The G191R variant in the PRSS2 gene does not play a role in protection against tropical calcific pancreatitis

The PRSS3P2 and TRY7 deletion copy number variant modifies risk for chronic pancreatitis

BACKGROUND

PRSS1 and PRSS2 constitute the only functional copies of a tandemly-arranged five-trypsinogen-gene cluster (i.e., PRSS1, PRSS3P1, PRSS3P2, TRY7 and PRSS2) on chromosome 7q35. Variants in PRSS1 and PRSS2, including missense and copy number variants (CNVs), have been reported to predispose to or protect against chronic pancreatitis (CP). We wondered whether a common trypsinogen pseudogene deletion CNV (that removes two of the three trypsinogen pseudogenes, PRSS3P2 and TRY7) might be associated with CP causation/predisposition.

METHODS

We analyzed the common PRSS3P2 and TRY7 deletion CNV in a total of 1536 CP patients and 3506 controls from France, Germany, India and Japan by means of quantitative fluorescent multiplex polymerase chain reaction.

RESULTS

We demonstrated that the deletion CNV variant was associated with a protective effect against CP in the French, German and Japanese cohorts whilst a trend toward the same association was noted in the Indian cohort. Meta-analysis under a dominant model yielded a pooled odds ratio (OR) of 0.68 (95% confidence interval (CI) 0.52-0.89; p = 0.005) whereas an allele-based meta-analysis yielded a pooled OR of 0.84 (95% CI 0.77-0.92; p = 0.0001). This protective effect is explicable by reference to the recent finding that the still functional PRSS3P2/TRY7 pseudogene enhancers upregulate pancreatic PRSS2 expression.

CONCLUSIONS

The common PRSS3P2 and TRY7 deletion CNV was associated with a reduced risk for CP. This finding provides additional support for the emerging view that dysregulated PRSS2 expression represents a discrete mechanism underlying CP predisposition or protection.

Association Analysis of PRSS1-PRSS2 and CLDN2-MORC4 Variants in Nonalcoholic Chronic Pancreatitis Using Tropical Calcific Pancreatitis as Model

OBJECTIVE

Association of PRSS1-PRSS2 (rs10273639) and CLDN2-MORC4 (rs12688220 and rs7057398) variants with alcohol-related chronic pancreatitis (CP) is established but with nonalcoholic CP is unclear. We addressed this inconsistency using tropical calcific pancreatitis (TCP) as model.

METHODS

We sequenced 5'-UTR of PRSS1 and genotyped CLDN2-MORC4 variants in 555 patients with TCP and 801 controls and performed association analysis. Gene-gene interaction between PRSS1 and CLDN2-MORC4 variants and with p.Asn34Ser SPINK1 and p.Leu26Val CTSB was also evaluated.

RESULTS

We observed significant association of rs10273639/rs4726576 in PRSS1-PRSS2 (odds ratio [OR] = 0.72; P = 3.50 × 10) and CLDN2-MORC4 variants, rs12688220 (OR = 1.54; P = 1.22 × 10) and rs7057398 (OR = 1.50; P = 1.22 × 10) with TCP. Patients carrying p.Asn34Ser SPINK1 were significantly younger than those with rs4726576 risk genotype (30.0 vs 38.0 years; P = 0.015) and those carrying both were even younger (22.0 years; P = 0.001). Presence of risk allele at rs12688220 in patients carrying p.Asn34Ser SPINK1 delayed the age of onset (32.0 vs 24.0 years; P = 0.013).

CONCLUSIONS

Our study establishes strong association of PRSS1-PRSS2 and CLDN2-MORC4 variants with TCP and thus with nonalcoholic CP. These variants independently interact with p.Asn34Ser SPINK1 and influence the age of onset in TCP. However, latter results need to be replicated in other cohorts.

Surgical considerations for patients with metastatic renal cell carcinoma

Among patients with renal cell carcinoma (RCC), 25-30% present with metastatic disease at the time of initial diagnosis. Despite the ever-increasing array of treatment options available for these patients, surgery remains one of the cornerstones of therapy. Proper patient selection for cytoreductive surgery is paramount to its effective use in the management of patients with metastatic RCC despite the decrease in reported morbidity rates. We explore the evolving role cytoreductive surgery in metastatic RCC spanning the immunotherapy era to the targeted therapy era. Despite significant advances in the management of patients with metastatic RCC, further evidence on the definitive role of cytoreductive surgery in the targeted therapy era is awaited through large randomized trials.

Genetic and phenotypic heterogeneity in tropical calcific pancreatitis

Tropical calcific pancreatitis (TCP) is a form of chronic non-alcoholic pancreatitis initially reported in the developing parts of the tropical world. The clinical phenotype of TCP has undergone marked changes since its first description in 1968. The disease is now seen in relatively older people with less severe symptoms. In addition, there are varying reports on the proportion of cases presenting with imaging abnormalities like calcification, ductal dilation, and glandular atrophy. Significant progress has also been made in understanding the etiopathology of TCP. The role of malnutrition and cassava toxicity in its pathogenesis is disproven and few studies have focused on the role of micronutrient deficiency and oxidative stress in the etiopathogenesis of TCP. Emerging evidence support an important role for genetic risk factors in TCP. Several studies have shown that, rather than mutations in trypsinogens, variants in serine protease inhibitor kazal type 1, cathepsin B, chymotrypsin C, cystic fibrosis transmembrane regulator, and carboxypeptidase A1, predict risk of TCP. These studies also provided evidence of mutational heterogeneity between TCP and chronic pancreatitis in Western populations. The current review summarizes recent advances that have implications in the understanding of the pathophysiology and thus, heterogeneity in genotype-phenotype correlations in TCP.

Comprehensive screening of chymotrypsin C (CTRC) gene in tropical calcific pancreatitis identifies novel variants

OBJECTIVE

In a previous study, the authors have shown that rather than variants in trypsinogen gene(s), mutations in pancreatic secretory trypsin inhibitor (encoded by SPINK1) and cathepsin B (CTSB) are associated with tropical calcific pancreatitis (TCP). Recently, chymotrypsin C (CTRC) variants that diminish its activity or secretion were found to predict susceptibility to chronic pancreatitis (CP). The authors analysed CTRC variants in a large, ethnically matched case-control TCP cohort.

DESIGN

The authors sequenced all eight exons and flanking regions in CTRC in 584 CP patients (497 TCP, 87 idiopathic CP) and 598 normal subjects and analysed the significance of association using χ(2) test. The authors also investigated interaction of CTRC variants with p.N34S SPINK1 and p.L26V CTSB mutations.

RESULTS

The authors identified 14 variants in CTRC, of which non-synonymous variants were detected in 71/584 CP patients (12.2%) and 22/598 controls (3.7%; OR 3.62, 95% CI 2.21 to 5.93; p=6.2 × 10(-8)). Rather than the commonly reported p.K247_R254del variant in Caucasians, p.V235I was the most common mutation in Indian CP patients (28/575 (4.9%); OR 7.60, 95% CI 2.52 to 25.71; p=1.01 × 10(-5)). Another pathogenic variant, p.A73T was identified in 3.1% (18/584) patients compared with 0.3% (2/598) in controls (OR=9.48, 95% CI 2.19 to 41.03, p=2.5 × 10(-4)). The authors also observed significant association for the synonymous variant c.180C>T (p.(=)) with CP (OR 2.71, 95% CI 1.79 to 4.12, p=5.3 × 10(-7)). Two novel nonsense mutations, p.G242AfsX9 and p.W113X were also identified exclusively in CP patients. No interaction between CTRC variants and p.N34S SPINK1 or p.L26V CTSB mutations was observed.

CONCLUSION

This study on a large cohort of TCP patients provides evidence of allelic heterogeneity and confirms that CTRC variants play a significant role in its pathogenesis.

Genetic analysis of the glycoprotein 2 gene in patients with chronic pancreatitis

OBJECTIVES

The aim of this study was to evaluate whether variations in the glycoprotein 2 gene (GP2) may potentially affect the risk of chronic pancreatitis.

METHODS

Six hundred sixty-one French white patients (idiopathic chronic pancreatitis, n = 590; familial chronic pancreatitis, n = 42; hereditary pancreatitis, n = 29), 445 Dravidian patients from India (tropical calcific pancreatitis, n = 306; idiopathic chronic pancreatitis, n = 139), and 962 unrelated healthy subjects (French white, n = 500; Dravidian, n = 462) participated in this case-control association study. The entire coding sequence of the GP2 gene was searched for conventional genetic variations by direct sequencing, whereas all 12 exons of the GP2 gene were screened for copy number variations by quantitative fluorescent multiplex-polymerase chain reaction.

RESULTS

Only 3 rare missense mutations (p.A137T, p.E250D, and p.V432M; only p.E250D was not detected in any control subjects) and 3 common synonymous polymorphisms (c.348C>T, c.714G>C, and c.1275A>G) were identified. The c.348C>T and c.1275A>G variations were found to be contradictorily associated with the disease (ranging from protective effects to disease-predisposing effects) in the French white and Indian populations.

CONCLUSION

The paucity of patient-specific missense mutations and contradictory findings with respect to 2 common polymorphisms in the 2 contrasting populations suggest that the GP2 gene is unlikely to play a major role in the etiology of chronic pancreatitis.

Chronic pancreatitis: genetics and pathogenesis

Chronic pancreatitis (CP) is a persistent inflammation of the pancreas. Over the past 12 years, genetic studies of hereditary, familial, and idiopathic forms of CP have made great progress in defining the disease pathogenesis. Identification of gain-of-function missense and copy number mutations in the cationic trypsinogen gene (PRSS1) and loss-of-function variants in both the pancreatic secretory trypsin inhibitor (SPINK1) and chymotrypsinogen C (CTRC) genes has firmly established the pivotal role of prematurely activated trypsin within the pancreas in the etiology of CP. Loss-of-function variants in the cystic fibrosis transmembrane conductance regulator (CFTR) and calcium-sensing receptor (CASR) genes also increase the risk of CP. Here, we review recent developments in this rapidly evolving field, highlight the importance of gene-gene and gene-environment interactions in causing the disease, and discuss the opportunities and challenges in identifying novel genetic factors that affect susceptibility/resistance to CP.