Development, validation, and comparison of gene analysis methods for detecting EGFR mutation from non-small cell lung cancer patients-derived circulating free DNA

The feasibility and required sensitivity of circulating free DNA (cfDNA)-based detection methods in second-line epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) treatment are not well elucidated. We examined T790M and other activating mutations of EGFR by cfDNA to assess the clinical usability. In 45 non-small cell lung cancer (NSCLC) patients harboring activating EGFR mutations, cfDNAs were prepared from the plasma samples. EGFR mutations in cfDNA were detected using highly sensitive methods and originally developed assays and these results were compared to tissue-based definitive diagnoses. The specificity of each cfDNA-based method ranged 96–100% whereas the sensitivity ranged 56–67%, indicating its low pseudo-positive rate. In EGFR-TKI failure cohort, 41–46% samples were positive for T790M by each cfDNA-based method, which was comparable to re-biopsy tissue-based T790M positive rates in literature. The concordance of the results for each EGFR mutation ranged from 83–95%. In eight patients, the results of the cfDNA-based assays and re-biopsy-derived tissue-based test were compared. The observed overall agreement ranged in 50–63% in T790M, and in 63–100% in activating EGFR mutations. In this study, we have newly developed three types of assay which have enough sensitivity to detect cfDNA. We also detected T790M in 44% of patients who failed prior EGFR-TKI treatment, indicating that cfDNA-based assay has clinical relevance for detecting acquired mutations of EGFR.

TAS-116, a highly selective inhibitor of heat shock protein 90α and β, demonstrates potent antitumor activity and minimal ocular toxicity in preclinical models

The molecular chaperone HSP90 plays a crucial role in cancer cell growth and survival by stabilizing cancer-related proteins. A number of HSP90 inhibitors have been developed clinically for cancer therapy; however, potential off-target and/or HSP90-related toxicities have proved problematic. The 4-(1H-pyrazolo[3,4-b]pyridine-1-yl)benzamide TAS-116 is a selective inhibitor of cytosolic HSP90α and β that does not inhibit HSP90 paralogs such as endoplasmic reticulum GRP94 or mitochondrial TRAP1. Oral administration of TAS-116 led to tumor shrinkage in human tumor xenograft mouse models accompanied by depletion of multiple HSP90 clients, demonstrating that the inhibition of HSP90α and β alone was sufficient to exert antitumor activity in certain tumor models. One of the most notable HSP90-related adverse events universally observed to differing degrees in the clinical setting is visual disturbance. A two-week administration of the isoxazole resorcinol NVP-AUY922, an HSP90 inhibitor, caused marked degeneration and disarrangement of the outer nuclear layer of the retina and induced photoreceptor cell death in rats. In contrast, TAS-116 did not produce detectable photoreceptor injury in rats, probably due to its lower distribution in retinal tissue. Importantly, in a rat model, the antitumor activity of TAS-116 was accompanied by a higher distribution of the compound in subcutaneously xenografted NCI-H1975 non-small cell lung carcinoma tumors than in retina. Moreover, TAS-116 showed activity against orthotopically transplanted NCI-H1975 lung tumors. Together, these data suggest that TAS-116 has a potential to maximize antitumor activity while minimizing adverse effects such as visual disturbances that are observed with other compounds of this class.

Abstract C129: TAS-116, an orally available HSP90α and β selective inhibitor, exhibits synergistic effects in combination with taxanes in EGFR-tyrosine kinase inhibitor-resistant human NSCLC xenograft models through the downregulation of key molecules involved in drug resistance of cancer chemotherapy

Background: In advanced NSCLC, EGFR-tyrosine kinase inhibitors (EGFR-TKI) have shown limited effect on lung squamous cell carcinoma (LSCC) or NSCLC harboring either a mutation in the K-RAS oncogene or lacking an activated mutation in EGFR. Though several cytotoxic drugs have been used in these EGFR-TKI-resistant settings, clinical outcomes have been generally poor.

It has been shown that several antiapoptotic molecules regulated by PI3K/AKT and MAPK signaling, are involved in drug resistance to cancer chemotherapy. One of the possible approaches to overcome such drug resistance is via simultaneous inhibition of multiple signaling pathways. We have previously reported on an orally available highly selective HSP90α and β inhibitor, TAS-116. Because TAS-116 leads to downregulation of multiple molecules involved in various signaling pathways through HSP90 inhibition, we investigated the potential utility of TAS-116 on LSCC and K-RAS mutated NSCLC in combination with taxanes.

Materials and Methods: In vitro drug combination effects were evaluated with calculation of combination index. The amount and the phosphorylation status of cellular proteins were determined by western blot with appropriate antibodies. Antitumor activities of TAS-116 alone and in combination with taxanes were evaluated in human NSCLC xenograft models. The inhibition and induction study of cytochrome P450 (CYP) by TAS-116 were evaluated using human liver microsomes and human cryopreserved hepatocytes, respectively.

Results: TAS-116 showed synergistic effects in combination with docetaxel (DTX) and paclitaxel (PTX) against LSCC cell lines. TAS-116 enhanced taxane-mediated apoptosis. To clarify the mode of action in these combinations, we measured the amount and the phosphorylation status of apoptosis-related proteins. TAS-116 decreased phosphorylation of BAD and YBX1, through the downregulation of upstream kinases, AKT and RAF1. TAS-116 synergistically inhibited tumor growth in both human LSCC and K-RAS mutated NSCLC xenograft models in combination with PTX or DTX. With regard to drug-drug interaction potential at effective concentrations, TAS-116 did not inhibit or induce CYP3A4 which is important in taxane metabolism.

Conclusion: TAS-116 in combination with taxanes enhanced apoptosis induction and exhibited synergistic antitumor activity against LSCC and K-RAS mutated NSCLC xenograft models through downregulation of key factors involved in drug resistance in cancer chemotherapy. The combination of TAS-116 and taxanes could be a promising approach to treat EGFR-TKI-resistant NSCLC including LSCC.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C129.

Citation Format: Hiromi Muraoka, Akira Kanoh, Akihiro Hashimoto, Kenjiro Ito, Takamasa Suzuki, Kouichi Takahashi, Chihoko Yoshimura, Makoto Kitade, Kazuhiko Yonekura, Shuichi Ohkubo, Teruhiro Utsugi. TAS-116, an orally available HSP90α and β selective inhibitor, exhibits synergistic effects in combination with taxanes in EGFR-tyrosine kinase inhibitor-resistant human NSCLC xenograft models through the downregulation of key molecules involved in drug resistance of cancer chemotherapy. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C129.

Abstract 4108: Syndecan-1 overexpression enhances colon cancer growth by modulating heparan sulfate binding growth factors sensitivity

Syndecan-1 is a multifaceted transmembrane heparan sulfate proteoglycan known for its significant role in a wide range of cellular processes by interacting with a multitude of extracellular components. Although loss of syndecan-1 correlates well with the gain of cancerous characteristics in a wide range of cancers, increased expression of syndecan-1 also corresponds to adverse outcomes in some cancers. The biological function is yet to be completely understood in most of malignancies, including colon cancer. In the present study, to evaluate biological functions of syndecan-1, its expression level was altered, and subsequent outcomes were examined using human colon cancer LoVo cells. Ectopic expression of syndecan-1 in LoVo cells (LoVo/SDC1) led to larger tumor formation than did control LoVo cells (LoVo/mock) in mice. Lower concentrations of HB-EGF and HGF could activate their receptors in LoVo/SDC1 than in LoVo/mock. And, the prolonged phosphorylation of EGFR induced by HB-EGF was observed in LoVo/SDC1. Furthermore, HB-EGF more effectively promoted cell growth of LoVo/SDC1 than that of LoVo/mock. Blockade of syndecan-1 using small-interfering RNA (siRNA) gene knockdown canceled sensitization of LoVo/SDC1 to HB-EGF and diminished LoVo/SDC1 cell growth stimulated by HB-EGF. These results suggest that syndecan-1 overexpression may contribute to heparan sulfate binding growth factors sensitization and their promoting effects to cancer growth. Finally, we examined the effects of syndecan-1 on chemotherapy in the presence of heparan sulfate binding growth factors. In comparison to LoVo/mock, LoVo/SDC1 was resistant to some cytotoxic drugs (paclitaxel, 5-FU, or CPT-11) in the presence of HB-EGF or HGF. Blockade of syndecan-1 using siRNA diminished chemotherapy resistance of LoVo/SDC1 caused by HB-EGF. These findings demonstrate that syndecan-1 confers chemotherapy resistance in colon cancer through concomitant heparan sulfate binding growth factors sensitization. In summary, our results identify syndecan-1 as a functional coreceptor for heparan sulfate binding growth factors that activate their receptors and promote their downstream pathway in colon cancer cells. Syndecan-1 overexpression may contribute to tumor growth and the chemotherapy resistance characteristic of colon cancer. Therefore, therapeutic invention aimed at inhibiting this molecule may be useful in cancer treatment.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4108.

Loss of UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase 3 and reduced O-glycosylation in colon carcinoma cells selected for hepatic metastasis

O-glycosylation of mucin is initiated by the attachment of N-acetyl-D-galactosamine (GalNAc) to serine or threonine residues in mucin core polypeptides by UDPGalNAc:polypeptide N-acetylgalactosaminyltransferases (ppGalNAc-Ts). It is not well understood how GalNAc attachment is regulated by multiple ppGalNAc-Ts in each cell. In the present study, the expression levels of murine ppGalNAc-Ts (mGalNAc-Ts), T1, T2, T3, T4, T6, and T7 were compared between mouse colon carcinoma colon 38 cells and variant SL4 cells, selected for their metastatic potentials, by using the competitive RT-PCR method. The expression levels of mGalNAc-T1, T2, and T7 were slightly higher in the SL4 cells than in the colon 38 cells, whereas the expression level of mGalNAc-T3 in the SL4 cells was 1.5% of that in the colon 38 cells. Products of enzymatic incorporations of GalNAc residues into FITCPTTTPITTTTK peptide by the use of microsome fractions of these cells as the enzyme source were separated and characterized for the number of attached GalNAc residues and their positions. The maximum number of attached GalNAc residues was 6 and 4 when the microsome fractions of the colon 38 cells and SL4 cells were used, respectively. When the microsome fractions of the colon 38 cells were treated with a polyclonal antibody raised against mGalNAc-T3, the maximum number of incorporated GalNAc residues was 4. These results strongly suggest that mGalNAc-T3 in colon 38 cells is involved in additional transfer of GalNAc residues to this peptide.

Interleukin-4 induces specific pp-GalNAc-T expression and alterations in mucin O-glycosylation in colonic epithelial cells

Mucus hypersecretion occurs as a consequence of the Th2 immune response in epithelia, yet it was not previously known whether the degree of O-glycosylation was modulated under such conditions. A colonic carcinoma cell line LS174T was used to assess the effect of interleukin (IL)-4 on the mRNA levels of eight pp-GalNAc-Ts. A three- to four-fold increase in pp-GalNAc-T1, T4, and T7 levels was observed. Lysates of untreated or IL-4-treated cells were examined for their ability to transfer GalNAc residues onto a peptide corresponding to the tandem repeat portion of human MUC2. The number of incorporated GalNAc residues was greater after incubation with lysates of IL-4-treated cells than with lysates of untreated cells. Mucin-like large glycoproteins secreted by IL-4-treated cells had higher binding capacity to PNA and VVA-B(4) than those secreted by untreated cells. The results indicated that IL-4-treated LS174T cells are able to produce mucins with a higher degree of O-glycosylation than untreated counterparts.

Ectopic expression of N-acetylglucosamine 6-O-sulfotransferase 2 in chemotherapy-resistant ovarian adenocarcinomas

Mucinous and clear cell adenocarcinomas are the major histological types of ovarian epithelial cancer and are associated with a poor prognosis due to their resistance to chemotherapy. A novel tumor marker specific for ovarian mucinous and clear cell adenocarcinomas would be helpful for overcoming these serious diseases. We showed previously by enzymological characterization and RT-PCR that colonic mucinous adenocarcinoma tissues ectopically express GlcNAc6ST-2, a member of the carbohydrate 6-O-sulfotransferase family (Seko, A. et al. (2002) Glycobiology 12, 379-388). Here, we prepared a GlcNAc6ST-2-specific polyclonal antibody for immunohistochemical analysis and found that GlcNAc6ST-2 is ectopically expressed by not only colonic mucinous adenocarcinomas but also ovarian mucinous, clear cell and papillary serous adenocarcinomas. In contrast, solid serous adenocarcinomas, endometrioid adenocarcinomas, and mucinous adenomas expressed GlcNAc6ST-2 much less frequently or not at all. RT-PCR analysis confirmed that GlcNAc6ST-2 transcripts are expressed in ovarian mucinous adenocarcinomas but not in mucinous adenomas. In addition, immunohistochemical analysis using sulfated glycan-specific monoclonal antibodies showed that ovarian adenocarcinoma cells express GlcNAc 6-O-sulfated glycans, including an L-selectin ligand and its related glycans. These results indicate that GlcNAc6ST-2 would be a novel tumor antigen that is specifically expressed in ovarian mucinous, clear cell and papillary serous adenocarcinomas.

Structures of the carbohydrate recognition domain of Ca2+-independent cargo receptors Emp46p and Emp47p

Emp46p and Emp47p are type I membrane proteins, which cycle between the endoplasmic reticulum (ER) and the Golgi apparatus by vesicles coated with coat protein complexes I and II (COPI and COPII). They are considered to function as cargo receptors for exporting N-linked glycoproteins from the ER. We have determined crystal structures of the carbohydrate recognition domains (CRDs) of Emp46p and Emp47p of Saccharomyces cerevisiae, in the absence and presence of metal ions. Both proteins fold as a beta-sandwich, and resemble that of the mammalian ortholog, p58/ERGIC-53. However, the nature of metal binding is distinct from that of Ca(2+)-dependent p58/ERGIC-53. Interestingly, the CRD of Emp46p does not bind Ca(2+) ion but instead binds K(+) ion at the edge of a concave beta-sheet whose position is distinct from the corresponding site of the Ca(2+) ion in p58/ERGIC-53. Binding of K(+) ion to Emp46p appears essential for transport of a subset of glycoproteins because the Y131F mutant of Emp46p, which cannot bind K(+) ion fails to rescue the transport in disruptants of EMP46 and EMP47 genes. In contrast the CRD of Emp47p binds no metal ions at all. Furthermore, the CRD of Emp46p binds to glycoproteins carrying high mannosetype glycans and the is promoted by binding not the addition of Ca(2+) or K(+) ion in These results suggest that Emp46p can be regarded as a Ca(2+)-independent intracellular lectin at the ER exit sites.

Expression levels of FUT6 gene transfected into human colon carcinoma cells switch two sialyl-Lewis X-related carbohydrate antigens with distinct properties in cell adhesion

A human colon carcinoma cell line KM12-LX, expressing low levels of monoclonal antibody (mAb) FH6 epitope, was transfected with alpha 1,3-fucosyltransferase VI cDNA. Clonal populations with high or intermediate expression levels of the mRNA, shown by RT-PCR (FT6hi and FT6in cells, respectively) were obtained. FT6hi cells were found to express both mAb FH6 and KM93 epitopes by flow-cytometric analysis, whereas FT6in cells expressed mAb FH6 epitopes but not mAb KM93 epitopes. The mAb FH6-binding was abrogated by endo-beta-galactosidase treatment of FT6in, but not FT6hi, cells. FT6hi but not FT6in cells adhered to Chinese-hamster-ovary cells expressing human E-selectin. FT6in cells adhered to sections of mouse liver and the adhesion was blocked by treatment of the cells with endo-beta-galactosidase. The results indicate that endo-beta-galactosidase-sensitive and mAb FH6-reactive carbohydrate chains are generated under the control of expression levels of FUT6 and involved in the adhesion of colon carcinoma cells to liver sections.

N-acetylgalactosamine incorporation into a peptide containing consecutive threonine residues by UDP-N-acetyl-D-galactosaminide:polypeptide N-acetylgalactosaminyltransferases

A limited number of glycosylation products were generated in a cell-free system from a portion of the MUC2 tandem repeat, PTTTPITTTTK, when microsome fractions of human colon carcinoma LS174T cells were used as the source of UDP-N-acetyl-D-galactosaminide:polypeptide N-acetylgalactosaminyltransferases (pp-GalNAc-T) in our previous work. The structures of all products suggested that there were only two biosynthetic pathways in the GalNAc incorporation into this peptide. In the present report, the putative biosynthetic intermediates, PTTT*PITTTTK (asterisk designates a GalNAc residue), PT*TTPITTTTK, PTT*T*PITT*T*TK, and PT*TTPIT*T*T*TK, of these two hypothetical pathways were used as acceptors to prove that these two pathways do exist. The incubation products of these glycopeptides, microsome fractions of LS174T cells, and UDP-GalNAc were fractionated by reverse-phase HPLC and their structures were determined using MALDI-TOF MS and peptide sequencing. The products from PTTT*PITTTTK were PTTT*PITTT*TK, PTTT*PITT*T*TK, PTT*T*PI-TT*T*TK, PTT*T*PIT*T*T*TK, PT*T*T*PIT*T*T*TK, and PT*T*T*PIT*T*T*T*K. The products from PTT*-T*PITT*T*TK exactly corresponded to the products with five to seven GalNAc residues from PTTT*PITTTTK. The products from PT*TTPITTTTK were PT*TTPITT*TTK, PT*TTPIT*T*TTK, and PT*TTPIT*T*T*TK. PT*TTP-IT*T*T*TK was not converted further under the applied condition. All the products detected and analyzed were the same as those obtained when the unsubstituted peptide and microsome fractions of LS174T cells were incubated. Immunocytochemical analysis indicated that LS174T cells contain at least four pp-GalNAc-Ts (-T1, -T2, -T3, and -T4), suggesting that control of the order and the maximum number of GalNAc incorporation into this peptide is regulated through the coordinated actions of these and possibly other pp-GalNAc-Ts.

Distinct orders of GalNAc incorporation into a peptide with consecutive threonines

Mucin O-glycosylation is initiated by a transfer of N-acetyl-d-galactosamine (GalNAc) to Ser and Thr residues in polypeptides with a family of UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferases (pp-GalNAc-Ts). In this paper, four human pp-GalNAc-Ts (pp-GalNAc-T1, T2, T3, and T4) were tested for their preferential orders of GalNAc incorporation into FITC-PTTTPITTTTK, a portion of the tandem repeat of human MUC2. The products were separated by reverse-phase HPLC and characterized by MALDI-TOF MS and peptide sequencing. pp-GalNAc-T1 showed preference for acceptor sites, but the order of the incorporation into these sites seemed to be random. In contrast, the GalNAc incorporation by pp-GalNAc-T2, T3, or T4 was not only site-specific but also according to the specific orders. Furthermore, pp-GalNAc-T2, T3, or T4 had distinct maximum numbers of GalNAc incorporations into this peptide.

[Vertical oculomotor disorders in progressive supranuclear palsy and spino-cerebellar degeneration]

We performed neuro-otological investigation of vertical oculomotor disorders in 35 patients with degenerative disease [progressive supranuclear palsy (PSP) and spino-cerebellar degeneration], and obtained the following results: 1) In the patients with PSP, in addition to vertical oculogyric disorder both saccade and pursuit eye movements were disturbed, and the disturbance of saccade movement was greater. Even the patients without an oculogyric disorder were all found to have decreased saccade velocity, suggesting that this disorder may occur earliest in PSP. 2) In olivo-ponto-cerebellar atrophy (OPCA), saccade movement was less disturbed than that in PSP. In contrast, pursuit movement was disturbed more frequently. 3) In late cortical cerebellar atrophy (LCCA), vertical ocular movement was hardly disturbed compared with OPCA. 4) Concerning dentate nuclear degeneration, we cannot reach a conclusion because of the few cases studied, but a variety of oculomotor disorders were seen; both saccade and pursuit movements were disturbed, but saccade movement was less disturbed than in PSP. 5) In visual suppression tests, enhancement in the light area was frequently seen in the patients with PSP and OPCA, but none with LCCA showed such change. In addition, enhancement of the light area under visual suppression was significantly correlated with vertical oculomotor disorder.