Biomarkers in the tumor microenvironment with impact on treatment response and survival in head and neck cancer
Abstract: Head and neck squamous cell cancer (HNSCC) is the sixth most common cancer type worldwide and disease detects at a locally advanced stage in approximately 60% of all patients with HNSCC. Despite the advances in both diagnosis and treatment of cancer, therapy failure with local recurrence and second primary tumors as consequences is still a huge problem. Furthermore, HNSCC is heterogeneous disease and treatment response differs largely within this patient’s group. Owing to such heterogeneity, the individually designed treatment approach, based on biomarkers predicting treatment response is needed. The personalized treatment strategy is a new and promising form of cancer therapy to improve effectiveness of anti-cancer treatment and reduce suffering in patients diagnosed with HNSCC.The main aim of this thesis was to search for new predictive biomarkers with potential to foresee treatment response in HNSCC patients by investigating components and properties of the tumor microenvironment, such as metabolism, hypoxia and cancer-associated fibroblasts (CAF).In paper I we developed an in vitro method for the measurement of intracellular glucose (18F FDG) uptake with gamma spectrometry (GS). Quantity of glucose uptake was associated with treatment (radiation or cetuximab) response, where the radiosensitive cell line and the most cetuximab-sensitive cell lines showed a significant decrease of glucose uptake after treatment. The results were compared with those of a clinical PET/CT scanner and the results in glucose uptake between radiated cells and controls were similar in both methods. Furthermore, we investigated GLUT1 mRNA expression in cell lines after cetuximab treatment and our analysis showed a significant increase of GLUT1 mRNA expression.In paper II, we found a negative impact of hypoxia on radiotherapy response in HNSCC cells and enhanced expression of epithelial–mesenchymal transition (EMT)- and cancer stem cells (CSC)-associated genes during culturing cells in hypoxic conditions. With cDNA microarrays analysis we identified a number of hypoxia regulated genes that were involved in multiple biological functions as well as support growth and proliferation of cancer cells. Furthermore, with use of siRNA silencing, we investigated a possible impact of a panel of hypoxia-responsive genes (HIF-1α, CDH2, CA9, SERPINE1, AREG and EREG) on radiotherapy treatment. Nevertheless, downregulation of these hypoxia regulated genes did not affect the sensitivity to radiotherapy of the investigated HNSCC cell lines.In the following study (paper III) we continued to investigate the most hypoxia-dysregulated genes from previous study (CA9, CASP14, LOX, GLUT3, SERPINE1, AREG, EREG, CCNB1 and KIF14), and their impact on the survival of HNSCC patients treated with radiotherapy. Patients with high KIF14 mRNA expression showed significantly longer overall survival (OS) compared with patients with low KIF14 mRNA expression. Moreover, HNSCC patients with high mRNA expression of KIF14 and low mRNA expression of CA9 (hypoxia marker) showed better OS compared with those with the opposite mRNA expression.In paper IV, we investigated the influence of cancer-associated fibroblasts (CAFs) on tumor cell gene expression profile. Cells were cultured in 2D and 3D models where HNSCC cells and CAFs derived from the same tumor were co-cultured. The microarray analysis revealed a higher number of CAF-regulated genes in tumor cells grown in spheroids compared to tumor cells grown in 2D. Next, the expression pattern of most changed CAF-regulated genes (MMP1, MMP9, POSTN, GREM1, FMOD, COL1A2, GREM1, IVL) was analyzed in normal oral tissue and in pretreatment biopsies from HNSCC patients treated with radiotherapy showing differences in gene expression between HNSCC tumor tissue and normal oral tissue. High mRNA expression of MMP9 and FMOD were found to be significantly associated with better overall survival (OS) in patients treated with radiotherapy.Taken together, we developed a reliable in vitro method for the measurement of intracellular glucose uptake with gamma spectrometry and glucose uptake was associated with treatment response. Furthermore, we found that hypoxia has a negative impact on radiotherapy in HNSCC cells and we identified a panel of hypoxia-dysregulated genes involved in the multiple biological functions in cancer cells, however downregulation of single hypoxia-regulated genes did not affect response to radiotherapy. Further analysis indicated KIF14 mRNA as potential predictor of radiotherapy response but more studies with a larger patient cohort are required. Beside hypoxia, CAFs have an important role in cancer progression. The gene expression profile in HNSCC cell lines was found to be dysregulated by CAF-derived signals in vitro. Additionally, CAF-regulated genes, MMP9 and FMOD are potential candidates as biomarkers of OS in HNSCC patients treated with radiotherapy, however more studies must be undertaken to investigate our hypothesis.
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