Cancer immunotherapies utilizing immune checkpoint blockade (ICB) therapy targeting CTLA-4 and PD-1/PD-L1 relieve tumor-induced immune suppression and induce durable tumor regression. The use of... Show moreCancer immunotherapies utilizing immune checkpoint blockade (ICB) therapy targeting CTLA-4 and PD-1/PD-L1 relieve tumor-induced immune suppression and induce durable tumor regression. The use of ICB therapy have demonstrated remarkable therapeutic efficacy in a proportion of patients with melanoma. However, still a substantial percentage of patients does not respond (durable) to ICB treatment and many questions remain. Therefore, in this thesis, the aim is to improve our understanding of ICB efficacy. We demonstrate the promise of neoadjuvant ICB therapy (approach in which ICB therapy is applied before surgery) and analyze different cohorts of melanoma patients. This results in the identification of several markers that are associated with prognosis, including IFN-y related gene signature score, Batf3 dendritic cell associated gene signature score, tumor mutational burden and systemic LRG1 expression. These markers can potentially be targeted and might facilitate rational combination therapies that can boost the efficacy of ICB therapy. For this purpose, we perform a repurposing compound screen that targets antigen cross-presentation. Togethers, this work increases our understanding of factors that determine ICB therapy efficacy and toxicity, with the goal to identify novel strategies to improve outcome of melanoma patients in a rationale and personal manner. Show less
While immune checkpoint blockade (ICB) (CTLA4/ PD1) therapy has resulted in durable responses in patients with advanced stage cutaneous melanoma, some patients do not benefit from this, due to... Show moreWhile immune checkpoint blockade (ICB) (CTLA4/ PD1) therapy has resulted in durable responses in patients with advanced stage cutaneous melanoma, some patients do not benefit from this, due to resistance mechanisms. This thesis aims to improve response of a subset of melanoma patients to immunotherapy. Firstly, mouse melanoma tumor models are developed that closely resemble some of the resistance mechanisms occurring in patient tumors, which are useful for research. Thereafter, a prognostic biomarker is used to identify the subset of melanoma patients that are unlikely to benefit from ICB therapy. It is then evaluated whether this subset of patients would benefit from combining histone deacetylase inhibitor with ICB. Despite encouraging pre-clinical results showing enhanced anti-tumor immune responses using this combination, this did not result in improved responses in the clinic. Furthermore, this thesis focuses on an immune cell subset, namely regulatory T cells (Tregs), which are known to suppress anti-tumor immune responses. Thus, their presence in the tumor microenvironment (TME) is detrimental to tumor cell killing. This thesis provides an increased understanding of the metabolic adaptation of Tregs to conditions in the TME and propose that targeting these adaptations might overcome the suppression by Tregs and enhance responses to immunotherapy. Show less
The aim of this thesis was to investigate if a text-mining tool is suitable for collecting real-world data from electronic health records to evaluate cancer treatments in clinical practice. By... Show moreThe aim of this thesis was to investigate if a text-mining tool is suitable for collecting real-world data from electronic health records to evaluate cancer treatments in clinical practice. By investigating a range of use cases including treatments of patients with renal cell carcinoma, hepatocellular carcinoma, melanoma, breast cancer, and COVID-19, it showed that the text-mining tool is a suitable method of data needed for the evaluation of treatment patterns, effectiveness, safety, prognostic factors, and guideline adherence. The discussion showed that enhancing the data quality and actively using real-world data for treatment evaluation regarding treatment policies are some of the next steps. Show less
Communication between cells is essential for the proper function of tissues in the human body. In cancer, this communication is disrupted. The signaling pathway initiated by Transforming Growth... Show moreCommunication between cells is essential for the proper function of tissues in the human body. In cancer, this communication is disrupted. The signaling pathway initiated by Transforming Growth Factor beta (TGF-beta) signaling molecules controls many processes in cells, including cell division, cell differentiation and cell migration. Dysregulation of TGF-beta signaling contributes to the formation and progression of many cancers. The inhibition of the TGF-beta signaling pathway is therefore an attractive anti-cancer therapy. Unfortunately, these therapies result in many side effects. The research described in this thesis aims to better understand TGF-beta signaling in different types of cancer. Through the development of new fluorescent tools, the activity and dynamics of TGF-beta signaling can be better studied in vitro and in vivo. In melanoma, the tumor microenvironment appeared to influence the effect of TGF-beta. In cervical cancer, TGF-beta activity levels could distinguish two subtypes of cervical cancer. In bladder cancer, a E3 ubiquitin ligase mediated a balance of BMP signaling, affecting bladder cancer progression. These studies all highlight the complexity of TGF-beta signaling and the need to fully understand TGF-beta signaling in different contexts to improve the use TGF-beta inhibition based therapies in the clinic. Show less
Death in all types of melanomas is generally caused by metastasis. Uveal melanoma (UM) is the most common intraocular melanoma, there are currently no (patient-derived) animal models that... Show moreDeath in all types of melanomas is generally caused by metastasis. Uveal melanoma (UM) is the most common intraocular melanoma, there are currently no (patient-derived) animal models that faithfully recapitulate metastatic dissemination of UM. Here we generate embryonic zebrafish models for both the primary and disseminated stage of ocular melanoma. In doing so we can recapitulate the etiology of cancer in its totality. Subsequently, we developed a patient-derived zebrafish xenograft (zf-PDX) model, using spheroid cultures generated from metastatic and primary UM tissues. Harnessing this versatile model, we reveal high sensitivity of circulating UM cells to ferroptosis induction in vivo by Erastin and RSL3, implicating ferroptosis as a new potential therapy in metastatic UM.Increased melanin levels in cutaneous melanoma are associated with decreased patient survival. Melanin levels in primary uveal melanoma patient cells positively correlate with their metastatic potential in zebrafish. Modulation of melanin levels of pan-melanoma cells results in enhanced/reduced metastatic potential upon increased or decreased melanin levels, respectively. Melanin depletion sensitizes melanoma cells to ferroptosis inducers in zebrafish leading to a decreased metastatic burden. Collectively, our data identify melanin biosynthetic enzymes as potential future target to treat melanoma and show that melanin protects metastasizing melanoma cells from ferroptosis. Show less
Being a member of a melanoma family is a major risk factor for cutaneous malignant melanoma. In this thesis clinical characteristics and management of melanoma families are discussed. In the first... Show moreBeing a member of a melanoma family is a major risk factor for cutaneous malignant melanoma. In this thesis clinical characteristics and management of melanoma families are discussed. In the first part of the thesis clinical and histological characteristics of melanoma (patients) from families with a (p16-Leiden) mutation in the high penetrance melanoma susceptibility gene CDKN2A were compared with the general population. Significant differences with respect to several characteristics are reported. In the second part of the thesis the yield, effectiveness, and causes for failure of surveillance of melanoma families are discussed. We report that surveillance is associated with a more favorable tumor stage. Several aspects of surveillance, including interval melanomas, surveillance interval, noncompliance, and overdiagnosis are discussed. Based on analyses of melanoma detection rates in families with different family and genetic characteristics, we propose a risk stratification for members of melanoma families. In the third part of the thesis we investigate the impact of dermoscopy on management decisions. It is demonstrated that dermoscopy by dermoscopy experts in the setting of melanoma family surveillance resulted in a considerable reduction of unnecessary excisions. This effect was considerably less in the setting of dermoscopy non-experts examining patients in general dermatology clinics. Show less
Melanoma is a malignancy that arises from melanocytes, the pigment-producing cells that can be predominantly found in the eye or the epidermal basal layer of the skin. Mainly due to increased UV... Show moreMelanoma is a malignancy that arises from melanocytes, the pigment-producing cells that can be predominantly found in the eye or the epidermal basal layer of the skin. Mainly due to increased UV exposure, the incidence of melanoma has doubled worldwide over the past three decades (200.000 new cases in 2008). Primary melanomas can be easily treated by surgical resection, leading to a good prognosis for stage I patients. However, metastasized melanoma is almost completely resistant to therapeutic modalities such as radio- and chemotherapy, resulting in a median overall survival of less than one year for this patient group. Despite considerable efforts, for over 20 years there was no melanoma treatment developed that could improve survival of stage IV patients. However, the treatment of unresectable metastasized melanoma has progressed markedly in recent years due to the development of both immunotherapies that stimulate anti-tumor immunity and targeted therapies that block oncogenic proteins. This thesis will focus on pre-clinical work concerning the optimization of melanoma treatment. In detail, it will address for both targeted therapies and immunotherapies factors that play a role in the identification of response-predictive biomarkers, the toxicity of treatments, and the potential efficacy of combination treatments. Show less
Cutaneous melanoma is the most aggressive form of skin cancer and its incidence among Caucasian populations has increased whereas mortality rates are stabilizing or decreasing. The total burden of... Show moreCutaneous melanoma is the most aggressive form of skin cancer and its incidence among Caucasian populations has increased whereas mortality rates are stabilizing or decreasing. The total burden of melanoma is expected to be increasing. As effective treatment options for advanced melanoma are lacking, melanoma prevention may be the key issue in melanoma disease control. Although sun protection programs have increased awareness, they have not resulted in a decreased melanoma incidence. In addition, most melanoma risk factors are not amenable. Alternative approaches such as cancer chemoprevention are, therefore, important research topics. Several agents, such as statins, non-steroidal anti-inflammatory drugs, and angiotensin-converting enzyme inhibitors, have been claimed to have chemopreventive properties. However, it is unknown which of these have the best potential to be useful. This thesis presents: - epidemiologic cancer registry-based studies from The Netherlands on the epidemiology of extracutaneous melanoma and on the burden of disease due to cutaneous melanoma - a qualitative review discussing candidate drugs for melanoma chemoprevention, their possible mechanisms of action, and evidence for their chemopreventive efficacy, safety and tolerability - pharmacoepidemiological studies testing hypotheses on chemopreventive activityof several drugs on melanoma - pharmacoepidemiological studies on the association between estrogen use and melanoma. Show less
Cutaneous and uveal melanoma are malignant tumours with no treatment available once the metastases occur. Despite both melanomas are highly immunogenic, and often despite the presence of potent... Show moreCutaneous and uveal melanoma are malignant tumours with no treatment available once the metastases occur. Despite both melanomas are highly immunogenic, and often despite the presence of potent anti-tumour immune cells in patients__ blood, in more than 95% of patients, tumour growth remains unaffected. Hereby we investigate the mechanisms that help melanomas to escape from the spontaneous or activated by vaccination cytotoxicity of T lymphocytes and discuss the impact of local microenvironment created by melanoma, focusing on the role of immunomodulatory dendritic cells. Show less
For a tumor cell to propagate, it must survive extremely stressful conditions that would normally trigger the cell to die. Cancer cells however survive, probably due to evasion of the apoptotic... Show moreFor a tumor cell to propagate, it must survive extremely stressful conditions that would normally trigger the cell to die. Cancer cells however survive, probably due to evasion of the apoptotic cell death pathway. It follows that a detailed understanding of the regulation of the apoptotic pathways in cancer cells can improve the anti-cancer treatments. Part 1 of this thesis describes our in vitro studies regarding the regulation of apoptosis in melanoma cells, since melanoma is a form of cancer that is highly resistant to anti-cancer therapies. c-Myc enhances the apoptosis sensitivity of the cells. The protein Apaf-1 is not involved in this sensitivity. A yet unidentified serine protease plays an important role in the initiation of apoptosis upon DNA damage. Part 2 of this thesis describes our studies regarding both the regulation of apoptosis in rectal carcinoma and its prognostic value for rectal cancer patients. To evaluate the impact of (radiation-induced) tumor cell apoptosis on clinical outcome of cancer patients, the level of apoptosis have been determined in non-irradiated and irradiated rectal carcinoma samples. The level of tumor cell apoptosis is scored by immunohistochemical stainings of the carcinoma samples, and by measuring caspase-3 activity. Both studies show that high levels of apoptosis is associated with a low local recurrence risk. A genetic approach is used to identify factors that play a role in the regulation of apoptosis in rectal carcinoma in vivo. After evaluation two microarray procedures, the most convenient procedure is used to compare the gene expression profiles of tumors with high levels of apoptosis with low-apoptotic tumors. The difference in expression of several of the identified genes are confirmed on protein expression level by immunohistochemistry, and show two subsets of high-apoptotic tumors. These data suggest two different regulations of apoptosis in vivo. The prognostic value of one of the identified proteins, HLA-DR, has been studied in more detail and epithelial HLA-DR expression is significantly associated with lower recurrences and better survival for rectal cancer patients. Show less
This thesis introduces a novel T cell vaccination method that uses a tattoo machine to inject DNA in the skin of the vaccinee. In comparison to other experimental vaccination methods DNA tattooing... Show moreThis thesis introduces a novel T cell vaccination method that uses a tattoo machine to inject DNA in the skin of the vaccinee. In comparison to other experimental vaccination methods DNA tattooing is very strong: besides small laboratory animals also large animals mount strong T cell responses upon tattoo DNA vaccination. Show less
This thesis describes several topics on angiogenesis and screening in uveal melanoma, the most frequent eye tumour in adults. The expression of vascular endothelial growth factor and other... Show moreThis thesis describes several topics on angiogenesis and screening in uveal melanoma, the most frequent eye tumour in adults. The expression of vascular endothelial growth factor and other angiostimulating factors in this tumour are described. In a second part, the use of different screening tests in screening for metastases of uveal melanoma is investigated. Show less
