PLK-1 inhibition has a functional impact on MYC and is a relevant target for high-risk mantle cell lymphoma patients

Abstract

types of B-cell lymphomas. However, the role of MYC in mantle cell lymphoma (MCL), a clinically diverse and incurable disease, needs to be further elucidated. The aim of this study is to evaluate MYC mRNA deregulation and explore the mechanism behind PLK-1 induced cell death, as a target for MYC-driven MCL. To achieve this, RNAscope® is used to detect and quantify MYC mRNA expression in a population-based cohort (BLISS) diagnosed with MCL and correlate it to patient outcome, MYC protein expression and other clinicopathological data. Additionally, PLK-1 is investigated as a candidate target to treat MYC-driven MCL patients by testing two anti-cancer compounds (Rigosertib, Volasertib). MYC expression was quantified by RNAscope® in 87 diagnostic MCL samples. The results revealed not only inter-patient but also intra-patient heterogeneity. A total of 25 patients were shown to overexpress MYC. These patients had significantly (p < 0.0001) worse clinical outcome than patients that did not overexpress MYC, with median survival time of 1.19 years and 5.29 years, respectively. MYC mRNA levels were strongly associated with MYC protein levels (R=0.74 p < 0.001). Additionally, MYC overexpression was significantly correlated to higher risk of death (HR=3.81, 95% CI 1.95-5.52) and also with PLK-1 expression levels (R=0.56, p < 0.001). PLK-1 influences the MYC-dependent kinase network, hence was tested as a potential target to reduce MYC expression in MCL-derived cell lines, using two anti-PLK-1 compounds (Rigosertib and Volasertib). Volasertib was more potent and induced effective cell death and proliferation inhibition with lower IC50 values in 4/5 cell lines compared to rigosertib. Volasertib, but not rigosertib, was shown to reduce both PLK-1 and MYC levels in 3/5 cell lines. In summary, it is shown that MYC overexpression is linked to worse patient outcome and can be used as a high-risk marker to stratify patients based on MYC status. This strengthens the use of PLK-1 as an indirect target for MYC-driven high-risk mantle cell lymphoma.

Popular Abstract

A druggable target as a weapon against an aggressive type of blood cancer

Cancer is the second most common cause of death worldwide. Mantle cell lymphoma is a type of blood cancer that affects the defenders of an organism, the immune system. The immune system is important for an organism to fight viruses and bacteria. The disease is caused by multiple alterations in a specific type of cells of the immune system, the so-called B-cells. These alterations result in aggressive production and dysfunctionality of the B-cells. The aim of this study is to investigate the role of a gene named MYC, that when overproduced, is observed to contribute to worse survival and death of patients diagnosed with different types of cancer. But why is this important to study? The short answer is that the role of MYC mRNA is less investigated in mantle cell lymphoma and this type of cancer does not have any treatment approaches that target patients with MYC deregulations. Therefore, it is important to also investigate possible targets that minimize the negative effects of MYC overproduction. This leads to the second aim which is to test anti-cancer drugs that can indirectly reduce the amount of the overproduced MYC protein levels. These drugs block a protein named PLK-1 which has been observed to regulate MYC production levels.

So, how does MYC affect mantle cell lymphoma? First it is important to detect and quantify MYC on cancer tissue collected from mantle cell lymphoma patients. This is done by using a method called RNAscope®, which allows to label and detect MYC. The tissue was then visualized and analysed with a software to quantify MYC. The results showed that high MYC levels are correlated to poor patient outcome. MYC also correlates to PLK-1 and other important dysfunctional components that contribute to a more aggressive disease. These results show that MYC is important to be further investigated to find possible treatment targets.

What about the second aim? Is it possible to verify that PLK-1 blockage reduces elevated MYC levels? This was shown here by treating in vitro mantle cell lymphoma models using drugs that inhibit PLK-1. Afterward, we evaluated the effect of the drugs by measuring cell death induction and the protein levels of MYC and PLK-1. We showed that one of the drugs, volasertib, was able to reduce both PLK-1 and MYC levels. We were able to show a correlation between PLK-1 and MYC in patient material and because PLK-1 inhibition seems to reduce MYC levels in cell lines, we suggest that PLK-1 could be potentially used as a target to treat MCL patients with high MYC levels.

Master’s Degree Project in Molecular Biology 60 credits 2022
Department of Biology, Lund University

Advisor: Sara Ek, Joana de Matos Rodrigues
Advisors Department: Dept. of Immunotechnology, Lund University

• author: Gkika, Eirinaios
• supervisor: Sara Ek
• organization: Degree Projects in Molecular Biology
• course: MOBN03 20212
• year: 2022
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 9085976
• date added to LUP: 2022-06-09 11:01:47
• date last changed: 2022-06-09 11:01:47