Johnson, Aaron Randall
(2023)
Myoglobin Attenuates Breast Cancer Cell Proliferation and Migration.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
The monomeric heme protein myoglobin (Mb), traditionally thought to be expressed exclusively in cardiac and skeletal muscle, is now known to be expressed in approximately 40% of breast tumors. While Mb expression is associated with better patient prognosis, the molecular mechanisms by which Mb limits cancer cell proliferation and migration are unclear. In muscle, the predominant function of Mb is oxygen storage and delivery; however, prior studies demonstrate that the low levels of Mb expressed in cancer cells preclude this. Recent studies have determined that Mb binds to fatty acids, generates oxidants, and scavenges nitric oxide (NO•) in other tissues, but these functions have not been examined in breast cancer cells. We hypothesized that Mb decreases proliferation and migration through fatty acid binding, oxidant generation, and NO• scavenging in cancer cells. Because fatty acid oxidation (FAO) is often upregulated in cancer cells and drives cell migration, we tested whether Mb-mediated fatty acid binding modulates FAO to decrease breast cancer cell migration. We demonstrate that the stable expression of human Mb in MDA-MB-231 breast cancer cells decreases cell migration, mitochondrial respiration, and FAO. We performed site-directed mutagenesis to disrupt fatty acid binding (but not heme coordination) to Mb (Mb K46M) or heme incorporation alone was disrupted (Apo-Mb). Only Apo-Mb restored respiration and cell migration to that of the control cells, suggesting that Mb modulates respiration and migration via a heme-dependent mechanism rather than through fatty acid binding. Mb heme iron generates oxidants, which modulate the actin-binding proteins profilin and cofilin and
v
scavenging of oxidants restores migration. These data demonstrate that Mb decreases breast cancer FAO and migration, and this effect is due to Mb-dependent oxidant production rather than fatty acid binding. NO•, produced by nitric oxide synthases (NOS), promotes cancer cell proliferation. We report that the expression of Mb scavenges NO• and limits NOS activity to attenuate NO•-dependent proliferation in breast cancer cells. Collectively, the data presented herein demonstrate that Mb-dependent oxidant production and NO• scavenging contribute to Mb-mediated attenuation of cancer cell proliferation and migration. These results will be discussed in the context of breast cancer pathogenesis.
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| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
| Creators | Email | Pitt Username | ORCID  |
|---|
| Johnson, Aaron Randall | arj61@pitt.edu | arj61 | |
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| ETD Committee: |
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| Date: |
29 September 2023 |
| Date Type: |
Publication |
| Defense Date: |
12 April 2023 |
| Approval Date: |
29 September 2023 |
| Submission Date: |
26 April 2023 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
136 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
School of Medicine > Pharmacology and Chemical Biology |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Mb, reactive oxygen species, ROS, fatty acid oxidation, FAO, fatty acid binding, nitric oxide, heme |
| Date Deposited: |
29 Sep 2023 19:21 |
| Last Modified: |
29 Sep 2023 19:21 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/44731 |
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