Altered expression of connexins 26 and 43 in Sertoli cells in seminiferous tubules infiltrated with carcinoma-in-situ or seminoma

Bilateral carcinoma in situ of the testis and cystic fibrosis transmembrane conductance regulator (CFTR) mutation in an azoospermic patient with late-onset 21beta-hydroxylase deficiency

Testicular cancer can impair spermatogenesis. In addition, chemotherapy or radiotherapy used for its treatment further damage testicular function mainly affecting highly proliferating germ cells. The multifaceted etiology of male infertility includes, among others, alterations of male reproductive tract differentiation such as monolateral or bilateral congenital absence of vas deferens and perturbations in adrenal steroid synthesis on a genetic basis such as 21beta-hydroxylase deficiency. Herein, we report the case of a male patient with primary infertility, probably related to a combination of genetic and acquired factors with different expressions over time.

From carcinoma in situ to testicular germ cell tumour

The mechanisms of invasive tumour development from pre-invasive CIS are unknown. We examined changes in functional parameters of the tubular wall according to the increase in CIS cells and tubular size. Immunohistochemistry was performed on 37 testicular specimens from 25 patients with carcinoma in situ and/or malignant germ cell tumour for the detection of actin/myosin in myocytes, and laminin/integrin alpha 6 in the basement membrane of seminiferous tubules. Tumour cells were detected by PlAP, Sertoli cells by inhibin alpha and vimentin and by cytokeratin 18/connexin 26 immunoreactivity, which is selectively expressed together with CIS. Areas showing clusters of tumour cells surrounded by a fibrous sheet could be identified as enlarged tubules because of focal Sertoli cell-specific co-expression of inhibin alpha, vimentin, cytokeratin 18, and connexin 26 immunoreaction. These clusters exhibited an intact basement membrane shown by a persistent laminin/integrin alpha 6 immunoreactivity, but myocytes had lost their contractility indicated by the loss of myosin/actin immunoreactivity. They often showed septa originating from the fibrous sheet containing numerous capillaries. Focal areas of syncytiotrophoblastic cells within classical seminoma also expressing inhibin alpha, cytokeratin 18, and connexin 26 could be differentiated from single Sertoli cells within tumor cell clusters by typical hCG but absence of vimentin immunoreactivity. In contrast to the current concept of CIS cells passing the tubular wall, these data provide evidence for an additional theory, i.e. that the switch from pre-invasive CIS to invasive tumour takes place in situ by tubular enlargement due to tumour cell proliferation followed by Sertoli cell degeneration and conversion of the tubular wall into connective tissue.

Disrupted traffic of connexin 43 in human testicular seminoma cells: overexpression of Cx43 induces membrane location and cell proliferation decrease

Connexins, the constitutive proteins of gap junctions, are considered to be tumour suppressive agents and are often impaired in the tumourigenic processes. In the present study, the expression of connexin 43 (Cx43), which is involved in the control of spermatogenesis through Sertoli/germ cell coupling, has been investigated in human testicular seminoma cells (tumours and the JKT-1 cell line). Cx43 was immunolocalized in the Golgi apparatus without membrane expression and was detected by immunoblotting in JKT-1 as exclusive 70 kD bands. No mutation could be found by sequencing the transcript obtained by RT-PCR. Transfection with a Cx43-V5 vector reproduced the same gel shift, identifying these 70 kD bands as Cx43. The Cx43-70 kD bands were also expressed in normal testicular tissue, associated with the classical 43 kD isoforms. Stable transfection of JKT-1 with a Cx43-GFP vector allowed restoration of Cx43 membrane expression, functional cell coupling, and inhibition of the cell proliferation rate. Storage of Cx43 in the Golgi apparatus may correspond during spermatogenesis to an intermittent physiological process that becomes permanent in malignant seminoma cells as a result of the tumourigenic process. By preventing Cx43 membrane expression, this disrupted traffic may itself participate in tumour promotion.

Aberrant Connexin 43 endocytosis by the carcinogen lindane involves activation of the ERK/mitogen-activated protein kinase pathway

Although worldwide concerns have emerged about environmental factors that display carcinogenic and reprotoxic effects, little is known about the mechanism(s) by which these chemicals alter testicular function. Using the 42GPA9 Sertoli cell line, we recently reported that one widely used lipid-soluble pesticide, Lindane impairs gap junctional intercellular communication by promoting the intracellular localization of Connexin 43 (Cx43), a tumor suppressor. We showed here that this chemical triggered the accumulation of Cx43 within Rab5 positive endosomes. Interestingly, evidence is provided that Lindane-induced Cx43 endocytosis did not stem on alteration of Cx43 partition in lipid rafts. Lindane induced concomitantly Cx43 phosphorylation and activation of extracellular signal-regulated kinases (ERK) but not of JNK and p38 mitogen- activated protein kinases. Inhibition of ERK pathway by PD98059, a MEK1-specific inhibitor, prevented Lindane-induced Cx43 phosphorylation, restored Cx43 membranous localization and gap junction coupling. Altogether, these findings provide the first evidence that Lindane-altered Cx43 endocytosis requires ERK activation. Such inappropriate activation of the mitogenic MAPK pathway and inactivation of the tumor suppressor Cx43 by Lindane may participate in the promotion of neoplastic cell growth.

Angiotensin I-converting enzyme and potential substrates in human testis and testicular tumours

The angiotensin I-converting enzyme (ACE, kininase II, CD143) shows a broad specificity for various oligopeptides. Besides the well-known conversion of angiotensin I to II, ACE degrades efficiently kinins and the tetrapeptide AcSDKP (goralatide) and thus equally participates in the renin-angiotensin system, the kallikrein-kinin system, and the regulation of stem cell proliferation. In the mammalian testis, ACE occurs in two isoforms. The testicular isoform (tACE) is exclusively expressed during spermatogenesis and is generally thought to represent the germ cell-specific isozyme. However, we have previously demonstrated that, in addition to tACE, the somatic isoform (sACE) is also present in human germ cells. Similar to other oncofoetal markers, sACE exhibits a transient expression during foetal germ cell development and appears to be a constant feature of intratubular germ cell neoplasm, the so-called carcinoma-in-situ (CIS) and, in particular, of classic seminoma. This demands the existence of specific paracrine functions during male germ cell differentiation and development of male germ cell tumours, which are mediated by either of the two ACE isoforms. Considering the complexity of current data about ACE, a logical connection is required between (I) the precise localisation of ACE isoforms, (I) the local access to potential substrates and (II) functional data obtained by knockout mice models. The present article summarises the current knowledge about ACE and its potential substrates with special emphasis on the differentiation-restricted ACE expression during human spermatogenesis and prespermatogenesis, the latter being closely linked to the pathogenesis of human germ cell tumours.