Masashi Tamaoki

Identification and characterization of CXCR4-positive gastric cancer stem cells

Diffuse-type solid tumors are often composed of a high proportion of rarely proliferating (i.e., dormant) cancer cells, strongly indicating the involvement of cancer stem cells (CSCs) Although diffuse-type gastric cancer (GC) patients have a poor prognosis due to high-frequent development of peritoneal dissemination (PD), it is limited knowledge that the PD-associated CSCs and efficacy of CSC-targeting therapy in diffuse-type GC. In this study, we established highly metastatic GC cell lines by in vivo selection designed for the enrichment of PD-associated GC cells. By microarray analysis, we found C-X-C chemokine receptor type 4 (CXCR4) can be a novel marker for highly metastatic CSCs, since CXCR4-positive cells can grow anchorage-independently, initiate tumors in mice, be resistant to cytotoxic drug, and produce differentiated daughter cells. In clinical samples, these CXCR4-positive cells were found from not only late metastasis stage (accumulated ascites) but also earlier stage (peritoneal washings). Moreover, treatment with transforming growth factor-β enhanced the anti-cancer effect of docetaxel via induction of cell differentiation/asymmetric cell division of the CXCR4-positive gastric CSCs even in a dormant state. Therefore, differentiation inducers hold promise for obtaining the maximum therapeutic outcome from currently available anti-cancer drugs through re-cycling of CSCs.

Modulation of Th1/Th2 Balance by Infliximab Rescues Postoperative Occurrence of Small-Intestinal Inflammation Associated with Ulcerative Colitis

In general, ulcerative colitis (UC) is defined as idiopathic inflammation limited to the colorectum, except for backwash ileititis and postcolectomy pouchitis. However, UC is also considered to be a systemic disease because of not only colonic inflammation but also joint, skin, and acute hepatic involvement. Recently, there have been several reports of UC patients with gastroduodenitis or enteritis [1–4]. Cases of gastroduodenitis or enteritis associated with UC are clinically rare but are an important issue for gastroenterologists in the point of no optimal treatment established. Here, we report a case of the postoperative occurrence of small-intestinal inflammation associated with UC successfully treated with infliximab.

Technical considerations for analyzing EMT–MET data from surgical samples

With an increase of neoadjuvant therapy, biopsy samples have become imperative for cancer research; however, what kind of difference between surgical and endoscopic biopsy samples in gene expression profiles was still unclear. Recently, we reported artificially induced epithelial-mesenchymal transition (aiEMT) in the surgical samples by comparison between gene expression profiles of both samples of the esophagus. This was also found in mouse epithelium under an ischemic condition for 4h. This study will evoke underestimation of the prognostic evaluation power of EMT related markers in past cancer research and prevalence of biopsy samples for in vivo expression profiling with low biases.

SIX1 maintains tumor basal cells via transforming growth factor-β pathway and associates with poor prognosis in esophageal cancer

Esophageal squamous cell carcinoma (ESCC) is one of the most common malignant tumors. Although improvement in both surgical techniques and neoadjuvant chemotherapy has been achieved, the 5‐year survival rate of locally advanced tumors was, at best, still 55%. Therefore, elucidation of mechanisms of the malignancy is eagerly awaited. Epithelial‐mesenchymal transition (EMT) by transforming growth factor‐β (TGF‐β) has been reported to have critical biological roles for cancer cell stemness, whereas little is known about it in ESCC. In the current study, a transcriptional factor SIX1 was found to be aberrantly expressed in ESCCs. SIX1 cDNA transfection induced overexpression of transforming growth factors (TGFB1 and TGFB2) and its receptor (TGFBR2). Cell invasion was reduced by SIX1 knockdown and was increased in stable SIX1‐transfectants. Furthermore, the SIX1‐transfectants highly expressed tumor basal cell markers such as NGFR, SOX2, ALDH1A1, and PDPN. Although mock‐transfectants had only a 20% PDPN‐high population, SIX1‐transfectants had 60–70%. In two sets of 42 and 85 ESCC patients receiving surgery alone or neoadjuvant chemoradiotherapy followed by surgery, the cases with high SIX1 mRNA and protein expression level significantly showed a poor prognosis compared with those with low levels. These SIX1 high cases also expressed the above basal cell markers, but suppressed the differentiation markers. Finally, TGF‐β signaling blockade suppressed ESCC cell growth in association with the reduction of PDPN‐positive tumor basal cell population. The present results suggest that SIX1 accelerates self‐renewal of tumor basal cells, resulting in a poor prognosis for ESCC patients.

Discovery of a Good Responder Subtype of Esophageal Squamous Cell Carcinoma with Cytotoxic T-Lymphocyte Signatures Activated by Chemoradiotherapy.

Definitive chemoradiotherapy (CRT) is a less invasive therapy for esophageal squamous cell carcinoma (ESCC). Five-year survival rate of locally advanced ESCC patients by definitive CRT were 37%. We previously reported that tumor-specific cytotoxic T-lymphocyte (CTL) activation signatures were preferentially found in long-term survivors. However, it is unknown whether the CTL activation is actually driven by CRT. We compared gene expression profiles among pre- and post-treatment biopsy specimens of 30 ESCC patients and 121 pre-treatment ESCC biopsy specimens. In the complete response (CR) cases, 999 overexpressed genes including at least 234 tumor-specific CTL-activation associated genes such as IFNG, PRF1, and GZMB, were found in post-treatment biopsy specimens. Clustering analysis using expression profiles of these 234 genes allowed us to distinguish the immune-activated cases, designating them as I-type, from other cases. However, despite the better CR rate in the I-type, overall survival was not significantly better in both these 30 cases and another 121 cases. Further comparative study identified a series of epithelial to mesenchymal transition-related genes overexpressed in the early relapse cases. Importantly, the clinical outcome of CDH2-negative cases in the I-type was significantly better than that of the CDH2-positive cases in the I-type. Furthermore, NK cells, which were activated by neutrophils-producing S100A8/S100A9, and CTLs were suggested to cooperatively enhance the effect of CRT in the CDH2-negative I-type. These results suggested that CTL gene activation may provide a prognostic advantage in ESCCs with epithelial characteristics.

Multiple roles of single-minded 2 in esophageal squamous cell carcinoma and its clinical implications

Degree of histological differentiation is an important characteristic of cancers and may be associated with malignant potential. However, in squamous cell carcinomas, a key transcriptional factor regulating tumor differentiation is largely unknown. Chemoradiotherapy (CRT) is a standard treatment for locally advanced esophageal squamous cell carcinoma; however, the survival rate is still below 40%. From microarray data, single‐minded 2 (SIM2) was overexpressed in the epithelial subtype. Here, we investigated the correlation between SIM2 expression and its clinical implication, and in vitro and in vivo functions of SIM2 in tumor differentiation and in CRT sensitivity. Although SIM2 was suppressed in cancerous tissues, SIM2‐high ESCC showed a favorable prognosis in CRT. Transient SIM2 expression followed by 3D culture induced expression of differentiation markers and suppressed epithelial‐mesenchymal transition‐ and basal‐cell markers. Levels of PDPN‐high tumor basal cells and of expression of genes for DNA repair and antioxidant enzymes were reduced in stable transfectants, and they showed high CDDP and H2O2 sensitivities, and their xenografts showed a well‐differentiated histology. Reduction of tumor basal cells was restored by knockdown of aryl hydrocarbon receptor nuclear translocator (ARNT) that interacted with SIM2. Together, SIM2 increases CRT sensitivity through tumor differentiation by cooperation with ARNT.

S-1 Salvage Chemotherapy for Esophageal Squamous Cell CarcinomaRefractory to the Standard Chemotherapy

Objective: Fluorouracil, cisplatin, and taxane are widely used in the standard chemotherapy regimens for esophageal squamous cell carcinoma (ESCC). Although S-1 is expected to demonstrate considerable efficacy for ESCC, there is any clinical data. The purpose of this retrospective study was to evaluate the efficacy and safety of S-1 as salvage chemotherapy for ESCC. Methods: From 2007 to 2014, fifteen patients with ESCC refractory or refusal to the standard chemotherapy were treated with S-1 as salvage treatment at the Kyoto University Hospital and their clinical records were reviewed retrospectively. Results: The median age was 70 years old (range: 63-77). A complete response (CR) was achieved in 1 case (7%). A stable disease (SD) and progressive disease (PD) were seen in 9 (60%) and 5 (33%) cases, respectively. After a follow-up duration of 13.9 months, median progression free survival and overall survival was 6.2 and 10.0 months, respectively. One-year survival rate was 33.3%. Toxicities greater than CTCAE grade 3 were observed in 3 of 15 patients (20%). Two patients had grade 3 neutropenia and one patient had grade 3 diarrhea. There was no treatment related death. Conclusions: S-1 salvage chemotherapy could be expected to be an effective and safe treatment option to improve the prognosis of patients with ESCC refractory to the standard chemotherapy.