Browsing by Author "Heine, Simon"

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Open Access
Cell‐derived and enzyme‐based decellularized extracellular matrix exhibit compositional and structural differences that are relevant for its use as a biomaterial
(2022) Nellinger, Svenja; Mrsic, Ivana; Keller, Silke; Heine, Simon; Southan, Alexander; Bach, Monika; Volz, Ann‐Cathrin; Chassé, Thomas; Kluger, Petra J.
Due to its availability and minimal invasive harvesting human adipose tissue‐derived extracellular matrix (dECM) is often used as a biomaterial in various tissue engineering and healthcare applications. Next to dECM, cell‐derived ECM (cdECM) can be generated by and isolated from in vitro cultured cells. So far both types of ECM were investigated extensively toward their application as (bio)material in tissue engineering and healthcare. However, a systematic characterization and comparison of soft tissue dECM and cdECM is still missing. In this study, we characterized dECM from human adipose tissue, as well as cdECM from human adipose‐derived stem cells, toward their molecular composition, structural characteristics, and biological purity. The dECM was found to exhibit higher levels of collagens and lower levels of sulfated glycosaminoglycans compared with cdECMs. Structural characteristics revealed an immature state of the fibrous part of cdECM samples. By the identified differences, we aim to support researchers in the selection of a suitable ECM‐based biomaterial for their specific application and the interpretation of obtained results.
Open Access
Novel functions of aberrant cyclin D1/CDK4 activity in mantle cell lymphoma and consequences for proteasome inhibitor treatment
(2022) Heine, Simon; Olayioye, Monilola (Prof. Dr.)
Mantle cell lymphoma (MCL) is an aggressive B cell-non-Hodgkin lymphoma with generally poor outcome and only transient responses to conventional chemotherapy. Cells of MCL patients are characterized by an aberrant high cyclin D1-driven cyclin-dependent kinase 4 (CDK4) activity. Recently, the ubiquitin proteasome system (UPS) inhibitor bortezomib has been approved for the treatment of relapsed/refractory MCL and has shown promising results in first-line treatment of MCL patients. However, little is known about how the aberrant cyclin D1-driven CDK4 activity does affect the treatment efficacy of UPS inhibitors in MCL. The present work aimed to identify novel functions for cyclin D1/CDK4 activity in MCL that regulate the efficacy of proteasome inhibitor treatment. In this study, the efficacy of proteasome inhibitor treatment was found to depend on the aberrant cyclin D1/CDK4 activity in MCL. Inhibition of cyclin D1/CDK4 activity with the CDK4 inhibitor palbociclib antagonized bortezomib induced cell death in MCL cells. Moreover, the antioxidant defense protein sestrin 3 was identified to be strongly regulated by cyclin D1-driven CDK4 activity. Although, bortezomib efficacy was demonstrated to be regulated by reactive oxygen species (ROS) or antioxidants, changes in sestrin 3 expression levels are not responsible for cell death regulation after UPS blockage in MCL. Furthermore, even though targeting cyclin D1/CDK4 activity with palbociclib induces cell cycle arrest, changes in cell cycle distribution after cyclin D1/CDK4 inhibition also do not mediate the antagonizing effect on bortezomib induced cell death. Astonishingly, it could be demonstrated that cyclin D1/CDK4 inhibition antagonizes the bortezomib induced cell death through a reduction of NOXA protein accumulation. It could also be shown that this mechanism is not exclusive for the proteasome inhibitor bortezomib but also applies to other agents that depend on NOXA protein accumulation for efficient cell death induction in MCL cells. Importantly, results of the present study revealed that this regulation of NOXA protein levels by cyclin D1/CDK4 activity is not associated with a reduction of NOXA transcript levels but is mediated by the regulation of NOXA protein stability. This identified novel function of cyclin D1/CDK4 to regulate NOXA protein half-life in the presence of UPS blockage is mediated by the autophagic degradation machinery. This study identified, the regulation of autophagic activity as a novel cell cycle independent function of cyclin D1/CDK4 activity in MCL. In this context, it was demonstrated that inhibition of cyclin D1/CDK4 activity by palbociclib treatment induces autophagic activity in MCL. Cyclin D1/CDK4 and autophagic activity, however, are not linked by the common autophagy regulating pathways, AMP-activated protein kinase (AMPK) or ROS. In addition, genetic or pharmacological inhibition of autophagic activity reverses the palbociclib mediated antagonism on bortezomib induced cell death and NOXA protein accumulation. Remarkably, this study demonstrates that the NOXA protein can be targeted for proteasomal as well as autophagosomal degradation. Targeting NOXA protein for degradation through selective autophagy might be mediated through a LC3-interacting region (LIR) motif that was identified in the amino acid sequence of the NOXA protein. Interestingly, combination of bortezomib with known autophagy inhibitors potentiates cell death induction as well as NOXA protein accumulation compared to bortezomib treatment alone. Furthermore, screening for a highly efficient combinatorial blockade of the UPS and the ALP revealed that the fatty acid synthase (FASN) inhibitor orlistat can be repositioned for autophagy inhibition. Consequently, the combinatorial treatment with bortezomib and orlistat leads to a very efficient NOXA protein induction and caspase dependent cell death in MCL cells. This cell death is again dependent on the aberrant high cyclin D1/CDK4 activity. The expression levels of certain other apoptotic proteins, however, are not affected by the combinatorial treatment. In conclusion, the present study revealed the regulation of autophagic activity as a novel function of cyclin D1/CDK4 activity in MCL. These findings are of utmost importance for the treatment of MCL patients, as combination of proteasome inhibitors with autophagy inhibitors could greatly improve therapy outcomes or overcome bortezomib resistances. In addition to known autophagy inhibitors, treatment options could include conventional drugs that are repurposed for targeting the autophagic degradation machinery. On the other hand, care must be taken when combining proteasome inhibitors with other chemotherapeutics that might impair cyclin D1/CDK4 activity or induce autophagy.