Sayaka Kanematsu

Requirement of p38 MAPK for a cell-death pathway triggered by vorinostat in MDA-MB-231 human breast cancer cells

Vorinostat is a histone deacetylase inhibitor that effectively suppresses cancer-cell proliferation by inducing cell-cycle arrest and/or apoptosis. We now show the involvement of p38 mitogen-activated protein kinase (MAPK) in the regulation of vorinostat-induced apoptosis in MDA-MB-231 human breast cancer cells. Vorinostat induced the hyperacetylation of histone H3, which correlated to apoptosis induction. Vorinostat-induced apoptosis occurred in parallel with the phosphorylation of p38 MAPK and the dephosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2). Knockdown of p38 MAPK prominently abrogated apoptosis induction and was accompanied by decreased caspase-3 cleavage. These findings support the notion that the activation of the p38 MAPK pathway followed by caspase-3 cleavage is responsible for vorinostat-induced apoptosis in MDA-MB-231 cells.

Retinal Degeneration Induced in Adult Mice by a Single Intraperitoneal Injection of N-Ethyl-N-Nitrosourea:

Seven-week-old female BALB/c mice received a single intraperitoneal injection of N-ethyl-N-nitrosourea (ENU) (50, 100, 200, 400, or 600 mg/kg), and retinal damage was evaluated after 7 days. Sequential morphological features of the retina and retinal apoptosis, as determined by the TUNEL assay, were analyzed 6, 12, 24, and 72 hr and 7 days after treatment with 600 mg/kg of ENU. Moreover, older mice (25 to 34 weeks of age) received an intraperitoneal injection of 600 mg/kg ENU and were sacrificed 7 days later. All animals were necropsied, and both eyes were examined histopathologically. Two of the 5 mice that received 600 mg/kg ENU died during the experimental period. Histopathologically, all mice that received 600 mg/kg of ENU experienced retinal degeneration characterized by the loss of photoreceptor cells (disappearance of the outer nuclear layer and photoreceptor layer) in both the central and peripheral retina within 7 days. One of 5 mice treated with 400 mg/kg ENU exhibited retinal damage that was restricted to the central retina. Older mice treated with 600 mg/kg ENU exhibited retinal damage that was similar to the retinal damage in younger mice. In the 600 mg/kg ENU-treated mice, TUNEL-positive photoreceptor cells peaked 72 hr after ENU treatment. Retinal thickness and the photoreceptor cell ratio in the central and peripheral retina were significantly decreased, and the retinal damage ratio was significantly increased 7 days after treatment. In conclusion, ENU induces retinal degeneration in adult mice that is characterized by photoreceptor cell apoptosis.

Effects of short-term estrogen treatment on the progression of N-methyl-N-nitrosourea-induced premalignant mammary lesions in female Lewis rats

We studied the effects of short-term estrogen treatment (STET) on the progression of mammary lesions from ductal hyperplasia (DH) through ductal carcinoma in situ (DCIS) to invasive ductal carcinoma (IDC) in the N-methyl-N-nitrosourea (MNU)-induced rat mammary carcinogenesis model. Three-week-old female Lewis rats (n = 40) received an intraperitoneal injection of MNU (50 mg/kg). Three weeks later, a 3-week-release, 0.25-mg, 17β-estradiol pellet was subcutaneously implanted for 2 weeks in 20 rats (STET); the remaining 20 rats did not receive the estradiol pellets (age-matched control). All rats were killed at 12 weeks of age, and their abdominal-inguinal mammary glands were histologically examined. The incidence and multiplicity of DHs were similar between groups (STET, 90% and 3.9 ± 0.6 vs. age-matched controls, 80% and 3.0 ± 0.5). However, DCIS and IDC did not develop in STET rats, whereas DCIS (25% and 1.4 ± 0.2) and IDC (35% and 1.4 ± 0.3) developed in the age-matched controls. Immunoscores of estrogen and progesterone receptors and positive rate of proliferative cell nuclear antigen (PCNA) in DH were similar in both groups, while the positive rate of cyclin D1 was significantly reduced in the STET group (P < 0.05). Thus, STET blocked the progression from DH to DCIS in MNU-induced mammary carcinogenesis, and decreased expression of cyclin D1 may play an important role in the blockade of cell transition from DH to DCIS.

Biphasic effect of short-term pregnancy hormone treatment on N-methyl-N-nitrosourea-induced mammary carcinogenesis in young and old rats

This study examined the development of N-methyl-N-nitrosourea (MNU)-induced mammary carcinomas in young and old female Lewis rats following short-term treatment with estrogen and progesterone to mimic pregnancy. Rats exposed at 4 weeks of age to MNU were treated at 6 weeks of age (early MNU/young E/P treatment) or at 24 weeks of age (early MNU/old E/P treatment) with a 21-day slow-release pellet containing 0.5 mg 17β-estradiol and 32.5 mg progesterone (E/P). Other rats were exposed to MNU at 22 and again at 23 weeks of age, and were treated with E/P at 24 weeks of age (late MNU/old E/P treatment). All experimental groups were compared with respective MNU-exposed age-matched E/P-untreated rats. Overt mammary carcinomas (≥1 cm in diameter) that were positive for hormone receptors were reduced in young E/P-treated rats, while hormone receptor-negative overt mammary carcinomas increased in old E/P-treated rats. The rate of development of small-sized mammary carcinoma (<1 cm in diameter) was similar in early MNU/young E/P-treated and late MNU/old E/P-treated groups, but higher in early MNU/old E/P-treated rats compared with respective E/P-untreated rats. At the termination of the experiment, normal mammary gland architecture had not been influenced by E/P treatment, although E/P treatment of older rats caused an increase in proliferating cell nuclear antigen (PCNA) labeling of the mammary tissue. Thus, the impact of short-term E/P treatment on MNU-induced rat mammary carcinogenesis is age-dependent and shows biphasic effects; the development of hormone-dependent overt mammary carcinomas was reduced in young rats but the development of hormone-independent overt mammary carcinomas increased in older rats. The enhanced outgrowth of hormone-independent overt mammary carcinomas by E/P treatment in old age is due to accelerated cell proliferation at the promotion/progression phase of mammary carcinogenesis. Age at short-term E/P treatment is crucial for breast cancer control.

Solitary fibrous tumor of soft tissue: a case report and immunohistochemical study

A case of solitary fibrous tumor (SFT) arising in the soft tissue of the left inguinal region is reported. A 57-year-old Japanese woman presented with a nonadherent, well-defined, oval mass that was 2 × 3 cm in diameter and located in the inguinal soft tissue. Microscopic evaluation showed proliferation of spindle-shaped, fibroblast-like cells by the coexistence of hypo- and hypercellular areas with mast cell infiltration separated by hemangiopericytoma-like blood vessels. Immunohistochemistry revealed strong expression of CD34 and CD99 in the fibroblast-like cells, supporting the diagnosis of SFT. Although the patient was free of symptoms such as hypoglycemia, immunoreactive insulin-like growth factor (IGF)-II was localized in the socalled Golgi area of the spindle-shaped cells. In conclusion, immunoreactive IGF-II was detected in SFT that was not associated with hypoglycemia.