Browsing by Author "Altinoz, Meric A."

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Mechanisms of Colorectal Cancer Prevention by Aspirin-A Literature Review and Perspective on the Role of COX-Dependent and -Independent Pathways
(MDPI, 2020-01-01) Sankaranarayanan, Ranjini; Kumar, D. Ramesh; Altinoz, Meric A.; Bhat, G. Jayarama
Aspirin, synthesized and marketed in 1897 by Bayer, is one of the most widely used drugs in the world. It has a well-recognized role in decreasing inflammation, pain and fever, and in the prevention of thrombotic cardiovascular diseases. Its anti-inflammatory and cardio-protective actions have been well studied and occur through inhibition of cyclooxygenases (COX). Interestingly, a vast amount of epidemiological, preclinical and clinical studies have revealed aspirin as a promising chemopreventive agent, particularly against colorectal cancers (CRC)
Minor Physical Anomalies in Bipolar Disorder
(W B SAUNDERS CO-ELSEVIER INC, 2020-01-01) Ince, Bahri; Altinoz, Meric A.; Ayran, Aylin Can; Cansiz, Alparslan; Altinbas, Kursat; Guloksuz, Sinan; Kurt, Erhan
Objective: High-arched palate is more frequent in schizophrenia and bipolar disorder (BD). Upto 40\% of patients develop schizophrenia in 22q11.2 Deletion Syndrome manifested with cleft lip and palate, which originate from the first pharyngeal arch in embryo. The auricle also originates from the dorsal ends of the first and second pharyngeal arches
Oxamate targeting aggressive cancers with special emphasis to brain tumors
(ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER, 2022-01-01) Altinoz, Meric A.; Ozpinar, Aysel
Cancer is one of the main causes of human mortality and brain tumors, including invasive pituitary adenomas, medulloblastomas and glioblastomas are common brain malignancies with poor prognosis. Therefore, the development of innovative management strategies for refractory cancers and brain tumors is important. In states of mitochondrial dysfunction - commonly encountered in malignant cells - cells mostly shift to anaerobic glycolysis by increasing the expression of LDHA (Lactate Dehydrogenase-A) gene. Oxamate, an isosteric form of pyruvate, blocks LDHA activity by competing with pyruvate. By blocking LDHA, it inhibits protumorigenic cascades and also induces ROS (reactive oxygen species)-induced mitochondrial apoptosis of cancer cells. In preclinical studies, oxamate blocked the growth of invasive pituitary adenomas, medulloblastomas and glioblastomas. Oxamate also increases temozolomide and radiotherapy sensitivity of glioblastomas. Oxamate is highly polar, which may preclude its clinical utilization due to low penetrance through cell membranes. However, this obstacle could be overcome with nanoliposomes. Moreover, different oxamate analogs were developed which inhibit LDHC4, an enzyme also involved in cancer progression and germ cell physiology. Lastly, phenformin, an antidiabetic agent, exerts anticancer effects via complex I inhibition in the mitochondria and leading the overproduction of ROS. Oxamate combination with phenformin reduces the lactic acidosis-causing side effect of phenformin while inducing synergistic anticancer efficacy. In sum, oxamate as a single agent and more efficiently with phenformin has high potential to slow the progression of aggressive cancers with special emphasis to brain tumors.
Potential Neurotoxic Effects of Glioblastoma-Derived Exosomes in Primary Cultures of Cerebellar Neurons via Oxidant Stress and Glutathione Depletion
(MDPI, 2022-01-01) Genc, Sidika; Pennisi, Manuela; Yeni, Yesim; Yildirim, Serkan; Gattuso, Giuseppe; Altinoz, Meric A.; Taghizadehghalehjoughi, Ali; Bolat, Ismail; Tsatsakis, Aristidis; Hacimuftuoglu, Ahmet; Falzone, Luca
High-grade gliomas are the most fatal brain tumors. Grade 4 gliomas are called glioblastoma multiforme (GBM), which are associated with the poorest survival and a 5-year survival rate of less than 4\%. Many patients with GBM developed concomitant cognitive dysfunctions and epilepsy. Although the cognitive decline is well defined in glioblastomas, the neurotoxic factors underlying this pathology are not well understood in GBM patients. In this study, we aimed to investigate whether GBM-derived exosomes play a role in neuronal toxicity. For this purpose, exosomes obtained from T98G and U373 GBM cells were applied to primary neuron culture at different concentrations. Subsequently, MTT, LDH, GSH, TAS, and TOS tests were performed. Both GBM-derived exosomes induced a dose-dependent and statistically significant increase of LDH release in cerebellar neurons. MTT assay revealed as both T98G and U373 GBM-derived exosomes induced dose-dependent neurotoxic effects in cerebellar neurons. To the best of our knowledge, this study is the first study demonstrating the toxic potential of GBM-derived exosomes to primary neurons, which may explain the peritumoral edema and cognitive decline in GBM patients.
Progesterone at high doses reduces the growth of U87 and A172 glioblastoma cells: Proteomic changes regarding metabolism and immunity
(WILEY, 2020-01-01) Altinoz, Meric A.; Ucal, Yasemin; Yilmaz, Muazzez C.; Kiris, Irem; Ozisik, Ozan; Sezerman, Ugur; Ozpinar, Aysel; Elmaci, Ilhan
While pregnancy may accelerate glioblastoma multiforme (GBM) growth, parity and progesterone (P4) containing treatments (ie, hormone replacement therapy) reduce the risk of GBM development. In parallel, low and high doses of P4 exert stimulating and inhibitory actions on GBM growth, respectively. The mechanisms behind the high-dose P4-suppression of GBM growth is unknown. In the present study, we assessed the changes in growth and proteomic profiles when high-dose P4 (100 and 300 mu M) was administered in human U87 and A172 GBM cell lines. The xCELLigence system was used to examine cell growth when different concentrations of P4 (20, 50, 100, and 300 mu M) was administered. The protein profiles were determined by two-dimensional gel electrophoresis in both cell lines when 100 and 300 mu M P4 were administered. Finally, the pathways enriched by the differentially expressed proteins were assessed using bioinformatic tools. Increasing doses of P4 blocked the growth of both GBM cells. We identified 26 and 51 differentially expressed proteins (fc > 2) in A172 and U87 cell lines treated with P4, respectively. Only the pro-tumorigenic mitochondrial ornithine aminotransferase and anti-apoptotic mitochondrial 60 kDa heat shock protein were downregulated in A172 cell line and U87 cell line when treated with P4, respectively. Detoxification of reactive oxygen species, cellular response to stress, glucose metabolism, and immunity-related proteins were altered in P4-treated GBM cell lines. The paradox on the effect of low and high doses of P4 on GBM growth is gaining attention. The mechanism related to the high dose of P4 on GBM growth can be explained by the alterations in detoxification mechanisms, stress, and immune response and glucose metabolism. P4 suppresses GBM growth and as it is nontoxic in comparison to classical chemotherapeutics, it can be used as a new strategy in GBM treatment in the future.
Treatment Strategies for Dopamine Agonist-Resistant and Aggressive Prolactinomas: A Comprehensive Analysis of the Literature
(GEORG THIEME VERLAG KG, 2021-01-01) Sari, Ramazan; Altinoz, Meric A.; Ozlu, Eylem Burcu Kahraman; Sav, Aydin; Danyeli, Ayca Ersen; Baskan, Ozdil; Er, Ozlem; Elmaci, Ilhan
Despite most of the prolactinomas can be treated with endocrine therapy and/or surgery, a significant percentage of these tumors can be resistant to endocrine treatments and/or recur with prominent invasion into the surrounding anatomical structures. Hence, clinical, pathological, and molecular definitions of aggressive prolactinomas are important to guide for classical and novel treatment modalities. In this review, we aimed to define molecular endocrinological features of dopamine agonist-resistant and aggressive prolactinomas for designing future multimodality treatments. Besides surgery, temozolomide chemotherapy and radiotherapy, peptide receptor radionuclide therapy, estrogen pathway modulators, progesterone antagonists or agonists, mTOR/akt inhibitors, pasireotide, gefitinib/lapatinib, everolimus, and metformin are tested in preclinical models, anecdotal cases, and in small case series. Moreover, chorionic gonadotropin, gonadotropin releasing hormone, TGF beta and PRDM2 may seem like possible future targets for managing aggressive prolactinomas. Lastly, we discussed our management of a unique prolactinoma case by asking which tumors' proliferative index (Ki67) increased from 5-6\% to 26\% in two subsequent surgeries performed in a 2-year period, exerted massive invasive growth, and secreted huge levels of prolactin leading up to levels of 1 605 671ng/dl in blood.