Thesis (Ph.D.) - Cairo University - Faculty of Medicine - Department of Medical Biochemistry

Background& Aim:Colorectal cancer (CRC) is one of the most common and lethal malignancies with poor prognosis in the majorityof cases. Cancer stem cells (CSCs) are type of cells within the tumor microenvironment that play a role in cancer initiation, progression, and recurrence.Thus, it is crucial to developnew therapeutic approachfor CRC treatmenteffective against CSCs.Granulocyte colony stimulating factor (G-CSF) is a hematopoietic growth factor currently used to treat neutropenia in cancer patients. Somestudies reported direct antitumor effect of G-CSF.The aim of our study is to investigate the effect of G-CSF on CRC cells' proliferation,the expression of CRC exosomal micro ribonucleic acid (miRNA), long non coding RNA (LncRNA) responsible for cancer progression, and to evaluate the capability of G-CSF to attenuate the potentiality of CRC exosomes to induce bone marrow derived mesenchymal stem cells (BM-MSCs)transdifferentiation intoCSCs. Materials & methods:CRC cells were cultured and divided into 2 groups. 1st group: untreated cancer cells; 2nd group:CRC cells treated with G-CSF. Cell proliferation of both groups was assessed by methyl thiazol tetrazolium (MTT) assay.Exosomes from both groups were isolatedfor molecular studies [Evaluation of the expression levels of exosomal miRNA-21, miRNA-215, LncRNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT-1), programmed cell death 4 (PDCD4), thymidylate synthase (TYMS), dihydrofolate reductase (DHFR), and beta catenin (Ý-catenin) by quantitative real time polymerase chain reaction (qRT PCR)], and then co-cultered with BM-MSCs.The transdifferentiation of BM-MSCs into CSCs under the effect of co-cultured exosomes was assessed by transmission electron microscopy (TEM), flow cytometry, and molecular studies. Results:Molecular studies revealed that:there was a significant decrease in the expression levels of miRNA-21, LncRNA MALAT-1, Ý-catenin, TYMS and DHFR, while there was a significant increase in the expression levels of miRNA-215 and PDCD4 in exosomes derived from CRC cells pre-treated with G-CSF compared to exosomes derived from untreated CRC cells

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