Biomedical subjects

Marcel A T M van Vugt

Publications and source records attributed to Marcel A T M van Vugt.

10 recordsLinked to original sources

PubMed2026

Mature Tertiary Lymphoid Structures in Breast Cancers Are Associated With Antitumor Immunity and Better Prognosis.

Tertiary lymphoid structures (TLSs) are immune cells accumulated in nonlymphoid tissues, with an inner core of B cells encompassed by T cells. The aim of this study was to evaluate the clinical importance of mature TLSs in breast cancer, including their association with immunotherapy response and their role in modulating the tumor immune microenvironment. We analyzed histopathological data of 726 consecutive primary breast cancers and transcriptomic data of 824 breast cancer samples from the publicly available The Cancer Genome Atlas database to estimate the clinical and immunological values of mature TLSs in breast cancer. Additionally, we utilized pretreatment transcriptomic data of 69 patients with breast cancer from the publicly available I-SPY2 clinical trial to investigate the relation between TLS-related gene signatures and patient responses to immune checkpoint inhibitors. The existence of mature TLSs was identified in ⁓5.6% (41/726) of all patients with breast cancer (hormone receptor-positive human epidermal growth factor receptor-2 negative (HR+HER2-): 0.92%; triple-negative breast cancer (TNBC): 14.96%; and human epidermal growth factor receptor-2 positive (HER2+): 10.98%) and was independently associated with improved recurrence-free survival after adjusting for subtypes, tumor-infiltrating lymphocyte levels, and tumor stage after the multivariable Cox regression analysis in our patient cohort. Notably, the presence of mature TLSs was related to immune cell infiltration in our breast cancer patient cohort. In line with these findings, TLS-related gene signatures analyzed through transcriptomic data reliably reflected the existence of mature TLSs and were related to better clinical responses to immune checkpoint inhibitors in patients with breast cancer. In conclusion, our findings show that mature TLS formation is linked with immune cell infiltration, contributes to a favorable prognosis, and may function as a potential complementary biomarker for immunotherapy response in breast cancer.

Humans↗

PubMed2006

Claspin: timing the cell cycle arrest when the genome is damaged.

DNA damage checkpoints maintain genomic integrity by delaying cell cycle progression in response to genotoxic stress and stalled replication forks. One central pathway in the checkpoint response is the ATR-Chk1 pathway, in which, upon DNA damage, ATR phosphorylates and activates the effector kinase Chk1. This process depends on the adaptor protein Claspin that bridges ATR and Chk1. Once the damage is repaired, this pathway must somehow be switched off to allow the cell to continue the cell division process, an event known as checkpoint recovery. Polo-like kinase 1 (Plk1) plays a central role during checkpoint recovery. Interestingly, the Xenopus homologue of Plk1, Plx1, is able to bind and phosphorylate Claspin, releasing it from DNA and thereby contributing to Chk1 inactivation. Moreover, it was recently demonstrated that Claspin levels are controlled by proteasomal degradation, and this is regulated by Plk1. Importantly, Plk1-mediated proteosomal degradation of Claspin appears to be essential for check-point recovery. Here we review these recent findings and discuss the mechanisms of checkpoint regulation by Claspin.

Adaptor Proteins, Signal Transducing↗

PubMed2005

CLIP-170 facilitates the formation of kinetochore-microtubule attachments.

CLIP-170 is a microtubule 'plus end tracking' protein involved in several microtubule-dependent processes in interphase. At the onset of mitosis, CLIP-170 localizes to kinetochores, but at metaphase, it is no longer detectable at kinetochores. Although RNA interference (RNAi) experiments have suggested an essential role for CLIP-170 during mitosis, the molecular function of CLIP-170 in mitosis has not yet been revealed. Here, we used a combination of high-resolution microscopy and RNAi-mediated depletion to study the function of CLIP-170 in mitosis. We found that CLIP-170 dynamically localizes to the outer most part of unattached kinetochores and to the ends of growing microtubules. In addition, we provide evidence that a pool of CLIP-170 is transported along kinetochore-microtubules by the dynein/dynactin complex. Interference with CLIP-170 expression results in defective chromosome congression and diminished kinetochore-microtubule attachments, but does not detectibly affect microtubule dynamics or kinetochore-microtubule stability. Taken together, our results indicate that CLIP-170 facilitates the formation of kinetochore-microtubule attachments, possibly through direct capture of microtubules at the kinetochore.

Cells, Cultured↗

PubMed2005

Restarting the cell cycle when the checkpoint comes to a halt.

The DNA damage checkpoint coordinates a block in cell proliferation with the DNA repair process that follows when lesions are inflicted on the genome. However, we do not know exactly how cell division can recommence following a DNA damage-induced arrest. Recent work from our lab has identified Polo-like kinase-1 and Cdc25B as two essential components of the machinery that sets the cell division process back in motion when the checkpoint response is abrogated. Here, we discuss these novel insights and discuss their possible implications for the treatment of cancer.

Animals↗

PubMed2005

Getting in and out of mitosis with Polo-like kinase-1.

Research in different species has shown that Polo-like kinases are essential for successful cell division. In human cells, Polo-like kinase-1 (Plk1) has been implicated in the regulation of different processes, including mitotic entry, spindle formation and cytokinesis. Recently, a range of new downstream targets of Plk1 has been identified, as well as a molecular mechanism that explains recruitment of Plk1 to potential substrate proteins through its polo-box domain. On the basis of these reports, we discuss possible mechanisms by which Polo-like kinases can exert their multiple functions during mitosis. Polo-like kinases also function in DNA damage checkpoints. Plk1 has been shown to be a target of the G2 DNA damage checkpoint, while Cdc5, the Polo-like kinase in Saccharomyces cerevisiae, has long been known to be required for adaptation to persistent DNA damage. Just recently, a similar requirement for Polo-like kinases during checkpoint adaptation was demonstrated in multicellular organisms. Moreover, Plk1 was also shown to be required for checkpoint recovery following checkpoint inactivation, that is, in cells where the damage is completely repaired. Thus, Plk1 appears to play a role at multiple points during a restart of the cell cycle following DNA damage. Based on these novel observations, we discuss possible consequences of using Plk1 as a target in anticancer strategies.

Cell Cycle Proteins↗

PubMed2005

Uncoupling anaphase-promoting complex/cyclosome activity from spindle assembly checkpoint control by deregulating polo-like kinase 1.

Polo-like kinase 1 (Plk1) plays a role in numerous events in mitosis, but how the multiple functions of Plk1 are separated is poorly understood. We studied regulation of Plk1 through two putative phosphorylation residues, Ser-137 and Thr-210. Using phospho-specific antibodies, we found that Thr-210 phosphorylation precedes Ser-137 phosphorylation in vivo, the latter occurring specifically in late mitosis. We show that expression of two activating mutants of these residues, S137D and T210D, results in distinct mitotic phenotypes. Whereas expression of both phospho-mimicking mutants as well as of the double mutant leads to accelerated mitotic entry, further progression through mitosis is dramatically different: the T210D mutant causes a spindle assembly checkpoint-dependent delay, whereas the expression of the S137D mutant or the double mutant results in untimely activation of the anaphase-promoting complex/cyclosome (APC/C) and frequent mitotic catastrophe. Using nonphosphorylatable Plk1-S137A and Plk1-T210A mutants, we show that both sites contribute to proper mitotic progression. Based on these observations, we propose that Plk1 function is altered at different stages of mitosis through consecutive posttranslational events, e.g., at Ser-137 and Thr-210. Furthermore, our data show that uncontrolled Plk1 activation can uncouple APC/C activity from spindle assembly checkpoint control.

Anaphase-Promoting Complex-Cyclosome↗

PubMed2005

Polo-like kinase-1: activity measurement and RNAi-mediated knockdown.

Polo-like kinase-1 (Plk-1) is an important cell cycle regulatory kinase that has been implicated in a multitude of cell cycle events. In this chapter we review those multiple functions of Plk-1 and describe the methods routinely used in our laboratory to purify Plk-1 from cellular lysates and measure Plk-1 kinase activity in vitro. In addition, we describe a method to analyze cell cycle progression after depletion of Plk-1 by RNA-interference in tissue culture cells.

Animals↗

PubMed2004

Checkpoint adaptation and recovery: back with Polo after the break.

S. cerevisiae cells that are unable to repair a double strand break ultimately escape the DNA damage checkpoint arrest and enter mitosis. This process called 'adaptation' depends on functional Cdc5, a Polo-like kinase, and was long thought to be limited to single-cell organisms. However, the recent finding that Xenopus extracts can adapt to a long-lasting stall in DNA replication indicates that checkpoint adaptation does also occur in multicellular organisms. Interestingly, the Xenopus Polo-like kinase (Plx1) plays an important role in this adaptation. To add to this, data from our laboratory have shown that the human Polo-like kinase (Plk1) is also required for cell cycle reentry following a DNA damage-induced arrest. But here, Plk1 was shown to be required for bona-fide checkpoint recovery, rather than adaptation. That is, Plk1 is required to restart the cell cycle once all of the damage is repaired and checkpoint signaling is turned off. While the target of Plx1 during adaptation is a component of the checkpoint machinery (Claspin), the target of Plk1 during recovery turns out to be a mitotic regulator (Wee1). Here, we discuss some of the remarkable similarities and subtle differences in the molecular mechanisms that control checkpoint adaptation and recovery, and the role of Polo-like kinases therein.

Adaptor Proteins, Signal Transducing↗

PubMed2004

Polo-like kinase-1 controls recovery from a G2 DNA damage-induced arrest in mammalian cells.

DNA damage triggers multiple checkpoint pathways to arrest cell cycle progression. Less is known about the mechanisms that allow resumption of the cell cycle once checkpoint signaling is silenced. Here we show that while in undamaged cells several redundant pathways can promote the onset of mitosis, this redundancy is lost in cells recovering from a DNA damage-induced arrest. We demonstrate that Plk1 is crucial for mitotic entry following recovery from DNA damage. However, Plk1 is no longer required in cells depleted of Wee1, and we could show that Plk1 is involved in the degradation of Wee1 at the onset of mitosis. Thus, our data show that the cell cycle machinery is reset in response to DNA damage and that cells become critically dependent on Plk1-mediated degradation of Wee1 for their recovery.

Cell Cycle Proteins↗

PubMed2004

Polo-like kinase-1 is required for bipolar spindle formation but is dispensable for anaphase promoting complex/Cdc20 activation and initiation of cytokinesis.

Polo-like kinase-1 (Plk1) performs multiple essential functions during the cell cycle. Here we show that human Plk1-deficient cells are unable to separate their centrosomes, fail to form a bipolar spindle, and undergo a Mad2/BubR1-dependent prometaphase arrest. However, electron microscopy demonstrates that kinetochore-microtubule interactions can be established in cells lacking Plk1. In addition, co-depletion of Plk1 and survivin allows mitotic exit. This indicates that Plk1 depletion does not prevent microtubule attachment, but specifically interferes with the generation of tension, as a consequence of a failure to form a bipolar spindle. Moreover, we find that after silencing of the spindle assembly checkpoint, degradation of cyclin B1 is unaffected in cells lacking Plk1. These data indicate that activation of the anaphase promoting complex or cyclosome (APC/C)-Cdc20 complex that is under control of the spindle assembly checkpoint does not require Plk1 activity. Finally, we find that translocation of chromosome passengers and initiation of cleavage furrow ingression is unaffected in cells depleted of Plk1. Thus, our data confirm an important role of Plk1 in bipolar spindle formation, and also demonstrate that Plk1 is dispensable for APC/C-Cdc20 activation and the initiation of cytokinesis.

Anaphase↗