Long-term results of combined liver-kidney transplantation for primary hyperoxaluria type 1: the French experience.

Primary hyperoxaluria type 1 (PH1) is a hepatic metabolic defect leading to end-stage renal failure. The posttransplant recurrence of kidney disease can suggest a need for combined liver-kidney transplantation (LKT). However, the risk of LKT is theoretically far higher than the risk of kidney-alone transplantation (KAT). An unselected consecutive series of 54 patients with PH1 was analyzed according to the type of transplantation initially performed between May 1979 and June 2010 at 10 French centers. The duration of dialysis, extrarenal lesions, age, and follow-up were similar between the groups. Postoperative morbidity and mortality did not differ between the groups, and 10-year patient survival rates were similar for the LKT (n = 33) and KAT groups (n = 21; 78% versus 70%). Kidney graft survival at 10 years was better after LKT (87% versus 13%, P < .001) . Four patients (12.1%) lost their first kidney graft in the LKT group, whereas 19 (90%) did in the KAT group (P < .001). The recurrence of oxalosis occurred in 11 renal grafts (52%) in the KAT group but in none in the LKT group (P < .001). End-stage renal failure resulting from rejection was also higher in the KAT group (19% versus 9%, P < 0.0001). A second kidney transplant was performed for 15 patients (71%) in the KAT group versus 4 patients (12%) in the LKT group (P < 0.001). In conclusion, LKT for PH1 provides better kidney graft survival, less rejection, and similar long-term patient survival and is not associated with an increased short-term mortality risk. LKT must be the first-line treatment for PH1 patients with end-stage renal disease.

Adenosine triphosphatase pontin is overexpressed in hepatocellular carcinoma and coregulated with reptin through a new posttranslational mechanism.

UNLABELLED: Reptin and Pontin are related ATPases associated with stoichiometric amounts in several complexes involved in chromatin remodeling, transcriptional regulation, and telomerase activity. We found that Reptin was up-regulated in hepatocellular carcinoma (HCC) and that down-regulation of Reptin led to growth arrest. We show here that Pontin messenger RNA (mRNA) is also up-regulated in human HCC 3.9-fold as compared to nontumor liver (P = 0.0004). Pontin expression was a strong independent factor of poor prognosis in a multivariate analysis. As for Reptin, depletion of Pontin in HuH7 cells with small interfering RNAs (siRNAs) led to growth arrest. Remarkably, Pontin depletion led to down-regulation of Reptin as shown with western blot, and vice versa. Whereas siRNAs induced a decrease of their cognate mRNA targets, they did not affect the transcripts of the partner protein. Translation of Pontin or Reptin was not altered when the partner protein was silenced. However, pulse-chase experiments demonstrated that newly synthesized Pontin or Reptin stability was reduced in Reptin- or Pontin-depleted cells, respectively. This phenomenon was reversed upon inhibition of proteasome or ubiquitin-activating enzyme (E1). In addition, proteasome inhibition could partly restore Pontin steady-state levels in Reptin-depleted cells, as shown by western blot. This restoration was not observed when cells were also treated with cycloheximide, thus confirming that proteasomal degradation in this setting was restricted to newly synthesized Pontin. CONCLUSION: Reptin and Pontin protein levels are strictly controlled by a posttranslational mechanism involving proteasomal degradation of newly synthesized proteins. These data demonstrate a tight regulatory and reciprocal interaction between Reptin and Pontin, which may in turn lead to the maintenance of their 1:1 stoichiometry.

Overexpression and role of the ATPase and putative DNA helicase RuvB-like 2 in human hepatocellular carcinoma.

UNLABELLED: Using a proteomic analysis of human hepatocellular carcinoma (HCC), we identified the overexpression in 4 tumors of RuvB-like 2 (RUVBL2), an ATPase and putative DNA helicase known to interact with beta-catenin and cellular v-myc myelocytomatosis viral oncogene homolog (c-myc). RUVBL2 expression was further analyzed in tumors with quantitative reverse-transcription polymerase chain reaction analysis and immunohistochemistry; in addition, RUVBL2 expression in a HuH7 cell line was silenced by small interfering RNA or increased with a lentiviral vector. RUVBL2 messenger RNA overexpression was confirmed in 72 of 96 HCC cases, and it was associated with poorly differentiated tumors (P = 0.02) and a poor prognosis (P = 0.02) but not with beta-catenin mutations or c-myc levels. Although RUVBL2 was strictly nuclear in normal hepatocytes, tumoral hepatocytes exhibited additional cytoplasmic staining. There was no mutation in the coding sequence of RUVBL2 in 10 sequenced cases. Silencing RUVBL2 in HuH7 HCC cells reduced cell growth (P < 0.001) and increased apoptosis, as shown by DNA fragmentation (P < 0.001) and caspase 3 activity (P < 0.005). This was associated with an increased expression of several proapoptotic genes and with an increased conformational activation of Bak-1 and Bax. On the other hand, HuH7 cells with an overexpression of RUVBL2 grew better in soft agar (P < 0.03), had increased resistance to C2 ceramide-induced apoptosis (P < 0.001), and gave rise to significantly larger tumors when injected into immunodeficient Rag2/gammac mice (P = 0.016). CONCLUSION: RUVBL2 is overexpressed in a large majority of HCCs. RUVBL2 overexpression enhances tumorigenicity, and RUVBL2 is required for tumor cell viability. These results argue for a major role of RUVBL2 in liver carcinogenesis.