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Up-regulated Dicer expression in patients with cutaneous melanoma.

Ma Z, Swede H, Cassarino D, Fleming E, Fire A, Dadras SS - PLoS ONE (2011)

Bottom Line: The expression of Dicer was significantly higher in melanomas compared to benign melanocytic nevi (P<0.0001).In patients with cutaneous melanomas, Dicer up-regulation was found to be significantly associated with an increased tumor mitotic index (P = 0.04), Breslow's depth of invasion (P = 0.03), nodal metastasis (P = 0.04) and a higher American Joint Committee on Caner (AJCC) clinical stage (P = 0.009).Understanding deregulation of Dicer and its influence on miRNA maturation is needed to predict the susceptibility of melanoma patients to miRNA-based therapy in the future.

View Article: PubMed Central - PubMed

Affiliation: Department of Genetics, Stanford University School of Medicine, Stanford, California, United States of America.

ABSTRACT

Background: MicroRNAs (miRNAs) are small non-coding RNAs (18-24 nucleotides) that have recently been shown to regulate gene expression during cancer progression. Dicer, a central enzyme in the multi-component miRNA biogenesis pathway, is involved in cutting precursor miRNAs to functionally mature forms. Emerging evidence shows that Dicer expression is deregulated in some human malignancies and it correlates with tumor progression, yet this role has not yet been investigated in skin cancers.

Methods and findings: Using an anti-human monoclonal antibody against Dicer and immunohistochemistry, we compared the expression of Dicer protein among 404 clinically annotated controls and skin tumors consisting of melanocytic nevi (n = 71), a variety of melanomas (n = 223), carcinomas (n = 73) and sarcomas (n = 12). Results showed a cell-specific up-regulated Dicer in 81% of cutaneous, 80% of acrolentiginous and 96% of metastatic melanoma specimens compared to carcinoma or sarcoma specimens (P<0.0001). The expression of Dicer was significantly higher in melanomas compared to benign melanocytic nevi (P<0.0001). In patients with cutaneous melanomas, Dicer up-regulation was found to be significantly associated with an increased tumor mitotic index (P = 0.04), Breslow's depth of invasion (P = 0.03), nodal metastasis (P = 0.04) and a higher American Joint Committee on Caner (AJCC) clinical stage (P = 0.009). Using western blot analysis, we confirmed the cell-specific up-regulation of Dicer protein in vitro. A pooled-analysis on mRNA profiling in cutaneous tumors showed up-regulation of Dicer at the RNA level in cutaneous melanoma, also showing deregulation of other enzymes that participate in the biogenesis and maturation of canonical miRNAs.

Conclusions: Increased Dicer expression may be a clinically useful biomarker for patients with cutaneous melanoma. Understanding deregulation of Dicer and its influence on miRNA maturation is needed to predict the susceptibility of melanoma patients to miRNA-based therapy in the future.

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Related in: MedlinePlus

Dicer was expressed at higher levels in cutaneous and acrolentiginous melanomas.A) Intradermal melanocytic nevus cells weakly expressed Dicer in a small group of cells in the superficial dermis (arrowheads) whereas melanoma cells diffusely expressed Dicer at higher levels (B). However, two independent individuals with cutaneous melanoma (CM), both excised from the thigh, expressed Dicer at different levels (B, left and right cores). C–D) Both tissue cores are shown at a higher magnification (CM, thigh-1 and CM, thigh-2). The immunoreactivity for Dicer in melanoma cells was granular and cytoplasmic. E) Cancer cells strongly expressed Dicer in an acrolentiginous melanoma while they were negative for Dicer in a mucosal melanoma (F). Original magnification: A–B, 100X; C, E–F, 200X and D, 400X.
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pone-0020494-g002: Dicer was expressed at higher levels in cutaneous and acrolentiginous melanomas.A) Intradermal melanocytic nevus cells weakly expressed Dicer in a small group of cells in the superficial dermis (arrowheads) whereas melanoma cells diffusely expressed Dicer at higher levels (B). However, two independent individuals with cutaneous melanoma (CM), both excised from the thigh, expressed Dicer at different levels (B, left and right cores). C–D) Both tissue cores are shown at a higher magnification (CM, thigh-1 and CM, thigh-2). The immunoreactivity for Dicer in melanoma cells was granular and cytoplasmic. E) Cancer cells strongly expressed Dicer in an acrolentiginous melanoma while they were negative for Dicer in a mucosal melanoma (F). Original magnification: A–B, 100X; C, E–F, 200X and D, 400X.

Mentions: We initially sought to determine if Dicer is expressed in any of the major categories of human cutaneous malignancies, namely melanoma, carcinoma or sarcoma. To this end, we tested a large clinical sample set of formalin-fixed paraffin-embedded (FFPE) benign and malignant tumors (n = 404) including melanocytic nevi (benign melanocytic hyperplasia), a variety of melanoma subtypes (cutaneous, acrolentiginous, mucosal, ocular and desmoplastic), a variety of carcinomas (squamous, basal cell and eccrine) and sarcomas (Table 1) using a monoclonal anti-human Dicer antibody and immunohistochemistry on tissue microarrays (TMAs) (Fig. 1A) and full tumor sections (Fig. S1A-F). After determining the immunostaining pattern for Dicer in normal skin and other organs, we established a semi-quantitative, four-point ordinal immunoreactivity scoring scale: negative (0), weakly positive (1), moderately positive (2) and strongly positive (3). Scores for multiple cores from one case were averaged, and final Dicer scores were categorized into a three-level grouping of Negative, Low (>0 and ≤1.5) or High (>1.6) for analyses that included all 404 patients (Table 1). In normal skin, epidermal keratinocytes expressed Dicer consistently at low levels (Fig. 1B). Carcinoma cells of skin (basal and squamous), adenocarcinoma cells (primary or metastatic) and sarcoma cells expressed none to very low levels of Dicer (Fig. 1C-E). In contrast, the cytoplasm of primary cutaneous and metastatic melanoma cells exhibited high levels of Dicer immunoreactivity (Fig. 1F-G). The majority of carcinomas (94.5%), sarcomas (100%) and tumors with neural differentiation (100%) of the skin was negative for Dicer or expressed it at low levels (Table 1). Among tumors with melanocytic differentiation, we observed low levels of Dicer immunoreactivity in the cytoplasm of melanocytic nevus cell (Fig. 2A) compared to the high levels seen in cutaneous and acrolentiginous melanomas (Fig. 2B-E). The cytoplasm of mucosal melanoma cells was devoid of Dicer immunoreactivity (Fig. 2F). Dicer was consistently expressed at high levels in the majority of metastatic (55.8%), acrolentiginous (55.0%) and cutaneous (46.4%) melanomas compared to mucosal melanoma (12.5%), conferring further cancer-cell specificity among different types of melanomas (Table 1). The remainder of Dicer-positive cutaneous melanomas expressed Dicer either at low levels (34.7%) or exhibited no expression (18.9%). Two different patients with cutaneous melanoma (both excised from the thigh) exemplified this variability in expression Dicer. The melanoma from patient 1 expressed Dicer at low levels (Fig. 2B and C) compared to that in patient 2 who expressed Dicer at high levels (Fig. 2B and D). Dicer expression was not associated with differences in gender (n = 328) or age (n = 335) in the examined cutaneous tumors (Table S3). Among the cutaneous (n = 93) and acrolentiginous (n = 40) melanomas examined, there was no statistically significant association between Dicer expression and the anatomic site (head and neck, trunk, upper and lower extremities or genital skin) (Table S4).


Up-regulated Dicer expression in patients with cutaneous melanoma.

Ma Z, Swede H, Cassarino D, Fleming E, Fire A, Dadras SS - PLoS ONE (2011)

Dicer was expressed at higher levels in cutaneous and acrolentiginous melanomas.A) Intradermal melanocytic nevus cells weakly expressed Dicer in a small group of cells in the superficial dermis (arrowheads) whereas melanoma cells diffusely expressed Dicer at higher levels (B). However, two independent individuals with cutaneous melanoma (CM), both excised from the thigh, expressed Dicer at different levels (B, left and right cores). C–D) Both tissue cores are shown at a higher magnification (CM, thigh-1 and CM, thigh-2). The immunoreactivity for Dicer in melanoma cells was granular and cytoplasmic. E) Cancer cells strongly expressed Dicer in an acrolentiginous melanoma while they were negative for Dicer in a mucosal melanoma (F). Original magnification: A–B, 100X; C, E–F, 200X and D, 400X.
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pone-0020494-g002: Dicer was expressed at higher levels in cutaneous and acrolentiginous melanomas.A) Intradermal melanocytic nevus cells weakly expressed Dicer in a small group of cells in the superficial dermis (arrowheads) whereas melanoma cells diffusely expressed Dicer at higher levels (B). However, two independent individuals with cutaneous melanoma (CM), both excised from the thigh, expressed Dicer at different levels (B, left and right cores). C–D) Both tissue cores are shown at a higher magnification (CM, thigh-1 and CM, thigh-2). The immunoreactivity for Dicer in melanoma cells was granular and cytoplasmic. E) Cancer cells strongly expressed Dicer in an acrolentiginous melanoma while they were negative for Dicer in a mucosal melanoma (F). Original magnification: A–B, 100X; C, E–F, 200X and D, 400X.
Mentions: We initially sought to determine if Dicer is expressed in any of the major categories of human cutaneous malignancies, namely melanoma, carcinoma or sarcoma. To this end, we tested a large clinical sample set of formalin-fixed paraffin-embedded (FFPE) benign and malignant tumors (n = 404) including melanocytic nevi (benign melanocytic hyperplasia), a variety of melanoma subtypes (cutaneous, acrolentiginous, mucosal, ocular and desmoplastic), a variety of carcinomas (squamous, basal cell and eccrine) and sarcomas (Table 1) using a monoclonal anti-human Dicer antibody and immunohistochemistry on tissue microarrays (TMAs) (Fig. 1A) and full tumor sections (Fig. S1A-F). After determining the immunostaining pattern for Dicer in normal skin and other organs, we established a semi-quantitative, four-point ordinal immunoreactivity scoring scale: negative (0), weakly positive (1), moderately positive (2) and strongly positive (3). Scores for multiple cores from one case were averaged, and final Dicer scores were categorized into a three-level grouping of Negative, Low (>0 and ≤1.5) or High (>1.6) for analyses that included all 404 patients (Table 1). In normal skin, epidermal keratinocytes expressed Dicer consistently at low levels (Fig. 1B). Carcinoma cells of skin (basal and squamous), adenocarcinoma cells (primary or metastatic) and sarcoma cells expressed none to very low levels of Dicer (Fig. 1C-E). In contrast, the cytoplasm of primary cutaneous and metastatic melanoma cells exhibited high levels of Dicer immunoreactivity (Fig. 1F-G). The majority of carcinomas (94.5%), sarcomas (100%) and tumors with neural differentiation (100%) of the skin was negative for Dicer or expressed it at low levels (Table 1). Among tumors with melanocytic differentiation, we observed low levels of Dicer immunoreactivity in the cytoplasm of melanocytic nevus cell (Fig. 2A) compared to the high levels seen in cutaneous and acrolentiginous melanomas (Fig. 2B-E). The cytoplasm of mucosal melanoma cells was devoid of Dicer immunoreactivity (Fig. 2F). Dicer was consistently expressed at high levels in the majority of metastatic (55.8%), acrolentiginous (55.0%) and cutaneous (46.4%) melanomas compared to mucosal melanoma (12.5%), conferring further cancer-cell specificity among different types of melanomas (Table 1). The remainder of Dicer-positive cutaneous melanomas expressed Dicer either at low levels (34.7%) or exhibited no expression (18.9%). Two different patients with cutaneous melanoma (both excised from the thigh) exemplified this variability in expression Dicer. The melanoma from patient 1 expressed Dicer at low levels (Fig. 2B and C) compared to that in patient 2 who expressed Dicer at high levels (Fig. 2B and D). Dicer expression was not associated with differences in gender (n = 328) or age (n = 335) in the examined cutaneous tumors (Table S3). Among the cutaneous (n = 93) and acrolentiginous (n = 40) melanomas examined, there was no statistically significant association between Dicer expression and the anatomic site (head and neck, trunk, upper and lower extremities or genital skin) (Table S4).

Bottom Line: The expression of Dicer was significantly higher in melanomas compared to benign melanocytic nevi (P<0.0001).In patients with cutaneous melanomas, Dicer up-regulation was found to be significantly associated with an increased tumor mitotic index (P = 0.04), Breslow's depth of invasion (P = 0.03), nodal metastasis (P = 0.04) and a higher American Joint Committee on Caner (AJCC) clinical stage (P = 0.009).Understanding deregulation of Dicer and its influence on miRNA maturation is needed to predict the susceptibility of melanoma patients to miRNA-based therapy in the future.

View Article: PubMed Central - PubMed

Affiliation: Department of Genetics, Stanford University School of Medicine, Stanford, California, United States of America.

ABSTRACT

Background: MicroRNAs (miRNAs) are small non-coding RNAs (18-24 nucleotides) that have recently been shown to regulate gene expression during cancer progression. Dicer, a central enzyme in the multi-component miRNA biogenesis pathway, is involved in cutting precursor miRNAs to functionally mature forms. Emerging evidence shows that Dicer expression is deregulated in some human malignancies and it correlates with tumor progression, yet this role has not yet been investigated in skin cancers.

Methods and findings: Using an anti-human monoclonal antibody against Dicer and immunohistochemistry, we compared the expression of Dicer protein among 404 clinically annotated controls and skin tumors consisting of melanocytic nevi (n = 71), a variety of melanomas (n = 223), carcinomas (n = 73) and sarcomas (n = 12). Results showed a cell-specific up-regulated Dicer in 81% of cutaneous, 80% of acrolentiginous and 96% of metastatic melanoma specimens compared to carcinoma or sarcoma specimens (P<0.0001). The expression of Dicer was significantly higher in melanomas compared to benign melanocytic nevi (P<0.0001). In patients with cutaneous melanomas, Dicer up-regulation was found to be significantly associated with an increased tumor mitotic index (P = 0.04), Breslow's depth of invasion (P = 0.03), nodal metastasis (P = 0.04) and a higher American Joint Committee on Caner (AJCC) clinical stage (P = 0.009). Using western blot analysis, we confirmed the cell-specific up-regulation of Dicer protein in vitro. A pooled-analysis on mRNA profiling in cutaneous tumors showed up-regulation of Dicer at the RNA level in cutaneous melanoma, also showing deregulation of other enzymes that participate in the biogenesis and maturation of canonical miRNAs.

Conclusions: Increased Dicer expression may be a clinically useful biomarker for patients with cutaneous melanoma. Understanding deregulation of Dicer and its influence on miRNA maturation is needed to predict the susceptibility of melanoma patients to miRNA-based therapy in the future.

Show MeSH
Related in: MedlinePlus