Strong apoptotic response of testis tumor cells following cisplatin treatment.

Most solid metastatic cancers are resistant to chemotherapy. However, metastatic testicular germ cell tumors (TGCT) are cured in over 80% of patients using cisplatin-based combination therapy. Published data suggest that TGCTs are sensitive to cisplatin due to limited DNA repair and presumably also to a propensity to undergo apoptosis. To further investigate this aspect, cisplatin-induced activation of apoptotic pathways was investigated in cisplatin-sensitive testis tumor cells (TTC) and compared to cisplatin-resistant bladder cancer cells. Apoptosis induction was investigated using flow cytometry, caspase activation and PARP-1 cleavage. Immunoblotting and RT-PCR were applied to investigate pro- and anti-apoptotic proteins. Transfections were performed to target p53- and Fas/FasL-mediated apoptotic signaling. Immunoblotting experiments revealed p53 to be induced in TTC, but not bladder cancer cells following cisplatin. Higher levels of pro-apoptotic Bax and Noxa were observed in TTC, anti-apoptotic Bcl-2 was solely expressed in bladder cancer cells. Cisplatin led to translocation of Bax to the mitochondrial membrane in TTC, resulting in cytochrome C release. Cisplatin increased the expression of FasR mRNA and FasL protein in all tumor cell lines. Targeting the apoptotic pathway via siRNA-mediated knockdown of p53 and FAS reduced death receptor-mediated apoptosis and increased cisplatin resistance in TTC, indicating the involvement of FAS-mediated apoptosis in the cisplatin TTC response. In conclusion, both the death receptor and the mitochondrial apoptotic pathway become strongly activated in TTC following cisplatin treatment, explaining, together with attenuated DNA repair, their unique sensitivity toward platinum-based anticancer drugs.

Differentially Tolerized Mouse Antigen Presenting Cells Share a Common miRNA Signature Including Enhanced mmu-miR-223-3p Expression Which Is Sufficient to Imprint a Protolerogenic State.

Dendritic cells (DCs) are pivotal for the induction and maintenance of antigen-specific tolerance and immunity. miRNAs mediate post-transcriptional gene regulation and control in part the differentiation and stimulation-induced immunogenic function of DCs. However, the relevance of miRNAs for the induction and maintenance of a tolerogenic state of DCs has scarcely been highlighted yet. We differentiated mouse bone marrow cells to conventional/myeloid DCs or to tolerogenic antigen presenting cells (APCs) by using a glucocorticoid (dexamethasone) or interleukin-10, and assessed the miRNA expression patterns of unstimulated and LPS-stimulated cell populations by array analysis and QPCR. Differentially tolerized mouse APCs convergingly down-regulated a set of miRNA species at either state of activation as compared with the corresponding control DC population (mmu-miR-9-5p, mmu-miR-9-3p, mmu-miR-155-5p). These miRNAs were also upregulated in control DCs in response to stimulation. In contrast, miRNAs that were convergingly upregulated in both tolerized APC groups at stimulated state (mmu-miR-223-3p, mmu-miR-1224-5p) were downregulated in control DCs in response to stimulation. Overexpression of mmu-miR-223-3p in DCs was sufficient to prevent stimulation-associated acquisition of potent T cell stimulatory capacity. Overexpression of mmu-miR-223-3p in a DC line resulted in attenuated expression of known (Cflar, Rasa1, Ras) mRNA targets of this miRNA species shown to affect pathways that control DC activation. Taken together, we identified sets of miRNAs convergingly regulated in differentially tolerized APCs, which may contribute to imprint stimulation-resistant tolerogenic function as demonstrated for mmu-miR-223-3p. Knowledge of miRNAs with protolerogenic function enables immunotherapeutic approaches aimed to modulate immune responses by regulating miRNA expression.

Inhibitors of ß-catenin affect the immuno-phenotype and functions of dendritic cells in an inhibitor-specific manner.

Many tumors are characterized by mutation-induced constitutive activation of ß-catenin which promotes tumor growth and survival. Consequently, the development of specific ß-catenin inhibitors for tumor therapy has come into the focus of drug development. ß-Catenin was also shown to contribute to the tolerance-promoting function of unstimulated dendritic cells (DCs). In response to activation, DCs acquire potent T cell stimulatory capacity and induce profound tumor antigen-specific immune responses. Here we asked for effects of pre-clinically established ß-catenin inhibitors (CCT-031374, iCRT-5, PNU-75654) on mouse bone marrow-derived (BM)DCs. All three inhibitors moderately increased surface expression of MHCII, CD80, and CD86 on unstimulated DCs, but had no enhancing effect on their capacity to stimulate the proliferation of ovalbumin (OVA) specific CD4(+) T cells. CCT-031374 interfered with upregulation of costimulators (CD40, CD86) and cytokines (IL-1ß, TNF-α, IL-6, IL-10, IL-12) by LPS-stimulated DCs. Accordingly, this DC population displayed an impaired CD4(+) T cell stimulatory activity. iCRT-5 and PNU-75654 had no detrimental effects on the immuno-phenotype of stimulated DCs. Hence, DCs treated with iCRT-5 in the course of stimulation exerted comparably strong T cell proliferation as did control DCs. In contrast, DCs stimulated in the presence of PNU-75654 induced less T cell proliferation than the control population despite enhanced uptake and processing of OVA. Our findings suggest that the differential effects of ß-catenin inhibitors on stimulated DCs reflect off target effects. Concerning potential application of ß-catenin inhibitors for tumor therapy, iCRT-5 may be most beneficial, since it did not exert detrimental effects on stimulated DCs.

Cisplatin sensitivity of testis tumour cells is due to deficiency in interstrand-crosslink repair and low ERCC1-XPF expression.

BACKGROUND: Cisplatin based chemotherapy cures over 80% of metastatic testicular germ cell tumours (TGCT). In contrast, almost all other solid cancers in adults are incurable once they have spread beyond the primary site. Cell lines derived from TGCTs are hypersensitive to cisplatin reflecting the clinical response. Earlier findings suggested that a reduced repair capacity might contribute to the cisplatin hypersensitivity of testis tumour cells (TTC), but the critical DNA damage has not been defined. This study was aimed at investigating the formation and repair of intrastrand and interstrand crosslinks (ICLs) induced by cisplatin in TTC and their contribution to TTC hypersensitivity. RESULTS: We observed that repair of intrastrand crosslinks is similar in cisplatin sensitive TTC and resistant bladder cancer cells, whereas repair of ICLs was significantly reduced in TTC. γH2AX formation, which serves as a marker of DNA breaks formed in response to ICLs, persisted in cisplatin-treated TTC and correlated with sustained phosphorylation of Chk2 and enhanced PARP-1 cleavage. Expression of the nucleotide excision repair factor ERCC1-XPF, which is implicated in the processing of ICLs, is reduced in TTC. To analyse the causal role of ERCC1-XPF for ICL repair and cisplatin sensitivity, we over-expressed ERCC1-XPF in TTC by transient transfection. Over-expression increased ICL repair and rendered TTC more resistant to cisplatin, which suggests that ERCC1-XPF is rate-limiting for repair of ICLs resulting in the observed cisplatin hypersensitivity of TTC. CONCLUSION: Our data indicate for the first time that the exceptional sensitivity of TTC and, therefore, very likely the curability of TGCT rests on their limited ICL repair due to low level of expression of ERCC1-XPF.

Cisplatin resistance: preclinical findings and clinical implications.

Cisplatin is used for the treatment of many types of solid cancers. While testicular cancers respond remarkably well to cisplatin, the therapeutic efficacy of cisplatin for other solid cancers is limited because of intrinsic or acquired drug resistance. Our understanding about the mechanisms underlying cisplatin resistance has largely arisen from studies carried out with cancer cell lines in vitro. The process of cisplatin resistance appears to be multifactorial and includes changes in drug transport leading to decreased drug accumulation, increased drug detoxification, changes in DNA repair and damage bypass and/or alterations in the apoptotic cell death pathways. Translation of these preclinical findings to the clinic is emerging, but still scarce. The present review describes and discusses the clinical relevance of in vitro models by comparing the preclinical findings to data obtained in clinical studies.

ERCC1 and XPF expression in human testicular germ cell tumors.

Nucleotide excision repair (NER) is one of the factors influencing the cellular sensitivity to anticancer drugs. In the present study we compared the expression of the NER proteins ERCC1 and XPF in 24 testicular germ cell tumors (TGCT) with the corresponding normal testicular tissue of the same patient. Using immunoblotting, we demonstrated in TGCT a significant increase of ERCC1 expression compared to the normal tissue. There was no significant increase in XPF expression in TCGT. Based on histological characteristics TGCT are subgrouped into seminomas and non-seminomas, the latter being clinically more aggressive. Investigating ERCC1 levels in seminomas we found a slightly increased expression compared to normal tissue, which was, however, not significant. Similarly, no significant difference was observed for XPF levels in seminomas compared to normal testis tissue. In non-seminomas, however, we found a significant increase in the expression of ERCC1 (p<0.017) and XPF (p<0.03) when compared with the corresponding normal tissue. Comparing seminomas with non-seminomas, we observed a significant increase in the expression of ERCC1 (p<0.05) and XPF (p<0.007) in the non-seminomas. Furthermore, a correlation between the expression of ERCC1 and XPF was observed. Our data demonstrate that non-seminomas are characterized by an increased expression of ERCC1 and XPF protein compared to seminomas and the normal testis tissue. The data indicate a possible up-regulation of ERCC1 and XPF during TGCT progression.