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Loss of the p53/p63 regulated desmosomal protein Perp promotes tumorigenesis.

Beaudry VG, Jiang D, Dusek RL, Park EJ, Knezevich S, Ridd K, Vogel H, Bastian BC, Attardi LD - PLoS Genet. (2010)

Bottom Line: Tumor development is associated with inactivation of both of Perp's known functions, in apoptosis and cell-cell adhesion.Interestingly, Perp-deficient tumors exhibit widespread downregulation of desmosomal constituents while adherens junctions remain intact, suggesting that desmosome loss is a specific event important for tumorigenesis rather than a reflection of a general change in differentiation status.Using gene expression profiling, we show further that Perp loss induces a set of inflammation-related genes that could stimulate tumorigenesis.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Division of Radiation and Cancer Biology, Stanford University School of Medicine, Stanford, California, USA.

ABSTRACT
Dysregulated cell-cell adhesion plays a critical role in epithelial cancer development. Studies of human and mouse cancers have indicated that loss of adhesion complexes known as adherens junctions contributes to tumor progression and metastasis. In contrast, little is known regarding the role of the related cell-cell adhesion junction, the desmosome, during cancer development. Studies analyzing expression of desmosome components during human cancer progression have yielded conflicting results, and therefore genetic studies using knockout mice to examine the functional consequence of desmosome inactivation for tumorigenesis are essential for elucidating the role of desmosomes in cancer development. Here, we investigate the consequences of desmosome loss for carcinogenesis by analyzing conditional knockout mice lacking Perp, a p53/p63 regulated gene that encodes an important component of desmosomes. Analysis of Perp-deficient mice in a UVB-induced squamous cell skin carcinoma model reveals that Perp ablation promotes both tumor initiation and progression. Tumor development is associated with inactivation of both of Perp's known functions, in apoptosis and cell-cell adhesion. Interestingly, Perp-deficient tumors exhibit widespread downregulation of desmosomal constituents while adherens junctions remain intact, suggesting that desmosome loss is a specific event important for tumorigenesis rather than a reflection of a general change in differentiation status. Similarly, human squamous cell carcinomas display loss of PERP expression with retention of adherens junctions components, indicating that this is a relevant stage of human cancer development. Using gene expression profiling, we show further that Perp loss induces a set of inflammation-related genes that could stimulate tumorigenesis. Together, these studies suggest that Perp-deficiency promotes cancer by enhancing cell survival, desmosome loss, and inflammation, and they highlight a fundamental role for Perp and desmosomes in tumor suppression. An understanding of the factors affecting cancer progression is important for ultimately improving the diagnosis, prognostication, and treatment of cancer.

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Perp-deficiency promotes tumorigenesis.A) Perp immunofluorescence images demonstrating the presence of Perp in the epidermis of control mice and the loss of Perp in the epidermis of K14CreER;Perpfl/fl mice. Green signal represents Perp staining, red signal represents staining for the desmosomal protein Desmoplakin (Dp), and blue signal represents DAPI, to mark nuclei. (Upper left) Low magnification images show an overview of the epidermis, and (Upper right) high magnification images show the punctate staining pattern typical of desmosomal proteins. (Lower panel) Punctate desmosomal pattern in the epidermis is comparable to that observed in wild-type mouse keratinocyte monolayers. B) Tumor study design. C) Kaplan-Meier analysis showing tumor latency in UVB-treated control (Perpfl/fl and Perpfl/+) and K14CreER;Perpfl/fl mice. Statistical significance was determined using the Log Rank test (* p = 0.0002). n =  25 for each genotype. D) (Left) Graph depicts the average number of SCCs per UVB-treated mouse +/− STDEV. Statistical analysis was performed using the Student's unpaired t-test (* p =  0.00049). (Right) Representative photographs of tumor burden in control and K14CreER;Perpfl/fl mice, with arrow indicating a tumor. E) Representative Hematoxylin and Eosin (H&E) stained images illustrating the various SCC grades. F) Table indicating the numbers of SCCs of different grades in UVB-treated control and K14CreER;Perpfl/fl mice.
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pgen-1001168-g001: Perp-deficiency promotes tumorigenesis.A) Perp immunofluorescence images demonstrating the presence of Perp in the epidermis of control mice and the loss of Perp in the epidermis of K14CreER;Perpfl/fl mice. Green signal represents Perp staining, red signal represents staining for the desmosomal protein Desmoplakin (Dp), and blue signal represents DAPI, to mark nuclei. (Upper left) Low magnification images show an overview of the epidermis, and (Upper right) high magnification images show the punctate staining pattern typical of desmosomal proteins. (Lower panel) Punctate desmosomal pattern in the epidermis is comparable to that observed in wild-type mouse keratinocyte monolayers. B) Tumor study design. C) Kaplan-Meier analysis showing tumor latency in UVB-treated control (Perpfl/fl and Perpfl/+) and K14CreER;Perpfl/fl mice. Statistical significance was determined using the Log Rank test (* p = 0.0002). n =  25 for each genotype. D) (Left) Graph depicts the average number of SCCs per UVB-treated mouse +/− STDEV. Statistical analysis was performed using the Student's unpaired t-test (* p =  0.00049). (Right) Representative photographs of tumor burden in control and K14CreER;Perpfl/fl mice, with arrow indicating a tumor. E) Representative Hematoxylin and Eosin (H&E) stained images illustrating the various SCC grades. F) Table indicating the numbers of SCCs of different grades in UVB-treated control and K14CreER;Perpfl/fl mice.

Mentions: To characterize the function of Perp during tumorigenesis, we examined its role in cancer of the epidermis, where it is critical for tissue integrity and homeostasis through its role in desmosomal cell-cell adhesion [43]. We examined the tumor predisposition of Perp-deficient mice using a well-defined model for squamous cell carcinoma (SCC) development in which mice are exposed to chronic UVB irradiation [44]. This model provides an accurate mimic of human SCC development, which is similarly driven by UVB irradiation. As Perp constitutive mice die postnatally, we utilized conditional Perp knockout mice (Perpfl/fl; fl = floxed) expressing a tamoxifen-inducible K14CreER transgene to drive tissue-specific deletion of the Perp locus in the epidermis [45], [46]. Immunofluorescence confirmed that Perp expression was successfully ablated in the epidermis of the majority of these mice 4 weeks after tamoxifen injection (Figure 1A). To induce SCC development, tamoxifen-treated 10-week old control and Perpfl/fl mice expressing a K14CreER transgene were exposed to chronic treatments (2.5 kJ/m2) of UVB irradiation three times weekly for 30 weeks (Figure 1B). Interestingly, Kaplan-Meier analysis revealed that mice lacking Perp in the epidermis developed SCCs with reduced average latency (32 wks) compared to control mice (51 wks; Figure 1C). In addition, the average number of SCCs per K14CreER;Perpfl/fl mouse was far greater than in control animals (Figure 1D). The prominent early tumor development and increased tumor number in Perp-deficient mice compared to controls suggest that Perp loss promotes tumor initiation. Histological analyses to grade the SCCs according to cellular morphology, invasiveness into the dermis, and overall architecture revealed that SCCs arising in K14CreER;Perpfl/fl mice had a greater propensity to progress to a poorly differentiated stage than tumors arising in control mice, suggesting that Perp loss may also contribute to tumor progression (Figure 1E, 1F). Despite the presence of invasive tumors, however, no metastases were apparent in the liver or lungs of mice from either cohort (data not shown). Together, these findings indicate that Perp is a key suppressor of skin carcinogenesis and provide the first in vivo demonstration that genetic loss of a desmosomal component can lead to accelerated carcinoma development, facilitating both tumor initiation and progression.


Loss of the p53/p63 regulated desmosomal protein Perp promotes tumorigenesis.

Beaudry VG, Jiang D, Dusek RL, Park EJ, Knezevich S, Ridd K, Vogel H, Bastian BC, Attardi LD - PLoS Genet. (2010)

Perp-deficiency promotes tumorigenesis.A) Perp immunofluorescence images demonstrating the presence of Perp in the epidermis of control mice and the loss of Perp in the epidermis of K14CreER;Perpfl/fl mice. Green signal represents Perp staining, red signal represents staining for the desmosomal protein Desmoplakin (Dp), and blue signal represents DAPI, to mark nuclei. (Upper left) Low magnification images show an overview of the epidermis, and (Upper right) high magnification images show the punctate staining pattern typical of desmosomal proteins. (Lower panel) Punctate desmosomal pattern in the epidermis is comparable to that observed in wild-type mouse keratinocyte monolayers. B) Tumor study design. C) Kaplan-Meier analysis showing tumor latency in UVB-treated control (Perpfl/fl and Perpfl/+) and K14CreER;Perpfl/fl mice. Statistical significance was determined using the Log Rank test (* p = 0.0002). n =  25 for each genotype. D) (Left) Graph depicts the average number of SCCs per UVB-treated mouse +/− STDEV. Statistical analysis was performed using the Student's unpaired t-test (* p =  0.00049). (Right) Representative photographs of tumor burden in control and K14CreER;Perpfl/fl mice, with arrow indicating a tumor. E) Representative Hematoxylin and Eosin (H&E) stained images illustrating the various SCC grades. F) Table indicating the numbers of SCCs of different grades in UVB-treated control and K14CreER;Perpfl/fl mice.
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Related In: Results  -  Collection

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pgen-1001168-g001: Perp-deficiency promotes tumorigenesis.A) Perp immunofluorescence images demonstrating the presence of Perp in the epidermis of control mice and the loss of Perp in the epidermis of K14CreER;Perpfl/fl mice. Green signal represents Perp staining, red signal represents staining for the desmosomal protein Desmoplakin (Dp), and blue signal represents DAPI, to mark nuclei. (Upper left) Low magnification images show an overview of the epidermis, and (Upper right) high magnification images show the punctate staining pattern typical of desmosomal proteins. (Lower panel) Punctate desmosomal pattern in the epidermis is comparable to that observed in wild-type mouse keratinocyte monolayers. B) Tumor study design. C) Kaplan-Meier analysis showing tumor latency in UVB-treated control (Perpfl/fl and Perpfl/+) and K14CreER;Perpfl/fl mice. Statistical significance was determined using the Log Rank test (* p = 0.0002). n =  25 for each genotype. D) (Left) Graph depicts the average number of SCCs per UVB-treated mouse +/− STDEV. Statistical analysis was performed using the Student's unpaired t-test (* p =  0.00049). (Right) Representative photographs of tumor burden in control and K14CreER;Perpfl/fl mice, with arrow indicating a tumor. E) Representative Hematoxylin and Eosin (H&E) stained images illustrating the various SCC grades. F) Table indicating the numbers of SCCs of different grades in UVB-treated control and K14CreER;Perpfl/fl mice.
Mentions: To characterize the function of Perp during tumorigenesis, we examined its role in cancer of the epidermis, where it is critical for tissue integrity and homeostasis through its role in desmosomal cell-cell adhesion [43]. We examined the tumor predisposition of Perp-deficient mice using a well-defined model for squamous cell carcinoma (SCC) development in which mice are exposed to chronic UVB irradiation [44]. This model provides an accurate mimic of human SCC development, which is similarly driven by UVB irradiation. As Perp constitutive mice die postnatally, we utilized conditional Perp knockout mice (Perpfl/fl; fl = floxed) expressing a tamoxifen-inducible K14CreER transgene to drive tissue-specific deletion of the Perp locus in the epidermis [45], [46]. Immunofluorescence confirmed that Perp expression was successfully ablated in the epidermis of the majority of these mice 4 weeks after tamoxifen injection (Figure 1A). To induce SCC development, tamoxifen-treated 10-week old control and Perpfl/fl mice expressing a K14CreER transgene were exposed to chronic treatments (2.5 kJ/m2) of UVB irradiation three times weekly for 30 weeks (Figure 1B). Interestingly, Kaplan-Meier analysis revealed that mice lacking Perp in the epidermis developed SCCs with reduced average latency (32 wks) compared to control mice (51 wks; Figure 1C). In addition, the average number of SCCs per K14CreER;Perpfl/fl mouse was far greater than in control animals (Figure 1D). The prominent early tumor development and increased tumor number in Perp-deficient mice compared to controls suggest that Perp loss promotes tumor initiation. Histological analyses to grade the SCCs according to cellular morphology, invasiveness into the dermis, and overall architecture revealed that SCCs arising in K14CreER;Perpfl/fl mice had a greater propensity to progress to a poorly differentiated stage than tumors arising in control mice, suggesting that Perp loss may also contribute to tumor progression (Figure 1E, 1F). Despite the presence of invasive tumors, however, no metastases were apparent in the liver or lungs of mice from either cohort (data not shown). Together, these findings indicate that Perp is a key suppressor of skin carcinogenesis and provide the first in vivo demonstration that genetic loss of a desmosomal component can lead to accelerated carcinoma development, facilitating both tumor initiation and progression.

Bottom Line: Tumor development is associated with inactivation of both of Perp's known functions, in apoptosis and cell-cell adhesion.Interestingly, Perp-deficient tumors exhibit widespread downregulation of desmosomal constituents while adherens junctions remain intact, suggesting that desmosome loss is a specific event important for tumorigenesis rather than a reflection of a general change in differentiation status.Using gene expression profiling, we show further that Perp loss induces a set of inflammation-related genes that could stimulate tumorigenesis.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Division of Radiation and Cancer Biology, Stanford University School of Medicine, Stanford, California, USA.

ABSTRACT
Dysregulated cell-cell adhesion plays a critical role in epithelial cancer development. Studies of human and mouse cancers have indicated that loss of adhesion complexes known as adherens junctions contributes to tumor progression and metastasis. In contrast, little is known regarding the role of the related cell-cell adhesion junction, the desmosome, during cancer development. Studies analyzing expression of desmosome components during human cancer progression have yielded conflicting results, and therefore genetic studies using knockout mice to examine the functional consequence of desmosome inactivation for tumorigenesis are essential for elucidating the role of desmosomes in cancer development. Here, we investigate the consequences of desmosome loss for carcinogenesis by analyzing conditional knockout mice lacking Perp, a p53/p63 regulated gene that encodes an important component of desmosomes. Analysis of Perp-deficient mice in a UVB-induced squamous cell skin carcinoma model reveals that Perp ablation promotes both tumor initiation and progression. Tumor development is associated with inactivation of both of Perp's known functions, in apoptosis and cell-cell adhesion. Interestingly, Perp-deficient tumors exhibit widespread downregulation of desmosomal constituents while adherens junctions remain intact, suggesting that desmosome loss is a specific event important for tumorigenesis rather than a reflection of a general change in differentiation status. Similarly, human squamous cell carcinomas display loss of PERP expression with retention of adherens junctions components, indicating that this is a relevant stage of human cancer development. Using gene expression profiling, we show further that Perp loss induces a set of inflammation-related genes that could stimulate tumorigenesis. Together, these studies suggest that Perp-deficiency promotes cancer by enhancing cell survival, desmosome loss, and inflammation, and they highlight a fundamental role for Perp and desmosomes in tumor suppression. An understanding of the factors affecting cancer progression is important for ultimately improving the diagnosis, prognostication, and treatment of cancer.

Show MeSH
Related in: MedlinePlus