Mitsuhiko Osaki1, Hikari Chinen2, Yuichi Yoshida3, Takahito Ohhira2, Naohiro Sunamura2, Osamu Yamamoto3, Hisao Ito4, Mitsuo Oshimura2, Hiroyuki Kugoh2. 1. Division of Molecular Genetics and Biofunction, Institute of Regenerative Medicine and Biofunction,, Division of Pathological Biochemistry, Department of Biomedical Sciences. 2. Division of Molecular Genetics and Biofunction, Institute of Regenerative Medicine and Biofunction. 3. Division of Dermatology, Department of Medicine of Sensory and Motor Organs. 4. Division of Organ Pathology, Department of Pathology, Tottori University Faculty of Medicine, 86 Nishi-cho Yonago, Tottori 683-8503, Japan.
Abstract
BACKGROUND: The pituitary homeobox 1 (PITX1) protein is a member of the bicoid-related homeobox transcription factors and has essential roles in human development. Recently, the PITX1 gene has been considered as a tumor suppressor gene in various human cancers. OBJECTIVE: This study examined the expression of PITX1 in the development and progression of human cutaneous malignant melanoma. MATERIALS & METHODS: Immunohistochemical and/or immunofluorescence analyses were performed to examine the histological expression of PITX1 in healthy skin and 40 cutaneous malignant melanoma cases, including 10 melanoma in situ cases. RESULTS: Expression of PITX1 was shown in nuclei of melanocytes in normal skin. PITX1 expression was positive (labeling index: ≥10%) in 21 (52.5%) cases and negative (labeling index: <10%) in 19 (47.5%) of 40 cases of primary cutaneous malignant melanoma. The mean tumor thickness in PITX1-negative cases (7.11 ± 10.3 mm) was significantly higher than that in the positive cases (1.90 ± 3.19 mm) (P<0.01). The numbers of cases showing metastasis were 1 (4.76%) of 21 cases in PITX1-positive cases and 7 (36.8%) of 19 cases in PITX1-negative cases; the frequency was significantly higher in PITX1-negative cases than the positive cases (P = 0.012). Moreover, the reduction in PITX1 expression correlated significantly with clinical stage (P<0.001). Interestingly, PITX1 expression was inversely correlated with cell proliferation of cutaneous malignant melanoma (P<0.001). CONCLUSIONS: Down-regulation of PITX1 expression might contribute to the progression of cutaneous malignant melanoma via promoting cell proliferative activity.
BACKGROUND: The pituitary homeobox 1 (PITX1) protein is a member of the bicoid-related homeobox transcription factors and has essential roles in human development. Recently, the PITX1 gene has been considered as a tumor suppressor gene in various humancancers. OBJECTIVE: This study examined the expression of PITX1 in the development and progression of humancutaneous malignant melanoma. MATERIALS & METHODS: Immunohistochemical and/or immunofluorescence analyses were performed to examine the histological expression of PITX1 in healthy skin and 40 cutaneous malignant melanoma cases, including 10 melanoma in situ cases. RESULTS: Expression of PITX1 was shown in nuclei of melanocytes in normal skin. PITX1 expression was positive (labeling index: ≥10%) in 21 (52.5%) cases and negative (labeling index: <10%) in 19 (47.5%) of 40 cases of primary cutaneous malignant melanoma. The mean tumor thickness in PITX1-negative cases (7.11 ± 10.3 mm) was significantly higher than that in the positive cases (1.90 ± 3.19 mm) (P<0.01). The numbers of cases showing metastasis were 1 (4.76%) of 21 cases in PITX1-positive cases and 7 (36.8%) of 19 cases in PITX1-negative cases; the frequency was significantly higher in PITX1-negative cases than the positive cases (P = 0.012). Moreover, the reduction in PITX1 expression correlated significantly with clinical stage (P<0.001). Interestingly, PITX1 expression was inversely correlated with cell proliferation of cutaneous malignant melanoma (P<0.001). CONCLUSIONS: Down-regulation of PITX1 expression might contribute to the progression of cutaneous malignant melanoma via promoting cell proliferative activity.