Cisplatin Induces Resistance by Triggering Differentiation of Testicular Embryonal Carcinoma Cells

Abstract

Although testicular germ cell tumors are generally quite responsive to treatment with cisplatin, a small fraction of them acquire resistance during therapy. Even when cisplatin treatment is successful the patient is often left with a residual teratoma at the site of the primary tumor suggesting that cisplatin may trigger differentiation in some tumors. Using the human embryonal carcinoma cell line NTera2/D1, we confirmed that exposure to the differentiating agent retinoic acid produced a reduction in pluripotency markers NANOG and POU5F1 (Oct3/4) and an acute concentration-dependent increase in resistance to both cisplatin and paclitaxel that reached as high as 18-fold for cisplatin and 61-fold for paclitaxel within four days. A two day exposure to cisplatin also produced a concentration-dependent decrease in the expression of the NANOG and POU5F1 and increased expression of three markers whose levels increase with differentiation including Nestin, SCG10 and Fibronectin. In parallel, exposure to cisplatin induced up to 6.2-fold resistance to itself and 104-fold resistance to paclitaxel. Paclitaxel did not induce differentiation or resistance to either itself or cisplatin. Neither retinoic acid nor cisplatin induced resistance in cervical or prostate cancer cell lines or other germ cell tumor lines in which they failed to alter the expression of NANOG and POU5F1. Forced expression of NANOG prevented the induction of resistance to cisplatin by retinoic acid. We conclude that cisplatin can acutely induce resistance to itself and paclitaxel by triggering a differentiation response in pluripotent germ cell tumor cells.

Influence of Nodal signalling on pluripotency factor expression, tumour cell proliferation and cisplatin-sensitivity in testicular germ cell tumours

“…Additionally, the slightly increased cisplatin-resistance observed following blockage of both Nodal and Activin signalling (using the high dose of SB431542), but not after specific inhibition of Nodal signalling, could indicate some redundancy between the Nodal and Activin pathways. We speculate that inhibition of Nodal signalling promotes downregulation of pluripotency factor expression in the malignant germ cells driving them towards a more differentiated phenotype, which is associated with reduced cisplatin-sensitivity [8][9][10][11][12]. However, since both ECs (high Nodal expression) and SEMs (low Nodal expression) are highly sensitive to cisplatin-based treatment [6,7], this may explain why we did not find pronounced effects on cisplatin-sensitivity upon manipulation of the Nodal signalling pathway.…”

“…The relationship between expression of pluripotency factors and cisplatin-sensitivity has also been examined in a TGCT-derived EC cell line, in which loss of pluripotency factor expression by siRNAmediated knockdown of OCT4, resulted in decreased sensitivity to cisplatin [9]. Moreover, treatment with retinoic acid to induce differentiation of the EC-derived NTera2 cell line along the neuroectodermal lineage, resulted in decreased expression of the pluripotency factor OCT4 and increased cisplatin-resistance [10][11][12], thus supporting the association between pluripotency factor expression and cisplatin-sensitivity. Although cisplatin-based chemotherapy has provided high cure rates for TGCTs, the treatment regimen is associated with long-term complications, including cardiovascular side effects and infertility as well as relapse [5,13].…”

Genomic evolution and chemoresistance in germ-cell tumours

“…4e, Supplementary Table 7). Taken together, chemotherapy-resistant germ-cell tumours are associated with continued progression of RLOH copy number events and loss of pluripotency markers in this clinical cohort, although it is uncertain whether the loss of pluripotency markers is a driver of chemoresistance 11,28 , a marker of methylation changes in a further differentiated histology post-chemotherapy 29 , or a feature of both processes.…”

Cisplatin resistance in germ cell tumours: models and mechanisms

“…Other groups have reported that loss of Oct4 expression leads to resistance in EC cells (Mueller et al ., , ; Koster et al ., ). Events that in addition to differentiation induced by RA can lead to down‐regulation of Oct4 are hypoxia (Wu et al ., ) and cisplatin treatment (Abada & Howell, ). All of these are known to have a negative impact on cisplatin sensitivity (Koch et al ., ; Abada & Howell, ), which is most likely mediated not only by down‐regulation of Noxa and Puma but also down‐regulation of miR‐17/‐106b family members, in turn leading to activation of p21 (Koster et al ., ).…”