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. 2016 Jul 19;7(29):46419-46432.
doi: 10.18632/oncotarget.10139.

Myosin 1e promotes breast cancer malignancy by enhancing tumor cell proliferation and stimulating tumor cell de-differentiation

Jessica L Ouderkirk-Pecone  1 , Gregory J Goreczny  1 , Sharon E Chase  1 , Arthur H Tatum  2 , Christopher E Turner  1 , Mira Krendel  1
Affiliations

Myosin 1e promotes breast cancer malignancy by enhancing tumor cell proliferation and stimulating tumor cell de-differentiation

Jessica L Ouderkirk-Pecone et al. Oncotarget. .

Abstract

Despite advancing therapies, thousands of women die every year of breast cancer. Myosins, actin-dependent molecular motors, are likely to contribute to tumor formation and metastasis via their effects on cell adhesion and migration and may provide promising new targets for cancer therapies. Using the MMTV-PyMT murine model of breast cancer, we identified Myosin 1e (MYO1E) as a novel tumor promoter. Tumor latency in mice lacking MYO1E was significantly increased, and tumors formed in the absence of MYO1E displayed unusual papillary morphology, with well-differentiated layers of epithelial cells covering fibrovascular cores, rather than solid sheets of tumor cells typically observed in this cancer model. These tumors were reminiscent of papillary breast cancer in humans that is typically non-invasive and often cured by tumor excision. MYO1E-null tumors exhibited decreased expression of the markers of cell proliferation, which was recapitulated in primary tumor cells derived from MYO1E-null mice. In agreement with our findings, meta-analysis of patient survival data indicated that MYO1E expression level was associated with reduced recurrence-free survival in basal-like breast cancer. Overall, our data suggests that MYO1E contributes to breast tumor malignancy and regulates the differentiation and proliferation state of breast tumor cells.

Keywords: animal models of cancer; breast cancer; myosin; therapeutic targets; tumor promotion and progression.

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Conflict of interest statement

The authors disclose no potential conflicts of interest.

Figures

Figure 1
Figure 1. MYO1E deletion does not grossly affect mammary gland development
A. Expression of MYO1E in the mouse mammary gland at 10 weeks of age in MYO1E wild type (WT) and MYO1E knockout (KO) mice as determined by Western blotting. Tubulin was used as a loading control. Molecular marker positions are indicated at 150 kDa and 50 kDa. Anti-MYO1E antibody labels a distinct band at 127 kDa in MYO1E WT mammary glands, which is absent in MYO1E KO mammary glands. B. the overall appearance of the mammary ducts in MYO1E WT and KO mice at 10 weeks of age using histological stains (Hematoxylin & Eosin and Masson's Trichrome) appears very similar, each with two distinct cell layers. The arrow labels the outer basal cell layer, while the arrowhead labels the inner luminal cell layer. Scale bar, 20 um. C. localization of basal epithelial cell marker (Cytokeratin 14 (CK14)) and luminal epithelial cell marker (Cytokeratin 8 (CK8)) in mammary glands of 5 week old MYO1E WT and KO mice. DAPI staining is shown in blue. The boxed region in the left most panel indicates the area that is enlarged in the panels on the right. Scale bar, 100 um. D. whole mount staining of MYO1E WT and KO mammary tissue at 5, 7 and 10 weeks of age shows no clear differences in mammary gland development in mice deficient for MYO1E.
Figure 2
Figure 2. PyMT mice deficient in MYO1E exhibit increased tumor latency but faster increase in volume compared to the MYO1E WT PyMT controls
A. Western blot of MYO1E in tumors from 16 week old mice. B. immunofluorescent staining for MYO1E in MYO1E WT tumors. DAPI staining is shown in blue. Scale bar, 100 um. C. tumor latency (in days) in MYO1E WT and KO PyMT mice; error bars indicate SEM. Latency of KO PyMT tumors was substantially increased compared to controls, averaging 74.7 days compared to 55.7 days for WT PyMT tumors (p<0.001). D. tumor number in 10 week old animals, error bars indicate SEM. KO PyMT tumor number was significantly decreased, with an average of 2.6 tumors/mouse compared to 5.9 tumors/mouse in WT PyMT mice (p<0.01). E. primary tumor volume relative to tumor age (time in weeks from tumor detection). KO tumors grew faster than WT tumors, although the difference was not statistically significant. WT PyMT mice had an average volume of 705 mm3 at 9 weeks of tumor age, compared to 1828 mm3 in KO PyMT mice. The error bars represent SEM.
Figure 3
Figure 3. Tumors formed in MYO1E KO PyMT mice display a papillary morphology
A. H&E staining of MYO1E WT and KO tumors at 7, 10 and 16 weeks of age. WT tumors are filled with solid sheets of tumor cells while MYO1E KO tumors contain cystic, papillary regions and small tumor acini. Arrowheads denote papillary areas in MYO1E KO tumors, while arrows label solid tumor acini. Scale bar, 100 um. B. immunofluorescent staining of papillary regions from 10 week old MYO1E KO PyMT mice for luminal epithelial cell marker (CK8) and basal epithelial cell marker (CK14). DAPI staining is shown in blue. Scale bar, 100 um. C. immunofluorescent staining of solid tumor regions in tumors from MYO1E WT and KO PyMT mice at 16 weeks of age for luminal epithelial cell marker (CK8) and basal epithelial cell marker (CK14). DAPI staining is shown in blue. Scale bar, 100 um.
Figure 4
Figure 4. Loss of MYO1E expression delays tumor progression and reduces cell proliferation
A. tumors from 16 week old MYO1E WT PyMT and KO PyMT mice stained with Cyclin D1 antibody and counterstained with hematoxylin at 10x (top) and 40x (bottom) magnification. Arrows indicate areas of peripheral Cyclin D1 enrichment in MYO1E KO tumors. Scale bar, 100 um. B. percentage of Cyclin-D1 positive cells in MYO1E WT and KO tumor acini that were localized to the periphery of the acini. This percentage is calculated relative to the total number of Cyclin D1-positive cells within the acini. For this analysis, three mice per genotype were examined, and 5 acini were analyzed per animal (p<0.05). Statistical analysis was performed on the percentage values from each mouse, rather than each individual acini. The error bar represents the standard deviation from three different mice. C. representative images of Ki-67 staining in tumors from 16 week old MYO1E WT and KO mice, with a hematoxylin counterstain. Scale bar, 100 um. D. percentage of Ki-67-positive cells in MYO1E WT and KO tumors at 16 weeks of age. For this analysis, three mice per genotype were examined, and 5 fields of view were analyzed per animal (p<0.05). The graph represents the average percent of Ki-67-positive cells in three mice, and statistical analysis was performed on the percentage values from each mouse, rather than each individual field of view. The error bar represents the standard deviation from three different mice. E. Western blot analysis of isolated tumor cells from MYO1E WT and KO PyMT mice indicates the presence of MYO1E in WT tumors cells and its absence in the KO tumor cells. F. representative images of Ki-67 staining in tumor cells isolated from MYO1E WT and KO PyMT mice. Ki-67 is shown in red, while DAPI is blue. G. graph showing percent of Ki-67 positive cells in MYO1E WT and KO tumor cells (p<0.001). Analysis was performed as detailed in D.
Figure 5
Figure 5. MYO1E expression correlates with poor breast cancer patient outcome and regulates tumor cell metastasis
A, B. Kaplan-Meier survival curves showing probability of relapse-free survival in patients with basal-like (A) or grade 1 (B) breast cancer with the low or high levels of MYO1E expression. The optimal expression threshold was autoselected by K-M plotter software. Hazard ratio (with confidence intervals) and logrank probability values are included on each graph. C. representative images of lungs dissected from MYO1E WT PyMT and KO PyMT mice at 16 weeks of age. A metastasis is labeled by an arrow. Scale bar, 100 um. D. number of mice showing lung metastasis in MYO1E WT PyMT and KO PyMT animals at 16 weeks of age (WT n=7, KO n=7).
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References

    1. ACS . Cancer Facts & Figures 2015. Atlanta: American Cancer Society; 2015.
    1. Wagner KU, McAllister K, Ward T, Davis B, Wiseman R, Hennighausen L. Spatial and temporal expression of the Cre gene under the control of the MMTV-LTR in different lines of transgenic mice. Transgenic research. 2001;10:545–553. - PubMed
    1. Guy CT, Cardiff RD, Muller WJ. Induction of mammary tumors by expression of polyomavirus middle T oncogene: a transgenic mouse model for metastatic disease. Molecular and cellular biology. 1992;12:954–961. - PMC - PubMed
    1. Smith BA, Shelton DN, Kieffer C, Milash B, Usary J, Perou CM, Bernard PS, Welm BE. Targeting the PyMT Oncogene to Diverse Mammary Cell Populations Enhances Tumor Heterogeneity and Generates Rare Breast Cancer Subtypes. Genes cancer. 2012;3:550–563. doi: 10.1177/1947601913475359. - DOI - PMC - PubMed
    1. Courtneidge SA, Smith AE. Polyoma virus transforming protein associates with the product of the c-src cellular gene. Nature. 1983;303:435–439. - PubMed

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