the pathogenesis of human cancers have also been investigated in MTC. The family of human RAS genes includes the highly homologous HRAS, KRAS, and NRAS genes that encode three distinct proteins. Activating mutations in specific hotspots of the RAS genes are found in about 30% of all human cancers. In thyroid neoplasias, RAS gene point mutations, mainly in NRAS, are detected in benign and malignant tumors arising from the follicular epithelium. However, recent reports have also described RAS mutations in MTC, namely in HRAS and KRAS. Overall, the prevalence of RAS mutations in sporadic MTC varies between 0-43.3%, occurring usually in tumors with WT RET and rarely in those harboring a RET mutation, suggesting that activation of these proto-oncogenes represents alternative genetic events in sporadic MTC tumorigenesis. Thus, the assessment of RAS mutation status can be useful to define therapeutic strategies in RET WT MTC. MTC patients with RAS mutations have an intermediate risk for aggressive cancer, between those with RET mutations in exons 15 and 16, which are associated with the worst prognosis, and cases with other RET mutations, which have the most indolent course of the disease. Recent results from exome sequencing indicate that, besides mutations in RET, HRAS, and KRAS, no other recurrent driver mutations are present in MTC. © 2015 Society for Endocrinology.0Comments 2Citations
- "Thirteen MTC harbored a somatic RET mutation; three of them, undetected by Sanger, were revealed by NGS, showing that targeted NGS has a higher sensitivity in the detection of mutations (these cases presented a proportion of RET mutated alleles below the 20% detection limit of Sanger analysis). One of the 13 RETmutated cases also had a p.Phe354Leu germline mutation in STK11, which has been found in Peutz–Jeghers syndrome (Forcet et al. 2005). Four of the seven RET WT MTC carried a RAS mutation (three in HRAS and one in KRAS) and the three remaining cases were WT for all the 50 cancer-related genes. "