氟尿嘧啶与生长抑素受体基因联合治疗鼠 胰腺癌移植瘤的研究

目的 ： 观察生长抑素二型受体(SSTR2)基因体内转染后裸鼠胰腺癌移植瘤对5-氟尿嘧啶（5-FU）的反应，并探讨其可能机制。方法 ：将人胰腺癌细胞株panc-1种植于裸鼠背部皮下形成胰腺癌移植瘤模型。成模后动物随机分成4组（每组6只）;I组为对照组;II组为腹腔注射5-FU治疗组;III组为瘤内注射pCMV-6C-SSTR2-脂质体转染SSTR2基因治疗组;IV组为基因治疗+5-FU治疗组。观察肿瘤生长速度，测量瘤体大小及重量。用免疫组织化学方法和免疫印迹技术(Westernblot)检测转染效率;用凋亡原位检测方法(Tunel)检测胰腺癌细胞的凋亡率。结果 ：体内转染后SSTR2可重新表达。5-FU和SSTR2基因联合治疗(IV)组肿瘤生长速度显著慢于单独基因治疗(III)组及单独5-FU治疗(II)组和空白对照(I)组（ P <0.01）;最终肿瘤大小，重量也显著小于其他3组（均 P <0.01），而癌细胞凋亡率显著高于其他3组（均 P <0.01）。结论 ：SSTR2重新表达后可增强胰腺癌细胞对化疗药物5-FU的敏感性，联合5-FU 和SSTR2基因治疗可望成为治疗胰腺癌新的途径。     

Somatostatin receptor subtype 2 gene therapy inhibits pancreatic cancer in vitro

BACKGROUND: Most human pancreatic adenocarcinoma cells do not express somatostatin receptors and somatostatin does not inhibit the growth of these cancers. We have demonstrated previously that somatostatin inhibits the growth of pancreatic cancers expressing somatostatin receptor subtype 2 (SSR2) but not receptor-negative cancers. SSR2 expression may be an important tumor suppressor pathway that is lost in human pancreatic cancer. We hypothesized that SSR2 gene transfer would restore the growth inhibitory response of human pancreatic cancer to somatostatin. METHODS: We created adenoviral constructs containing the SSR2 or Lac-Z gene and transfected somatostatin receptor-negative human pancreatic cancer cells (Panc-1). Presence of functional cell surface SSR2 protein was assessed by whole-cell competitive binding assays. Parental cells, Lac-Z-transfected, and SSR2-transfected cells were cultured in the presence and absence of somatostatin. The rate of cell growth was determined by direct cell counting using a hemacytometer (n = 8 wells/group). Cells were analyzed for expression of tumor suppressor proteins by Western blot. RESULTS: Panc-1 cells transfected with the SSR2 transgene demonstrated high-affinity specific binding of (125)I-somatostatin at physiologic concentrations. Expression of somatostatin receptors caused 60% inhibition of cell growth compared with the Lac-Z virus-treated controls (P < 0.05 by Kruskal-Wallis/Bonferroni). There was no additional inhibition of cell proliferation with exogenous somatostatin. Furthermore, addition of somatostatin ligand antibody did not diminish the effect of SSR2 expression on cell proliferation. Western blot analysis revealed an upregulation of the cyclin-dependent kinase inhibitor p27 in the SSR2-transfected cells. CONCLUSIONS: Expression of SSR2 by human pancreatic cancer causes significant slowing of cell division by a mechanism independent of somatostatin. The mechanism may involve upregulation of known tumor suppressor proteins. Restoration of SSR2 gene expression deserves further study as a potential gene therapy strategy in human pancreatic cancer.     

生长抑素受体基因对胰腺癌细胞侵袭转移影响的研究

目的探讨腺病毒介导的生长抑素受体2（SSTR2）基因对胰腺癌BXPC-3细胞浸润、转移的抑制作用及其机制.方法利用腺病毒载体Adv-GFP-SSTR2将人类SSTR2全长cDNA转染导入胰腺癌细胞株BXPC-3,用RT-PCR及Westen-blot检测SSTR2在mRNA水平及蛋白水平上的表达.利用Transwell小室测定转染SSTR2前、后及转染空载体后细胞的穿膜侵袭运动能力;RT-PCR检测转染SSTR2前后及转染空载体细胞的MMP-2和TIMP-2的表达.结果Adv-GFP-SSTR2腺病毒转染胰腺癌BXPC-3后,可以稳定表达SSTR2;细胞计数示转染后胰腺癌细胞穿透基底膜的数量较转染前明显减少（P＜0.01）,细胞侵袭力明显减弱;MMP-2转染后较转染前表达明显上调（P＜0.01）、TIMP-2表达明显下调（P＜0.01）,MMP-2/TIMP-2比例下降.结论转染SSTR2可明显抑制胰腺癌细胞的侵袭转移,其可能的机制是通过改变MMP-2/TIMP-2的比例而抑制肿瘤细胞对细胞外基质的降解.     

Expression of somatostatin receptor and effects of somatostatin analog on pancreatic endocrine tumors

Abstract. Purpose: Somatostatin analogs have been administered to patients with pancreatic endocrine tumors in an attempt to inhibit hormone hypersecretion and prevent tumor growth. It is speculated that their efficacy is correlated with the expression of specific subtypes of somatostatin receptors. The aim of this study was to immunohistochemically evaluate the expression of somatostatin receptor subtypes in human pancreatic endocrine tumors, and to determine whether the expression of these subtypes is correlated with the effectiveness of the somatostatin analogs. Methods: Somatostatin receptor subtypes 1, 2, and 3 (sst 1, 2, and 3) were immunohistochemically investigated in seven pancreatic endocrine tumors: four insulinomas, one VIPoma, and two nonfunctioning tumors associated with multiple endocrine neoplasia type I, using paraffin sections. Three of the four patients with insulinoma were given an octreotide injection. Results: Cells were homogeneously stained in the tumor region. More than 85% of the specimens expressed sst 1, 2, and 3. There was no difference among the immunohistochemical stainings of somatostatin receptor subtypes according to most tumor characteristics; however, the expression of sst 2 was extremely positive, and the expression of sst 3 was moderately positive in the specimen from a patient in whom the octreotide injection had proven very effective. Conclusion: These findings indicate that the efficacy of octreotide may be correlated with the density of sst 2 and 3 in an immunohistological study using paraffin sections. Received: May 18, 2001 / Accepted: November 20, 2001     

The Levels of Somatostatin Receptors in Causative Tumors of Oncogenic Osteomalacia Are Insufficient for Their Agonist to Normalize Serum Phosphate Levels

Oncogenic osteomalacia (OOM) is a rare disease characterized by renal phosphate wasting and osteomalacia and is caused by the secretion of fibroblast growth factor 23 (FGF-23) from causative tumors. Scintigraphy with octreotide, which binds to somatostatin receptors (SSTRs), is a useful way to locate causative tumors in OOM patients. However, the therapeutic effects of octreotide acetate are still controversial. Two OOM patients were administered octreotide acetate intramuscularly. Ten causative OOM tumors, including two resected from the patients participating in the octreotide administration study, were examined for expression of genes encoding SSTRs by quantitative real-time RT-PCR and immunohistochemistry. Octreotide therapy did not improve hypophosphatemia in either case, despite temporal decreases in FGF-23 levels in one patient. The mean expression levels of SSTR1, SSTR3, and SSTR5 were similar in the OOM and non-OOM tumors. Expression of SSTR2 was significantly higher in the OOM tumors than in the non-OOM tumors. Immunohistochemical examinations revealed the presence of SSTR2A, SSTR2B, and SSTR5 in both the OOM and non-OOM tumors. The expression of SSTR genes in OOM tumors contributes to positive imaging using octreotide scintigraphy. However, the levels of SSTRs seem to be insufficient for the octreotide therapy to improve hypophosphatemia. Further studies are needed to clarify the mechanisms by which FGF-23 secretion from OOM tumors is suppressed by octreotide acetate.     

Somatostatin, Somatostatin Receptors, and Pancreatic Cancer

Somatostatin may play an important role in the regulation of cancer growth including pancreatic cancer by interaction with somatostatin receptors (SSTRs) on the cell surface. Five SSTRs were cloned, and the function of these SSTRs is addressed in this review. SSTR-2, SSTR-5, and SSTR-1 are thought to play major roles in inhibiting pancreatic cancer growth both in vitro and in vivo. SSTR-3 may be involved in mediating apoptosis, but the role of SSTR-4 is not clear. In most pancreatic cancers, functional SSTRs are absent. Reintroduction of SSTR genes has been shown to inhibit pancreatic cancer growth in cell cultures and animal models.     

Recent advances in treatment of pancreatic neuroendocrine tumors

The recent consensus on the diagnosis and treatment of pancreatic neuroendocrine tumors (PNET) is described. The selective arterial secretagogue injection test and somatostatin receptor scintigraphy are essential for the localization of PNET. A few characteristic clinicopathologic findings of PNET in patients with multiple endocrine neoplasia type 1 (MEN 1) have been elucidated and contributed to improved surgical treatment for these tumors, such as pancreas-preserving total duodenectomy for multiple duodenal gastrinomas in patients with MEN 1 and Zollinger-Ellison syndromes, or distal pancreatectomy for patients with MEN 1 and hypoglycemia. Early diagnosis and early surgical resection of PNET are recommended for complete cure of disease. In liver metastasis of PNET, mass reduction surgery with hepatectomy improves the prognosis of patients, and octreotide LAR has been shown to be useful for reducing complications and inhibiting the growth of tumors.     

Somatostatin analogue in treatment of coexisting glucagonoma and pancreatic pseudocyst: dissociation of responses

After an acute episode of pancreatitis, a 63-year-old man was found to have a pancreatic glucagonoma. The tumor was resected without evidence of metastases. Three years later he had symptoms of uncontrolled diabetes, no skin lesions, and diarrhea and was found to have a pancreatic pseudocyst and multiple hepatic metastases. Glucagon concentrations were raised but were suppressible by glucose and somatostatin and responded to arginine stimulation. He was treated for 6 months with octreotide (Sandostatin), which reduced his symptoms; the pseudocyst resolved, but liver metastases continued to grow. Although spontaneous resolution of the pseudocyst is possible, this case appears to illustrate differences in sensitivity of endocrine and exocrine tissues to suppression by Sandostatin.     

光动力治疗裸小鼠胰腺移植癌的实验研究

目的 研究光动力治疗（ＰＤＴ）对胰腺癌的治疗效果,为胰腺癌寻找有效的治疗手段。方法 接种人胰腺癌细胞ＳＷ１９９０于裸小鼠皮下,建立移植癌模型,以血卟淋衍生物（ＨｐＤ）作为光敏剂,采用腹腔和瘤内局部注射两种不同方式给药,继以波长６３２．８ｎｍ的Ｈｅ－Ｎｅ激光照射肿瘤局部,观察光动力治疗后肿瘤的生长速度和组织形态学变化,并测定了肿瘤组织内脂质过氧化产物丙二醛（ＭＤＡ）的含量,对其治疗机制进行了初步探讨     

Prognostic impact of somatostatin receptor expression in advanced bladder cancer

Introduction and objectivesSomatostatin receptors (SSTR) recently have been identified as potential targets for treatment of solid tumors. Furthermore, they have been shown to be of high relevance for tumor biology and prognosis in various types of cancer. However, there is a lack of clinical data for SSTR in bladder cancer (BC). Aim of this study was to determine the expression of all relevant somatostatin receptor subtypes in benign urothelium and tumor tissue of patients with muscle invasive BC. Furthermore, their potential role as prognostic factor for cancer-specific survival (CSS) and overall survival (OS) was evaluated.MethodsThe collective included BC and benign urothelium tissue of 103 patients (Median age 69; range 32–84, 79 male, 24 female) who underwent a radical cystectomy. A tissue microarray with subsequent immunohistochemical staining was used to assess membranous expression of SSTR1–5. Results were correlated to clinical and histopathological data as well as CSS and OS.ResultsExpressions of SSTR1-4 were significantly decreased in BC compared to benign urothelium (P < 0.002 each), whereas SSTR5 expression was increased (P = 0.0017). Expression of SSTR1 was associated with organ–confined disease (≤pT2) (P = 0.0477). No correlation between SSTR1-5 expression and N- and M-stage was observed. Univariate analyses showed a significantly longer CSS and OS in patients with high expression of SSTR3 (P = 0.0316 and 0.0044). Multivariate analyses confirmed SSTR3 expression as independent marker of improved CSS and OS (P = 0.0324 and 0.0076).ConclusionsThe majority of somatostatin receptor subtypes exhibit decreased expression in BC compared to benign bladder tissue. Expression of SSTR3 is an indicator for favorable prognosis in patients with muscle-invasive BC. These results support preclinical investigations using somatostatin receptor analogues such as octreotide to influence BC growth.     

The Hypofunctional Effect of P335L Single Nucleotide Polymorphism on SSTR5 Function

Background

Somatostatin receptor subtype 5 (SSTR5) mediates the inhibitory effect of somatostatin on insulin expression/secretion and cell proliferation. A number of single nucleotide polymorphisms (SNPs) of SSTR5 have been identified, including P335L, a nonsynonymous SNP located in the protein C-terminal region and encrypted by the codon CCG (proline) or the codon CTG (leucine). In the present study we sought to determine the distribution of the SSTR5 P335L SNP in a cohort of pancreatic cancer patients and whether the P335L SNP affected cellular function of SSTR5 in human pancreatic cancer.

Methods

The P335L germline genotype of 246 patients with pancreatic cancer (213 Caucasians, 16 Hispanics, and 17 African Americans) and 17 human pancreatic cell lines was determined with the TaqMan SNP Genotyping assay. Human SSTR5 leucine variant (L335) was generated by performing site-directed mutagenesis using SSTR5 proline variant (P335) as a template. Transient transfections were performed in HEK293, Mia PaCa-2, and ??-TC-6 cells using Lipofectamine 2000. The expression of SSTR5 L335 was determined with a mouse monoclonal anti-SSTR5 L335 antibody generated in our laboratory. The cell proliferation rate was measured by performing MTS assays. Insulin concentration was measured by performing ELISA assays.

Results

Genotyping of the patients?? blood indicated that the frequency of the T allele (CT and TT genotypes) in codon 335 of SSTR5 in Caucasians, Hispanics, and African Americans was 52, 69, and 35%, respectively, which was race-dependent. Statistical analysis indicated that association between the frequency of the T allele and the existence of pancreatic cancer in each race missed significance perhaps due to limited sample size. In 17 tested human pancreatic cancer cell lines, 5 (Capan-2, HPAF-II, Panc03.27, Panc-1, and -3) were homozygous (TT genotype) and 9, including Mia PaCa-2, were heterozygous (CT genotype). Overexpression of SSTR5 L335 in Mia PaCa-2 cells enhanced cell proliferation compared to overexpression of SSTR5 P335. Overexpression of SSTR5 P335 enhanced the inhibitory effect of SSTR5 agonist RPL-1980 on cell proliferation of Mia PaCa-2 cells and glucose-stimulated insulin secretion from mouse insulinoma cells, while overexpression of SSTR5 L335 blocked the inhibitory effect of RPL-1980. Overexpression of SSTR5 L335 enhanced PDX-1 expression in Mia PaCa-2 cells. A specific monoclonal antibody was generated to detect SSTR5 P335L.

Conclusion

SSTR5 P335L SNP widely exists in the human population, in patients with pancreatic cancer, and is race-dependent. The SNP is also present in selected human pancreatic cancer cell lines. In contrast to SSTR5 P335, overexpression of the SSTR5 L335 variant resulted in cellular proliferation and PDX-1 overexpression in human pancreatic cancer cells. Its overexpression blocked the inhibitory effect of an SSTR5-specific analog on human pancreatic cancer cell proliferation and on glucose-stimulated insulin secretion from mouse insulinoma cells. These data suggest that SSTR5 P335L is a hypofunctional protein with a potentially harmful effect on function, as well as potential latent effect, and therefore it could affect the clinical response to somatostatin analog therapy for patients with pancreatic cancer.     

Effect of somatostatin analogue and cholecystokinin receptor antagonist on bile-induced acute canine pancreatitis.

To determine whether a synthetic somatostatin analogue, octreotide, and a cholecystokinin receptor antagonist, L-364,718, may be beneficial in acute pancreatitis, 33 dogs were assigned to four groups. Each dog underwent laparotomy with injection of autologous bile into the dorsal pancreatic duct. Thirty minutes after the induction of pancreatitis, Group 1 received a subcutaneous injection of octreotide (200 micrograms/kg), Group 2 received an equal volume of the octreotide carrier, Group 3 received an hourly intravenous bolus of L-364,718 (60 micrograms/kg), and Group 4 received an equal volume of the L-364,718 carrier. Hemodynamic profiles, arterial blood gases, plasma glucose, and serum amylase were obtained before laparotomy, at bile injection, and at hourly intervals. The pancreas was removed after 8 hours for gross evaluation, measurement of water content, and histologic examination. A significant decrease in cardiac index and a significant increase in serum amylase and pancreatic edema occurred in all four groups 8 hours after the induction of pancreatitis (P less than 0.05), but there was no statistical difference between any group. Likewise, there was no difference in gross or histologic changes in the pancreas of any group. The somatostatin analogue, octreotide, and the cholecystokinin receptor antagonist, L-364,718, did not ameliorate the effects of severe, bile-induced pancreatitis in dogs.     

转染SSTR2对胰腺癌细胞的促凋亡作用

目的 通过包含SSTR2基因的重组腺病毒(AdCAG-SSTR2)转染人胰腺癌细胞,观察对胰腺癌细胞肿瘤特性的影响.方法 分别应用空载体、AdCAG-SSTR2转染SSTR2阴性的人胰腺癌细胞株BxPC-3.逆转录.聚合酶链反应(RT-PCR)和Western blot法分析检测SSTR2在细胞中的表达.非转染细胞、转染空载体细胞和转染AdCAG.SSTR2细胞直接计数测定细胞生长速度.采用膜联蛋白Ⅴ/碘化丙锭(Annexin V/PI)标记法检测细胞凋亡.RT-PCR检测PCNA、bax和bcl-xl的表达.结果 AdCAG.SSTR2转染胰腺癌细胞后可以检测到SSTR2 mRNA和蛋白的稳定表达,转染AdCAG-SSTR2后细胞生长受到抑制,与对照组差异有统计学意义(P＜0.01);细胞凋亡率较对照组明显升高(P＜0.01);PCNA的表达无明显变化,是对照组的1.04倍;bax的表达明显升高,是对照组的3.18倍;bcl-xl的表达明显降低,是对照组的0.34倍.结论 SSTR2通过诱导胰腺癌细胞凋亡发挥抗肿瘤增殖的作用,其机制与上调bax的表达,下调bcl-xl的表达有关.     

胰腺癌特异性受体基因载体的构建及环氧合酶2L启动子的作用

目的构建环氧合酶-2L启动子（Cox-2L）及2型生长抑素受体（SSTR2）基因重组腺病毒载体，以研究SSTR2重新表达及腺病毒感染对胰腺癌细胞的影响。方法用逆转录-聚合酶链反应（RT—PCR）法从人正常胰腺组织中调取SSTR2基因，以HL60细胞基因组DNA为模板，以PCR法调取Cox-2L基因，以SSTR2及Cox-2L基因片段为模板，以PCR法扩增Cox-2L—SSTR2融合基因并连入TaKaRa公司pAxcwit腺病毒载体中，以电穿孔法转化E．Coli后挑选阳性克隆进行PCR及酶切鉴定。以pAxcwit—Cox-2L—SSTR2转染HEK293细胞获得重组腺病毒颗粒，进行PCR、酶切鉴定。结果调取并连接后的基因片段经测序证实为Cox-2L、SSTR2及Cox-2L-SSTR2融合基因，Cox-2L-SSTR2基因片段及PolyA克隆入T载体，经酶切并测序证实PMD18-T—Cox-2L—SSTR2-PolyA构建成功。pAxcwit—Cox-2L—SSTR2-PolyA经酶切及PCR鉴定，Cox-2L—SSTR2-PolyA融合基因正确连入腺病毒载体。结论成功构建了Cox-2L—SSTR2基因重组腺病毒载体，为进一步研究SSTR2在胰腺癌细胞中的表达及作用奠定了基础。