Mammalian target of rapamycin pathway activity in hepatocellular carcinomas of patients undergoing liver transplantation

BACKGROUND: Because mammalian target of rapamycin (mTOR) inhibitors combine anticancer and immunosuppressive properties we investigated: 1) the activation status and prognostic significance of the mTOR pathway in hepatocellular carcinoma (HCC) tissues of patients undergoing orthotopic liver transplantation (OLT) for HCC, and 2) the single and combinatorial efficacy of RAD001 in HCC cells. METHODS: PTEN, p-AKT, p-mTOR, p-p70S6K, and p-4EBP-1 were analyzed by immunohistochemistry in explanted HCCs of 166 patients undergoing OLT. Efficacy of RAD001 as mono- and combination therapy with doxorubicin was tested in Hep3B and SNU398 cells. RESULTS: The mTOR pathway is activated in about 40% of patients undergoing OLT for HCC but no direct correlation between up- and downstream proteins was observed. We found no influence of mTOR pathway protein expression on disease free survival (DFS) or overall survival (OS). There was a marked single agent and chemo-sensitizing effect of RAD001 against HCC cells in vitro. CONCLUSION: The mTOR pathway is active in 40% of patients with HCC undergoing OLT, but has no influence of DFS or OS. No direct correlation was observed between up- and downstream proteins limiting the use of upstream proteins to predict mTOR activity. Prospective clinical trials are needed to test whether the activation status of the mTOR pathway in HCCs predicts the antitumor effect of rapamycin derivative in the posttransplantation course.     

Mammalian target of rapamycin: A new target in prostate cancer

Molecular targets in prostate cancer are continually being explored, especially in the poor-prognosis androgen-independent phase of the disease, for which there are currently few therapeutic options. One such target is the mammalian target of rapamycin (mTOR) protein. Activation of mTOR results in sequential activation of downstream molecules, which ultimately results in cell division. In this review, we consider the rationale for pursuing mTOR as a therapeutic target in prostate cancer and summarize preclinical and clinical studies of mTOR inhibition in prostate cancer.     

哺乳动物雷帕霉素靶蛋白调控前列腺癌22RV1细胞雄激素受体及Akt磷酸化

目的:探索哺乳动物雷帕霉素靶蛋白mTORC1和mTORC2在前列腺癌22RV1细胞增殖及凋亡中的作用。方法:噻唑蓝(MTT)比色法检测mTORC1和mTORC2沉默后前列腺癌22RV1细胞增殖改变;流式细胞术(FCM)检测mTORC1和mTORC2沉默后前列腺癌22RV1细胞凋亡;Western印迹检测mTORC1和mTORC2沉默后前列腺癌22RV1细胞雄激素受体(AR)和Akt磷酸化表达。结果:MTT显示mTORC1沉默后,前列腺癌22RV1细胞的生长率无明显变化(P>0.05),而mTORC2沉默后,细胞的增殖受到了显著抑制(P<0.01);FCM显示mTORC1沉默后,细胞的凋亡率明显增加(P<0.01),而mTORC2沉默后,细胞的凋亡率无明显变化(P>0.05);Western印迹检测显示mTORC1沉默后,前列腺癌22RV1细胞中AR和Akt磷酸化表达显著增加(P<0.05),而mTORC2沉默后则显著抑制了前列腺癌22RV1细胞中AR和Akt磷酸化表达(P<0.05)。结论:mTORC2对于前列腺癌22RV1细胞的存活是必需的,mTORC2有可能成为治疗前列腺癌的一个有意义的靶点。     

Preemptive use of Mammalian target of rapamycin inhibitors in living donor transplantation

Sirolimus (SRL) has demonstrated beneficial impacts on the development of chronic allograft dysfunction (CAD). In living donor transplantation, strategies mostly seek to prevent graft dysfunction and respond to a decline in renal function. The present study focused on proactive, preemptive SRL administration for patients with repeated renal transplantations and those engrafted with an extended criteria donor organ.

Material and Methods

This retrospective, monocenter study describes 7 renal transplant recipients with stable graft function receiving SRL within the first year posttransplantation and 3 recipients of second transplantations who started SRL treatment before obtaining their repeat grafts.

Results

A proactive use of SRL revealed stable renal function parameters at 1 year after SRL introduction: Creatinine 1.33 ± 0.21 mg/dL; Modification of Diet in Renal Disease (MDRD) equation glomerular filtration rate, 57 ± 19 mL/min; PU 452 ± 338 mg/24 hours. Cell counts, hemoglobin concentrations, as well as triglyceride and total cholesterol levels did not differ over the 1-year follow-up. SRL administration before retransplantation provided good graft survival and renal function with a creatinine of 1.2 ± .32 mg/dL, MDRD of 60 ± 28 mg/dL, and PU 502 ± 432 mg/24 hour. Cell counts, hemoglobin concentrations, as well as triglyceride and total cholesterol levels did not differ over 1-year follow-up.

Conclusion

Preemptive SRL-induction before signs of graft deterioration or chronic injury may be a useful approach to prevent CAD.     

Mammalian target of rapamycin inhibition halts the progression of proteinuria in a rat model of reduced renal mass

Many kidney transplant patients experience an increase in proteinuria when converted from a calcineurin inhibitor-based regimen to one based on a mammalian target of rapamycin (mTOR) inhibitor, and preexisting proteinuria and poor renal function have been identified as risk factors for this increase. Our aim was to evaluate the effect of sirolimus, an mTOR inhibitor, on renal function and histology in a proteinuric model of reduced renal mass. Sirolimus-treated animals had approximately half as much proteinuria as vehicle-treated animals (P < 0.05), and had less glomerulosclerosis, tubular atrophy, interstitial fibrosis, and inflammation. Immunohistochemistry showed that sirolimus attenuated the increased expression of renal vascular endothelial growth factor (VEGF), as well as the expression of VEGF receptors 1 and 2. In conclusion, sirolimus halted the progression of proteinuria and structural damage in a rat model of reduced renal mass, possibly through a reduction in renal VEGF activity.     

自噬相关哺乳动物雷帕霉素靶蛋白信号通路在脊髓损伤中的作用研究进展

<正>脊髓损伤(SCI)可导致严重且不可逆的神经功能缺损甚至终身瘫痪,其常见病因包括交通事故、坠落伤及重物砸伤等。SCI造成的神经系统创伤至今仍是脊柱外科的治疗难题。自噬是一种主要依赖溶酶体介导的分解代谢途径,可使功能失调的细胞成分降解以应对各种形式的压力^[1]。微管相关蛋白1轻链3Ⅱ(LC3Ⅱ)、Beclin-1和p62被认为是自噬的3种标志物,自噬通量的高低可以通过自噬标志物的水平来评估,LC3Ⅱ或LC3Ⅱ/LC3Ⅰ比值、Beclin-1增加以及p62蛋白表达减少都可以表明自噬水平上升^[2]。哺乳动物雷帕霉素靶蛋白(mTOR)是一种丝氨酸/苏氨酸蛋白激酶,是信号网络的核心和细胞生长的中央控制器,它在调节细胞代谢、死亡、存活和增殖方面发挥着重要作用,被认为是自噬的主要负调节因子^[3]。     

Antitumor efficacy of Mammalian target of rapamycin inhibitor therapy in liver transplant recipients with oncological disease: a case-control study

Introduction

The reported incidences of de novo malignancy following orthotopic liver transplantation (OLT) are significantly greater than those in the general population. We have analyzed the efficacy of mammalian target of rapamycin inhibitor (mTORi) as immunosuppressant therapy in patients with de novo malignancies or those engrafted because of a primary liver cancer.

Methods

We performed a case-control study of patients with hepatocellular carcinoma (HCC; n = 119), cholangiocarcinoma (n = 1) or de novo malignancies (n = 73). Thirty-seven patients with these tumors were treated with mTORi, and 167, with calcineurin inhibitors (CNI). Switching to mTORi was performed progressively, withdrawing the CNI over 15 days, until obtaining levels of 5-10 ng/dL.

Results

No incidence of rejection, serious adverse events, or death was observed with an overall actuarial survival of 68.5% in the mTORi group versus 45.7% among the CNI group. Overall rates of tumor recurrence were 15.2% and 36.8%, respectively (P < .05). Among patients with HCC, survival was 100% of mTORi with and 61.5% among CNI patients, with tumor recurrence rates of 6.2% and 19.1%, respectively (P < .05).

Discussion

Surprising differences in survival and tumor recurrence rates were observed among the mTORi-treated group compared with controls. Switching from CNI to mTORi immunosuppressant therapy appeared to be safe. It seems to be reasonable to employ this strategy in liver transplant patients with primary hepatic or “de novo” neoplasms.     

The future role of target of rapamycin inhibitors in renal transplantation

Immunosuppressant nephrotoxicity is among the major contributors to chronic renal allograft failure, which is the primary cause of graft loss. Because of a lack of alternatives to the inherently nephrotoxic calcineurin inhibitors for maintenance immunosuppression, long-term survival rates for renal allografts have not increased in proportion to the rise in short-term graft survival. Clinical studies have shown that mammalian target of rapamycin-based immunosuppression in combination with calcineurin inhibitors, mycophenolate mofetil, or azathioprine is safe and efficacious. These data suggest that a target of rapamycin antagonist (sirolimus/everolimus) should be used initially in combination with calcineurin antagonists in order to prevent early acute rejection. After 3-6 months, a maintenance immunosuppressive regimen can then be individually tailored to each patient on the basis of their clinical and histological status. Those patients at high immunological risk should remain on full-dose triple therapy. All other patients should receive either a calcineurin inhibitor or corticosteroid-sparing regimen, with a maintenance dose of a target of rapamycin inhibitor. This regimen should result in less immunosuppressant nephrotoxicity and a reduction in the serious side effects of steroids, such as diabetes and osteoporosis. Whether the proposed individually designed immunosuppressive regimen, based on protocol biopsies and mammalian target of rapamycin inhibition, will result in prolonged graft and patient survival remains to be determined.     

Targeting the dysregulated mammalian target of rapamycin pathway in organ transplantation: killing 2 birds with 1 stone

Dysregulation and hyperactivation of the mammalian target of rapamycin (mTOR) pathway define the molecular basis of the hamartoma syndromes, including Cowden syndrome, tuberous sclerosis complex (TSC)/lymphangioleiomyomatosis, and Peutz-Jeghers syndrome. Loss of the tumor suppressors phosphatase and tensin homolog (PTEN), TSC1, TSC2, and LKB1 results in uncontrolled growth of usually benign tumors in various organs that, however, frequently lead to organ failure. Therefore, organ transplantation is a common therapeutic option in distinct patients with hamartoma syndromes, especially those with TSC/lymphangioleiomyomatosis. mTOR inhibitors are currently used in allogeneic transplantation as immunosuppressants and for the treatment of a growing number of cancers with dysregulated mTOR/phosphoinositide 3-kinase pathway. This dual targeting provides the unique opportunity for mTOR inhibitors to affect hamartoma syndromes at the molecular level along with potent immunosuppression in transplanted individuals. Here, we review the molecular mechanisms of hamartoma syndromes and discuss the recent clinical progress in transplant patients with hamartomas. Combining the identification of novel molecular targets of the phosphoinositide 3-kinase/mTOR pathway with insights into the clinical effectiveness of current therapeutic strategies sets the stage for a broader translational potential essential for further progress both in the treatment of cancer and for transplantation.     

Mammalian target of rapamycin inhibitors are associated with lower rates of hepatocellular carcinoma recurrence after liver transplantation: a systematic review

Calcineurin inhibitors (CNIs) have been associated in a dose‐dependent fashion with an increased risk of post‐transplant hepatocellular carcinoma (HCC) recurrence. The mammalian target of rapamycin inhibitors (mTORi) (sirolimus/everolimus) might represent an alternative immunosuppressive regimen with antineoplastic effect. In the present systematic review, the association between mTORi and HCC recurrence after liver transplantation (LT) was evaluated and compared against that of CNIs‐treated patients. In total, 3666 HCC liver transplant recipients from 42 studies met the inclusion criteria. Patients under CNIs developed HCC recurrence significantly more frequently, compared with patients under mTORi (448/3227 or 13.8% vs. 35/439 or 8%, P < 0.001), although patients treated with CNIs had a higher proportion of HCC within Milan criteria (74% vs. 69%) and lower rates of microvascular invasion, compared with mTORi‐treated patients (22% vs. 44%) (P < 0.05). Patients on everolimus had significantly lower recurrence rates of HCC, compared with those on sirolimus or CNIs (4.1% vs. 10.5% vs. 13.8%, respectively, P < 0.05), but everolimus‐treated recipients had shorter follow‐up period (13 vs. 30 vs. 43.2 months, respectively) and more frequently been transplanted for HCC within Milan criteria (84% vs. 60.5% vs. 74%, respectively, P < 0.05). Our findings favor the use of mTORi instead of CNIs to control HCC recurrence after LT, but comparative studies with longer follow‐up are needed for final conclusions.     

mTOR信号转导通路在自体移植静脉中的表达及意义

目的研究哺乳类动物雷帕霉素靶蛋白(mTOR)在自体移植静脉中表达的动态变化规律。方法Wistar大鼠64只,建立自体静脉移植模型,随机分为8组,分别在移植后6 h,1、3 d,1、2、4、6、8周切取移植静脉。逆转录PCR结合原位杂交研究移植血管中mTOR的tuRNA表达,Western blot联合免疫组化检测mTOR蛋白产物表达的变化,同时检测增殖细胞核抗原(PCNA)。结果逆转录PCR扩增在静脉移植1-3 d即出现mTOR mRNA表达增强,1-2周达到高峰,表达值分别为(48±18)％和(33±11)％,与其他组比较差异有统计学意义(P<0．01),6-8周逐渐恢复正常。免疫组化及Western蛋白印迹均提示mTOR蛋白在移植3 d表达明显增多,2-4周达到高峰,分别为(29±8)％和(31±6)％,与其他组比较差异有统计学意义(P<0．01),8周恢复至正常水平。mTOR蛋白产物表达与PCNA表达呈正相关(r=0．756,P<0．01)。结论mTOR在血管移植后的过程中被激活,与内膜增生关系密切,可能是防治移植血管狭窄、闭塞的干预靶点。     

A cyclic guanosine monophosphate-dependent pathway can regulate net hepatic glucose uptake in vivo

We previously showed that hepatic nitric oxide regulates net hepatic glucose uptake (NHGU), an effect that can be eliminated by inhibiting hepatic soluble guanylate cyclase (sGC), suggesting that the sGC pathway is involved in the regulation of NHGU. The aim of the current study was to determine whether hepatic cyclic guanosine monophosphate (cGMP) reduces NHGU. Studies were performed on conscious dogs with transhepatic catheters. A hyperglycemic-hyperinsulinemic clamp was established in the presence of portal vein glucose infusion. 8-Br-cGMP (50 μg/kg/min) was delivered intraportally, and either the glucose load to the liver (CGMP/GLC; n = 5) or the glucose concentration entering the liver (CGMP/GCC; n = 5) was clamped at 2× basal. In the control group, saline was given intraportally (SAL; n = 10), and the hepatic glucose concentration and load were doubled. 8-Br-cGMP increased portal blood flow, necessitating the two approaches to glucose clamping in the cGMP groups. NHGU (mg/kg/min) was 5.8 ± 0.5, 2.7 ± 0.5, and 4.8 ± 0.3, whereas the fractional extraction of glucose was 11.0 ± 1, 5.5 ± 1, and 8.5 ± 1% during the last hour of the study in SAL, CGMP/GLC, and CGMP/GCC, respectively. The reduction of NHGU in response to 8-Br-cGMP was associated with increased AMP-activated protein kinase phosphorylation. These data indicate that changes in liver cGMP can regulate NHGU under postprandial conditions.     

Nonimmunosuppressive effects of mammalian target of rapamycin inhibitors

Mammalian target of rapamycin (mTOR) integrates nutrient and hormonal signals involved in cell growth. Development of mTOR inhibitor drugs as therapeutic agents for major human diseases such as obesity, diabetes, atherosclerosis, or cancer will experience an important increase in the next years. The incidence of these diseases is particularly increased among organ transplant recipients being a limiting factor for transplant success. Transplant teams carry on significant experience in treating patients with mTOR inhibitors for preventing acute rejection or reducing nephrotoxicity. Preliminary data showed that these drugs are effective for reducing posttransplant malignancy. Transplant teams have the unique opportunity to analyze whether mTOR inhibitors are also effective for the prevention of cardiovascular diseases, obesity, and diabetes.