RESUMO
As confusion mounts over RNA isoforms involved in phenotypic plasticity, aberrant CpG methylation-mediated disruption of alternative splicing is increasingly recognized as a driver of intratumor heterogeneity (ITH). Protease serine 3 (PRSS3), possessing four splice variants (PRSS3-SVs; PRSS3-V1-V4), is an indispensable trypsin that shows paradoxical effects on cancer development. Here, we found that PRSS3 transcripts and their isoforms were divergently expressed in lung cancer, exhibiting opposing functions and clinical outcomes, namely, oncogenic PRSS3-V1 and PRSS3-V2 versus tumor-suppressive PRSS3-V3, by targeting different downstream genes. We identified an intragenic CpG island (iCpGI) in PRSS3. Hypermethylation of iCpGI was mediated by UHRF1/DNMT1 complex interference with the binding of myeloid zinc finger 1 (MZF1) to regulate PRSS3 transcription. The garlic-derived compound diallyl trisulfide cooperated with 5-aza-2'-deoxycytidine to exert antitumor effects in lung adenocarcinoma cells through site-specific iCpGI demethylation specifically allowing MZF1 to upregulate PRSS3-V3 expression. Epigenetic silencing of PRSS3-V3 via iCpGI methylation (iCpGIm) in BALF and tumor tissues was associated with early clinical progression in patients with lung cancer but not in those with squamous cell carcinoma or inflammatory disease. Thus, UHRF1/DNMT1-MZF1 axis-modulated site-specific iCpGIm regulates divergent expression of PRSS3-SVs, conferring nongenetic functional ITH, with implications for early detection of lung cancer and targeted therapies.
RESUMO
Pancreatic acinar cells synthesize pancreatic lipase related protein 1 (PLRPl), which has a high degree of sequence and structural homology with pancreatic triglyceride lipase (PTL). PTL is required for efficient dietary triglyceride digestion, while the physiological role of PLRPl has not been elucidated, although some investigations have shown that its expression level is changed under some physiological or pathological conditions. Specific antigenic peptides were fused to glutathione S-transferase (GST) and purified recombinant fusion protein was used to generate polyclonal antisera by immunization of rabbits. The antisera could detect the antigen as low as 0.6 ng and PLRPI protein in 3 μg of mouse pancreatic juice extracts. The high specificity was verified in Western blot and immunohistochemistry analysis by using PLRPl knockout (KO) mice as the control. Furthermore, it was showed that food intake could increase the exocrine secretion of PLRPl into pancreatic juice. This implied that PLRPl may fulfill dietary digestion function in the digestion track.