The incidence of male genital tumors: a cellular model for the age dependence.

Most human tumors, including most male genital tumors, exhibit an exponential increase in incidence with advancing age of the host. This exponential age-incidence pattern can be explained by the accumulation of mutations in the stem cells of the tissues of tumor origin. The age-incidence pattern for testicular tumors, however, is unique with a large linear increase in incidence from age 14 to 30 and a linear decline in incidence from age 30 to 60. After age 60, the incidence of testicular tumors remains low and constant. The probability of testicular tumorigenesis is determined by the susceptibility of male germ cells to neoplastic mutation and/or the neoplastic mutagenicity of the male germ cell environment. Since there is no evidence for an environmental mutagen which is specific for male germ cells, and since male germ cells are unusually susceptible to mutation, we interpret the variation in testicular tumor incidence with age as a reflection of the susceptibility of male germ cells to neoplastic mutation. Cell are most susceptible to mutation during genome replication and we propose a model for testicular tumorigenesis which is consistent with the available data on male germ cell proliferation and with the data on testicular tumor incidence.     

Turning germ cells into stem cells

Primordial germ cells (PGCs), the embryonic precursors of the gametes of the adult animal, can give rise to two types of pluripotent stem cells. In vivo, PGCs can give rise to embryonal carcinoma cells, the pluripotent stem cells of testicular tumors. Cultured PGCs exposed to a specific cocktail of growth factors give rise to embryonic germ cells, pluripotent stem cells that can contribute to all the lineages of chimeric embryos including the germline. The conversion of PGCs into pluripotent stem cells is a remarkably similar process to nuclear reprogramming in which a somatic nucleus is reprogrammed in the egg cytoplasm. Understanding the genetics of embryonal carcinoma cell formation and the growth factor signaling pathways controlling embryonic germ cell derivation could tell us much about the molecular controls on developmental potency in mammals.     

Testicular germ cell tumors. Classification based on fine needle aspiration biopsy

Fine needle aspiration (FNA) biopsy was performed preoperatively on 13 patients with testicular germ cell tumors. The cytologic typing of the tumors was based on the presence or absence of seminoma, embryonal carcinoma, yolk-sac tumor, choriocarcinoma and teratoma in the aspirate. The cytologic findings showed good agreement with the histologic findings. Only four cases showed a single type of tumor; the other nine cases showed as many as four different tumor components. A few characteristic cytologic features proved to be sufficient for tumor typing; this suggests that FNA biopsy cytology can also be useful in identifying metastatic germ cell tumors in extra-gonadal sites.     

Cytoskeleton of human embryonal carcinoma cells

Monoclonal antibodies to cytoskeletal proteins were used to study the intermediate filament proteins of human embryonal carcinoma (EC) cell lines, tumors produced in nude mice from these cell lines, and surgically removed testicular germ cell tumors. It was found that all cells of tumor lines 2102Ep, 1156 and Tera 1 react with antibodies to low molecular weight keratin proteins. By immunoblotting of SDS gels it was found that these lines expressed three keratin polypeptides (40K, 45K and 52K). Clonal line NTera-2 derived from Tera-2 differed from the above listed cell lines in that only 10% of the cells expressed the 40K keratin polypeptide. Upon treatment with retinoic acid 70% of NTera-2 cells became reactive with the antibody to the 40K keratin polypeptide. All cell lines contained a small population of vimentin-positive cells. The number of vimentin-positive cells could be increased by retinoic acid treatment of NTera-2 cells or by seeding the 2102Ep cells at low cell density. Neurofilament-positive cells could be induced in the cell line NTera-2 by retinoic acid treatment. Tumors produced from NTera-2 cells injected into nude mice contained cells reacting with antibodies to keratin, vimentin, neurofilament proteins and desmin. Keratin polypeptides were immunohistochemically demonstrated in embryonal carcinoma, yolk sac carcinoma and trophoblastic components of solid human germ cell tumors. Atypical intratubular cells ('carcinoma in situ') also reacted with antibodies to keratin.     

Differentiation potential of human embryonal carcinoma cell lines

We have established 17 embryonal carcinoma (EC) cell lines from human testicular germ cell tumors by using three different methods of in vitro cultivation. Cultures of only three of these cell lines, and of clones derived from two of them, differentiate extensively when the cells are seeded at low density. A comparison is presented of the results obtained with the three methods used to establish and maintain these cell lines, and some properties of the three pluripotential EC lines are summarized.     

Serum AFP, hCG and CEA in the management of patients with testicular, ovarian and extragonadal germ cell tumors.

Serum levels of AFP, hCG and CEA were initially and serially measured in 59 patients with testicular germ cell tumors, and serially in 37 with ovarian and 3 with extragonadal germ cell tumors. Patients with seminoma/dysgerminoma or mature teratoma had normal serum AFP and sporadically slightly elevated hCG. Some patients with embryonal carcinoma, pure or with admixture of seminoma, had serum AFP elevated to maximum 100 U/ml, yet its use for monitoring therapy was limited. Patients with yolk sac tumors had elevated AFP and sometimes CEA levels, those with choriocarcinoma had elevated hCG, and those with compound tumors had one or more of the markers highly elevated. High AFP and/or hCG levels indicated the presence of the relevant tumor cells both in the primary and in residual tumor and/or metastases, also those missed in histological material, and thus were useful in restaging. Unfortunately, their absence in serum did not exclude the presence of marker-negative subpopulations of tumor cells. Changes in marker values paralleled the effects of treatment: the level increasing from any nadir heralded recurrence in patients in remission; elevated or increasing levels during therapy implied resistance to the therapy; decreasing levels indicated regression even though a return to the normal range did not mean eradication of all tumor cells.     

Comparative Study on the Ability of Various Teratocarcinomas to Form Chimeric Mouse Embryos

Various embryonal carcinoma cells of different origins were compared as to the ability to form chimeric blastocysts by means of aggregating with normal 8-cell stage mouse embryos. The teratocarcinoma lines examined were OTT6050 and five newly established ones including a spontaneous testicular teratocarcinoma STT-2. The present results have revealed that distinct differences existed in the ability of colonizing blastocysts among teratocarcinomas and also among embryonal carcinoma cell lines.
Since STT-2 stem cells were found to be incorporated into blastocysts most efficiently, further development of the blastocysts were examined in utero. It was found that STT-2 stem cells could be incorporated into the fetuses up to the 7-to 28-somite stages. This is the first case to demonstrate that testicular teratocarcinoma cells with the male germ cell origin have the developmental potency to participate into mouse embryogenesis.     

Human embryonal carcinoma tumor antigen,Gp200/GCTM-2, is podocalyxin

We previously characterized a peanut agglutinin-binding tumor antigen, gp200, a surface membrane glycoprotein expressed on human embryonal carcinoma, a malignant stem cell of testicular tumors. Gp200 is remarkably similar to another embryonal carcinoma antigen, GCTM-2, a cell differentiation marker that is also detected in blood of testis cancer patients, yet neither molecular identity is known. We now report the identity of gp200 as podocalyxin. Protein sequence results of gp200 peptides match with podocalyxin sequence. Furthermore, two distinct monoclonal antibodies, specific for podocalyxin, react positively with gp200. Therefore, gp200 is a testicular tumor form of podocalyxin, a surface membrane glycoprotein that was originally discovered as a scaffolding extracellular matrix protein of kidney podocyte cells. Podocalyxin is also expressed on subsets of hematopoietic cells where it has a putative function as a cell adhesion protein. This is the first report of podocalyxin expression on malignant cells.     

Le carcinome in situ du testicule — un précurseur du cancer à cellule germinale. Revue de la pathogenèse et aspects cliniques

Testicular germ cell tumors are different than other solid tumours with regard to their epidemiology and certain biological aspects. Pathogenesis of this malignancy remains unknown with the exception that all types of germ cell tumours in young adults originate from a common precursor:carcinoma in situ (CIS) cell. A recent dramatic increase in the incidence of testicular cancer suggests that environmental factors, especially those acting during development, may play a role. This review summarises the most important biological features of testicular CIS and discusses clinical management.     

Chromosome X modulates incidence of testicular germ cell tumors in <Emphasis Type="Italic">Ter</Emphasis> mice

Germ cell tumor development in humans has been proposed to be part of testicular dysgenesis syndrome (TDS), which manifests as undescended testes, sterility, hypospadias, and, in extreme cases, as germ cell tumors. Males of the Ter mouse strain show interesting parallels to TDS because they either lack germ cells and are sterile or develop testicular germ cell tumors. We found that these defects in Ter mice are due to mutational inactivation of the Dead-end (Dnd1) gene. Here we report that chromosome X modulates germ cell tumor development in Ter mice. We tested whether the X or the Y chromosome influences tumor incidence. We used chromosome substitution strains to generate two new mouse strains: 129-Ter/Ter that carry either a C57BL/6J (B6)-derived chromosome (Chr) X or Y. We found that Ter/Ter males with B6-Chr X, but not B6-Chr Y, showed a significant shift in propensity from testicular tumor development to sterile testes phenotype. Thus, our studies provide unambiguous evidence that genetic factors from Chr X modulate the incidence of germ cell tumors in mice with inactivated Dnd1. Electronic Supplementary Material The online version of this article (doi: ) contains supplementary material, which is available to authorized users.     

Differentiation capabilities of human germ cell tumors

It is well known that human germ cell tumors are an excellent model to study not only differentiation capacity of tumor cells but also human normal somatic cell differentiation. A variety of polyclonal and monoclonal antibodies were developed against cell surface antigens of murine embryos and teratocarcinomas. Accumulated data has revealed that these antigens are sequentially expressed on embryonic cells in a well-programmed manner. They have also been shown to be useful markers to investigate somatic cell differentiation in fetal and adult tissue. In humans, however, little is known about the cellular differentiation mechanism in early embryos and whether they could be studied, i.e. whether they occur in human germ cell tumors. In present review, we discussed newly established monoclonal antibodies which were raised from human embryonal carcinoma cells. We have been studying differentiation capacity of human germ cell tumor cells by using these antibodies. Some of these antibodies clearly indicates their usefulness to specify the developmental stage of normal tissue.     

An Alkylphenol Mix Promotes Seminoma Derived Cell Proliferation through an ERalpha36-Mediated Mechanism

Long chain alkylphenols are man-made compounds still present in industrial and agricultural processes. Their main use is domestic and they are widespread in household products, cleansers and cosmetics, leading to a global environmental and human contamination. These molecules are known to exert estrogen-like activities through binding to classical estrogen receptors. In vitro, they can also interact with the G-protein coupled estrogen receptor. Testicular germ cell tumor etiology and progression are proposed to be stimulated by lifelong estrogeno-mimetic exposure. We studied the transduction signaling pathways through which an alkyphenol mixture triggers testicular cancer cell proliferation in vitro and in vivo. Proliferation assays were monitored after exposure to a realistic mixture of 4-tert-octylphenol and 4-nonylphenol of either TCam-2 seminoma derived cells, NT2/D1 embryonal carcinoma cells or testis tumor in xenografted nude mice. Specific pharmacological inhibitors and gene-silencing strategies were used in TCam-2 cells in order to demonstrate that the alkylphenol mix triggers CREB-phosphorylation through a rapid, ERα36-PI3kinase non genomic pathway. Microarray analysis of the mixture target genes revealed that this pathway can modulate the expression of the DNA-methyltransferase-3 (Dnmt3) gene family which is involved in DNA methylation control. Our results highlight a key role for ERα36 in alkylphenol non genomic signaling in testicular germ cell tumors. Hence, ERα36-dependent control of the epigenetic status opens the way for the understanding of the link between endocrine disruptor exposure and the burden of hormone sensitive cancers.     

Differentiation-related changes in the distribution of glycoconjugates in rat testis.

The distribution of glycoconjugates in differentiating rat testis was investigated by fluorescein labeled lectins during embryogenesis and postnatal development. Double immunofluorescence with rhodamine coupled laminin antibodies was used to delineate testicular cords from the interstitium in embryonic testes. Rat testis was found to be rich in various glycoconjugates, with distinct differentiation-related changes in their distribution. All types of germ cells contained carbohydrate rich compounds in their cytoplasm. Glycosylation in the embryonic testis was different from that in the adult rat. At an early stage of testicular differentiation, the labeling of germ cells and other testicular cells was almost identical. The lectin binding patterns of embryonic germ cells and somatic cells were related to the developmental age of the animal, with a graded disappearance of galactose containing glycoconjugates in embryonal spermatogonia. Spermatogenic cell differentiation was characterized by striking changes in lectin binding patterns of germ cells, particularly in the acrosomes of developing spermatids, in relation to their functional activation and the emergence of adult type of glycosylation during the postnatal maturation of the testis. As the knowledge of regular glycosylation throughout tissue differentiation is of significance for the analysis of aberrant glycosylations occurring in pathologic disorders, our findings suggest the usefulness of lectin histochemistry for the studies on germ cell differentiation.