الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Cancer resistance to chemotherapy is a clinical dilemma that eventually
leads to increased mortality. It has been widely accepted that breast cancer
(BC) is heterogenous in nature holding within a rare subpopulation termed
cancer stem cells (CSCs). These CSCs have a pivotal role in tumor initiation,
development of chemo and radiotherapy resistance, and subsequent disease
relapse. Therefore, recent treatment strategies aim to mainly target CSCs
rather than the bulk tumor cells. Conventional chemotherapeutics are disabled
to eliminate CSCs, not to mention, their CSCs enriching effect which mediate
the associated treatment failure and disease recurrence. Lately, NSAIDs have
shown a promise to combat CSCs in multiple cancer types. Thus, we addressed
for the first time the effect of indomethacin on cisplatin (CDDP)-resistant
murine BC along with the relevant mechanisms. Ehrlich ascites carcinoma
(EAC) cells were made resistant by exposure to CDDP and the surviving cells
were then analyzed by flow cytometry for the breast CSCs (BCSCs) markers
(CD44+CD24-). CDDP heavily enriched the CSCs population and the
surviving cells after CDDP treatment were considered as CDDP-resistant.
This resistant (or CSCs-enriched) population was subsequently injected into
female mice (250×105 cells per mouse). Meanwhile, an equivalent number of
the parent EAC cells were injected into another group of mice to compare the
tumorigenicity of the two cell phenotypes and whether there would have been
a differential response to treatment. After induction of tumors, mice bearing
either parental solid Ehrlich carcinoma (SEC) or CSCs-enriched population
were treated with CDDP, indomethacin, co-treatment with both drugs, or left
untreated. The tumor volumes were routinely measured and the tumor growth
rates were calculated thereof. Upon termination of the treatment period, the
tumors were excised and analyzed by quantitative reverse transcription PCR
(qRT-PCR) for the relative expression of drug resistance-mediating
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microRNAs (miRNAs) such as miR-7, miR-145, miR-21, and miR-22. The
tumors were also subjected to histopathological examination. Additionally,
blood samples were collected from the CSCs-enriched population bearing
mice to measure the perturbation in the percentage of CSCs in response to
CDDP, indomethacin, and the combination. The frequency of the immune
cells’ markers (CD4, CD62L, and CD117) were examined as well. Although
CDDP has dramatically decreased the tumor sizes in the parent SEC bearing
mice, it is effect was not that significant in the CDDP-resistant tumors. In
contrast, indomethacin drastically diminished the tumorigenicity of CDDPresistant
cells along with enhancing its chemo-sensitivity to CDDP despite its
antitumor effect was not significant in the sensitive tumors. This points out to
the selective CSCs-targeting of indomethacin. These effects were correlated
with its suppressing ability of the percentage of CD44+CD24- cells unlike
CDDP which further enriched the BCSCs. Moreover, indomethacin
downregulated the expression of the oncogenes; miR-21 and miR-22 while
enhanced the tumor suppressor; miR-7 expression. CDDP, on the other hand,
further downregulated the tumor suppressors; miR-7 and miR-145 whereas it
upregulated miR-21. Besides, indomethacin expanded the pool of immune
cells that impart antitumor response. Conversely, CDDP was associated with
deficiency in circulating CD4+, CD62L+, and CD117+ cells. Overall, it seems
that indomethacin combat BCSCs through manipulating the expression
patterns of drug-resistance related miRNAs as well as triggering antitumor
immune response. As such, indomethacin through targeting CSCs may confer
better outcome than conventional chemotherapeutics in treatment of resistant
or recurrent BC.