Molecular Investigations of Mantle Cell Lymphoma

Abstract

In recent years, overall survival was significantly prolonged in Mantle Cell Lymphoma (MCL) patients due to improved treatment regimen. However, there is still a subgroup of patients that relapse after a short time. Better understanding of the underlying genetic and non-genetic events can be used to achieve personalized medicine for each patient. MCL is associated with the translocation t(11;14)(q13,q32), that leads to Cyclin D1 overexpression. This primary genetic event is known to be the hallmark and the putative initial oncogenic driver. However, there are secondary mutations that contribute to MCL development and some of them are associated with a more aggressive course of the disease. TP53 is found to be one of the most frequently mutated genes in MCL. TP53 mutations involve cell cycle and apoptosis related signaling pathways in the B-cell. Causing patients to have a more aggressive disease characterized by drug resistance, short overall survival (OS) and poor prognosis.

This study aims to investigate if assessment of p53 using immunohistochemistry has prognostic value and compare manual scoring with the digital image software HALO. In later analysis, which is outside the scope of this study, targeted sequencing will be used to correlate TP53 mutations with p53 protein level. Secondly, this study aims to identify targeted drugs active in MCL, and with retained and/or enhanced efficacy in TP53 mutated cells. In conclusion, we show that the fraction of p53 positive cells is negatively associated with overall survival rate (p=0.001, Hazard Ration (HR)=1.03). Since, every 1% increase of p53 positive cells is associated with 3% risk that the patient will have shorter OS. Small molecular drug screening showed that a high number of drugs are effective across WT and mutated TP53 cell lines, including Aurora kinase inhibitors, HSP inhibitors, and CDK inhibitors. We further elucidated that in TP53 mutated cells, few targets showed higher sensitivity to inhibition compared to WT cells. These include FAK inhibitor, HDAC inhibitor, and PARP inhibitors.

Popular Abstract

Mantle Cell Lymphoma Towards a Brighter Future

Malignant lymphoma is a type of cancer that arises in immune cells responsible for fighting infections called lymphocytes. Lymphocytes can be either T-lymphocytes (T-cell), B-lymphocytes (B-cells), or Natural Killers (NK). There are three main types of lymphoma: Hodgkin lymphoma and Non-Hodgkin lymphoma.

Accordingly, Mantle Cell Lymphoma (MCL) is a malignant B-cell lymphoma. MCL is an aggressive and rare disease characterized by poor prognosis and high relapse rate. MCL is associated with a primary genetic event that is known to be the hallmark of the disease: an abnormal rearrangement between chromosomes 11 and 14. Symptoms associated with MCL are weight loss; appetite loss ; fever and night sweat; abdominal pain associated with indigestion, vomiting, nausea, and bloating. In Europe 0.5 patients per 100,000 individuals are diagnosed every year with MCL. Their average age is 60 years old, and the average survival period ranges from 5 to 7 years. In addition, men are three times more likely to develop the disease than women.

However, other genetic aberrations besides the primary genetic event contribute to the development of MCL and they are associated with a more aggressive course of the disease. Tumor protein p53 (TP53) is found to be one of the most frequently mutated genes in MCL. TP53 mutated MCL patients have a more aggressive disease characterized by drug resistance, short Overall Survival, and poor prognosis. TP53 is a gene that encodes the protein p53. p53 is known as the guardian of the genome and it is one of the cell protectors against cancer. Hence, mutations on TP53 will produce a defected p53, which is favoured by cancer cells. That is why 50% of human cancers are found to have mutations on the TP53 gene.

We wanted to see how mutated TP53 would affect different treatment targets. Mutated cells were treated with different anti-cancer compounds and we measured the percentage of cell death and cell proliferation to see if the mutated cells responded to the drug the same way the non-mutated cells did. At the end we found that indeed they differ, as some drugs were more effective on the non-mutated, some other drugs were more effective on the mutated, and some drugs were as effective in both groups. This is due to the different targets these drugs inhibit to kill cancer. Some targets are found to be affected by the mutations; hence they will either not respond to the drug or be more sensitive to it. Finally, we were trying to check if we can diagnose mutated TP53 cases by using immunohistochemistry (IHC). It is an immunostaining technique that mainly stains proteins in the cells. We took samples from MCL patients and stained against p53 to measure the amount of p53 inside the cells. Then we compared the amount with the overall survival of the patients. We found that the more p53 trapped inside the cell, the shorter the time the patient lived.

In conclusion, understanding of such genetic events can be used to improve the treatment and diagnosis of MCL.

Master’s Degree Project in Molecular Biology, 60 credits 2019
Department of Biology, Lund University
Advisor: Sara Ek
Immunothechnology Department, LTH, Lund University

• author: Hassan, May
• supervisor: Sara Ek
• organization: Degree Projects in Molecular Biology
• course: MOBN03 20182
• year: 2019
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 8989996
• date added to LUP: 2019-07-04 12:10:45
• date last changed: 2019-07-04 12:10:45