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The phospholipase Cγ1 (PLCγ1) is essential for T-cell signaling and activation in hepatic cancer immune response, which has a regulatory Src homology 3 (SH3) domain that can specifically recognize and interact with the PXXP-containing decapeptide segment (185 QPPVPPQRPM194 , termed as SLP76185-194 peptide) of adaptor protein SLP76 following T-cell receptor ligation. The isolated peptide can only bind to the PLCγ1 SH3 domain with a moderate affinity due to lack of protein context support. Instead of the traditional natural residue mutagenesis that is limited by low structural diversity and shifted target specificity, we herein attempt to improve the peptide affinity by replacing the two key proline residues Pro187 and Pro190 of SLP76185-194 PXXP motif with nonnatural N-substituted amino acids, as the proline is the only endogenous N-substituted amino acid. The replacement would increase peptide flexibility but can restore peptide activity by establishing additional interactions with the domain. Structural analysis reveals that the domain pocket can be divided into a large amphipathic region and a small negatively charged region; they accommodate hydrophobic, aromatic, polar, and moderate-sized N-substituted amino acid types. A systematic replacement combination profile between the peptide residues Pro187 and Pro190 is created by structural modeling, dynamics simulation, and energetics analysis, from which six improved and two reduced N-substituted peptides as well as native SLP76185-194 peptide are identified and tested for their binding affinity to the recombinant protein of the human PLCγ1 SH3 domain using fluorescence-based assays. Two N-substituted peptides, SLP76185-194 (N-Leu187/N-Gln190) and SLP76185-194 (N-Thr187/N-Gln190), are designed to have high potency (Kd = 0.67 ± 0.18 and 1.7 ± 0.3 μM, respectively), with affinity improvement by, respectively, 8.5-fold and 3.4-fold relative to native peptide (Kd = 5.7 ± 1.2 μM).

Background and Aim Aryl-hydrocarbon receptor nuclear translocator 2 (ARNT2) is a transcriptional regulator and member of the basic helix-loop-helix/Per-ARNT-SIM (bHLH/PAS) superfamily. Recently, evidence of that ARNT is involved in carcinogenesis and cancer progression has emerged. The aim of current study was to investigate the role of ARNT2, a homolog of ARNT, in tumor growth, invasion, and prognosis of hepatocellular carcinoma (HCC). Methods Tissue microarray and immunohistochemical staining were used to examine the expression of ARNT2 in 195 HCC tissues. Factors associated with ARNT2 levels were assessed by univariate and multivariate Cox regression analyses. Cell proliferation, migration, and invasion assays were performed by using ARNT2 silencing and overexpressing HCCLM6 cell line. Orthotopic xenograft HCC model was used to elucidate the effects of ARNT2 on HCC progression in vivo. Results High intratumoral of ARNT2 level was well correlated with longer overall survival (OS) and lower tumor to recurrence (TTR) of HCC patients after resection. Multivariate analysis revealed that intratumoral ARNT2 overexpression was an independent prognostic factor for both OS and TTR. Knockdown of ARNT2 in HCCLM6 cells was significantly enhanced while overexpression of ARNT2 significantly inhibited the ability of cell proliferation, invasion, and migration. In animal studies, downregulation of ARNT2 in HCCLM6 cells promoted, whereas upregulation of ARNT2 in HCCLM6 cells reduced HCCLM6 growth in vivo. Conclusions Our data demonstrate that ARNT2 plays an inhibitory role in HCC progression and suggest that ARNT2 may be a potential prognostic predictor and therapeutic target for HCC.

Background and Aim The purpose of the present study was to determine whether lamivudine in combination with transarterial chemoembolization (TACE) could reduce hepatitis B virus (HBV) activation and improve the survival of patients with hepatocellular carcinoma (HCC). Methods From July 2008 to October 2011, a total of 181 consecutive HBV-related HCC patients undergoing TACE were randomized to two groups (92: lamivudine, 89: control). Follow up was every 3 months. Primary and secondary end-points were time to progression (TTP) and overall survival (OS), respectively, both of which were evaluated by the Kaplan–Meier technique and summarized by the hazard ratio. Results The level of HBV-DNA became undetectable in 42 (45.6%) patients in the lamivudine group, compared with 10 (11.2%) in the control group (P

bHLH/PAS proteins play important roles in tumor progression. Lost or reduced expression of single-minded homolog 2 (SIM) as well as aryl hydrocarbon receptor repressor (AHRR) has been observed in cancerous human tissues. Here, we investigated the role of aryl hydrocarbon receptor nuclear translocator (ARNT), another bHLH/PAS protein, in hepatocellular carcinoma (HCC). Using tissue microarray and immunohistochemistry, we found that intratumoral ARNT was inversely correlated with time to recurrence and overall survival of HCC patients after resection. Knockdown of ARNT in HepG2, HCCLM3 and HCCLM6 cells significantly shortened cell doubling time, increased S-phase cell populations and accelerated in vivo HCCLM6 growth and metastasis. After ARNT expression was rescued, prolonged cell doubling time and decreased S-phase cell populations were observed in HepG2, HCCLM3 and HCCLM6 cells. And, HCCLM6 growth and metastasis in vivo were remarkably inhibited. Screening by quantitative reverse-transcription PCR and PCR arrays revealed that cyclin E1, CDK2, Fos and Jun were negatively regulated by ARNT, whereas CDKN1C, CNKN2A, CDKN2B, MAPK11 and MAPK14 were positively regulated in HCC. According to the results of immunoprecipitation assay, both ARNT/ARNT and ARNT/AHRR complexes were clearly formed in HCCLM6 xenograft with increased ARNT expression. In summary, ARNT is an important regulator of HCC growth and metastasis and could be a promising prognostic candidate in HCC patients.