PRL PTPs: mediators and markers of cancer progression

Aberrant protein tyrosine phosphorylation resulting from the altered activity of protein tyrosine phosphatases (PTPs) is increasingly being implicated in the genesis and progression of human cancer. Accumulating evidence indicates that the dysregulated expression of members of the phosphatase of regenerating liver (PRL) subgroup of PTPs is linked to these processes. Enhanced expression of the PRLs, notably PRL-1 and PRL-3, promotes the acquisition of cellular properties that confer tumorigenic and metastatic abilities. Up-regulation of PRL-3 is associated with the progression and eventual metastasis of several types of human cancer. Indeed, PRL-3 shows promise as a biomarker and prognostic indicator in colorectal, breast, and gastric cancers. However, the substrates and molecular mechanisms of action of the PRLs have remained elusive. Recent findings indicate that PRLs may function in regulating cell adhesion structures to effect epithelial-mesenchymal transition. The identification of PRL substrates is key to understanding their roles in cancer progression and exploiting their potential as exciting new therapeutic targets for cancer treatment.     

Selective Chk1 inhibitors differentially sensitize p53-deficient cancer cells to cancer therapeutics

The majority of cancer therapeutics induces DNA damage to kill cells. Normal proliferating cells undergo cell cycle arrest in response to DNA damage, thus allowing DNA repair to protect the genome. DNA damage induced cell cycle arrest depends on an evolutionarily conserved signal transduction network in which the Chk1 kinase plays a critical role. In mammalian cells, the p53 and RB pathways further augment the cell cycle arrest response to prevent catastrophic cell death. Given the fact that most tumor cells suffer defects in the p53 and RB pathways, it is likely that tumor cells would depend more on the Chk1 kinase to maintain cell cycle arrest than would normal cells. Therefore Chk1 inhibition could be used to specifically sensitize tumor cells to DNA-damaging agents. We have previously shown that siRNA-mediated Chk1 knockdown abrogates DNA damage-induced checkpoints and potentiates the cytotoxicity of several DNA-damaging agents in p53-deficient cell lines. In this study, we have developed 2 potent and selective Chk1 inhibitors, A-690002 and A-641397, and shown that these compounds abrogate cell cycle checkpoints and potentiate the cytotoxicity of topoisomerase inhibitors and gamma-radiation in p53-deficient but not in p53-proficient cells of different tissue origins. These results indicate that it is feasible to achieve a therapeutic window with 1 or more Chk1 inhibitors in potentiation of cancer therapy based on the status of the p53 pathway in a wide spectrum of tumor types.     

Protein tyrosine phosphatase activities are involved in apoptotic cancer cell death induced by GL331, a new homolog of etoposide

GL331 is a semisynthetic topoisomerase II inhibitor derived from a plant toxin podophyllotoxin. In 72-h exposure assays, LD₅₀ values of GL331 range from 0.5 to 2 μM, which are three- to ten-fold lower than those of its homologous compound etoposide (VP-16), depending on different cancer cell lines including nasopharyngeal, hepatocellular, gastric, cervical and colon cancer types. Apoptotic DNA ladders could be detected when cancer cells were treated with GL331 for 24 h even if the Bcl-2 and Bax protein levels were not altered during the period. Besides acting as topoisomerase II inhibitors, both GL331 and VP-16 decrease the cellular protein tyrosine kinase (PTK) activities in cancer cells. The activities of protein tyrosine phosphatase (FTP) are significantly increased after GL331 treatment but are not affected by VP-16. GL331-induced inter-nucleosomal cleavage can be efficiently prevented by two inhibitors of PTP, sodium orthovanadate and zinc chloride, but not by okadaic acid, which inhibits serine/threonine phosphatase activity. These results indicate that GL331 may induce apoptotic cell death, and that activation of protein tyrosine phosphatases may be involved in this process.     

Targeting hypoxia in the treatment of small cell lung cancer

Small cell lung cancer (SCLC) is an extremely aggressive disease for which minimal therapeutic improvements have been made over the last few decades. Patients still rely on non-targeted, chemotherapeutic drugs complemented by irradiation. Although initial response is very good, the majority of SCLC patients invariably relapse with therapy-resistant tumours. Despite the link between pathologically low oxygen levels and therapy resistant tumours, hypoxia has gained little attention in the development of novel therapies for SCLC. In contrast, the advantages of targeting hypoxic cells in many other cancer types have been studied extensively. This review describes the reasons for targeting hypoxia in SCLC and outlines strategies undertaken to enhance hypoxic tumour cell death, including the use of bioreductive prodrugs, the targeting of HIF-1α and the induction of cell death through acidosis. Therapy directed towards hypoxic tumour regions has the potential to greatly enhance the response of SCLC tumours to current treatment regimens and represents an area of research in need of greater attention. Such research could lead to the much sought after development of targeted drugs against SCLC tumours.     

Targeting L1 cell adhesion molecule expression using liposome-encapsulated siRNA suppresses prostate cancer bone metastasis and growth

The L1 cell adhesion molecule (L1CAM) has been implicated in tumor progression of many types of cancers, but its role in prostate cancer and its application in targeted gene therapy have not been investigated. Herein, we demonstrated that the L1CAM was expressed in androgen-insensitive and highly metastatic human prostate cancer cell lines. The correlation between L1CAM expression and prostate cancer metastasis was also validated in serum samples of prostate cancer patients. Knockdown of L1CAM expression in prostate cancer cells by RNA interference significantly decreased their aggressive behaviors, including colony formation, migration and invasion in vitro, and tumor formation in a metastatic murine model. These anti-malignant phenotypes of L1CAM-knockdown cancer cells were accompanied by G0/G1 cell cycle arrest and suppression of matrix metalloproteinase (MMP)-2 and MMP-9 expression and nuclear factor NF-κB activation. In vivo targeting of L1CAM expression using liposome-encapsulated L1CAM siRNAs effectively inhibited prostate cancer growth in mouse bone, which was associated with decreased L1CAM expression and cell proliferation by tumor cells. These results provide the first evidence for L1CAM being a major contributor to prostate cancer metastasis and translational application of siRNA-based L1CAM-targeted therapy.     

小细胞肺癌治疗的新探索

与其他癌症相同,小细胞肺癌（ＳＣＬＣ）也秉承分期治疗的原则,手术只适用于早期患者,且能实施手术的患者仅占全部患者的５％,因此化疗、放疗仍是ＳＣＬＣ治疗的主要策略。近年来,胸部放疗提高局限期ＳＣＬＣ患者的３年生存率约５％,减少胸部复发风险约２５％,而预防性脑照射（ＰＣＩ）也进一步改善了ＳＣＬＣ的临床预后,新的治疗药物、靶点及策略不断涌现为ＳＣＬＣ的治疗带来了希望。     

去甲斑蝥素对食管癌细胞株Eca-109中hTERT的表达和PTPRO基因启动子甲基化影响的实验研究

目的 探索去甲斑蝥素（NCTD）诱导食管癌细胞Eca-109对人端粒酶逆转录酶（hTERT）表达和受体O型蛋白酪氨酸磷酸酶（PTPRO）基因启动子甲基化的影响。方法 MTT比色法检测不同浓度（0、1、2、4、8、16 μg／ml） NCTD及不同作用时间（12、24 h）对食管癌细胞Eca-109增殖的影响;TUNEL法配合激光共聚焦扫描显微镜检测NCTD+Eca-109组（实验组）和Eca-109组（对照组）细胞凋亡情况;甲基化特异性PCR（MSP）检测实验组和对照组中PTPRO基因启动子的甲基化状态,Western blotting检测实验组和对照组hTERT蛋白的表达。结果 MTT检测显示,NCTD 可抑制Eca-109细胞增殖,呈时间和浓度依赖性,不同作用时间和浓度的细胞增殖抑制率的差异有统计学意义（P＜0.05）;TUNEL法结合激光共聚焦扫描显微镜观察显示,实验组细胞内部结构发生剧烈的变化,较对照组细胞核染色质致密浓染,核形缩小;MSP检测显示,对照组PTPRO基因启动子发生明显甲基化;Western blotting检测显示,实验组hTERT蛋白表达较对照组明显降低（P＜0.05）。结论 NCTD对食管癌细胞Eca-109有细胞毒性,能够抑制细胞生长,其机制可能与下调hTERT蛋白表达和PTPRO基因启动子去甲基化有关。     

The DNA damage mark pH2AX differentiates the cytotoxic effects of small molecule HDAC inhibitors in ovarian cancer cells

High grade epithelial ovarian cancers are relatively sensitive to DNA damaging platinum-based chemotherapy, suggesting that the dependencies of ovarian tumors on DNA damage response pathways can be harnessed for therapeutic purposes. Our goal was to determine if the DNA damage mark gamma-H2AX phosphorylation (pH2AX) could be used to identify suitable cytotoxic histone deacetylase inhibitors (HDACi) for ovarian cancer treatment. Nineteen chemically diverse HDACi compounds were tested in 7 ovarian cancer cell lines. Fluorescent, biochemical and cell-based assays were performed to assess DNA damage by induction of pH2AX and to measure cell viability and apoptosis. The relationships between pH2AX and the cellular effects of cell viability and apoptosis were calculated. Selected HDACi were tested in combination with cisplatin and other DNA damaging agents to determine if the HDACi improved upon the effects of the DNA damaging agents. The HDACi compounds induced differing levels of pH2AX expression. High levels of pH2AX in HDACi-treated ovarian cancer cells were tightly associated with decreased cell viability and increased apoptosis. Consequently, a ketone-based HDACi was chosen and found to enhance the effects of cisplatin, even in ovarian cancer cells with extreme resistance to DNA damaging drugs. In conclusion, a fluorescent-based assay for pH2AX can be used to determine cellular responses to HDACi in vitro and may be a useful tool to identify potentially more effective HDACi for the treatment of ovarian cancer. In addition, these results lend support to the inclusion of ketone-derived HDACi compounds for future development.     

New oral small molecules in the treatment of chronic lymphocytic leukemia

There has been a dramatic change in therapy for chronic lymphocytic leukemia (CLL) over the last 20 years. In 1990, available therapy produced complete responses in <5% of treated patients. This is in marked contrast to modern regimens, which are reported to reliably produce complete responses in approximately 40% to 50% of patients. This remarkable improvement has been attributable to combination chemoimmunotherapy agents that have contributed to the backbone of therapy for patients with CLL. However, the disease is still incurable and these modern treatment regimens have been somewhat limited to the treatment of younger, physically “fit” patients with CLL due to their increased toxicity, including enhanced myelosuppression and immunosuppression. In addition, because patients receive multiple therapies during the course of their lifetime, the mounting toxicities as well as decreased efficacy often limit the repeated use of these more aggressive combination therapies. Fortunately, over the past 5 years, there has been an explosion of new active agents that have demonstrated remarkable activity in patients with recurrent/refractory disease as well as those who harbor poor cytogenetic abnormalities. The current review focuses on some of the novel small molecules that have either been approved or are at the forefront of clinical development in the treatment of patients with CLL. Cancer 2015;121:1917–1926. © 2015 American Cancer Society.     

Immediate versus delayed treatment with EGFR tyrosine kinase inhibitors after first-line therapy in advanced non-small-cell lung cancer

Objective: To analyze the outcomes of patients who received TKI immediately after the first-line without progression as maintenance treatment (immediate group) vs. those received delayed treatment upon disease progression as second-line therapy (delayed group). Methods: The study included 159 no-small-cell lung cancer (NSCLC) patients who received gefitinib or erlotinib as maintenance treatment in the immediate group (85 patients) or as second-line therapy in the delayed group (74 patients). The primary end...     

小细胞肺癌患者血清中Wip1的表达水平及其临床意义

目的：探讨野生型 p53 诱导的磷酸酶 1（wild-type p53-induced phosphatase 1,Wip1）在小细胞肺癌（small-cell lung cancer,SCLC）细胞及血清中的表达及其与临床预后的关系。方法：采用实时荧光定量PCR（qPCR）法检测SCLC细胞及血清标本中Wip1的表达,分析其表达的临床意义。结果：Wip1在SCLC耐药细胞H69R中的表达较敏感细胞H69明显增加（P<0.01）。Wip1在SCLC血清中的表达较正常对照组明显升高（P<0.05）;且Wip1 在化疗耐药患者血清中的表达较化疗敏感者者明显升高（P<0.05）;血清中Wip1表达与SCLC患者的疾病分期、化疗敏感性及患者的生存状态关联（均P<0.05）。血清Wip1水平预测SCLC化疗疗效的ROC曲线下面积为0.836（95%CI：0.8230～0.9600,P<0.01）;Wip1的表达与SCLC患者的无进展生存时间及总生存时间明显关联（均P<0.05）。疾病分期、化疗敏感性及血清Wip水平是SCLC患者预后的独立影响因素（均P<0.05）。结论：SCLC患者血清中Wip1的表达可能与化疗敏感性及患者预后有关,Wip1可能是SCLC患者潜在的疗效及预后评估的生物标志物。     

Discovery of fruquintinib,a potent and highly selective small molecule inhibitor of VEGFR 1, 2, 3 tyrosine kinases for cancer therapy

VEGF/VEGFR signal axis has been proven to be an important target for development of novel cancer therapies. One challenging aspect in small molecular VEGFR inhibitors is to achieve sustained target inhibition at tolerable doses previously seen only with the long-acting biologics. It would require high potency (low effective drug concentrations) and sufficient drug exposures at tolerated doses so that the drug concentration can be maintained above effective drug concentration for target inhibition within the dosing period. Fruquintinib (HMPL-013) is a small molecule inhibitor with strong potency and high selectivity against VEGFR family currently in Phase II clinical studies. Analysis of Phase I pharmacokinetic data revealed that at the maximum tolerated dose of once daily oral administration fruquintinib achieved complete VEGFR2 suppression (drug concentrations were maintained above that required to produce >85% inhibition of VEGFR2 phosphorylation in mouse) for 24 hours/day. In this article, the preclinical data for fruquintinib will be described, including kinase enzyme activity and selectivity, cellular VEGFR inhibition and VEGFR-driven functional activity, in vivo VEGFR phosphorylation inhibition in the lung tissue in mouse and tumor growth inhibition in a panel of tumor xenograft and patient derive xenograft models in mouse. Pharmacokinetic and target inhibition data are also presented to provide a correlation between target inhibition and tumor growth inhibition.     

Transformation to small-cell lung cancer following treatment with EGFR tyrosine kinase inhibitors in a patient with lung adenocarcinoma

We report the case of a 52-year-old woman with lung adenocarcinoma treated with EGFR tyrosine kinase inhibitor (TKI) therapy. After disease progression, histological examination of a secondary biopsy specimen revealed small-cell lung cancer (SCLC) that was sensitive to standard SCLC treatment. Tumor markers, including ProGRP and NSE, were elevated. Transformation to SCLC is a mechanism for acquired resistance to EGFR-TKI therapy. Secondary biopsy is important for evaluation of genetic and histological changes and selection of appropriate treatment. Furthermore, ProGRP and NSE may be useful for early detection of SCLC transformation in cases resistant to EGFR-TKI therapy.     

A Novel BCL-2 Inhibitor APG-2575 Exerts Synthetic Lethality With BTK or MDM2-p53 Inhibitor in Diffuse Large B-Cell Lymphoma

Despite therapeutic advances, the effective treatment for relapsed or refractory diffuse large B-cell lymphoma (DLBCL) remains a major clinical challenge. Evasion of apoptosis through upregulating antiapoptotic B-cell lymphoma-2 (BCL-2) family members and p53 inactivation, and abnormal activation of B-cell receptor signaling pathway are two important pathogenic factors for DLBCL. In this study, our aim is to explore a rational combination of BCL-2 inhibitor plus Bruton’s tyrosine kinase (BTK) blockade or p53 activation for treating DLBCL with the above characteristics. We demonstrated that a novel BCL-2 selective inhibitor APG-2575 effectively suppressed DLBCL with BCL-2 high expression via activating the mitochondrial apoptosis pathway. BTK inhibitor ibrutinib combined with BCL-2 inhibitors showed synergistic antitumor effect in DLBCL with mean expression of BCL-2 and myeloid cell leukemia-1 (MCL-1) through upregulating the expression level of BIM and modulating MCL-1 and p-Akt expression. For p53 wild-type DLBCL with high expression of BCL-2, APG-2575 showed strong synergic effect with mouse double minute 2 (MDM2)–p53 inhibitor APG- 115 that can achieve potent antitumor effect and markedly prolong survival in animal models. Collectively, our data provide an effective and precise therapeutic strategy through rational combination of BCL-2 and BTK or MDM2–p53 inhibitors for DLBCL, which deserves further clinical investigation.     

Clinical significance and regulation of the costimulatory molecule B7-H1 in pancreatic cancer

We investigated the expression pattern and clinical significance of the costimulatory ligands B7-1, B7-2, B7-H1, and B7-DC, and their counter-receptors CTLA-4 and PD-1 in pancreatic cancer. Gene expression of all examined costimulatory molecules was significantly upregulated in pancreatic cancer tissues. B7-1, B7-2, B7-H1, and B7-DC protein was detectable in pancreatic cancer cells. Only the expression of B7-H1 significantly correlated with postoperative survival (p<0.0001). B7-H1 was inducible in cultured pancreatic cancer cells by IFN-gamma and significantly correlated with the level of IFN-gamma expression in human pancreatic cancer tissues (Spearman rho=0.4536,p=0.0029). B7-H1 positive tumors showed an increased prevalence of tumor-infiltrating regulatory T cells (T(regs)) compared to B7-H1 negative tumors. Among the investigated costimulatory molecules only tumor-associated B7-H1 seems to be of prognostic relevance in pancreatic cancer. B7-H1 might, therefore, be involved in the downregulation of antitumor responses through regulation of T(regs) in pancreatic cancer. Our findings also suggest a dual role of IFN-gamma in antitumor response. Through induction of B7-H1 in pancreatic cancer cells IFN-gamma might contribute to the evasion of antitumor immunity.     

Impact of tumor microenvironment on the efficacy of epidermal growth factor receptor‐tyrosine kinase inhibitors in patients with EGFR‐mutant non‐small cell lung cancer

We retrospectively investigated the impact of the tumor microenvironment (TME) on the efficacy of epidermal growth factor receptor (EGFR)‐tyrosine kinase inhibitors (TKIs) as first‐line treatment in 70 patients with advanced EGFR‐mutant non‐small cell lung cancer and who were seen at Osaka City University Hospital (Osaka, Japan) between August 2013 and December 2017. Using immunohistochemical staining with 28‐8 and D7U8C Abs, the tumor proportion score was assessed for programmed cell death‐1 ligand‐1 (PD‐L1), as high (50% or more) or low (less than 50%), and ligand‐2 (PD‐L2) expression, respectively. The extent of CD8⁺ tumor‐infiltrating lymphocytes was evaluated on a scale of 0‐3, with 0‐1 as low and 2‐3 as high. The TME of the 52 evaluable pretreatment specimens was categorized into 4 subtypes, according to the respective PD‐L1 tumor proportion and CD8⁺ scores, as follows: (a) high/high (13.5%, n = 7); (b) low/low (42.3%, n = 22); (c) high/low (17.3%, n = 9); and (d) low/high (26.9%, n = 14). Expression of PD‐L2 was significantly the highest in type 1 (57.1% vs 4.5% vs 11.1% vs 7.1%, respectively; P = .0090). Response rate was significantly the lowest in type 1 (14.3% vs 81.8% vs 66.7% vs 78.6%, respectively; P = .0085). Progression‐free survival was the shortest in type 1 and the longest in type 4 (median, 2.4 vs 11.3 vs 8.4 vs 17.5 months, respectively; P = .00000077). The efficacy of EGFR‐TKIs differed according to the TME, and the phenotype with high PD‐L1 and CD8⁺ expression might be the subset that would poorly benefit from such treatment.