Hiroaki Kanda

Obesity-induced gut microbial metabolite promotes liver cancer through senescence secretome

Obesity has become more prevalent in most developed countries over the past few decades, and is increasingly recognized as a major risk factor for several common types of cancer. As the worldwide obesity epidemic has shown no signs of abating, better understanding of the mechanisms underlying obesity-associated cancer is urgently needed. Although several events were proposed to be involved in obesity-associated cancer, the exact molecular mechanisms that integrate these events have remained largely unclear. Here we show that senescence-associated secretory phenotype (SASP) has crucial roles in promoting obesity-associated hepatocellular carcinoma (HCC) development in mice. Dietary or genetic obesity induces alterations of gut microbiota, thereby increasing the levels of deoxycholic acid (DCA), a gut bacterial metabolite known to cause DNA damage. The enterohepatic circulation of DCA provokes SASP phenotype in hepatic stellate cells (HSCs), which in turn secretes various inflammatory and tumour-promoting factors in the liver, thus facilitating HCC development in mice after exposure to chemical carcinogen. Notably, blocking DCA production or reducing gut bacteria efficiently prevents HCC development in obese mice. Similar results were also observed in mice lacking an SASP inducer or depleted of senescent HSCs, indicating that the DCA–SASP axis in HSCs has key roles in obesity-associated HCC development. Moreover, signs of SASP were also observed in the HSCs in the area of HCC arising in patients with non-alcoholic steatohepatitis, indicating that a similar pathway may contribute to at least certain aspects of obesity-associated HCC development in humans as well. These findings provide valuable new insights into the development of obesity-associated cancer and open up new possibilities for its control.

Methylation silencing of SOCS-3 promotes cell growth and migration by enhancing JAK/STAT and FAK signalings in human hepatocellular carcinoma

We identified that suppressor of cytokine signaling-3 (SOCS-3) gene was aberrantly methylated in its CpG island in three of 10 human hepatocellular carcinoma (HCC) cell lines. SOCS-3 RNA was undetectable in five of the 10 HCC cell lines including the three methylated cell lines, and a demethylating agent, 5-aza-2′-deoxycytidine, reactivated SOCS-3 expression in three cell lines tested. The DNA region where we found aberrant DNA methylation includes a signal transducers and activators of transcription (STAT) binding consensus sequence. When the DNA region was used as a promoter, DNA methylation markedly reduced promoter activity. SOCS-3 was also aberrantly methylated in six of 18 primary HCC samples. SOCS-3 expression was reduced in three of the three methylated and one of the three unmethylated primary samples examined. Restoration of SOCS-3 in cells lacking SOCS-3 expression suppressed STAT3 phosphorylation and cell growth. We found that IL-6 acted as a growth factor in HCC cells. Inhibition of SOCS-3 expression in cells whose growth was induced by IL-6 enhanced STAT3 phosphorylation and cell growth. In addition, AG490, a chemical JAK2 inhibitor, suppressed cell growth and downregulated STAT3 phosphorylation, but not FAK phosphorylation. We also found that SOCS-3 physically interacted with phosphorylated FAK and Elongin B in HCC cells. Restoration of SOCS-3 decreased FAK phosphorylation as well as FAK protein level. Inhibition of SOCS-3 expression increased FAK phosphorylation, resulting in enhancement of cell migration. These data indicate that SOCS-3 negatively regulates cell growth and cell motility by inhibiting Janus kinase (JAK)/STAT and FAK signalings in HCC cells. Thus, loss of SOCS-3 by the associated DNA methylation confers cells advantage in growth and migration.

Possible association of p53 overexpression and mutation with high-grade chondrosarcoma.

Overexpression and point mutation of the p53 protein/ gene was investigated in a series of chondrosarcoma by an immunohistochemical approach, and direct sequencing of the genomic DNA. respectively. In 2 of the 16 cases studied, both of which were high grade chondrosarcomas (grade III), immunodetectable p53 was identified. Histologically. one was ordinary type and the other a clear cell variant. However, no positivity was observed in the other cases including nine of low grade, ordinary type, three of low grade, clear cell type, and two of extraskeletal myxoid chondrosarcoma. Direct sequencing, following polymerase chain reaction amplification of exons 5–9 of the p53 gene in 14 cases, in which fresh materials were available. successfully demonstrated base substitution mutations in only two cases with detectable p53 overexpression on immunohistochemistry. Their details were GTC (valine) to TTC (phenylalanine) at codon 157 in exon 5. and CGT (arginine) to CAT (histidine) at codon 273 in exon 8. No mutation was detected in the other 12 cases which were negative for p53 immunostaining. These findings strongly suggest that p53 mutation plays a crucial role in the biologically aggressive subtype, and possibly in the process of tumor progression in human chondrosarcoma.

Association of loss of heterozygosity at the p53 locus with chemoresistance in osteosarcomas

Although the osteosarcoma is considered to be among the most chemosensitive malignancies and preoperative chemotherapy is commonly applied, an appreciable proportion of cases are in fact quite insensitive. Predictive markers for chemosensitivity are therefore desirable in order to develop effective treatment strategies. Thirty‐two cases of conventional osteosarcomas treated at the Cancer Institute Hospital, Tokyo, were analyzed. The sensitivity to preoperative chemotherapy was investigated with reference to loss of heterozygosity (LOH) at the 17p13 (p53) and 13q14 (Rb) loci and expression of the cell‐cycle associated proteins, p53, Rb, p21/Waf‐1, mdm‐2 and Ki‐67, as detected immunohistochemically. LOH was detected by analyzing polymerase chain reaction products at marker microsatellite loci. The efficacy of chemotherapy was evaluated both radiologically and histologically. LOH at p53 or Rb loci was seen in 54% (13/24) and 58% (14/24) of cases, respectively. Only 15% of osteosarcomas with LOH at the p53 locus were sensitive to preoperative chemotherapy, as compared to 64% of tumors without such loss (P<0.05). A similar but much less distinct tendency was observed with LOH at the Rb locus. No relationship was evident between chemosensitivity and immunohistochemical staining patterns for p53, Rb, p21/Waf‐1, mdm‐2 or Ki‐67. The results suggest that p53 gene deletion, but not the other parameters investigated, may be useful for predicting chemoresistance of osteosarcomas.

Gut microbiota promotes obesity-associated liver cancer through pge2-mediated suppression of antitumor immunity

Obesity increases the risk of cancers, including hepatocellular carcinomas (HCC). However, the precise molecular mechanisms through which obesity promotes HCC development are still unclear. Recent studies have shown that gut microbiota may influence liver diseases by transferring its metabolites and components. Here, we show that the hepatic translocation of obesity-induced lipoteichoic acid (LTA), a Gram-positive gut microbial component, promotes HCC development by creating a tumor-promoting microenvironment. LTA enhances the senescence-associated secretory phenotype (SASP) of hepatic stellate cells (HSC) collaboratively with an obesity-induced gut microbial metabolite, deoxycholic acid, to upregulate the expression of SASP factors and COX2 through Toll-like receptor 2. Interestingly, COX2-mediated prostaglandin E2 (PGE2) production suppresses the antitumor immunity through a PTGER4 receptor, thereby contributing to HCC progression. Moreover, COX2 overexpression and excess PGE2 production were detected in HSCs in human HCCs with noncirrhotic, nonalcoholic steatohepatitis (NASH), indicating that a similar mechanism could function in humans.Significance: We showed the importance of the gut-liver axis in obesity-associated HCC. The gut microbiota-driven COX2 pathway produced the lipid mediator PGE2 in senescent HSCs in the tumor microenvironment, which plays a pivotal role in suppressing antitumor immunity, suggesting that PGE2 and its receptor may be novel therapeutic targets for noncirrhotic NASH-associated HCC. Cancer Discov; 7(5); 522-38. ©2017 AACR.This article is highlighted in the In This Issue feature, p. 443.

Significance of the fibrous stroma in bone invasion by human gingival squamous cell carcinomas

Gingival squamous cell carcinomas (SCCs) frequently invade the mandible or maxilla, and this invasion is associated with a worse prognosis. Although previous studies have suggested that bone destruction caused by gingival SCC is mediated by osteoclastic bone resorption rather than by tumor cells directly, the mechanism underlying the bone invasion remains poorly understood. We histopathologically investigated mandibular invasion patterns in 97 cases of primary gingival SCC and evaluated the correlations between bone invasion patterns and clinicopathological factors. Based on the histological examination of the mandibular invasion pattern, we classified the cases into 2 categories: expansive type and infiltrative type. Of the 97 cases, 52 were expansive type and 45, infiltrative type. Varying numbers of Howships lacunae and osteoclasts were detected on the bone surface adjacent to the tumor cells. Compared to the expansive type, the infiltrative type showed increased numbers of osteoclasts at the interface of the tumor and the resorbing bone. Tumor cells showed no direct contact with osteoclasts and the adjacent bones, and in all cases varying amounts of fibrous connective tissues intervened between the tumor cells and the bone. The number of fibroblasts was significantly greater in the infiltrative type than in the expansive type. We also found a positive correlation between the number of osteoclasts and fibroblasts at the interface of the tumor and the resorbing bone. Immunohistochemistry revealed RANKL expression in the fibroblastic cells that were adjacent to the osteoclasts in the area of bone resorption. In coculture experiments, human gingival SCC cells (BHY) stimulated the expression of mouse RANKL mRNA in murine osteoblastic cells (MC3T3-E1). These results indicate that the fibrous stroma plays critical roles in osteoclastic bone resorption by gingival SCC through the RANKL-dependent pathways.

Malignant transformation and EGFR activation of immortalized mouse liver epithelial cells caused by HBV enhancer-X from a human hepatocellular carcinoma.

We have previously observed that all human hepatocellular carcinomas (HCCs) from HBV carriers examined had the integrated X region. In this study, HBV DNA was isolated from an integration site in one HCC that had a single, very small integrated viral DNA including the X region, but it had no expression of X gene as poly(A)RNA. It was found that HBV DNA was present between alphoid repetitive sequences, and it included Enhancer and X regions, encompassing the adr sequence from 910 to 1811. Nucleotides for 8 amino acids at the 3’ end, a stop codon of X gene and a poly(A) signal downstream of X gene were lost by integration, and nucleotides for 7 amino acids and a stop codon were substituted by a connected alphoid sequence. When this cloned HBV DNA was transfected with an expression vector to an immortalized mouse liver epithelial cell line, MLE‐10, malignant transformation occurred. Transformants having expressed poly(A)RNA of the X gene showed anchorage‐independent growth in soft agar and tumor formation in the subcutis of nude mice. The mRNA level of EGFR was found to be remarkably enhanced in X‐transformed cells, in contrast with the absence of this mRNA in parental and ras‐transformed MLE‐10. Our data provide evidence that the Enhancer‐X region alone is the key contributor to the malignant change of pre‐malignant liver cells in HBV carriers through activation of some specific genes, such as EGFR. Int. J. Cancer 85:518–522, 2000.

Ablation of the p16 INK4a tumour suppressor reverses ageing phenotypes of klotho mice

The p16INK4a tumour suppressor has an established role in the implementation of cellular senescence in stem/progenitor cells, which is thought to contribute to organismal ageing. However, since p16INK4a knockout mice die prematurely from cancer, whether p16INK4a reduces longevity remains unclear. Here we show that, in mutant mice homozygous for a hypomorphic allele of the α-klotho ageing-suppressor gene (klkl/kl), accelerated ageing phenotypes are rescued by p16INK4a ablation. Surprisingly, this is due to the restoration of α-klotho expression in klkl/kl mice and does not occur when p16INK4a is ablated in α-klotho knockout mice (kl−/−), suggesting that p16INK4a is an upstream regulator of α-klotho expression. Indeed, p16INK4a represses α-klotho promoter activity by blocking the functions of E2Fs. These results, together with the observation that the expression levels of p16INK4a are inversely correlated with those of α-klotho throughout ageing, indicate that p16INK4a plays a previously unrecognized role in downregulating α-klotho expression during ageing.

A Japanese patient with Li-Fraumeni syndrome who had nine primary malignancies associated with a germline mutation of the p53 tumor-suppressor gene

We describe a patient who had nine primary malignant tumors and a germline mutation in the p53 tumor-suppressor gene, characteristically found in the Li-Fraumeni syndrome (LFS). A 15-year-old girl with no family history of cancer was referred to our hospital because of pain and swelling of the right knee. Osteosarcoma was diagnosed. The patient received chemotherapy followed by surgery and had a remission. After the age of 28 years, nine primary malignant tumors developed successively, including right breast cancer, colon cancer, malignant fibrous histiocytoma (MFH) of the abdominal wall, right lung double cancers, bilateral breast cancers, and MFH of the left thigh. This is the second highest number of types of primary malignant tumors to be reported in LFS. All tumors were treated by a multidisciplinary approach, including surgery. Genetic analysis revealed a germline missense mutation in the p53 gene (c.659 A > G), resulting in Y220C, which has been reported in three families with LFS. The patient died of lung metastasis from MFH at the age of 37 years. Despite the multiple tumors, repeated induction of remissions resulted in long survival. Our findings suggest that a multidisciplinary approach to treatment, including surgery, is beneficial in patients with LFS.

Spontaneously regressed Kaposi's sarcoma and human herpesvirus 8 infection in a human immunodeficiency virus-negative patient

Kaposi’s sarcoma occurring in a 78‐year‐old woman, with the absence of the human immunodeficiency virus infection, was correctly diagnosed by immunohistochemistry using anti‐human herpesvirus 8 (HHV8) antibody (PA1‐73N) for the first time. The patient suffered from chronic respiratory failure and was treated with a low dose of steroids for 2.5 years. After her medication dosage was increased for the exacerbation of the respiratory failure, multiple skin tumors in her feet and legs suddenly developed. Histopathologically, skin tumors were suspected as Kaposi’s sarcoma at the first biopsy and reactive angiomatosis at the second biopsy. Polymerase chain reaction and immunohistochemistry, however, revealed the presence of HHV8 DNA fragment and positive staining in the majority of spindle cells in the skin tumors. Serological examination confirmed the positivity of anti‐HHV8 antibodies. HHV8 infection and steroid‐induced immunosuppression, as well as environmental factors played a role in the development of Kaposi’s sarcoma in this patient, because she was born in Okinawa, which is a well‐known endemic area of Kaposi’s sarcoma in Japan. As her general condition improved, the skin lesions regressed without any specific treatment, and disappeared completely 8 months later, in which regression may be associated with evidence of numerous CD8 cell infiltration in the second biopsy tissues. No recurrence was observed during the following 6 month follow up.