Significance of the metastasis-promoting protein S100A4 in chemotherapy sensitivity of colorectal cancer cell lines

Colorectal cancer (CRC) is a common type of cancer, and at present the TNM staging system is the only tool in routine clinical use for predicting patient outcome and making treatment decisions. Nuclear expression of the metastasis associated protein S100A4 is a promising prognostic biomarker in CRC, and has been shown to identify a subset of TNM II patients with poor prognosis. This suggests that patients in TNM II which express nuclear S100A4 might benefit from adjuvant chemotherapy, which is usually given only to TNM III patients. In this project, we investigated the significance of S100A4 expression on sensitivity towards four commonly used chemotherapeutic drugs in CRC, 5-flourouracil (5FU), irinotecan (IRI), oxaliplatin (OXA) and cetuximab (CET). Two human CRC cell lines (HCT116 and SW620) were experimentally modified to express different levels of S100A4, and were exposed to increasing drug concentrations in 2D and 3D cultures. Cell viability assessed by the MTS assay was used as a screening tool, and some results were followed up using clonogenic survival and spheroid assays. HCT116 cells were generally more sensitive to the drugs than SW620 cells, while both cell lines were resistant to CET. S100A4 related differences in sensitivity were observed with the MTS assay in HCT116 treated with 5FU and SW620 treated with OXA, while there was no variation with IRI treatment. For OXA, the differences were observed at concentrations that are probably not relevant in cancer treatment in humans, whereas for 5FU the concentration range was probably relevant, but the differences could not be confirmed using other methods. In conclusion, S100A4 expression did not substantially influence in vitro sensitivity towards the drugs in the two investigated models. However, results from in vitro experiments cannot be directly translated into the clinic, and the relevance of S100A4 expression on drug sensitivity still warrants further investigations. An immunohistochemical study of S100A4 expression is ongoing in primary tumors from patients treated with adjuvant 5FU in a phase III trial. If S100A4 expression is associated with drug efficacy, additional in vitro studies will be necessary and the models systems established in this work may become useful

Hypoxia-independent gene expression signature associated with radiosensitisation of prostate cancer cell lines by histone deacetylase inhibition

Background: Histone deacetylase inhibitors (HDACis) like vorinostat are promising radiosensitisers in prostate cancer, but their effect under hypoxia is not known. We investigated gene expression associated with radiosensitisation of normoxic and hypoxic prostate cancer cells by vorinostat. Methods: Cells were exposed to vorinostat under normoxia or hypoxia and subjected to gene expression profiling before irradiation and clonogenic survival analysis. Results: Pretreatment with vorinostat led to radiosensitisation of the intrinsically radioresistant DU 145 cells, but not the radiosensitive PC-3 and 22Rv1 cells, and was independent of hypoxia status. Knockdown experiments showed that the sensitisation was not caused by repression of hypoxia-inducible factor HIF1 or tumour protein TP53. Global deregulation of DNA repair and chromatin organisation genes was associated with radiosensitisation under both normoxia and hypoxia. A radiosensitisation signature with expression changes of 56 genes was generated and valid for both conditions. For eight signature genes, baseline expression also correlated with sensitisation, showing potential as pretreatment biomarker. The hypoxia independence of the signature was confirmed in a clinical data set. Conclusions: Pretreatment with HDACi may overcome radioresistance of hypoxic prostate tumours by similar mechanisms as under normoxia. We propose a gene signature to predict radiosensitising effects independent of hypoxia status