The clinical potential of applying synthetic lethality to cancer treatment is famously demonstrated by the BRCA1/PARP1 paradigm: a tumor specific defect in BRCA1 – a component of the DNA double... Show moreThe clinical potential of applying synthetic lethality to cancer treatment is famously demonstrated by the BRCA1/PARP1 paradigm: a tumor specific defect in BRCA1 – a component of the DNA double-strand break (DSB) repair pathway homologous recombination (HR) – results in a remarkable sensitivity to PARP1 inhibition (PARPi). Despite spectacular initial responses in patients, resistance to PARPi treatment may develop and must be overcome to maximally exploit this interaction in the clinic. Genetically engineered (mouse) model systems have shown that PARPi resistance may arise through inactivation of the 53BP1 pathway. The 53BP1 pathway normally protects DSB ends from resection and the removal of this “brake” restores HR in the absence of BRCA1. However, how the 53BP1 pathway protects DSB ends from resection has remained elusive. In this thesis, advances in 3D tumor organoid culture protocols and CRISPR/Cas9 (screening) technology were applied to identify and validate new components of the 53BP1 pathway that render BRCA1 deficient cells resistant to PARPi upon their loss. Furthermore, a new acquired vulnerability that can be therapeutically exploited to deplete such PARPi resistant cells is described. Together, this thesis provides mechanistic insight in DSB repair and illustrates how such fundamental knowledge may stand at the basis to combat resistance. Show less
The studies in this thesis contribute to more accurate risk assessment and prognosis prediction for DCIS and to better response evaluation of IBC treatment.For the Ductal Carcinoma In Situ (DCIS)... Show moreThe studies in this thesis contribute to more accurate risk assessment and prognosis prediction for DCIS and to better response evaluation of IBC treatment.For the Ductal Carcinoma In Situ (DCIS) studies, unbiased cohorts were used within the international Grand Challenge PRECISION consortium, funded by Cancer Research UK and KWF Dutch Cancer Society. DCIS is graded as low-, intermediate-, or high-grade depending on how abnormal the DCIS-cells look like. However, we showed that pathologists often disagree on grade. To overcome this limitation, we found that almost all DCIS scored as non-high-grade by the majority of pathologists express the estrogen receptor (ER) and are negative for the growth factor receptor HER2, whereas high-grade DCIS is mixed in expression for ER and HER2. We also provided insights in the recurrence risks of DCIS after treatment. See also https://cancergrandchallenges.org/teams/precision.The studies on Invasive Breast Cancer (IBC) were performed on a hospital-based cohort. We found for example substantial variation in tumour response evaluation for HER2-positive IBC after pre-operative chemotherapy due to different guidelines used. For accurate outcome analysis, reducing such variation is mandatory. Therefore, we are working on reaching international consensus of response evaluation. Show less
This thesis describes the effects of shortterm fasting on chemotherapy outcome in patients with breast cancer and the IGF-1 and insulin pathway as a target for cancer therapy and as a biomarker for... Show moreThis thesis describes the effects of shortterm fasting on chemotherapy outcome in patients with breast cancer and the IGF-1 and insulin pathway as a target for cancer therapy and as a biomarker for chemotherapy outcome.Preclinical research is evaluated, which shows that short-term fasting during chemotherapy is effective. The effects of short-term fasting in humans is not evident yet. Although the first small clinical studies of short-term fasting as adjunct to chemotherapy are promising in terms of decreased toxicity and enhanced efficacy, the exact mechanism and effects are not established yet. More studies and a longer follow-up are needed to prove this.Insulin-like growth factor 1 (IGF-1) and insulin are members of the IGF-1 pathway, which is involved in cell growth and proliferation. The effects of the IGF-1 pathway on chemotherapy outcome and the pathway itself as target for cancer therapy are described. The disappointing results of clinical studies of IGF-1R inhibitors may be caused by the complexity of the IGF-1R pathway. Lowering both insulin and IGF-1, perhaps with a short-term fasting intervention, serves as a possible target in cancer therapy. Show less
Invasive lobular carcinoma (ILC) is the second most common type of breast cancer. Hallmarks of ILC include disruption of adherens junctions and hyperactivation of phosphoinositide 3-kinase (PI3K)... Show moreInvasive lobular carcinoma (ILC) is the second most common type of breast cancer. Hallmarks of ILC include disruption of adherens junctions and hyperactivation of phosphoinositide 3-kinase (PI3K)-mTOR signaling. The tumor suppressor PTEN regulates PI3K signaling. We present a preclinical mouse model of ILC metastasis, based on inactivation of the adherens junction protein E-cadherin and the tumor suppressor p53 and surgical excision of primary tumors. In this model, pharmacological mTOR inhibition blocks growth of primary tumors as well as metastatic disease, and this response is partially dependent on the adaptive immune system. Loss of E-cadherin mouse mammary epithelium leads to apoptosis, and PTEN activation alone results in squamous metaplastic mammary tumors, but a combination of these events leads to ILC formation, indicating a causal role of PI3K signaling together with E-cadherin loss in ILC. Combined somatic loss of the adherens junction molecule p120 and p53 in the mouse mammary gland leads to metaplastic mammary tumors, and loss of p120 in breast cancer cell lines promotes anoikis resistance through hypersensitization of growth factor receptor (GFR) signaling. Combined inactivation of E-cadherin, p120 and p53 induces basal-like tumors, with an epithelial-to- mesenchymal-transition (EMT) phenotype, and no ILC formation. Show less
Since cancer survival rates are rising, there is growing attention for longterm side effects of cancer and its treatment. A common side effect is the negative impact of treatment on sexuality of... Show moreSince cancer survival rates are rising, there is growing attention for longterm side effects of cancer and its treatment. A common side effect is the negative impact of treatment on sexuality of patients and their partners. Patient and partners as well as healthcare professionals experience several barriers to discuss this topic, like lack of time and lack of knowlegde. Two-thirds of the cancer patients reported to be in need of information regarding sexual health; especially those who were younger, who reported a negative impact of cancer on sexuality and those who were diagnosed less than two years ago. Patients and partners reported to prefer to discuss sexual health with nurse practitioners throughout the treatment proces. Besides, satisfaction with sexual life after treatment is related to satisfaction before treatment, not only with current sexual function.Widely available information and defining responsibility within the oncology treatment team would be helpful to improve communication around sexual health in cancer care. Additionally, specialized clinics would tackle soms frequently reported barriers of discussing sexuality. More reseach is needed on the implementation of sexual healthcare in oncology practice to deliver continuum of care, which will ultimately improve patient care. Show less
Tumors are complex ecosystems containing not just cancer cells, but a large variety of cell types, including immune cells. Moreover, tumors have a systemic influence: they can signal long distances... Show moreTumors are complex ecosystems containing not just cancer cells, but a large variety of cell types, including immune cells. Moreover, tumors have a systemic influence: they can signal long distances using soluble molecules and hijack non-neoplastic cells (such as immune cells) in distant organs for their own benefit, thus maximising their metastatic potential. The phenotype of immune cells in tumors and in systemic environments is therefore a key determinant of cancer progression and response to therapy.This thesis aims to understand what governs the tumor-immune ecosystem. We argue that cancer-intrinsic genetic aberrations have a dominant role in determining the tumor immune contexture, as well as systemic inflammatory activation. Understanding the intricate connection between the genetics of breast cancer and anti-tumor immune responses will help develop personalised immune intervention strategies for cancer, tailored to the genetic makeup of a patient’s tumor. Furthermore, we examine in detail the role of neutrophils in cancer-induced systemic inflammation, and how they influence the progression and spread of breast cancer. While tumors can be highly heterogeneous in nature, we show that neutrophils themselves also have a tremendous phenotypic diversity. Mapping this heterogeneity in neutrophil phenotypes may help to utilise these cells in cancer immunotherapy. Show less
Over a century ago, the systematic evaluation of medical treatment outcomes was first described by Ernest Codman. At that time a too progressive thought, while the value of measuring the quality of... Show moreOver a century ago, the systematic evaluation of medical treatment outcomes was first described by Ernest Codman. At that time a too progressive thought, while the value of measuring the quality of care is seen nowadays.The NABON Breast Cancer Audit (NBCA) provides insight into the various care processes that are part of the complex multidisciplinary treatment of patients diagnosed with breast cancer. Results of the NBCA show a good and still improving quality of care for patients diagnosed with breast cancer. In addition, this thesis provides insight into a sub-area where variation between hospitals is found; the performance of an immediate breast reconstruction in patients undergoing mastectomy. Many factors influence this hospital variation, such as patient and tumour factors, hospital factors and differences in indications for immediate breast reconstruction between surgeons and plastic surgeons. Physicians should inform patients about the various breast cancer treatment options. Informing a patient about immediate breast reconstruction results in a 14 times higher chance of actually undergoing a breast reconstruction after mastectomy.These factors should to be evaluated and improved as quality of life is higher for patients with immediate breast reconstruction than with mastectomy alone. By continuously measuring, providing feedback and acting on the data found at both a national level and in the consultation room, Ernest Codman's heritage will certainly be realized. Show less
