Overexpression of heat shock protein 90 through the downregulation of miR-9-5p in extramammary Paget's disease

Heat shock protein 90 (HSP90) facilitates diverse cellular processes by interacting process with more than 200 client proteins. Overexpression of HSP90 contributes to the pathogenesis of various malignant tumors, and HSP90 inhibitors attenuate the progression of malignant tumors in vitro/vivo. Numerous clinical trials have used HSP90 inhibitors to treat several cancers, and pimitespib (an HSP90 inhibitor) is covered by insurance for advanced gastrointestinal stromal tumor in Japan. In this study, we investigated the expression pattern of HSP90 and analyzed its clinical significance in extramammary Paget's disease (EMPD). All 77 EMPD tissues investigated were positive for HSP90 expression. The immunoreactivity of HSP90 in fetal cases due to EMPD tended to be highly stained. Although there was no significant difference in HSP90 mRNA levels between 24 paired lesional and nonlesional tissues, microRNA-inhibiting HSP90 levels in tumor tissues were significantly decreased compared with those in normal tissues. Thus, HSP90 may play an important role in the pathogenesis of EMPD and may be a novel therapeutic target for EMPD.

PIK3CA mutations in cutaneous squamous cell carcinoma

Oncogenic PIK3CA mutation activates phosphoinositide 3-kinase (PI3K) enzyme, and PI3K-AKT signaling activation induces several growth-regulatory transcription factors. PIK3CA mutations have attracted attention as biomarker in clinical trials of various inhibitors including PI3K inhibitors. About 80% of PIK3CA mutations in human cancers are observed in 'hot spot' regions: exon 9 (E542K and E545K) and exon 20 (H1047R). There were few reports about clinical significance of PIK3CA mutations in cutaneous cell carcinoma (cSCC). Thus, we investigate the prevalence of three PIK3CA hot spot mutations in 143 cases with cSCC and evaluate the correlation between the presence of these mutations and clinical characteristics by using ddPCR. The frequency of each E542K, E545K and H1047R PIK3CA mutations was 1.4% (2/143), 2.8% (4/143), and 0.7% (1/143) respectively. No significant correlation was found between PIK3CA mutations and clinical characteristics. Although additional basic researches and clinical trials are necessary, various inhibitors may be effective therapeutics for PIK3CA mutation-positive cSCC. Our study revealed the prevalence of PIK3CA mutations in cSCC.

Intertumor and intratumor heterogeneity of PIK3CA mutations in extramammary Paget's disease

Although the prognosis of patients with extramammary Paget's disease (EMPD) treated with radical resection is good, the prognosis of EMPD with distant metastasis is very poor. PIK3CA mutations predict a good response to PIK3CA inhibitors. The aim of this study was to investigate the occurrence rate of PIK3CA mutations (including multiple mutations [MM]) related to the intertumor and intratumor heterogeneity in EMPD and to evaluate the correlation between these mutations and clinical parameters of EMPD. We performed droplet digital polymerase chain reaction to detect PIK3CA mutations (E542K, E545K, H1047R, and MM) in 68 patients with EMPD. In addition, we investigated the presence of PIK3CA mutations at multiple sites in 16 patients with PIK3CA mutations to assess the intratumor heterogeneity of PIK3CA mutations in EMPD. The frequency of one or more PIK3CA mutations in patients with EMPD was 30.8% (21/68). The frequency of E542K, E545K, H1047R, and MM were 10.2% (7/68), 13.2% (9/68), 11.7% (8/68), and 4.4% (3/68), respectively. No significant correlation was found between PIK3CA mutation patterns and clinical parameters. Of the 21 patients with PIK3CA mutations, 16 with tissue samples that could be analyzed at multiple sites were examined. The proportion of patients with the same PIK3CA mutations at all sites was 12.5% (2/16). The proportion of patients with the same PIK3CA mutations at least two or more sites, but not at all sites, was 31.2% (5/16). The proportion of patients with no PIK3CA mutations at other sites was 37.5% (6/16). The proportion of patients with other PIK3CA mutations at other sites was 18.7% (3/16). There is intertumor and intratumor heterogeneity of PIK3CA mutations. PIK3CA mutations in EMPD may be progressor mutations in EMPD.

Inhibition of Endoglin Exerts Antitumor Effects through the Regulation of Non-Smad TGF-β Signaling in Angiosarcoma

Angiosarcoma is a rare malignant tumor derived from endothelial cells, and its prognosis is poor because advanced angiosarcoma is often resistant to taxane therapy. Endoglin (CD105) acts as a coreceptor for TGF-β signaling and is overexpressed in tumor-associated endothelial cells and enhances tumor angiogenesis. Numerous clinical trials are testing the effectiveness of anti-endoglin antibodies in various types of malignancies. Here, we investigated the role of endoglin in the pathogenesis of angiosarcoma and whether endoglin inhibition results in antitumor activity. Endoglin was overexpressed in angiosarcoma, and its inhibition was effective in promoting apoptosis and the suppression of migration, invasion, tube formation, and Warburg effect in angiosarcoma cells. Knockdown of endoglin activated caspase 3/7 that is essential for apoptosis, reduced survivin levels, and decreased paxillin and vascular endothelial cadherin phosphorylation and matrix metalloproteinase 2 and matrix metalloproteinase 9 activities in angiosarcoma cells. Although endoglin is a coreceptor that regulates TGF-β signaling, the antitumor effect of endoglin in angiosarcoma was not based on Smad signaling regulation but on non-Smad TGF-β signaling. Taken together, these results indicated that endoglin could be a novel therapeutic target for angiosarcoma.

The expression of EpCAM in extramammary Paget's disease

Extramammary Paget's disease (EMPD) is a rare skin malignant tumor. The prognosis of EMPD with distant metastasis is poor, however an effective therapy has not yet established. Recently, EpCAM (epithelial cell adhesion molecule, CD326) has attracted attention as both prognostic marker and therapeutic target in several cancers. Besides, EpCAM is an important surface marker of circulating tumor cell (CTC) in the collection of CTC. Thus, the purpose of our study was to examine the expression levels of EpCAM and evaluate the correlation between its intensity of EpCAM and the clinical characteristics of EMPD. The expression of EpCAM in EMPD was examined using immunohistochemistry. Skin samples were obtained from 32 patients with EMPD. We found that almost all EMPD tissues (90.6%, 29/32) were positive for EpCAM. Furthermore, the staining intensity of EpCAM protein negatively correlated with the presence of distant metastasis. Overexpression of EpCAM in EMPD cells suggests that EpCAM may be a novel therapeutic target and the research of CTC may be newly developed in EMPD. Based on these findings, EpCAM may be a meaningful molecule in EMPD.

Intratumor dihydropyrimidine dehydrogenase mRNA expression levels are decreased in extramammary Paget's disease

S-1, a 5-fluorouracil (5-FU)-based anti-cancer agent, is an important drug for treating metastatic extramammary Paget's disease (EMPD). Although intratumor expression levels of 5-FU metabolism enzymes have been studied widely in many solid tumors, no studies have examined on the expression levels of thymidylate synthase (TS), orotate phosphoribosyl-transferase (OPRT) or dihydropyrimidine dehydrogenase (DPD) in skin cancers. The aim of this study was to estimate the intratumoral mRNA expression levels of these genes in EMPD by real time PCR. Intratumoral DPD mRNA levels were decreased in EMPD compared to those in normal skin, but its intratumoral DPD mRNA expression levels were not correlated with clinical manifestations. Intratumoral DPD mRNA levels were positively correlated with OPRT mRNA levels in EMPD. Based on these results, low expression of intratumoral DPD mRNA in EMPD may contribute to the pathogenesis of this disease.