Background: Cell culture models of normal urothelial cells are important for studying differentiation, disease mechanisms and anticancer drug development. Beyond primary cultures with their limitations in lifespan, interindividual heterogeneity and s

Cisplatin-based regimens are routinely employed for the treatment of urothelial carcinoma. However, therapeutic success is hampered by the primary presence of or the development of cisplatin resistance. This chemoresistance is executed by multiple cellular pathways. In recent years, the cellular process of autophagy has been identified as a prosurvival pathway of cancer cells. On the one hand, autophagy enables cancer cells to survive conditions of low oxygen or nutrient supply, frequently found in tumors. On the other hand, autophagy supports chemoresistance of cancer cells. Here, we aimed at investigating the involvement of autophagy for cisplatin resistance in different urothelial carcinoma cell lines. We analyzed the expression levels of different autophagy-related proteins in cisplatin-sensitive and cisplatin-resistant urothelial carcinoma cell lines. Furthermore, we performed cell viability assays and caspase activity assays with cells treated with cisplatin, non-specific or specific autophagy inhibitors (chloroquine, 3-methyladenine, SAR405) or combinations thereof. We found that autophagy-related proteins are up-regulated in different cisplatin-resistant urothelial carcinoma cells compared to the sensitive parental cell lines. Furthermore, inhibition of autophagy, in general, or of the autophagy-inducing class III PtdIns3K complex, in particular, sensitized both sensitive and resistant urothelial carcinoma cells to cisplatin-induced cytotoxic effects. We propose that targeting the autophagic machinery might represent a suitable approach to complement or even increase cisplatin efficacy in order to overcome cisplatin resistance in urothelial carcinoma.

Therapeutic efficacy of cisplatin-based treatment of late stage urothelial carcinoma (UC) is limited by chemoresistance. To elucidate underlying mechanisms and to develop new approaches for overcoming resistance, we generated long-term cisplatin treated (LTT) UC cell lines, characterised their cisplatin response, and determined the expression of molecules involved in cisplatin transport and detoxification, DNA repair, and apoptosis. Inhibitors of metallothioneins and Survivin were applied to investigate their ability to sensitise towards cisplatin. Cell growth, proliferation, and clonogenicity were examined after cisplatin treatment by MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, EdU (5-ethynyl-2’-deoxyuridine) incorporation assay, and Giemsa staining, respectively. Cell cycle distribution and apoptosis were quantified by flow cytometry. mRNA and protein expressions were measured by real-time quantitative (qRT)-PCR, western blot, or immunofluorescence staining. LTTs recovered rapidly from cisplatin stress compared to parental cells. In LTTs, to various extents, cisplatin exporters and metallothioneins were induced, cisplatin adduct levels and DNA damage were decreased, whereas expression of DNA repair factors and specific anti-apoptotic factors was elevated. Pharmacological inhibition of Survivin, but not of metallothioneins, sensitised LTTs to cisplatin, in an additive manner. LTTs minimise cisplatin-induced DNA damage and evade apoptosis by increased expression of anti-apoptotic factors. The observed diversity among the four LTTs highlights the complexity of cisplatin resistance mechanisms even within one tumour entity, explaining heterogeneity in patient responses to chemotherapy.

Background: Germ cell tumours (GCTs) are the most common solid malignancies in young men. Although high cure rates can be achieved, metastases, resistance to cisplatin-based therapy and late toxicities still represent a lethal threat, arguing for the need of new therapeutic options. In this study, we analysed the potential of cyclin-dependent kinase 4/6 (CDK4/6) inhibitors palbociclib and ribociclib (PaRi) as molecular drugs to treat cisplatin-resistant and -sensitive paediatric and adult GCTs. Methods: Ten GCT cell lines, including cisplatin-resistant subclones and non-malignant controls, were treated with PaRi and screened for changes in viability (triphenyl tetrazolium chloride (XTT) assay), apoptosis rates (flow cytometry, caspase assay), the cell cycle (flow cytometry), the transcriptome (RNA-sequencing, quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) and on protein level (western blot). Expression profiling was performed on paediatric and adult GCT tissues (expression microarrays, qRT-PCR, immunohistochemistry, ‘The Cancer Genome Atlas’ database). Results: We demonstrate that adult GCTs highly express CDK4, while paediatric GCTs strongly express CDK6 instead. Thus, both GCT types are potentially treatable by PaRi. GCTs presented as highly sensitive towards PaRi, which caused a decrease in viability, cell cycle arrest and apoptosis. Although GCTs mainly arrested in the G1/G0 phase, some embryonal carcinoma cell lines were able to bypass the G1/S checkpoint and progressed to the G2/M phase. We found that upregulation of CDK3 and downregulation of many mitosis regulation factors, like the HAUS genes, might be responsible for bypassing the G1/S checkpoint and termination of mitosis, respectively. We postulate that GCT cells do not tolerate these alterations in the cell cycle and eventually induce apoptosis. Conclusion: Our study highlights PaRi as therapeutic options for cisplatin-resistant and -sensitive paediatric and adult GCTs.

Yolk‐sac tumours (YSTs), a germ cell tumour subtype, occur in newborns and infants as well as in young adults of age 14‐44 years. In clinics, adult patients with YSTs face a poor prognosis, as these tumours are often therapy‐resistant and count for many germ cell tumour related deaths. So far, the molecular and (epi)genetic mechanisms that control development of YST are far from being understood. We deciphered the molecular and (epi)genetic mechanisms regulating YST formation by meta‐analysing high‐throughput data of gene and microRNA expression, DNA methylation and mutational burden. We validated our findings by qRT‐PCR and immunohistochemical analyses of paediatric and adult YSTs. On a molecular level, paediatric and adult YSTs were nearly indistinguishable, but were considerably different from embryonal carcinomas, the stem cell precursor of YSTs. We identified FOXA2 as a putative key driver of YST formation, subsequently inducing AFP, GPC3, APOA1/APOB, ALB and GATA3/4/6 expression. In YSTs, WNT‐, BMP‐ and MAPK signalling‐related genes were up‐regulated, while pluripotency‐ and (primordial) germ cell‐associated genes were down‐regulated. Expression of FOXA2 and related key factors seems to be regulated by DNA methylation, histone methylation / acetylation and microRNAs. Additionally, our results highlight FOXA2 as a promising new biomarker for paediatric and adult YSTs.