Heterozygous germ-line mutations in BRCA1 and BRCA2 predispose to several types of cancer. Owing to their roles in the error-free repair of DNA double-strand breaks (DSBs) via homologous... Show moreHeterozygous germ-line mutations in BRCA1 and BRCA2 predispose to several types of cancer. Owing to their roles in the error-free repair of DNA double-strand breaks (DSBs) via homologous recombination (HR), lack of BRCA1/2 in these tumors results in DNA damage defects that can be specifically targeted by the inhibition of Poly-(ADP-ribose) polymerase 1 (PARP1). PARP1 is a key sensor of DNA damage and its inhibition has been shown to be synthetically lethal with deficiencies in HR, resulting in the selective killing of BRCA1/2-deficient tumor cells, while sparing BRCA1/2-proficient non-tumor cells. The success of this approach has resulted in the approval of four PARP1 inhibitors (PARPi) for the treatment of ovarian, breast, prostate and pancreatic cancers. However, drug resistance poses a major obstacle as, despite initial responses, patients receiving PARPi often develop resistance to the treatment. Understanding the molecular mechanisms behind PARPi resistance is therefore crucial to identify key determinants of PARPi response and to find combination treatment strategies to overcome resistance to PARPi by preventing, delaying or targeting resistant clones. In this thesis, we expanded our insights into the molecular mechanisms underlying PARPi resistance by conducting functional genetic screens in PARPi-resistance cell lines. Show less
Wester, L.; Venneker, S.; Hazenoot, M.; Pont, C.M.; Koedoot, E.; Timmermans, A.M.; ... ; Water, B. van de 2022
Antiestrogen resistance of breast cancer has been related to enhanced growth factor receptor expression and activation. We have previously shown that ectopic expression and subsequent activation of... Show moreAntiestrogen resistance of breast cancer has been related to enhanced growth factor receptor expression and activation. We have previously shown that ectopic expression and subsequent activation of the insulin-like growth factor-1 receptor (IGF1R) or the epidermal growth factor receptor (EGFR) in MCF7 or T47D breast cancer cells results in antiestrogen resistance. In order to identify novel therapeutic targets to prevent this antiestrogen resistance, we performed kinase inhibitor screens with 273 different inhibitors in MCF7 cells overexpressing IGF1R or EGFR. Kinase inhibitors that antagonized antiestrogen resistance but are not directly involved in IGF1R or EGFR signaling were prioritized for further analyses. Various ALK (anaplastic lymphoma receptor tyrosine kinase) inhibitors inhibited cell proliferation in IGF1R expressing cells under normal and antiestrogen resistance conditions by preventing IGF1R activation and subsequent downstream signaling; the ALK inhibitors did not affect EGFR signaling. On the other hand, MEK (mitogen-activated protein kinase kinase)1/2 inhibitors, including PD0325901, selumetinib, trametinib and TAK-733, selectively antagonized IGF1R signaling-mediated antiestrogen resistance but did not affect cell proliferation under normal growth conditions. RNAseq analysis revealed that MEK inhibitors PD0325901 and selumetinib drastically altered cell cycle progression and cell migration networks under IGF1R signaling-mediated antiestrogen resistance. In a group of 219 patients with metastasized ER + breast cancer, strong pMEK staining showed a significant correlation with no clinical benefit of first-line tamoxifen treatment. We propose a critical role for MEK activation in IGF1R signaling-mediated antiestrogen resistance and anticipate that dual-targeted therapy with a MEK inhibitor and antiestrogen could improve treatment outcome. Show less
Burger, G.A.; Water, B. van de; Le Dévédec, S.E.; Beltman, J.B. 2022
The ability of cancer cells to invade neighboring tissue from primary tumors is an important determinant of metastatic behavior. Quantification of cell migration characteristics such as migration... Show moreThe ability of cancer cells to invade neighboring tissue from primary tumors is an important determinant of metastatic behavior. Quantification of cell migration characteristics such as migration speed and persistence helps to understand the requirements for such invasiveness. One factor that may influence invasion is how local tumor cell density shapes cell migration characteristics, which we here investigate with a combined experimental and computational modeling approach. First, we generated and analyzed time-lapse imaging data on two aggressive Triple-Negative Breast Cancer (TNBC) cell lines, HCC38 and Hs578T, during 2D migration assays at various cell densities. HCC38 cells exhibited a counter-intuitive increase in speed and persistence with increasing density, whereas Hs578T did not exhibit such an increase. Moreover, HCC38 cells exhibited strong cluster formation with active pseudopod-driven migration, especially at low densities, whereas Hs578T cells maintained a dispersed positioning. In order to obtain a mechanistic understanding of the density-dependent cell migration characteristics and cluster formation, we developed realistic spatial simulations using a Cellular Potts Model (CPM) with an explicit description of pseudopod dynamics. Model analysis demonstrated that pseudopods exerting a pulling force on the cell and interacting via increased adhesion at pseudopod tips could explain the experimentally observed increase in speed and persistence with increasing density in HCC38 cells. Thus, the density-dependent migratory behavior could be an emergent property of single-cell characteristics without the need for additional mechanisms. This implies that pseudopod dynamics and interaction may play a role in the aggressive nature of cancers through mediating dispersal. Show less
This thesis assessed the quality of breast cancer care on different level by analyzing data from a tertiary cancer center and multiple nationwide databases.In order to do so, we first provided... Show moreThis thesis assessed the quality of breast cancer care on different level by analyzing data from a tertiary cancer center and multiple nationwide databases.In order to do so, we first provided insight into breast cancer patients changing hospital and the medical impact of a second opinion. The results demonstrated that a hospital transfer after diagnosis is a delaying factor for primary treatment, specifically for those who undergo surgery. Furthermore, we assessed in a reproducible manner that second opinions can have a significant impact on diagnostics and primary treatment strategies. In the second part, we assess the delaying impact of postmastectomy immediate breast reconstruction on the continuity of the adjuvant chemotherapy pathway. This part furthermore highlights the importance of timely initiation of adjuvant chemotherapy on survival in patients diagnosed with triple-negative breast cancer. Finally, we evaluate the use of breast‐contour preservation and safety of oncoplastic strategies on an (inter)national level. We demonstrate that a breast reconstruction using a direct‐to‐implant compared to a two‐stage technique is associated with a lower unplanned revision. Although the total breast‐contour preservation rate in the Netherlands is similar to Denmark, different strategies are used. Furthermore, oncoplastic techniques seem a safe option regarding re‐excision and conversion to mastectomy. Hereby, the findings in this thesis may contribute to different dimensions of the quality of breast cancer care. Show less
In the last decade, the tumor microenvironment has shown to play an important role in tumor progression. Still, no markers concerning the microenvironment have been implemented in clinical decision... Show moreIn the last decade, the tumor microenvironment has shown to play an important role in tumor progression. Still, no markers concerning the microenvironment have been implemented in clinical decision making. The research presented in this thesis emphasizes the prognostic value of the tumor-stroma ratio (TSR), a method focusing on the tumor microenvironment. The TSR assessment is performed by the scoring method developed by Mesker et al. on routine hematoxylin and eosin (H&E) stained tissue slides of the primary tumor. Various validation studies demonstrated that the TSR is a reliable, simple, quick and inexpensive parameter with a good to a very good inter-observer agreement. The new insights presented in this thesis contribute to a better understanding of the role of the TSR on predicting clinical outcome in subgroups of breast cancer patients and in combination with other prognostic parameters. Furthermore, the described research is important for further research toward clinical implementation of the TSR and might finally be useful for decision-making regarding therapy. Moreover, molecular research of the stromal compartment in the near future is desirable for the development of new diagnostic, prognostic, monitoring and therapeutic markers. Show less
A family history of breast cancer is one of the most important risk factors for the disease. Over the last decades many genetic loci associated with breast cancer risk have been discovered. In... Show moreA family history of breast cancer is one of the most important risk factors for the disease. Over the last decades many genetic loci associated with breast cancer risk have been discovered. In spite of this, only approximately half of the familial relative risk (FRR) for breast cancer can be explained by the currently known genetic risk factor. In this thesis we have explored the role of rare genetic variants in familial breast cancer with the help of next generation sequencing. Through this approach we have not been able to identify any novel high-risk breast cancer susceptibility alleles. Although there are likely still several extremely rare risk alleles to be discovered and the presence of high-risk alleles outside of protein-coding regions cannot be excluded, it seems presently unlikely that these will explain a substantial proportion of familial breast cancer. Both our work and that of others has suggested that most non BRCA1/2 familial breast cancer cases are likely explained by a combination of low-, and moderate-risk susceptibility alleles. Show less
Graauw, M. de; Cao, L.; Winkel, L.; Miltenburg, M.H.A.M. van; Dévédec, S.E. le; Klop, M.; ... ; Water, B. van de 2014
