Browsing by Author "Temel, Sehime Gulsun"

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Biphasic ROS production, p53 and BIK dictate the mode of cell death in response to DNA damage in colon cancer cells
(2017) Kutuk, Ozgur; Aytan, Nurgul; Karakas, Bahriye; Kurt, Asli Giray; Acikbas, Ufuk; Temel, Sehime Gulsun; Basaga, Huveyda; 0000-0001-9854-7220; 28796811; AAH-1671-2019
Necrosis, apoptosis and autophagic cell death are the main cell death pathways in multicellular organisms, all with distinct and overlapping cellular and biochemical features. DNA damage may trigger different types of cell death in cancer cells but the molecular events governing the mode of cell death remain elusive. Here we showed that increased BH3-only protein BIK levels promoted cisplatin-and UV-induced mitochondrial apoptosis and biphasic ROS production in HCT-116 wild-type cells. Nonetheless, early single peak of ROS formation along with lysosomal membrane permeabilization and cathepsin activation regulated cisplatin-and UV-induced necrosis in p53-null HCT-116 cells. Of note, necrotic cell death in p53-null HCT-116 cells did not depend on BIK, mitochondrial outer membrane permeabilization or caspase activation. These data demonstrate how cancer cells with different p53 background respond to DNA-damaging agents by integrating distinct cell signaling pathways dictating the mode of cell death.
Consistency Of Variant Interpretations Among Bioinformaticians And Clinical Geneticists In Hereditary Cancer Panels
(2022) Agaoglu, Nihat Bugra; Unal, Busra; Dogan, Ozlem Akgun; Kanev, Martin Orlinov; Zolfagharian, Payam; Sag, Sebnem Ozemri; Temel, Sehime Gulsun; Doganay, Levent; https://orcid.org/0000-0002-9802-0880; 35132179
Next-generation sequencing (NGS) is used increasingly in hereditary cancer patients' (HCP) management. While enabling evaluation of multiple genes simultaneously, the technology brings to light the dilemma of variant interpretation. Here, we aimed to reveal the underlying reasons for the discrepancy in the evidence titles used during variant classification according to ACMG guidelines by two different bioinformatic specialists (BIs) and two different clinical geneticists (CGs). We evaluated final reports of 1920 cancer patients and 189 different variants from 285 HCP were enrolled to the study. A total of 173 of these variants were classified as pathogenic (n = 132) and likely pathogenic (n = 41) by the BI and an additional 16 variants, that were classified as VUS by at least one interpreter and their classification would change the clinical management, were compared for their evidence titles between different specialists. The attributed evidence titles and the final classification of the variants among BIs and CGs were compared. The discrepancy between P/LP final reports was 22.5%. The discordance between CGs was 30% whereas the discordance between two BIs was almost 75%. The use of PVS1, PS3, PP3, PP5, PM1, PM2, BP1, BP4 criteria markedly varied from one expert to another. This difference was particularly noticeable in PP3, PP5, and PM1 evidence and mostly in the variants affecting splice sites like BRCA1(NM_007294.4) c.4096 + 1 G > A and CHEK2(NM_007194.4) c.592 + 3 A > T. With recent advancements in precision medicine, the importance of variant interpretations is emerging. Our study shows that variant interpretation is subjective process that is in need of concrete definitions for accurate and standard interpretation.
A novel homozygous nonsense mutation in CAST associated with PLACK syndrome
(2019) Temel, Sehime Gulsun; Karakas, B.; Seker, U.; Turkgenc, B.; Zorlu, O.; Saricaoglu, H.; Ogur, C.; Kutuk, O.; Kelsell, D. P.; Yakicier, M. C.; 0000-0001-9854-7220; 31392520; AAH-1671-2019
Peeling skin syndrome is a heterogeneous group of rare disorders. Peeling skin, leukonychia, acral punctate keratoses, cheilitis and knuckle pads (PLACK syndrome, OMIM616295) is a newly described form of PSS with an autosomal recessive mode of inheritance. We report a 5.5-year-old boy with features of PLACK syndrome. Additionally, he had mild cerebral atrophy and mild muscle involvements. Whole exome sequencing was performed in genomic DNA of this individual and subsequent analysis revealed a homozygous c.544G > T (p.Glu182*) nonsense mutation in the CAST gene encoding calpastatin. Sanger sequencing confirmed this variant and demonstrated that his affected aunt was also homozygous. Real-time qRT-PCR and immunoblot analysis showed reduced calpastatin expression in skin fibroblasts derived from both affected individuals compared to heterozygous family members. In vitro calpastatin activity assays also showed decreased activity in affected individuals. This study further supports a key role for calpastatin in the tight regulation of proteolytic pathways within the skin.
RAB25 confers resistance to chemotherapy by altering mitochondrial apoptosis signaling in ovarian cancer cells
(2020) Temel, Sehime Gulsun; Giray, Asli; Karaka, Bahriye; Gul, Ozgur; Kozanoglu, Ilknur; Celik, Husnu; Basaga, Huveyda; Acikbas, Ufuk; Sucularli, Ceren; Oztop, Sidika; Aka, Yeliz; Kutuk, Ozgur; 0000-0001-5653-6080; 0000-0001-9854-7220; 0000-0002-5268-1210; 32901335; AAJ-7911-2020; AAH-1671-2019; AAE-1241-2021
Ovarian cancer remains one of the most frequent causes of cancer-related death in women. Many patients with ovarian cancer suffer from de novo or acquired resistance to chemotherapy. Here, we report that RAB25 suppresses chemotherapy-induced mitochondrial apoptosis signaling in ovarian cancer cell lines and primary ovarian cancer cells. RAB25 blocks chemotherapy-induced apoptosis upstream of mitochondrial outer membrane permeabilization by either increasing antiapoptotic BCL-2 proteins or decreasing proapoptotic BCL-2 proteins. In particular, BAX expression negatively correlates with RAB25 expression in ovarian cancer cells. BH3 profiling assays corroborated that RAB25 decreases mitochondrial cell death priming. Suppressing RAB25 by means of RNAi or RFP14 inhibitory hydrocarbon-stapled peptide sensitizes ovarian cancer cells to chemotherapy as well as RAB25-mediated proliferation, invasion and migration. Our data suggest that RAB25 is a potential therapeutic target for ovarian cancer.