Abstract 1001: Urinary metabolite diagnostic and prognostic liquid biopsy biomarkers of lung cancer - never smokers versus tobacco smokers

Introduction: Never smokers account for 10-13% of all lung cancer cases in the United States. The etiology is attributed to multiple causes including exposure to passive smoking, parental smoking, asbestos and radon. However, these lung cancer cases do not fit the current United States Government-funded criterion of low-dose computed tomography that identifies early stages of lung cancer with higher survival following surgical removal.

Methods: The cancer urinary biomarkers, creatine riboside (CR) and N-acetylneuraminic acid (NANA), were analyzed and quantified by liquid chromatography-mass spectrometry to determine if never smokers with non-small cell lung cancer (NSCLC) can also be identified alongside tobacco smoker NSCLC cases as compared with gender and age-matched non-cancer population controls.

Results: These cancer biomarkers were significantly higher and comparable in never-smokers and tobacco smokers cases compared to population controls. Receiver Operating Characteristics (ROC) analysis in never smokers was equivalent for CR and NANA levels area under the curve (AUC) 0.91. In contrast, combined CR and NANA levels resulted in better predictive performance (AUC 0.94). Kaplan-Meier survival curves showed that high levels of CR and NANA were associated (p<0.05) with increased cancer-specific death in never-smokers and tobacco smokers. Therefore these metabolites are independent of Tobacco smoking. NANA metabolite category factor, histology and stage were independent predictors of survival (p<0.05) in multivariate analyses for never smokers as shown in Table 1.

Conclusions: These results indicate that measuring CR and NANA in liquid biopsy urine could identify never-smoking lung cancer candidates for LDCT screening and warrant prospective studies of these biomarkers in high-risk environments.

Table 1. Univariate and multivariate regression analysis for factors associated with survival in the never smokers population Univariate Analysis Multivariate analysis Factors Levels N HR 95%CI P-value HR 95%CI P-value Stage Early Stage (I & II); Late Stage (III & IV) 145 3.52 2.3, 5.3 <0.001 3.94 2.2, 6.8 <0.001 Histology Adenocarcinoma; Squamous cell carcinoma 114 1.62 0.7, 3.5 0.26 3.42 1.4, 7.9 0.01 CR Category Low; High 166 1.34 0.8-2.1 0.19 1.67 0.9, 3.0 0.08 NANA Category Low; High 166 2.11 1.1-3.9 0.009 2.31 1.0, 5.0 0.02 Age N=166 166 1.00 0.9, 1.0 0.50 0.99 0.9, 1.0 0.4 Sex Male; Female 166 0.87 0.5, 1.2 0.49 0.90 0.5, 1.5 0.7 Race African American; European American 166 0.82 0.2, 2.5 0.75 0.40 0.1, 1.3 0.2

Citation Format: Bhavik Dalal, Takeshi Tada, Daxesh P. Patel, Mohammed Khan, Takahiro Oike, Yasuyuki Kanke, Amelia Parker, Majda Haznadar, Leila Toulabi, Kristopher Krausz, Ana Robles, Elise Bowman, Frank Gonzalez, Curtis Harris. Urinary metabolite diagnostic and prognostic liquid biopsy biomarkers of lung cancer - never smokers versus tobacco smokers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1001.

Creatine riboside is a cancer cell-derived metabolite associated with arginine auxotrophy

The metabolic dependencies of cancer cells have substantial potential to be exploited to improve the diagnosis and treatment of cancer. Creatine riboside (CR) is identified as a urinary metabolite associated with risk and prognosis in lung and liver cancer. However, the source of high CR levels in patients with cancer as well as their implications for the treatment of these aggressive cancers remain unclear. By integrating multiomics data on lung and liver cancer, we have shown that CR is a cancer cell–derived metabolite. Global metabolomics and gene expression analysis of human tumors and matched liquid biopsies, together with functional studies, revealed that dysregulation of the mitochondrial urea cycle and a nucleotide imbalance were associated with high CR levels and indicators of a poor prognosis. This metabolic phenotype was associated with reduced immune infiltration and supported rapid cancer cell proliferation that drove aggressive tumor growth. CR^hi cancer cells were auxotrophic for arginine, revealing a metabolic vulnerability that may be exploited therapeutically. This highlights the potential of CR not only as a poor-prognosis biomarker but also as a companion biomarker to inform the administration of arginine-targeted therapies in precision medicine strategies to improve survival for patients with cancer.

Short-term outcomes of neoadjuvant chemotherapy with capecitabineplus oxaliplatin for patients with locally advanced rectal cancerfollowed by total or tumor-specific mesorectal excision with orwithout lateral pelvic lymph node dissection

Background: The standard strategy in Japan for locally advanced rectal cancer is total mesorectal excision plus adjuvant chemotherapy. However, large tumors significantly restrict pelvic manipulation of the distal side of the tumor during surgery; therefore, from an oncological point of view, it is better to shrink the tumor as much as possible preoperatively to optimize the circumferential resection margin. In recent years, advances in systemic chemotherapy have significantly improved the tumor reduction effect, enabling such drug therapy prior to surgery for locally advanced rectal cancer. We herein retrospectively evaluated the clinical, short-term outcomes of patients treated by neoadjuvant chemotherapy (NAC) using capecitabin and oxaliplatin (CAPOX), focusing on overall safety as well as clinical and pathological staging responses to NAC.

Methods: We applied the preoperative chemotherapy protocol to T3-4, any N, M0 or M1a (with resectable metastases) (UICC 8^th) Ra/Rb rectal cancers. The chemotherapy regimen consisted of four cycles of CAPOX. After NAC, curative intent surgery with total mesorectal excision/tumor-specific mesorectal excision with/without metastasectomy was performed. Adverse effects (AEs) and compliance with NAC, surgical complications, clinical and pathological staging were evaluated. All patients undergoing the protocol between January 2017 and June 2021 at Fukushima Medical University were enrolled.

Results: Twenty cases were enrolled. No severe AEs were observed either preoperatively or perioperatively. Preoperative assessment of NAC showed no cases of progressive disease (PD). Radical resection was achieved in all cases. Histological therapeutic grading after NAC revealed one grade 3, four grade 2, three grade 1b, eleven grade 1a and one grade 0 among all cases.

Conclusion: This study suggests that NAC for locally advanced rectal cancer is likely to be acceptable because there were no severe AEs pre- or perioperatively, radical resection was achieved in all cases, and there were no cases of PD.

SH2D4A downregulation due to loss of chromosome 8p is associated with poor prognosis and low T cell infiltration in colorectal cancer

BACKGROUND

Colorectal cancer (CRC) develops through chromosomal instability (CIN) or microsatellite instability (MSI) due to deficient mismatch-repair (dMMR). We aimed to characterise novel cancer-associated genes that are downregulated upon malignant transformation in microsatellite stable (MSS) CRCs, which typically exhibit CIN with proficient mismatch-repair (pMMR).

METHODS

Comprehensive screening was conducted on adenomas, MSI/MSS CRCs and cell lines, followed by copy number analysis, and their genetic and prognostic relevance was confirmed in microarray and RNA-seq cohorts (n = 3262, in total). Immunohistochemistry for SH2D4A was performed in 524 specimens of adenoma, carcinoma in situ and dMMR/pMMR CRC. The functional role of SH2D4A was investigated using CRC cell lines.

RESULTS

A set of 11 genes, including SH2D4A, was downregulated during the adenoma-carcinoma sequence in MSS/CIN CRCs, mainly due to chromosome 8p deletions, and their negative prognostic impact was validated in independent cohorts. All adenomas were SH2D4A positive, but a subset of CRCs (5.3%) lacked SH2D4A immunohistochemical staining, correlating with poor prognosis and scarce T cell infiltration. SH2D4A depletion did not affect cell proliferation or IL-6-induced STAT3 phosphorylation.

CONCLUSIONS

Our findings suggest that downregulation of multiple genes on chromosome 8p, including SH2D4A, cooperatively contribute to tumorigenesis, resulting in the immune cold tumour microenvironment and poor prognosis.

Validation of Gene Expression-Based Predictive Biomarkers for Response to Neoadjuvant Chemoradiotherapy in Locally Advanced Rectal Cancer

BACKGROUND

Neoadjuvant chemoradiotherapy (nCRT) followed by surgery is widely used for patients with locally advanced rectal cancer. However, response to nCRT varies substantially among patients, highlighting the need for predictive biomarkers that can distinguish non-responsive from responsive patients before nCRT. This study aimed to build novel multi-gene assays for predicting nCRT response, and to validate our signature and previously-reported signatures in multiple independent cohorts.

METHODS

Three microarray datasets of pre-therapeutic biopsies containing a total of 61 non-responders and 53 responders were used as the discovery cohorts to screen for genes that were consistently associated with nCRT response. The predictive values of signatures were tested in a meta-analysis using six independent datasets as the validation cohorts, consisted of a total of 176 non-responders and 99 responders.

RESULTS

We identified four genes, including BRCA1, GPR110, TNIK, and WDR4 in the discovery cohorts. Although our 4-gene signature and nine published signatures were evaluated, they were unable to predict nCRT response in the validation cohorts.

CONCLUSIONS

Although this is one of the largest studies addressing the validity of gene expression-based classifiers using pre-treatment biopsies from patients with rectal cancer, our findings do not support their clinically meaningful values to be predictive of nCRT response.

[A Case of Laparoscopic Surgery for Preoperatively Diagnosed Gastric Metastasis of Lung Cancer]

The patient was a 66-year-old male who had undergone an operation for lung cancer and solitary brain metastases. Follow- up PET-CT after 1 year detected FDG accumulation in the stomach. We performed esophagogastroscopy and found an approximately 20 mm-sized Type 2 tumor on the greater curvature of the upper stomach. A pathological diagnosis of lung adenocarcinoma metastasis in the stomach was made. Laparoscopic surgery was performed on the metastatic lesion to prevent bleeding and perforation, and resection was achieved with minimal invasion. The current development of chemotherapy, including immunotherapy, has contributed to the improved prognosis of cancer patients, including those with lung metastasis in the stomach. Considering these backgrounds, preventive surgical resection under laparoscopy may be an effective approach for improving prognosis and preventing acute life-threatening adverse events. We report this case along with a literature review.

Circulating tumor cells after neoadjuvant chemotherapy are related with recurrence in esophageal squamous cell carcinoma

BACKGROUND

Circulating tumor cells (CTCs) are known to be a systemic process of malignant progression of cancer cells and there is a possibility that analysis for CTCs as a liquid biopsy become predictive or prognostic tools for cancer patients.

METHODS

In the present study with the novel CTCs detection system (Celsee system^®), we performed quantitative and qualitative analysis of CTCs in patients with esophageal squamous cell carcinoma (ESCC) receiving neoadjuvant chemotherapy (NAC) with 5FU + CDDP regimen. CTCs are defined as having both DAPI positive and CD45 negative. Vimentin-positive CTCs were defined as mesenchymal-type CTCs (M-CTCs), while epithelial-type CTCs (E-CTCs) were only positive for pan-cytokeratin.

RESULTS

At the baseline, there are detectable amounts of CTCs in all patients (n = 30) at all stages, and there were no significant differences of total CTCs, E-CTCs, or M-CTCs numbers between stages. Of importance, among total CTCs, M-CTCs are more dominant than E-CTCs in number. Also, there was no significant change of detectable amounts and phenotype of CTCs before and after NAC (n = 24). Of note, early recurrent group indicated that there was an elevated total CTCs number before NAC and an increased M-CTCs after NAC in comparison to those in non-recurrent group.

CONCLUSIONS

Quantitative and qualitative analysis of CTCs may provide useful complementary predictive and prognostic information in ESCC.

Stromal expression of cancer-associated fibroblast-related molecules, versican and lumican, is strongly associated with worse relapse-free and overall survival times in patients with esophageal squamous cell carcinoma

Cancer-associated fibroblasts (CAFs) in the tumor microenvironment play an essential role in the tumor progression of esophageal squamous cell carcinoma (ESCC). The present study aimed to investigate the expression of CAF-related molecules, versican, periostin and lumican, in cancer stroma, to provide prognostic stratification for patients with ESCC after surgery. A total of 106 patients with ESCC who underwent curative esophagectomy without preoperative chemotherapy or radiotherapy were enrolled. The expression of CAF-related stromal proteins, including versican, periostin and lumican, was examined using immunohistochemistry, and the prognostic value was assessed by Kaplan-Meier survival analysis, and univariate and multivariate Cox regression models. The expression of versican, periostin and lumican was found specifically in the stromal component of ESCC. Kaplan-Meier analysis demonstrated that, compared with a low expression level, a high expression level of versican, periostin or lumican in the cancer stroma was significantly associated with worse relapse-free survival (RFS) and overall survival times in patients with ESCC. The prognostic values of stromal versican and lumican remained significant in a stratified analysis of stage I patients. Moreover, univariate and multivariate analysis revealed that high stromal versican or lumican expression was an independent prognostic factor for RFS in the patients. The present study demonstrated that CAF-related molecules, including versican, periostin and lumican, were expressed in the stroma of ESCC, and that stromal expression of versican and lumican in particular may have clinical utility as a prognostic biomarker for poor RFS in postoperative patients with ESCC.

Neoadjuvant Chemotherapy Induces IL34 Signaling and Promotes Chemoresistance via Tumor-Associated Macrophage Polarization in Esophageal Squamous Cell Carcinoma

The tumor microenvironment (TME) plays a key role in the efficacy of neoadjuvant chemotherapy (NAC) in solid tumors including esophageal squamous cell carcinoma (ESCC). However, the TME profile of ESCC treated with NAC is not fully understood. In this study, we investigated the effect of NAC on the TME especially tumor-associated macrophages (TAM), the important immunosuppressive components of the TME, in ESCC. We quantified the expression of CD163, a crucial marker of TAM, in pretherapeutic biopsy and surgically resected ESCC specimens from patients who received NAC (n = 33) or did not receive NAC (n = 12). We found that NAC dramatically increased the expression of CD163 on TAMs in ESCC. Colony-stimulating factor 1 (CSF-1) and IL34 are crucial cytokines that recruit monocytes into tumor sites and differentiate them into TAMs. Interestingly, NAC significantly upregulated the expression of IL34 but not CSF-1 on tumor cells, and the frequencies of CD163⁺ TAMs were significantly correlated with IL34 expression in ESCC after NAC. The expression of IL34 in NAC-nonresponsive patients was significantly higher than that in NAC-responsive patients, and patients with IL34-high ESCC exhibited worse prognosis as compared with patients with IL34-low ESCC. We also demonstrated that 5-fluorouracil (5-FU)/cisplatin preferentially increased mRNA expression of IL34 on human ESCC cell lines. Human peripheral blood monocytes co-cultured with ESCC cells treated with 5-FU/cisplatin increased the expression of CD163, which was attenuated by the treatment with CSF-1R inhibitors. These data suggest that IL34 expression by NAC shifts the TME toward CD163⁺ TAM-rich immunosuppressive and chemo-insensitive microenvironment in ESCC. IMPLICATIONS: The blockade of IL34 signaling may offer a novel therapeutic strategy against chemoresistance in ESCC by inhibiting M2-TAM polarization.

[A Case of Pelvic Liposarcoma Resected by Hybrid Approach]

Surgical resection is the most effective treatment for liposarcoma, a retroperitoneal malignant soft tissue tumor, and a reliable negative margin is required because of the high risk of local recurrence. We reported a case of pelvic liposarcoma that could be resected by laparoscopic and transsacral hybrid approach. A 60's-man had a mixed liposarcoma occupying the right rear of the pelvis in the rectum. The operation was preceded by a laparoscopic operation, and the right internal iliac artery and vein and the superior rectal artery were dissected. The tumor was separated along the right pelvic wall. The oral rectum was transected and the colon was elevated by the extraperitoneal route. After conversion to the Jackknife position, the anterior sacrum was exfoliated with the right transsacral approach, the coccyx was resected, and the rectal anus, tumor, and surrounding fatty tissue were removed as an en bloc fasion. Histopathological examination showed mixed type of liposarcoma and negative margin of the stump. The patient is alive without recurrence 8 months after the surgery.

Improved detection and precise relative quantification of the urinary cancer metabolite biomarkers - Creatine riboside, creatinine riboside, creatine and creatinine by UPLC-ESI-MS/MS: Application to the NCI-Maryland cohort population controls and lung cancer cases

Creatine riboside (CR) is a novel metabolite of cancer metabolism. It is a urinary diagnostic biomarker of lung and liver cancer risk and prognosis. The level of CR is highly positive correlated in tumor and urine indicating that it is derived from human lung and liver cancers. A precise and sensitive ultra-pressure liquid chromatography-tandem mass spectrometry (UPLC-ESI-MS/MS) method was developed and validated for simultaneous quantification of the noninvasive biomarker CR, along with creatinine riboside (CNR), and their precursors creatine and creatinine, utilizing the labeled internal standard creatine riboside-13C,15N2 (CR-13C,15N2). Chromatography was carried out on a hydrophilic interaction chromatography column under a gradient mobile phase condition. MRM transitions were monitored for CR (264.1 > 132.1, m/z), CNR (246.1 > 113.9, m/z), creatine (132.0 > 72.0, m/z), creatinine (114.0 > 85.8, m/z) and CR-13C,15N2 (267.1 > 134.9, m/z) with a 11.0 min run time in the positive mode ionization. The calibration plot of the method was linear over the concentration range of 4.50-10,000 nM. Method validation was performed according to regulatory guidelines established for sensitivity, selectivity, calibration curve, stability at different storage conditions, reinjection reproducibility, ruggedness with acceptable accuracy, and precision. This assay was applied for the quantification of CR along with CNR, creatine and creatinine in a subset of urine and serum samples from the National Cancer Institute - Maryland (NCI-MD) cohort population controls and lung cancer cases. It can be standardized and used in multiple laboratories for cancer diagnosis and determining the efficacy of cancer therapy and monitoring cancer recurrence.

Tn Antigen Expression Defines an Immune Cold Subset of Mismatch-Repair Deficient Colorectal Cancer

Colorectal cancer (CRC) cells often express Tn antigen, a tumor-associated truncated immature O-glycan (GalNAcα-O-Ser/Thr) that can promote tumor progression. Immunotherapies against Tn antigen have been developed and are being evaluated in clinical trials. Tn antigen can also be considered a novel immune checkpoint that induces immunosuppressive signaling through glycan-biding lectins to lead effector T cell apoptosis. We evaluated the correlation of Tn antigen expression by immunohistochemistry with mismatch-repair (MMR) status, tumor-infiltrating lymphocytes, tumor cell PD-L1 expression, and clinicopathological characteristics in 507 CRC patients. Although 91.9% of CRCs showed negative or weak Tn antigen staining (Tn-negative/weak), we identified a small subset of CRCs (8.1%) that displayed particularly intense and diffuse distribution of Tn antigen immunoreactivity (Tn-strong) that closely related to deficient MMR (dMMR). Moreover, 40 dMMR CRCs were stratified into 24 Tn-negative/weak dMMR tumors (60.0%) exhibiting dense CD8+ lymphocyte infiltrate concomitant with a high rate of PD-L1 positivity, and 16 Tn-strong dMMR tumors (40.0%) that demonstrated CD8+ T cell exclusion and a lack of PD-L1 expression, which was comparable to those of proficient MMR. Our finding suggests that the immune cold subset of patients with Tn-strong dMMR CRC may be effectively treated with immune checkpoint blockade therapy or cellular immunotherapy targeting Tn antigen.

Expression profile of CADM1 and CADM4 in triple negative breast cancer with primary systemic therapy

Triple negative breast cancer (TNBC) is defined by a lack of ER, PgR, and HER2 expression, and to date there have been no significant advances in treatment by targeted therapies against those molecules. Therefore, primary systemic therapy (PST) followed by surgery is the standard therapy for patients with advanced TNBC. According to gene expression analysis, TNBC has a distinct profile when compared with non-TNBC, suggesting that a unique gene affects the treatment efficacy of PST. Cell adhesion molecule (CADM) genes encode an immunoglobulin superfamily molecule involved in cell-to-cell adhesion in a variety of human epithelial cells. While it has been reported that inactivation of CADM1 and CADM4 serves a pivotal role in the progression of breast cancer, a full analysis has not been completed for TNBC. Previous studies have reported that CADM1 and CADM4 expression is less likely to be decreased in TNBC than in non-TNBC. In the present study, CADM1 and CADM4 expression was evaluated in patients with TNBC who had received PST. The present study revealed that loss or weak expression of CADM1 was frequently observed in non-pathological complete response patients. Furthermore, while the majority of TNBC cases exhibited high CADM1 expression, a small number of cases exhibited low CADM1 expression and low therapeutic response of PST for TNBC. These results suggest that CADM1 has a pivotal role in anti-PST efficacy in patients with TNBC.

Abstract A18: Diagnostic and prognostic utility of urinary creatine riboside for early stage non-small cell lung cancer

This abstract is being presented as a short talk in the scientific program. A full abstract is printed in the Proffered Abstracts section (PR02) of the Conference Proceedings.

Citation Format: Takahiro Oike, Yasuyuki Kanke, Amelia Parker, Majda Haznadar, Kristopher W. Krausz, Elise D. Bowman, Ana I. Robles, Frank J. Gonzalez, Curtis C. Harris. Diagnostic and prognostic utility of urinary creatine riboside for early stage non-small cell lung cancer [abstract]. In: Proceedings of the Fifth AACR-IASLC International Joint Conference: Lung Cancer Translational Science from the Bench to the Clinic; Jan 8-11, 2018; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(17_Suppl):Abstract nr A18.

Upregulated HOXA9 expression is associated with lymph node metastasis in colorectal cancer

Homeobox A (HOXA) cluster genes, members of the HOX family, perform an important role in normal organ development. It has previously been reported that HOXA gene expression in various types of cancer is associated with poor patient outcomes. However, the role of HOXA genes, as well as their expression, in colorectal cancers (CRC) remains unknown. Therefore, the present study investigated HOXA gene expression in patients with CRC and revealed that HOXA9 expression was significantly increased in tumor tissues compared with non-tumor tissues. Additionally, the functional role of HOXA9 was assessed by knocking down the HOXA9 gene in CRC cells and by evaluating cell growth. Regarding gene expression, cases with positive HOXA9 expression (as detected by immunohistochemical staining) were significantly associated with higher TNM stage and positive lymph node metastasis, although no association was observed between increased HOXA9 levels and the rate of overall survival in the present cohort. Regarding the functional role, HOXA9 expression was demonstrated to be upregulated in patients with CRC and was associated with lymph node metastasis.

Upregulated solute carrier family 37 member 1 in colorectal cancer is associated with poor patient outcome and metastasis

Solute carrier (SLC) drug transporters exchange various molecules without energy from adenosine triphosphate hydrolysis, indicating an association with anticancer drug resistance. However, the expression and role of SLC transporters in malignant tumors has not yet been fully elucidated. Therefore, in the current study, the expression of SLC37A family genes was evaluated in patients with colorectal cancer (CRC), and it was revealed that SLC family 37 member 1 (SLC37A1) expression was significantly increased in tumorous tissues compared with that in non-tumorous tissues. The cases with upregulated expression of SLC37A1 by immunohistochemical staining were significantly associated with positive venous invasion and liver metastasis. Furthermore, upregulated SLC37A1 expression was associated with poor overall survival time in the present cohort. These results indicated that SLC37A1 is involved in the hematogenous metastasis of CRC. To investigate whether SLC37A1 is associated with hematogenous metastasis and glycolipid metabolism, SLC37A1 was knocked down in colon cancer cells, and the expression of sialyl Lewis A and sialyl Lewis X was observed to be decreased. In summary, upregulation of SLC37A1 was observed in patients with CRC, and was associated with poor patient outcomes and survival. To the best of our knowledge, the present study is the first to propose a key role of SLC37A1 in CRC, and additional studies are warranted to reveal the functional role of SLC37A1 in CRC development.

Enhanced expression of KIF4A in colorectal cancer is associated with lymph node metastasis

Kinesin family member 4A (KIF4A) is a member of the kinesin 4 subfamily of kinesin-related proteins and serves an important role in cell division. The expression levels of KIF4A have been investigated in numerous types of cancer, including cervical, lung, oral, and breast cancer, and are established to be associated with poor patient prognosis. However, the role of KIF4A, as well as its expression in colorectal cancer (CRC), remains to be elucidated. Therefore, the current study investigated KIF4A expression levels in patients with CRC and demonstrated that its levels were increased in tumor tissues compared with non-tumor tissues. To investigate the functional role of KIF4A, KIF4A was knocked down in CRC cells and cell viability was evaluated. CRC cells with KIF4A knockdown exhibited lower cell proliferation compared with control cells. In addition, KIF4A expression levels, as determined by immunohistochemistry, were compared with the expression of Ki-67, but no significant associations were observed in the patients with CRC. Therefore, KIF4A was found to be upregulated in patients with CRC and downregulation of KIF4A reduced cell proliferation in CRC cells. These results suggest that KIF4A may be a potential therapeutic target, which may improve the outcomes of patients with CRC.

Annexin A1 is involved in resistance to 5-FU in colon cancer cells

Resistance to 5-fluorouracil (5‑FU), a key drug in the treatment of colorectal cancer, is one of the major reasons for poor patient prognosis during cancer treatment. Annexin A1 (ANXA1) is a calcium‑dependent phospholipid‑linked protein that is associated with drug resistance, anti‑inflammatory effects, regulation of cellular differentiation, proliferation and apoptosis. Although there have been several studies investigating ANXA1 expression in drug resistant cells, the role of ANXA1 is yet to be fully understood. We therefore, in this study, generated SW480 cells resistant to 5‑FU (SW480/5‑FU) to evaluate ANXA1 expression. When compared to the control cells, ANXA1 expression was significantly induced in the SW480/5‑FU cells. We then revealed the role of ANXA1 expression in 5‑FU resistance by using overexpression and knockdown methods in colon cancer cells. Overexpression of ANXA1 induced a significant increase of cell viability to 5‑FU, whereas ANXA1 knockdown induced a significant decrease of cell viability to 5‑FU. Further experiments revealed that ANXA1 expression was induced by hypoxia in colon cancer cells. These results suggest that ANXA1 expression may play a critical role in 5‑FU resistance and may be induced by hypoxia during cancer progression. Our results provide a possible strategy to overcome 5‑FU resistance by modulating ANXA1 expression.

Immunosuppression involving increased myeloid-derived suppressor cell levels, systemic inflammation and hypoalbuminemia are present in patients with anaplastic thyroid cancer

Anaplastic thyroid carcinoma (ATC) is one of the most aggressive neoplasms in humans and myeloid-derived suppressor cells (MDSCs) contribute to the negative regulation of immune responses in the context of cancer and inflammation. In order to investigate the pathophysiology of thyroid cancer, peripheral blood mononuclear cells (PBMCs) were obtained from 49 patients with thyroid cancer, 18 patients with non-cancerous thyroid diseases and 22 healthy volunteers. The MDSC levels were found to be higher in patients with any type of thyroid cancer (P<0.05), patients with ATC (P<0.001) and patients with medullary thyroid carcinoma (P<0.05), when compared to patients with non-cancerous thyroid diseases. The MDSC levels were also higher in patients with stage III-IV thyroid cancer compared to those in patients with non-cancerous thyroid diseases (P<0.05). The stimulation index (SI) of phytohemagglutinin (PHA)-induced lymphocyte blastogenesis was significantly lower, the C-reactive protein (CRP) levels were significantly higher and the serum albumin levels were significantly lower in patients with ATC compared to those in patients with non-cancerous thyroid diseases. The SI was significantly lower in stage III and IV thyroid cancer compared to that in non-cancerous thyroid disease (P<0.05). Furthermore, the CRP levels were higher and the concentration of albumin was lower in stage IV thyroid cancer compared to those in non-cancerous thyroid disease (P<0.05). Patients with thyroid carcinoma were then classified into one of two groups according to a %PBMC of MDSC cut-off level of 1.578, which was the average %PBMC of MDSC of patients with any type of thyroid carcinoma. In patients with higher MDSC levels, the production of CRP and interleukin (IL)-10 was significantly higher (P<0.05) and the albumin levels were significantly lower (P<0.05) compared to those in patients with lower MDSC levels. These data indicate that MDSCs are increased in patients with ATC. Furthermore, these patients exhibited suppression of cell-mediated immune responses, chronic inflammation and nutritional impairment.

Circulating myeloid-derived suppressor cells (MDSC) and correlation to poor prognosis, Th2-polarization, inflammation, and nutritional damages in patients with gastric cancer

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Background: Recent studies have shown that myeloid-derived suppressor cells (MDSC), which have been identified in most patients, are potent suppressors of T cell activation. MDSC have been reported to be correlated with tumorigenesis and the progression of tumors. We have previously reported significant correlations of MDSC with nutritional damage and inflammation in many types of cancer. In this study the quantitative detection of MDSC in peripheral blood was analyzed in the prognosis in patients with gastric cancer. Methods: We tested PBMCs from 29 preoperative patients with gastric cancer and 18 healthy volunteers using flow cytometric analysis (CD14-CD11b+CD33+). Markers for nutritional status (serum levels of total protein), inflammation (NLR: neurphil/lymphocyte ratio, serum levels of vascular endothelial growth factor: VEGF) and Th2-polarization (PBMC’s production of IL-6 and IL-10) were measured in this study. The prognosis of the patients was assessed by Kaplan-Meier tests for correlation with levels of MDSC. Results: MDSC levels in 29 preoperative patients with gastric cancer were significantly higher than in normal volunteers. These levels were not associated with pathological characteristics. However they were significantly correlated with the production of IL-6 and IL-10, VEGF levels and NLR. A significant inverse correlation with levels of total protein was obtained. MDSCs were increased in stage IV patients compared with healthy volunteer and 2-year survival rate of the patients with higher levels of MDSC (> 1.104%PBMC) was significantly poorer (median OS, 498 vs 473 days; p = 0.048), while there was no significant difference in patients with stages I, II, and III. Conclusions: These data suggest that increased MDSC is an effective biomarker for immunosuppression due to Th2-polarization, nutritional impairment, systemic inflammation and poor prognosis in advanced patients with gastric cancer.

Molecular nature of ultraviolet B light-induced deletions in the murine epidermis

Depletion of the stratospheric ozone layer leads to an increase in ambient UV loads, which are expected to raise skin cancer incidences. Tumor development in the skin could be a multistep process in which various genetic alterations, such as point mutations and deletions, occur successively. Here, we demonstrate that UVB irradiation efficiently induces deletions in the epidermis using a novel transgenic mouse, gpt delta. In this mouse model, deletions in lambda DNA integrated in the chromosome are preferentially selected as Spi(-) (sensitive to P2 interference) phages, which can then be subjected to molecular analysis. The mice were exposed to UVB at single doses of 0.3, 0.5, 1.0, 1.5, and 2.0 kJ/m(2). After 4 weeks, lambda phage was rescued from the genomic DNA of the epidermis by in vitro packaging reactions. The mutant frequencies of Spi(-) with large deletions in the epidermis increased >15-fold at a UVB dose of 0.5 kJ/m(2) over the control. Molecular sizes of most of the large deletions were >1000 bp. More than one-half of the large deletions occurred between short direct-repeat sequences from 1 to 6 bp, and the remainder had flush ends. In the unirradiated mouse, almost all of the Spi(-) mutants were 1-bp frameshifts in runs of identical bases. These results suggest that UVB irradiation induces deletions in the murine epidermis, and most of the deletions are generated through end-joining of double strand breaks in DNA.

Dietary n-3 polyunsaturated fatty acid and status of immunocompetent cells involved in innate immunity in female rats

The aim of this study was to estimate the contributions of dietary n-3 polyunsaturated fatty acid (PUFA), a representative dietary immunosuppressant, to the activity of both alveolar macrophages (AM) and natural killer (NK) cells, and compare them to those of n-6 PUFA. Twelve 5-week-old female Sprague-Dawley rats were divided into two dietary groups, one fed a 10% fat diet for 9 weeks enriched with n-3 PUFA (n-3 diet) and the other an n-6 PUFA (n-6 diet). AM reduced the release of nitric oxide, monocyte chemoattractant protein 1 and tumor necrosis factor alpha in the rats fed the n-3 diet, compared with rats fed the n-6 diet. NK cell activity was reduced by consumption of the n-3 diet. This study suggests that consumption of n-3 PUFA can ameliorate pulmonary inflammatory disorders which are affected by the reduction of not only proinflammatory cytokines but also chemokine released from AM.

Dietary docosahexaenoic acid can alter the surface expression of CD4 and CD8 on T cells in peripheral blood

The effect of dietary docosahexaenoic acid (DHA) on T cell states in peripheral blood was investigated. Weanling male C57Bl/6N mice were kept on one of three 10% fat diets containing various amounts of DHA and linoleic acid for 4 weeks. Changing the concentration of dietary DHA did not alter the proportion of T cells expressing CD4 or CD8. However, increasing the concentration of dietary DHA lowered the expression of CD4 and CD8 on the cell surface. The decreased expression of these surface molecules involved in T cell proliferation has serious implications in the role of DHA as an immunosuppressant.

Mutagenicity of 2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP) in the new gpt delta transgenic mouse

Gender differences and organ specificity of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-induced mutagenesis were examined with the new gptdelta transgenic mouse (T. Nohmi, M. Katoh, H. Suzuki, M. Matsui, M. Yamada, M. Watanabe, M. Suzuki, N. Horiya, O. Ueda, T. Shibuya, H. Ikeda, T. Sofuni, A new transgenic mouse mutagenesis test system using Spi-and 6-thioguanine selections (Environ. Mol. Mutagen. 28 (1996) 465-470). In this mouse model, two distinct selections are employed to efficiently detect different types of mutations, i.e 6-thioguanine (6-TG) selection for point mutations and Spi-selection for deletions, respectively. In both selections, the highest mutant frequencies were observed in colon, followed by in spleen and liver. No increases in mutations were observed in testis, brain and bone marrow in PhIP-treated male mice. No significant differences in 6-TG and Spi- mutant frequencies were observed in colon and liver between male and female treated mice. The correlation between PhIP-induced mutagenesis and carcinogenesis in colon is discussed.

Defective control of apoptosis and mitotic spindle checkpoint in heterozygous carriers of ATM mutations

Ataxia telangiectasia (AT) carrier-derived lymphoblastoid cell lines (AT-LCLs/hetero) with suboptimal ATM protein expression were examined for the regulation of radiosensitivity, apoptosis, and mitotic spindle checkpoint in response to DNA-damaging agents. Although AT-LCLs/hetero showed intermediate radiation sensitivity, as determined by clonogenic assay, they were resistant to early-onset apoptosis, as much as AT patient-derived LCLs (AT-LCLs/homo). Furthermore, two of three AT-LCLs/hetero showed defective mitotic spindle checkpoint control in response to X-ray irradiation, which is a recently characterized biological feature in AT-LCLs/homo. Our findings indicate that carriers of ATM mutation have biological abnormalities due to haploinsufficiency of ATM protein or dominant-negative effect of mutant ATM protein. Thus, although it is still controversial whether ATM mutation carriers are at higher risk for cancer during adulthood, our findings based on in vitro biological indicators support the notion that at least some of such carriers are at a higher risk for cancer development than those without ATM mutation. Our findings may help to reevaluate epidemiological studies on cancer susceptibility in AT carriers.

Effects of isothiocyanates on growth and metastaticity of B16-F10 melanoma cells

3-Methylthiopropyl (MTPITC) and 5-methylthiopentyl isothiocyanate (MTPeITC), natural compounds found in human diets, were assayed for an inhibitory activity against the growth of B16-F10 murine melanoma cells in culture. MTPITC and MTPeITC showed a potent cytostatic effect; the two agents exhibited median inhibitory concentrations of 48 and 170 nM, respectively. Oral administration of 10 mumol MTPeITC on Day 1 after intravenous tumor cell injection achieved a marked reduction of pulmonary colonization in syngeneic mice. However, it caused atrophy of the thymus and selective loss of CD4+CD8+ cells in thymocytes. On the other hand, treatment with MTPITC showed no influence on pulmonary metastaticity or thymocytes. Neither MTPITC nor MTPeITC caused significant changes in the responsiveness of the splenocytes and thymocytes to mitogen. These results suggest that MTPeITC can protect against metastaticity as well as cell growth of tumor cells, regardless of the disadvantageous action on the thymus.

Secretion and excretion of immunoglobulin A to cecum and feces differ with type of indigestible saccharides

The study was conducted to elucidate the effects of orally administered indigestible saccharides (IDS) on immunoresponses of the intestinal tracts, especially secretion and excretion of immunoglobulin A (IgA). Male 4-week-old Sprague-Dawley rats were fed diets containing several kinds of IDS (cellulose, corn husk, glucomannan, curdlan and lactulose) at 5% for three weeks. The results indicated that the proportion of IgA-presenting lymphocytes in the cecal mucosa of the tested IDS groups increased significantly or tended to increase compared with that of the cellulose group. No significant differences among the experimental groups were observed in the CD4(+)- and CD8(+)-presenting lymphocytes and the CD4+/CD8+ ratios in the small intestine, cecum and mesenteric lymph nodes. IgA amounts in the cecal contents increased significantly in the glucomannan and curdlan groups as compared with that in the cellulose group. The inconsistent results were observed in the cecal IgA amounts of the lactulose group. Although IgA excretion into feces increased periodically in the cellulose, hardly any changes were observed in the glucomannan and curdlan groups. These results revealed that IgA secretion from cecal mucosa to contents was promoted, and its excretion to feces was decreased by the oral administration of highly fermentable IDS, respectively, while non- or low-fermentable IDS functioned adversely to IgA responses in the intestinal tract. It is suggested that the response of IgA in the intestinal immune system differs with the type of IDS ingested.

Effects of dietary docosahexaenoic acid on surface molecules involved in T cell proliferation

It is known that n-3 polyunsaturated fatty acids (PUFA) such as docosahexaenoic acid (DHA) suppress immunity as compared with n-6 PUFA such as linoleic acid (LA), but the mechanism involved in this phenomenon is still unclear. The present study was designed to assess the effect of dietary DHA on the surface molecules involved in T cell proliferation. Weanling male C57BL/6 mice were divided into four dietary groups that were fed a 10% fat diet for 4 weeks varying in amounts of DHA and LA. As the dietary DHA concentration increased, the surface expression of CD4 and CD8 on splenic T cells decreased, while that of CD28 increased. The surface expression of CD3, however, was invariable in all dietary groups. DNA synthesis of splenic T cells, induced by CD3 crosslinkage with anti-CD3 epsilon monoclonal antibody in the presence of CD28-mediated costimulation, increased as the DHA concentration was elevated. These observations suggest that diets rich in DHA exert some of their immunomodulatory effects by a downregulation of surface expression of CD4 and CD8 and by an upregulation of CD28-mediated costimulatory signal.

DNA damage-associated cell cycle and cell death control is differentially modulated by caffeine in clones with p53 mutations

Caffeine is known to potentiate the cytotoxic effects of DNA damaging agents and increases the sensitivity of p53-deficient cells to X-irradiation (X-IR). We have analyzed the cell cycle and cell death control after X-IR in the absence or presence of caffeine in hematological cell lines with various configurations of the p53 gene; EBV-immortalized lymphoblastoid cells with heterozygous p53 mutation (wt/mt), human leukemia cell lines HL60 and KOPM28 with no and mutant p53 expression, respectively. These cell lines display an impaired G0/G1 checkpoint and G2 delay following X-IR, and resistance to apoptosis, which are in accordance with findings previously reported. When irradiated in combination with caffeine, all these cell lines overrode the G2 delay and accumulated at G0/G1. The cell cycle modifications in these cell lines correlated with the increase in radiation-induced p34Cdc2 kinase activity by caffeine. These cell cycle control modifications by caffeine, however, were not associated with enhancement of radiation-induced apoptosis or reduction of clonogenic growth activity in these cell lines. These results suggest that the cytocidal effect of caffeine may need to be verified independently of its cell cycle regulatory activities at least in some cases with p53 mutation.

UVB-induced gpt mutations in the skin of gpt delta transgenic mice

Ultraviolet light B (UVB)-induced mutagenesis was studied in gpt delta transgenic mice, which contain the lambdaEG10 shuttle vector as a transgene. The mice were exposed to UVB at single doses of 0.3, 0.5, 1.0, 1.5, and 2.0 kJ/m(2). At 4 weeks after irradiation, the mutant frequencies (MF) of the gpt gene were determined in the epidermis and the dermis, and the gpt mutations in the epidermis were identified by DNA sequencing. The epidermis exhibited a higher sensitivity to UVB than the dermis at doses of 0.3 and 0.5 kJ/m(2) UVB: the MF of the epidermis were more than nine times higher than those of the nonirradiated mice, whereas the MF of the dermis were only two to three times higher than the nonirradiated level at the doses used. The UVB-induced mutation spectrum in the epidermis was dominated by G:C to A:T transitions at dipyrimidine sites, such as 5'-TC-3', 5'-CC-3', and 5'-T/C-CG-3'. Tandem transitions such as CC to TT were also observed. Interestingly, a remarkable bias towards the template strand of the gpt gene was observed in the single transitions at 5'-TC-3' and 5'-CC-3' sites, but not at 5'-T/C-CG-3' site. In contrast, G:C to A:T transitions at CpG sites and deletions were observed in nonirradiated mice. Hot spots of transitions were observed at different sites in UVB-irradiated and nonirradiated mice. These results indicate that gpt delta transgenic mouse is a suitable model for studying in vivo UVB-induced mutations at the molecular level.

Defective control of apoptosis, radiosensitivity, and spindle checkpoint in ataxia telangiectasia

We examined the regulation of apoptosis, radiosensitivity, and spindle checkpoint in response to DNA-damaging agents in ataxia telangiectasia (AT)-derived lymphoblastoid cell lines (AT-LCLs), which lack AT mutated (ATM) protein expression. In addition to the previous findings that AT-LCLs are defective in regulation of cell cycle at the G1, S, and G2-M checkpoints in response to X-ray irradiation (X-IR) and are highly sensitive to X-IR (J. Biol. Chem., 271: 20486-20493, 1996), we showed for the first time that AT-LCLs were defective in X-IR-associated spindle checkpoint control. The cells were also resistant to early apoptosis as much as LCLs derived from patients with Li-Fraumeni syndrome (LFS-LCLs). Terminal deoxynucleotidyl transferase-mediated nick end labeling assay of LCLs, however, demonstrated a significant increase in apoptotic cells among AT-LCLs cultured over a longer period after X-IR. These findings were in contrast to those of LFS-LCL, which showed very little increase in terminal deoxynucleotidyl transferase-mediated nick end labeling-positive population, even in cells with hyperploidy. Thus, although early apoptosis and cell cycle controls in response to DNA damage are disrupted in both ATM and p53 mutations, cells from AT patients are much more susceptible to late-onset apoptosis than those of LFS. These differences may depend on the level of accumulation of DNA damage and/or threshold that triggers late-onset cell death in ATM or p53 mutations. Our findings allow a better understanding of the role of ATM in p53-dependent and independent signal transduction pathways in response to DNA damaging agents.

Effects of dietary n-3-to-n-6 polyunsaturated fatty acid ratio on mammary carcinogenesis in rats

We investigated the effects of the dietary n-3-to-n-6 polyunsaturated fatty acid (PUFA) ratio (n-3/n-6 ratio) on mammary carcinogenesis induced by 7,12-dimethylbenz[a]anthracene in rats by feeding them several types of dietary fat with a fixed PUFA-to-saturated fatty acid ratio. Dietary fat was fed to the rats as 10% of the total feed weight, starting two weeks before the initiation. An increase in the n-3/n-6 ratio did not suppress the incidence or reduce the latency of mammary tumor development. The number and weight of mammary tumors per tumor-bearing rat tended to be large in the group with an n-3/n-6 ratio of 7.84 compared with those in the other groups. As the n-3/n-6 ratios were elevated, the total number and weight of tumors increased gradually. The prostaglandin E2 (PGE2) concentration in mammary tumor tissue was markedly low in the group with an n-3/n-6 ratio of 1.03 compared with the group with an n-3/n-6 ratio of 0.01. In addition, PGE2 concentrations were almost constant when n-3/n-6 ratios were > 1.03. These results suggested that the increase in the n-3/n-6 ratio of dietary fat with the fixed PUFA-to-saturated fatty acid ratio cannot suppress the mammary carcinogenesis but can promote development of tumors, despite reduced PGE2 concentration in the tumor.

Effect of indigestible saccharides on B lymphocyte response of intestinal mucosa and cecal fermentation in rats

The effects of water-soluble and -insoluble indigestible saccharides (IDS) on immune responses of the intestinal tract were studied. Male 4-week-old Sprague Dawley rats were fed for three weeks on diets containing several kinds of IDS at 5%. The results revealed that the proportion of kappa-light chain and IgA-presenting lymphocytes in small intestinal and cecal mucosa differed in increased number depending on the type of IDS. The response of colonic mucosa was not pronounced. The amounts of short-chain fatty acid (SCFA) and lactic acid in the cecal contents of the other test groups except the celfur group tended to be higher than those in the cellulose group, particularly in the lactulose group where many acids showed significant increases. The correlation between the proportion of kappa-light chain and IgA-presenting lymphocytes in the cecal mucosa and lactic acid in the cecal contents was significant, but that between the proportion of both lymphocytes and SCFA was not. Based on the above, we concluded that the oral administration of IDS induces the proliferation of kappa-light chain and IgA-producing B lymphocytes in small intestinal and cecal mucosa, but the degree of response differs depending on the type of IDS. It is thus suggested that IDS are involved in the intestinal immune system of rats.

High phosphorus diet rapidly induces nephrocalcinosis and proximal tubular injury in rats

The development of nephrocalcinosis and the time course of changes in kidney function, especially proximal tubular function, were studied in young male rats fed a high-phosphorus diet. The animals were fed a purified diet with a phosphorus content of either 0.5% (normal phosphorus diet) or 1.5% (high-phosphorus diet). In the group fed the high-phosphorus diet, nephrocalcinosis was found in 4 of 42 rats after 1 d of feeding and in all rats of this group at 3 d. The degree of nephrocalcinosis gradually increased with time. Upon histological observation by electron microscopy, vacuoles, lysosomes and swelling of microvilli in the proximal tubules were observed in rats fed the high-phosphorus diet after 1 d of feeding. Giant lysosomes with deposition of calcium and deposition of hydroxyapatite in mitochondria were observed in the proximal tubules of rats fed the high-phosphorus diet at 3 d. Albumin concentration in the urine of these rats was significantly increased at 3 d. The activity of N-acetyl-beta-D-glucosaminidase in the urine was also significantly increased after 1 d of feeding the high-phosphorus diet, and then reached a plateau. The beta 2-microglobulin concentration in the urine of rats fed the high-phosphorus diet was significantly increased at 14 d, and increased more toward 21 d. We concluded that nephrocalcinosis and injury to the proximal tubules are rapidly induced in rats fed a high-phosphorus diet.

Changes in blood coagulation, platelet aggregation, and lipid metabolism in rats given lipids containing docosahexaenoic acid

In order to identify an adequate intake level of docosahexaenoic acid (DHA), changes in various parameters related to health benefits were studied in rats fed on diets containing 10% test lipids at different n-3(DHA)/n-6 ratios for two weeks. An evaluation of the critical level of the dietary n-3/n-6 ratio which had a significant effect on the parameters of several tissues indicated that the response to the dietary ratios differed according to the parameter, the variation in ratio ranging approximately from 0.20 to 1.77 with either a positive or negative effect on the health benefit. These results suggest that a suitable intake level of DHA would be within this range. In view of safety, however, the critical level for the dietary n-3/n-6 ratio may be around 0.56, as shown by a detailed analysis on the lower limit level of the harmful parameters. We thus propose that the dietary intake of DHA should not be more than 0.56 in terms of the n-3/n-6 ratio.

Effects of human diets of two different Japanese populations on cancer incidence in rat hepatic drug-metabolizing and antioxidant enzyme systems

Hepatic enzyme systems of drug metabolism and antioxidation were investigated in rats fed the complete human diets consumed in the two Japanese prefectures, Akita and Okinawa, where the incidence of cancers was quite different: Okinawa had the lowest and Akita the highest age-adjusted mortality rate. In rats fed the human diet consumed in Okinawa, hepatic glutathione S-transferase activity was higher and lipid peroxide content was lower than in rats fed the diet consumed in Akita. These data might indicate that the number and/or quantity of the dietary components attributed to the detoxification of carcinogens and the scavenging reactive carcinogen species was much higher in the foods consumed in the population having lower cancer mortality rate.

Space-Group Determination of the Orthorhombic Form of NaV6O11

The unit cell and space group of orthorhombic NaV6O11 (low-temperature form) are found by an X-ray single-crystal diffraction study at 300 K (hexagonal, P63/mmc), 100 K (hexagonal, P63 mc) and 20 K (orthorhombic). The orthorhombic form (o) shows no superstructure and its unit cell is related to the hexagonal one (h): a o ≃ a h + b h , a o ≃ −a h + b h and c o ≃ c h . Bijvoet-pair examination confirms that it crystallizes in the noncentrosymmetric space group Cmc21. The hexagonal (P63 mc)-orthorhombic (Cmc21) structural phase transition is proved to be of second order.