Journal: Cancers
Article Title: Truncated DAPK Variants Restore Tumor Suppressor Activity and Synergize with Standard Therapies in High-Grade Serous Ovarian Cancer
doi: 10.3390/cancers17121910
Figure Lengend Snippet: Effects of DAPK1 reactivation on the survival of primary HGSOC cells. ( A ) Patient-derived organoids were transfected with 2 μg of ΔDAPK1-IVT mRNA. On day 2, following transfection with 2 μg of ΔDAPK1-IVT mRNA, HGSOC organoids are depicted in representative photos ( left panels ), and a live/dead assay was performed. Flag and β-actin antibodies were used to perform WB on the lysates of HGSOC organoids mock or transfected with ΔDAPK1-IVT mRNA ( lower left panel ). The Caspase-Glo 3/7 assay was used to analyze mock- or ΔDAPK1-IVT mRNA-transfected HGSOC organoids ( right panel ; n = 3). * p < 0.05; unpaired, two-tailed Student’s t -test. ImageJ 1.0 was used to calculate the size of the organoids ( middle panel ; n = 20). ** unpaired, two-tailed Student’s t -test; p < 0.01. ( B ) Targeted reactivation of DAPK1 in ovarian cancer cells and resulting changes in cellular signaling. Ovarian cancer lacking DAPK1 exhibits a reduced expression of p14ARF, enabling MDM2 to stably bind to p53, resulting in its ubiquitination and degradation. This degradation impairs the transcription of p53-dependent apoptotic effectors and cell cycle regulators, promoting cancer cell proliferation and survival. In contrast, the reactivation of DAPK1 using an IVT-mRNA triggers multiple pathways that stabilize and activate p53, promoting cell cycle arrest and triggering cell death through the p53-dependent transcription of apoptosis and cell cycle effectors. Furthermore, active DAPK1 promotes Caspase-2 activation, which targets MDM2 for cleavage, thus preventing p53 degradation. Additionally, DAPK1 phosphorylates p53 at S20, further enhancing its activity. Reactivated DAPK1 also indirectly increases p14ARF expression, stabilizing p53 and facilitating the transcriptional activation of apoptosis and cell cycle regulatory genes. Finally, DAPK1 promotes the conversion of LC3A/B-I to LC3A/B-II, and both processes are crucial in inducing autophagy. Hence, the vector-based and IVT-mRNA-dependent reactivation of DAPK1 demonstrates a dual role in promoting p53 stability and autophagy, emphasizing its therapeutic potential in targeting ovarian cancer.
Article Snippet: Antibodies were used at the following concentrations: DAPK1 (ab109382) (1:1000; Abcam, Cambridge, United Kingdom), mouse monoclonal PLK1 (F-8:sc-17783) (1:1000; Santa Cruz, Biotechnology Heidelberg, Germany), p53 (sc-126) (1:1000; Santa Cruz), MDM2 (sc-965) (1:1000; Santa Cruz), β-Actin (AC-15:A1978) (1:200.000; Sigma-Aldrich, Taufkirchen, Germany), Flag (M2:A8592) (1:1000; Sigma-Aldrich), p16 (#18769) (1:1000; Cell Signaling, Danvers, MA, USA), Noxa (#14766) (1:1000; Cell Signaling), p14ARF (#74560) (1:1000; Cell Signaling), Caspase-2 (#2224) (1:1000; Cell Signaling, Danvers, MA, USA), LC3A/B (#12741) (1:1000; Cell Signaling), p53-pS20 (#9287) (1:1000; Cell Signaling, Danvers, MA, USA), p21 (#2947) (1:1000; Cell Signaling), PARP (#9542) (1:1000; Cell Signaling, Danvers, MA, USA), Puma (#98672) (1:1000; Cell Signaling, Danvers, MA, USA), Bax (AF820) (1:1000; R&D systems, MN, USA), and HRP-conjugated secondary antibodies (1:5000; GE Healthcare and Jackson Laboratory, Bar Harbor, ME, USA).
Techniques: Derivative Assay, Transfection, Live Dead Assay, Caspase-Glo Assay, Two Tailed Test, Expressing, Stable Transfection, Ubiquitin Proteomics, Activation Assay, Activity Assay, Plasmid Preparation