Alpha-fetoprotein producing cells act as cancer progenitor cells in human cholangiocarcinoma

We aimed to demonstrate that alpha-fetoprotein (AFP)-producing cells in cholangiocarcinomas possessed cancer stem cell (CSC)-like properties. AFP enhancer/promoter-driven EGFP gene was transfected into human cholangiocarcinoma cell lines. One cell line, RBE, expressed both AFP and EGFP. Clonal analyses revealed that one EGFP-positive cell generated both EGFP-positive and EGFP-negative cell fractions. However, one EGFP-negative cell never produced EGFP-positive cells. The EGFP-positive cells had a greater tumorigenic potential. Only the EGFP-positive cells expressed Notch1. AFP and Notch1 expression was observed in clinical intrahepatic cholangiocarcinomas. The AFP-producing cells were suggested to be CSCs. The Notch pathway might play an important role in maintaining the CSC characteristics.     

Establishment of an alpha-fetoprotein-producing gastric cancer cell line in serum-free media.

A new cell line, designated ISt-1, was established in serum-free medium from a 63-year-old gastric cancer patient with an extremely high serum level of alpha-fetoprotein (AFP). ISt-1 exhibited a typical morphology of epithelial cells in culture. The population doubling time was 31 hours. Production of AFP was demonstrated by immunohistochemical study and high levels of AFP were detected in the conditioned medium of ISt-1 cells. ISt-1 is considered to be an AFP-producing gastric cancer cell line and will provide a useful tool for the study of production and secretion of AFP from cells.     

12-lipoxygenase metabolite 12(S)-HETE stimulates human pancreatic cancer cell proliferation via protein tyrosine phosphorylation and ERK activation.

We previously reported that inhibition of the 12-lipoxygenase pathway abolished proliferation and induced apoptosis in several pancreatic cancer cell lines. Furthermore, the 12-lipoxygenase product 12(S)-HETE stimulated pancreatic cancer cell proliferation and reversed 12-lipoxygenase inhibitor-induced growth inhibition. We investigated the underlying mechanism for 12(S)-HETE-induced pancreatic cancer cell proliferation, using 2 human pancreatic cancer cell lines, PANC-1 and HPAF. Cell proliferation was monitored by both thymidine incorporation and cell number. Western blotting was used to investigate the effect of 12(S)-HETE on cellular protein tyrosine phosphorylation as well as ERK, P38 MAPK and JNK/SAPK phosphorylation. 12(S)-HETE markedly stimulated proliferation of pancreatic cancer cells in a time- and concentration-dependent manner. In parallel, 12(S)-HETE induced tyrosine phosphorylation of multiple cellular proteins, while inhibition of tyrosine kinase by genestein abolished 12(S)-HETE-induced proliferation, indicating that intracellular protein tyrosine kinase activation is involved in the mitogenic effects of 12(S)-HETE. Following treatment with 12(S)-HETE, both ERK and P38 MAPK, but not JNK/SAPK, were phosphorylated. The specific MEK inhibitors PD098059 and U0126, which in turn suppress ERK, abolished 12(S)-HETE-stimulated proliferation. In contrast, inhibition of P38 MAPK with SB203580 did not affect 12(S)-HETE-stimulated pancreatic cancer cell proliferation. Furthermore, 12(S)-HETE-stimulated ERK phosphorylation was inhibited by genestein, indicating that tyrosine phosphorylation is essential for ERK activation. These findings suggest that both ERK and cellular protein tyrosine kinase activation are involved in 12(S)-HETE-induced pancreatic cancer cell proliferation but P38 and JNK/SAPK are not involved in this mitogenic effect.     

Production of alpha-fetoprotein, normal serum proteins, and human chorionic gonadotropin in stomach cancer: histologic and immunohistochemical analyses of 35 cases

By immunoperoxidase histochemical staining of formalin-fixed paraffin-embedded sections, the production of alpha-fetoprotein(AFP), albumin(ALB), transferrin(TF), alpha-1-antitrypsin(AAT), and human chorionic gonadotropin(HCG) was examined in 35 operatively resected stomach cancers with elevated serum AFP levels (higher than 20 ng/ml as determined by radioimmunoassay). Cells positive for AFP were found in 19 cases (54%). In 29 cases (83%), some tumor cells contained normal serum proteins (ALB, TF, or AAT). All 19 tumors with AFP-positive cells also stained positively for two or three kinds of normal serum proteins. In some cases, AFP and normal serum proteins were localized in the same cells. There were two cases in which metastatic tumors produced AFP, whereas the primary sites did not. In nine cases (26%), HCG was present in tumor cells and HCG- and AFP-positive cells were coexistent in six tumors. Histologic examination of AFP-producing stomach tumors revealed medullary or papillotubular arrangements with marked nuclear atypia and eosinophilic granular or clear cytoplasms containing no glycogen or mucin. Some tumors with medullary patterns resembled liver cell carcinomas. Concordant phenotypic expression of AFP and normal serum protein production appears to be a general feature of AFP-producing tumors such as liver cell carcinoma, yolk sac tumor, and stomach cancer.     

Detection of membrane-bound alpha-fetoprotein in human hepatoma cell lines by monoclonal antibody 19F12

Monoclonal antibodies against human alpha-fetoprotein (AFP) were obtained by the hybridoma technique and studied with regard to their reactivities with the human hepatoma cell lines PLC/PRF/5 and KN, and a spontaneously immortalized cell line derived from fetal liver, NuE, all of which synthesize AFP. One of the monoclonal antibodies, 19F12 (IgG2b) became bound to free AFP which was used as the immunogen with an affinity constant of 3.4 X 10(8) M-1. This value was not much higher than those of two other antibodies, 19B1 (IgG1) and 9D12 (IgG2b). However, only antibody 19F12 showed definite reactivity with AFP-producing cells in analysis using flow cytometry. Immunofluorescence microscopy showed that antibody 19F12 detected AFP over the surface of NuE and PLC/PRF/5 cells with a uniform distribution, whereas definite reactivities of antibodies 19B1 and 9D12 to these cells were not detected. These antibodies did not show the specific binding to a non-AFP-producing human lung cancer cell line, PC-9, or to human peripheral blood lymphocytes. The binding ability of 19F12 to hepatoma cells was shown in both viable and fixed cells. Addition of free AFP inhibited the binding of antibody 19F12 to PLC/PRF/5 cells in a concentration-dependent manner. The specific reactivity of 19F12 to human AFP was also confirmed by immunostaining of a tissue section of human cancer proved to be AFP positive with AFP-specific antisera. In two-dimensional polyacrylamide gel electrophoresis of the antigen (from membrane fraction of PLC/PRF/5 cells)-antibody (19F12) complex, spots derived from the antibody and a spot (pI 4.7, Mr 65,000) corresponding in pI and molecular weight to AFP were detected. Western blot analysis showed that material in the membrane fraction of PLC/PRF/5 cells recognized by antibody 19F12 has the same molecular weight as human AFP derived from placenta. In a study of reactivities to PLC/PRF/5 cells treated with various enzymes, the reactivity of this antibody decreased when cells were treated with protease and trypsin and increased when lipase was used. The binding of 19F12 to AFP was not inhibited by concanavalin A. The antibody 19F12 appeared to recognize an epitope that is considered to be part of the peptide area of AFP. These results indicate that the reactivity, the amount of bound antibodies, and the distribution of monoclonal antibodies on antigen-producing cells vary, respectively, even though these antibodies were produced using the same antigen as an immunogen.(ABSTRACT TRUNCATED AT 400 WORDS)     

Cell-specific expression of the diphtheria toxin A-chain coding sequence under the control of the upstream region of the human alpha-fetoprotein gene

BACKGROUND AND OBJECTIVES: Development of the system to express a suicide gene selectively in tumor cells is essential for gene therapy. We constructed a plasmid containing the diphtheria toxin A (DTA) fragment linked to human alpha-fetoprotein (AFP) promoter and enhancer, and tested whether it can exert its cytocidal effect selectively on AFP-producing cells. METHODS: The chloramphenical acetyltransferase (CAT) reporter gene or DTA gene was linked to the 5' upstream region of the AFP gene. The plasmids were transfected into AFP-producing or non-producing cells by the lipopolyamine-coated DNA method. Expression of CAT activity and effects on cell growth of transfected cells were assessed. RESULTS: When the AFP-producing cells HuH-7 or HepG2 were cotransfected with CAT reporter plasmid and pAF5.1DTA plasmid, the CAT activity was greatly suppressed. In contrast, cotransfection with pAF5.1DTA-R, the inversely inserted DTA gene, did not inhibit CAT activity. Furthermore, cell growth of HuH-7 cells transfected with pAF5.1DTA plasmid was significantly inhibited compared with HuH-7 cells transfected with DTA-R plasmid. CONCLUSIONS: Our results indicate that selective killing of AFP-producing cells will be attained by introducing the DTA gene linked to the promoter and enhancer region of AFP.     

Identification of pancreatic cancer stem cells

Emerging evidence has suggested that the capability of a tumor to grow and propagate is dependent on a small subset of cells within a tumor, termed cancer stem cells. Although data have been provided to support this theory in human blood, brain, and breast cancers, the identity of pancreatic cancer stem cells has not been determined. Using a xenograft model in which primary human pancreatic adenocarcinomas were grown in immunocompromised mice, we identified a highly tumorigenic subpopulation of pancreatic cancer cells expressing the cell surface markers CD44, CD24, and epithelial-specific antigen (ESA). Pancreatic cancer cells with the CD44(+)CD24(+)ESA(+) phenotype (0.2-0.8% of pancreatic cancer cells) had a 100-fold increased tumorigenic potential compared with nontumorigenic cancer cells, with 50% of animals injected with as few as 100 CD44(+)CD24(+)ESA(+) cells forming tumors that were histologically indistinguishable from the human tumors from which they originated. The enhanced ability of CD44(+)CD24(+)ESA(+) pancreatic cancer cells to form tumors was confirmed in an orthotopic pancreatic tail injection model. The CD44(+)CD24(+)ESA(+) pancreatic cancer cells showed the stem cell properties of self-renewal, the ability to produce differentiated progeny, and increased expression of the developmental signaling molecule sonic hedgehog. Identification of pancreatic cancer stem cells and further elucidation of the signaling pathways that regulate their growth and survival may provide novel therapeutic approaches to treat pancreatic cancer, which is notoriously resistant to standard chemotherapy and radiation.     

Establishment of an α-Fetoprotein-producing Gastric Cancer Cell Line in Serum-free Media

A new cell line, designated Ist-1, was established in serum-free medium from a 63-year-old gastric cancer patient with an extremely high serum level of α-fetoprotein (AFP). ISt-1 exhibited a typical morphology of epithelial cells in culture. The population doubling time was 31 hours. Production of AFP was demonstrated by immmunohistochemical study and high levels of AFP were detected in the conditioned medium of ISt-1 cells. Ist-1 is considered to be an AFP-producing gastric cancer cell line and will provide a useful tool for the study of production and secretion of AFP from cells.     

Distribution of alpha-fetoprotein-producing cells and proliferating cells in human hepatoma cells transplanted into athymic mice

To clarify the relationship between alpha-fetoprotein (AFP) production and cell growth in hepatocellular carcinoma an immunohistochemical method was used to examine the geographical distribution of AFP-producing cells and DNA-synthesizing cells in hepatoma tissue which was formed by subcutaneous transplantation of the human hepatoma cell line, HuH-7, into athymic mice. DNA-synthesizing cells were localized to the perivascular restricted areas where AFP-producing cells were preferentially demonstrated. The fall of the labeling index of bromodeoxyuridine was accompanied by a decrease in AFP production. The results indicate that AFP is produced mainly by the cells participating in tumor growth but not by quiescent cells.     

人前列腺癌肿瘤干细胞12-LOX表达的初步研究

目的：研究花生四烯酸12-脂氧化酶（12-LOX）在人前列腺癌肿瘤干细胞中的表达情况,并探讨其意义。方法：采用反转录聚合酶链反应（RT—PCR）技术和蛋白质印迹法,检测12-LOX在人前列腺癌细胞系DU145细胞和从其中分离出来的Du145侧群细胞中的表达情况;采用免疫荧光4通道激光扫描共聚焦显微镜技术,检测12-LOX在7例前列腺癌组织肿瘤干细胞和10例正常前列腺组织干细胞中的表达情况。结果：在细胞水平,应用RT—PCR技术和蛋白质印迹法分别证实,12-LOX mRNA和12-L0x蛋白在具有肿瘤干细胞特性DU145侧群细胞中的表达水平明显高于对应的母系DU145细胞;在组织水平,应用免疫荧光4通道激光扫描共焦显微镜检测证实,12-LOX蛋白在所有7例前列腺癌组织的肿瘤干细胞中均为阳性表达,而在所有10例正常前列腺组织的前列腺干细胞中均无表达。结论：12-LOX在人前列腺癌的肿瘤干细胞中有特异性的高表达,从而有望成为前列腺癌肿瘤干细胞一个新的、特异性的标志,并进一步有望成为前列腺癌肿瘤干细胞一个新的治疗靶位。     

Pancreatic cancer stem cells: implications for the treatment of pancreatic cancer

Pancreatic cancer is a highly lethal disease that is usually diagnosed at a late stage for which there are few effective therapies. Emerging evidence has suggested that malignant tumors are quite heterogeneous and that they are composed of a small subset of distinct cancer cells (usually defined by cell surface marker expression) that are responsible for tumor initiation and propagation, termed cancer stem cells. These cells are termed cancer stem cells because, like normal stem cells, they possess the ability to self-renew and make differentiated progeny. Recent studies of human pancreatic cancers have shown a population of pancreatic cancer stem cells that have aberrantly activated developmental signaling pathways, are resistant to standard chemotherapy and radiation, and have up-regulated signaling cascades that are integral for tumor metastasis. An improved understanding of the biological behavior of these cells may lead to more effective therapies to treat pancreatic cancer. In this review, approaches to develop and test therapeutics targeting pancreatic cancer stem cells are discussed.     

A case of AFP-producing gastric cancer with hepatic metastases that accompanied early gastric cancer treated effectively by chemotherapy

We report a case of alphafetoprotein (AFP)-producing gastric cancer that accompanied early gastric cancer and was treated effectively by chemotherapy. The patient was a 73-year-old male. A type 1 tumor was observed in the upper gastric body and a 0-IIa tumor was noted on the anterior wall of the lower gastric body. Abdominal CT showed multiple metastatic lesions in the liver. A subtotal gastrectomy was performed, and the pathological examination revealed that the type 1 tumor was positive for AFP and the 0-IIa tumor was negative for AFP. After 5 courses of postoperative administration of S-1, hepatic metastatic lesions disappeared on imaging. The serum AFP level, which had increased to the maximum of 49,660 ng/ml, was normalized. After 60 months, there has been no sign of recurrence. We encountered a case of AFP-producing gastric cancer that accompanied early gastric cancer and was treated effectively by S-1. Various therapies for AFP-producing gastric cancer have been reported; however, a standardized regimen has not been established. Since the concurrence of AFP-producing gastric cancer and tubular adenocarcinoma is rare, and hepatic metastatic lesions disappeared, the case under study is considered to be of interest. Therefore, we report this case with a review of the literature.     

A case of AFP-producing gastric cancer responding to low-dose CPT-11 and low-dose cisplatin combination chemotherapy

Gastric cancers that produce alpha feto protein (AFP) usually have a poor prognosis. We report an AFP-producing gastric cancer that showed a partial response to low-dose CPT-11 and low-dose cisplatin combination chemotherapy. AFP-producing gastric cancers successfully treated with chemotherapy have been reported, but to our knowledge this is the first report of successful treatment with low-dose CPT-11 and low-dose cisplatin combination chemotherapy. Case: A 49 year-old woman who had gastric cardiac cancer with esophageal invasion was admitted to our institution. Since AFP-positive cells were demonstrated immunohistochemically in biopsy specimens and levels of AFP in serum were high, AFP-producing cancer was diagnosed. Because of metastasis to Virchow's node and the paraaortic lymph nodes, the tumor was considered unresectable. The patient's poor general condition necessitated chemotherapy with low toxicity and high efficacy. She was treated with low-dose CPT-11 and low-dose cisplatin combination chemotherapy. After two cycles of this treatment, the tumor volume and the serum levels of AFP had decreased markedly. The only side effect of the treatment was leukopenia.     

Survival regulation in pancreatic cancer cells by c-Jun

Over 90% of human pancreatic cancers harbor an activating point mutation in the K-ras gene at codon 12. However, it is not clear whether all downstream K-ras are activated and which downstream contributes to the cell survival and proliferation of pancreatic cancer cells. MEK kinase 1 (MEKK1)-c-Jun N-terminal kinase (JNK)-c-Jun pathway has an important role in cell proliferation, survival and apoptosis in various cells. We previously demonstrated that the dominant negative form of MEKK1 (DN-MEKK) inhibits the survival of human pancreatic cancer cell lines. In this study we investigated whether JNK-c-Jun, the downstream pathway of DN-MEKK, affects the survival of human pancreatic cancer cell lines. Colony formation assays indicated that c-Jun failed to inhibit the survival of pancreatic cancer cells, whereas c-Jun remarkably inhibited the cell survival of non-pancreatic cancer cells. Reporter gene assays using Gal4-c-Jun and gel retardation assays indicated that c-Jun functions were activated in growing pancreatic cancer cells. These results revealed that c-Jun activation does not prevent the cell survival of pancreatic cancer cells in contrast to non-pancreatic cancer cells. It appears that MEKK1-JNK-c-Jun pathway fails to act as a negative regulator for the cell survival of pancreatic cancer cells. Greater understanding of these mechanisms may be helpful in the treatment of pancreatic cancer.     

Biosynthesis of alpha fetoprotein by MCF-7 human breast cancer cells

Direct evidence was obtained for de novo synthesis of AFP by MCF-7 human breast cancer cells per se. Synthesis was demonstrated by L-14C-leucine and L-35S-methionine incorporation into immunochemically isolated AFP, and confirmed by radioimmunodiffusion and radioimmunoelectrophoresis. This information indicates that AFP synthesis is associated with normal and neoplastic cells of several different histotypes, and suggests that AFP detected and measured previously in primary human breast cancer tissue cytosol (Sarcione et al., 1983) also resulted from in situ biosynthesis by breast cancer cells per se rather than uptake of exogenous AFP originating from extracellular sources. Evidence that AFP obtained after treatment of 14C-leucine radiolabelled MCF-7 breast cancer cell protein with 0.4 M KCl contained 2.6 times more radioactivity than did AFP obtained before such salt treatment is interpreted as indicating that two different molecular species of de novo synthesized AFP existed in breast cancer cells: (1) larger amount of non-immunoreactive AFP which became immunoreactive and measurable after KCl treatment, and (2) smaller amounts of free immunoreactive AFP. 14C-radiolabelled AFP obtained before and after treatment of cell protein with 0.4 M KCl codiffused, comigrated with alpha 1 electrophoretic mobility and gave an identical radioimmunologic reaction both with each other and with added carrier human cord serum AFP. Furthermore, preliminary studies indicated that radiolabelled non-immunoreactive AFP could be separated from lower-molecular-weight free AFP by chromatography on Sephadex G-200. Taken together, these findings suggest that synthesized free AFP was bound as a non-immunoreactive high-molecular-weight macromolecular complex rather than being covalently linked. Our current working hypothesis is that most of the de novo synthesized endogenous AFP in MCF-7 human breast cancer cells was rapidly and reversibly bound by hydrophobic bonding to a specific cytoplasmic AFP-receptor.     

Alpha-fetoprotein-producing renal cell carcinoma

A case of alpha-fetoprotein (AFP)-producing renal cell carcinoma with multiple bone and lung metastases, but without liver involvement is reported. The stain specific to AFP (avidin-biotin complex) proved the presence of the AFP in the cytoplasms of some cells of the renal tumors. In addition, three other cases of AFF-producing renal cancer recently published in the literature in Japan are reviewed. These four cases indicate that mesoderm-originating malignant tumors such as renal cell carcinomas can produce AFP in some situations. So, AFP is probably more universal than believed, although it is generally a popular and useful tumor marker for hepatocellular carcinomas and yolk sac tumors. The knowledge of the presence of AFP-producing renal cell carcinomas will make a new contribution to the study of the oncogenesis of AFP-producing tumors.     

High frequency of c-Met expression in gastric cancers producing alpha- fetoprotein

Gastric cancers producing alpha-fetoprotein (AFP) have a poor prognosis and a high incidence of liver metastasis. Hepatocyte growth factor (HGF) and its receptor, c-Met, are known to induce mitosis and cell movement and to promote tumor progression. In the present study, c-Met and HGF expression in AFP-producing gastric cancer was compared with those gastric cancers that do not produce AFP. Twenty-six patients with AFP-producing gastric cancers [AFP(+)] and 26 patients stage-matched gastric cancers without AFP production [AFP(-)] were evaluated for c-Met and HGF expression and proliferating cell nuclear antigen-labelling index using immunohistochemical analysis. A higher frequency of c-Met expression was observed in the AFP(+) group than in the AFP(-) group (p < 0.01). A higher expression of c-Met might be one explanation for the poorer prognosis of AFP-producing gastric cancers.     

Targeting the K-Ras - JNK axis eliminates cancer stem-like cells and prevents pancreatic tumor formation

Cancer cells with self-renewal and tumor-initiating capacity, either quiescent (cancer stem cells, CSCs) or proliferating (cancer stem-like cells, CSLCs), are now deemed responsible for the pervasive therapy resistance of pancreatic cancer, one of the deadliest human cancers characterized by high prevalence of K-Ras mutation. However, to date, much remains unknown how pancreatic CSCs/CSLCs are regulated. Here we show that the K-Ras – JNK axis plays a pivotal role in the maintenance of pancreatic CSCs/CSLCs. In vitro inhibition of JNK, either pharmacological or genetic, caused loss of the self-renewal and tumor-initiating capacity of pancreatic CSLCs. Importantly, JNK inhibition in vivo via systemic JNK inhibitor administration, which had no discernible effect on the general health status of mice, efficiently depleted the CSC/CSLC population within pre-established pancreatic tumor xenografts. Furthermore, knockdown of K-Ras in pancreatic CSLCs with K-Ras mutation led to downregulation of the JNK pathway as well as in loss of self-renewal and tumor-initiating capacity. Together, our findings suggest that pancreatic CSCs/CSLCs are dependent on K-Ras activation of JNK and also suggest that the K-Ras – JNK axis could be a potential target in CSC/CSLC-directed therapies against pancreatic cancer.     

Silencing alpha-fetoprotein expression induces growth arrest and apoptosis in human hepatocellular cancer cell

The expression of alpha-fetoprotein (AFP), a tumor-associated antigen, is silenced in normal adult hepatocyte but reactivated in human hepatocellular carcinoma (HCC). To investigate the roles of AFP in the regulation of cell growth, we silenced AFP expression in the HCC cell line Huh7 by transfection of specific Stealth RNAi. After the transfection for 48 h, the expression of AFP gene was almost abolished, the cell proliferation was inhibited by 46.15%, and the number of cells undergoing early apoptosis was significantly increased to 63.93%. Inhibition of AFP expression also resulted in an increased in Bax/Bcl-2 ratio, the release of cytochrome c from mitochondria and activation of caspase-3. The results suggest that AFP may positively regulate cell proliferation by enhancing the apoptosis resistance via dysfunction of the p53/Bax/cytochrome c/caspase-3 signaling pathway in AFP-producing HCC cell line. As such, the knockdown of AFP gene should be further investigated in vivo as a novel approach to HCC treatment.