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Transformation of enriched mammary cell populations with polyomavirus middle T antigen influences tumor subtype and metastatic potential.

Drobysheva D, Smith BA, McDowell M, Guillen KP, Ekiz HA, Welm BE - Breast Cancer Res. (2015)

Bottom Line: Breast cancer exhibits significant molecular, histological, and pathological diversity.In the present study, we assessed the molecular, histological, and metastatic outcomes in distinct mammary cell populations transformed with the PyMT gene.The data demonstrate that luminal CD133+ cells give rise to less metastatic tumors, luminal CD133- cells preferentially establish basal tumors, and the cell of origin for squamous metaplasia likely resides in the basal and stem cell populations.

View Article: PubMed Central - PubMed

Affiliation: Department of Oncological Sciences, University of Utah, 315 South 1400 East, Salt Lake City, UT, 84112, USA. daria.drobysheva@hci.utah.edu.

ABSTRACT

Introduction: Breast cancer exhibits significant molecular, histological, and pathological diversity. Factors that impact this heterogeneity are poorly understood; however, transformation of distinct normal cell populations of the breast may generate different tumor phenotypes. Our previous study demonstrated that the polyomavirus middle T antigen (PyMT) oncogene can establish diverse tumor subtypes when broadly expressed within mouse mammary epithelial cells. In the present study, we assessed the molecular, histological, and metastatic outcomes in distinct mammary cell populations transformed with the PyMT gene.

Methods: Isolated mouse mammary epithelial cells were transduced with a lentivirus encoding PyMT during an overnight infection and then sorted into hormone receptor-positive luminal (CD133+), hormone receptor-negative luminal (CD133-), basal, and stem cell populations using the cell surface markers CD24, CD49f, and CD133. Each population was subsequently transplanted into syngeneic cleared mouse mammary fat pads to generate tumors. Tumors were classified by histology, estrogen receptor status, molecular subtype, and metastatic potential to investigate whether transformation of different enriched populations affects tumor phenotype.

Results: Although enriched mammary epithelial cell populations showed no difference in either the ability to form tumors or tumor latency, differences in prevalence of solid adenocarcinomas and squamous, papillary, and sebaceous-like tumors were observed. In particular, squamous metaplasia was observed more frequently in tumors derived from basal and stem cells than in luminal cells. Interestingly, both molecularly basal and luminal tumors developed from luminal CD133+, basal, and stem cell populations; however, luminal CD133- cells gave rise exclusively to molecularly basal tumors. Tumors arising from the luminal CD133-, basal, and stem cell populations were highly metastatic; however, luminal CD133+ cells generated tumors that were significantly less metastatic, possibly due to an inability of these tumor cells to escape the primary tumor site.

Conclusions: Expression of PyMT within different mammary cell populations influences tumor histology, molecular subtype, and metastatic potential. The data demonstrate that luminal CD133+ cells give rise to less metastatic tumors, luminal CD133- cells preferentially establish basal tumors, and the cell of origin for squamous metaplasia likely resides in the basal and stem cell populations.

No MeSH data available.


Related in: MedlinePlus

Tumor microarray gene expression profiling. Tumors were analyzed by microarray gene expression profiling and hierarchically clustered with mouse mammary tumor models using an intrinsic gene set identified by Herschkowitz et al. [7]. Vertical lines indicate individual tumors. Each enriched mammary epithelial cell population is indicated by a different color: green = luminal CD133+; blue = luminal CD133−; red = basal; black = stem cells. Mouse mammary tumor models that generate molecularly luminal tumors are shown in dark blue, and those predominantly within the basal subgroup are displayed in dark red. Normal mouse mammary tissue is represented in brown (n = number of tumors). DMBA 7,12-dimethylbenz[a]anthracene, MMTV mouse mammary tumor virus, PyMT polyomavirus middle T antigen
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Fig3: Tumor microarray gene expression profiling. Tumors were analyzed by microarray gene expression profiling and hierarchically clustered with mouse mammary tumor models using an intrinsic gene set identified by Herschkowitz et al. [7]. Vertical lines indicate individual tumors. Each enriched mammary epithelial cell population is indicated by a different color: green = luminal CD133+; blue = luminal CD133−; red = basal; black = stem cells. Mouse mammary tumor models that generate molecularly luminal tumors are shown in dark blue, and those predominantly within the basal subgroup are displayed in dark red. Normal mouse mammary tissue is represented in brown (n = number of tumors). DMBA 7,12-dimethylbenz[a]anthracene, MMTV mouse mammary tumor virus, PyMT polyomavirus middle T antigen

Mentions: We next tested whether MEC populations influenced the molecular classification of the tumors they generate. Tumors derived from each MEC population were classified by hierarchical analysis of microarray gene expression data. This classification method has previously been used to cluster tumors from a variety of mouse models into basal and luminal subgroups [7]. We analyzed between 6 and 11 tumors generated from each enriched MEC population. An intrinsic 669-gene set consisting of genes differentially expressed in mouse tumors representing basal and luminal subgroups was used to determine the molecular classification [7], and gene set expression data were hierarchically clustered with 12 mouse models of breast cancer. On the basis of this analysis, we found that luminal CD133+, basal cell, and stem cell enriched MECs were able to give rise to tumors of both basal and luminal subgroups (Fig. 3), with no correlation to tumor histology or ESR1 status (data not shown). However, protein analysis of AKT, SRC, and ERK did reveal a difference in AKT phosphorylation in the basal subgroup (Additional file 5, panel b). Interestingly, the luminal CD133− population, which is enriched in luminal progenitors [34], exclusively established tumors within the basal subgroup. To determine the significance of this observation, we compared the distribution of basal and luminal subgroups generated from each cell population with the distribution we observed when unsorted MECs were transduced with the EF1α-PyMT-ZsGreen lentivirus [8]. Compared with unsorted MECs, the basal-restricted distribution of tumors derived from luminal CD133− cells was statistically significant (p = 0.017) (Additional file 6: Table S1). In contrast, all other cell populations generated tumors of both basal and luminal subgroups at a frequency similar to that of unsorted MECs. These data demonstrate that the stem, basal, and luminal CD133+ MEC populations can establish tumors that classify within either molecular subgroup, whereas CD133− luminal cells preferentially establish tumors of the basal subgroup.Fig. 3


Transformation of enriched mammary cell populations with polyomavirus middle T antigen influences tumor subtype and metastatic potential.

Drobysheva D, Smith BA, McDowell M, Guillen KP, Ekiz HA, Welm BE - Breast Cancer Res. (2015)

Tumor microarray gene expression profiling. Tumors were analyzed by microarray gene expression profiling and hierarchically clustered with mouse mammary tumor models using an intrinsic gene set identified by Herschkowitz et al. [7]. Vertical lines indicate individual tumors. Each enriched mammary epithelial cell population is indicated by a different color: green = luminal CD133+; blue = luminal CD133−; red = basal; black = stem cells. Mouse mammary tumor models that generate molecularly luminal tumors are shown in dark blue, and those predominantly within the basal subgroup are displayed in dark red. Normal mouse mammary tissue is represented in brown (n = number of tumors). DMBA 7,12-dimethylbenz[a]anthracene, MMTV mouse mammary tumor virus, PyMT polyomavirus middle T antigen
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4589945&req=5

Fig3: Tumor microarray gene expression profiling. Tumors were analyzed by microarray gene expression profiling and hierarchically clustered with mouse mammary tumor models using an intrinsic gene set identified by Herschkowitz et al. [7]. Vertical lines indicate individual tumors. Each enriched mammary epithelial cell population is indicated by a different color: green = luminal CD133+; blue = luminal CD133−; red = basal; black = stem cells. Mouse mammary tumor models that generate molecularly luminal tumors are shown in dark blue, and those predominantly within the basal subgroup are displayed in dark red. Normal mouse mammary tissue is represented in brown (n = number of tumors). DMBA 7,12-dimethylbenz[a]anthracene, MMTV mouse mammary tumor virus, PyMT polyomavirus middle T antigen
Mentions: We next tested whether MEC populations influenced the molecular classification of the tumors they generate. Tumors derived from each MEC population were classified by hierarchical analysis of microarray gene expression data. This classification method has previously been used to cluster tumors from a variety of mouse models into basal and luminal subgroups [7]. We analyzed between 6 and 11 tumors generated from each enriched MEC population. An intrinsic 669-gene set consisting of genes differentially expressed in mouse tumors representing basal and luminal subgroups was used to determine the molecular classification [7], and gene set expression data were hierarchically clustered with 12 mouse models of breast cancer. On the basis of this analysis, we found that luminal CD133+, basal cell, and stem cell enriched MECs were able to give rise to tumors of both basal and luminal subgroups (Fig. 3), with no correlation to tumor histology or ESR1 status (data not shown). However, protein analysis of AKT, SRC, and ERK did reveal a difference in AKT phosphorylation in the basal subgroup (Additional file 5, panel b). Interestingly, the luminal CD133− population, which is enriched in luminal progenitors [34], exclusively established tumors within the basal subgroup. To determine the significance of this observation, we compared the distribution of basal and luminal subgroups generated from each cell population with the distribution we observed when unsorted MECs were transduced with the EF1α-PyMT-ZsGreen lentivirus [8]. Compared with unsorted MECs, the basal-restricted distribution of tumors derived from luminal CD133− cells was statistically significant (p = 0.017) (Additional file 6: Table S1). In contrast, all other cell populations generated tumors of both basal and luminal subgroups at a frequency similar to that of unsorted MECs. These data demonstrate that the stem, basal, and luminal CD133+ MEC populations can establish tumors that classify within either molecular subgroup, whereas CD133− luminal cells preferentially establish tumors of the basal subgroup.Fig. 3

Bottom Line: Breast cancer exhibits significant molecular, histological, and pathological diversity.In the present study, we assessed the molecular, histological, and metastatic outcomes in distinct mammary cell populations transformed with the PyMT gene.The data demonstrate that luminal CD133+ cells give rise to less metastatic tumors, luminal CD133- cells preferentially establish basal tumors, and the cell of origin for squamous metaplasia likely resides in the basal and stem cell populations.

View Article: PubMed Central - PubMed

Affiliation: Department of Oncological Sciences, University of Utah, 315 South 1400 East, Salt Lake City, UT, 84112, USA. daria.drobysheva@hci.utah.edu.

ABSTRACT

Introduction: Breast cancer exhibits significant molecular, histological, and pathological diversity. Factors that impact this heterogeneity are poorly understood; however, transformation of distinct normal cell populations of the breast may generate different tumor phenotypes. Our previous study demonstrated that the polyomavirus middle T antigen (PyMT) oncogene can establish diverse tumor subtypes when broadly expressed within mouse mammary epithelial cells. In the present study, we assessed the molecular, histological, and metastatic outcomes in distinct mammary cell populations transformed with the PyMT gene.

Methods: Isolated mouse mammary epithelial cells were transduced with a lentivirus encoding PyMT during an overnight infection and then sorted into hormone receptor-positive luminal (CD133+), hormone receptor-negative luminal (CD133-), basal, and stem cell populations using the cell surface markers CD24, CD49f, and CD133. Each population was subsequently transplanted into syngeneic cleared mouse mammary fat pads to generate tumors. Tumors were classified by histology, estrogen receptor status, molecular subtype, and metastatic potential to investigate whether transformation of different enriched populations affects tumor phenotype.

Results: Although enriched mammary epithelial cell populations showed no difference in either the ability to form tumors or tumor latency, differences in prevalence of solid adenocarcinomas and squamous, papillary, and sebaceous-like tumors were observed. In particular, squamous metaplasia was observed more frequently in tumors derived from basal and stem cells than in luminal cells. Interestingly, both molecularly basal and luminal tumors developed from luminal CD133+, basal, and stem cell populations; however, luminal CD133- cells gave rise exclusively to molecularly basal tumors. Tumors arising from the luminal CD133-, basal, and stem cell populations were highly metastatic; however, luminal CD133+ cells generated tumors that were significantly less metastatic, possibly due to an inability of these tumor cells to escape the primary tumor site.

Conclusions: Expression of PyMT within different mammary cell populations influences tumor histology, molecular subtype, and metastatic potential. The data demonstrate that luminal CD133+ cells give rise to less metastatic tumors, luminal CD133- cells preferentially establish basal tumors, and the cell of origin for squamous metaplasia likely resides in the basal and stem cell populations.

No MeSH data available.


Related in: MedlinePlus