Expression of truncated bile salt-dependent lipase variant in pancreatic pre-neoplastic lesions

Abstract

Pancreatic adenocarcinoma (PDAC) is a dismal disease. The lack of specific symptoms still leads to a delay in diagnosis followed by death within months for most patients. Exon 11 of the bile salt-dependent lipase (BSDL) gene encoding variable number of tandem repeated (VNTR) sequences has been involved in pancreatic pathologies. We hypothesized that BSDL VNTR sequences may be mutated in PDAC. The amplification of BSDL VNTR from RNA extracted from pancreatic SOJ-6 cells allowed us to identify a BSDL amplicon in which a cytosine residue is inserted in a VNTR sequence. This insertion gives rise to a premature stop codon, resulting in a truncated protein and to a modification of the C-terminal amino-acid sequence; that is PRAAHG instead of PAVIRF. We produced antibodies directed against these sequences and examined pancreatic tissues from patients with PDAC and PanIN. Albeit all tissues were positive to anti-PAVIRF antibodies, 72.2% of patient tissues gave positive reaction with anti-PRAAHG antibodies, particularly in dysplastic areas of the tumor. Neoplastic cells with ductal differentiation were not reactive to anti-PRAAHG antibodies. Some 70% of PanIN tissues were also reactive to anti-PRAAHG antibodies, suggesting that the C insertion occurs early during pancreatic carcinogenesis. Data suggest that anti-PRAAHG antibodies were uniquely reactive with a short isoform of BSDL specifically expressed in pre-neoplastic lesions of the pancreas. The detection of truncated BSDL reactive to antibodies against the PRAAHG C-terminal sequence in pancreatic juice or in pancreatic biopsies may be a new tool in the early diagnosis of PDAC.

The mucinous domain of pancreatic carboxyl-ester lipase (CEL) contains core 1/core 2 O-glycans that can be modified by ABO blood group determinants

“…Neither the CEL-HYB variant (the allele predisposing for chronic pancreatitis) nor specific CEL VNTR lengths were enriched among pancreatic cancer cases compared with controls (8,35). Nevertheless, the identification and characterization of FAPP, a postulated oncofetal variant of CEL with six VNTR repeats, has raised the possibility that glycoisoforms of CEL could serve as diagnostic markers or even targets for treatment in pancreatic cancer (27)(28)(29)36).…”

Pancreatic adenocarcinoma, chronic pancreatitis, and MODY-8 diabetes: is bile salt-dependent lipase (or carboxyl ester lipase) at the crossroads of pancreatic pathologies?

“…The findings obtained up to now show that: 1) a deletion of a single base within the BSDL (CEL) gene segment encoding VNTR leads to exocrine dysfunction and MODY-8 symptoms with beta-cell failure and pancreatic exocrine disease [ 112 ], 2) an insertion of a cytosine within any VNTR of BSDL leads to the expression of a new BSDL isoform in dysplastic areas and pre-neoplastic lesions of the exocrine pancreas [ 163 ], 3) a recombined allele of the BSDL gene and BSDL pseudogene confers susceptibility to chronic pancreatitis [ 138 ], 4) all these mutations or recombinations in BSDL are predicted to give rise to DNA encoding truncated proteins with a functional catalytic site.…”

“…Although VNTR length polymorphisms do not represent a risk for pancreatic cancer [ 162 ], a BSDL transcript in which a cytosine residue is inserted into the VNTR (BSDL-InsC) was recently detected in a cohort of French patients with PAC [ 163 ]. This insertion, which could not be detected in DNA extracted from blood samples from a cohort of control individuals [ 163 ], gives rise to a premature stop codon, resulting in a truncated protein and a modification of the C-terminal amino acid sequence – that is, GAPPRAAHG instead of KEAQMPAVIRF (Figure 2 ) [ 11 , 163 ]. While all human tissue samples are positive to anti-PAVIRF antibodies, in this study 72.2% of pancreatic tumor tissue samples reacted positively with anti-PRAAHG antibodies, particularly in dysplastic areas of the tumor in contrast to neoplastic cells with ductal differentiation.…”

“…While the expression of BSDL – and likely that of any variant – is decreased in differentiated PAC [ 182 ], BSDL variants could play an important role in pre-neoplasia [ 163 ]. However, variation in BSDL expression levels may not be so central to pancreatic pathologies such as chronic pancreatitis, MODY-8, and PAC.…”

E-cadherin is a structuring component of invadopodia in pancreatic cancer

“…Images were captured with LSM 880 Zeiss confocal microscope equipped with ZEN Software. Human pancreatic cancer samples were obtained as previously described (51).…”