A new disulfide-linked dimer of a single-chain antibody fragment against human CD47 induces apoptosis in lymphoid malignant cells via the hypoxia inducible factor-1α pathway.

CD47 belongs to the immunoglobulin superfamily and is associated with ß-integrins. Recently it was reported that CD47 ligation rapidly induces apoptosis in B-chronic lymphocytic leukemia (CLL) cells. Chronic lymphocytic leukemia is still an incurable hematological malignancy even with the novel therapeutic agents; therefore, new and effective agents for the treatment of CLL in clinical settings are urgently needed. We generated a murine monoclonal antibody against an extracellular domain of human CD47 (designated MABL). Subsequently, we created a disulfide-stabilized dimer of a single-chain antibody fragment of MABL (S-S diabody) to get rid of the adverse effect of MABL such as hemagglutination. In this study, we analyzed the effects of this new antibody on cellular proliferation, and the molecular mechanism of CD47-mediated apoptosis in human lymphoid malignant cells. Treatment with S-S diabody alone induced apoptosis of CD47-positive primary B-CLL and leukemic cells (MOLT-4 and JOK-1). In addition, administration of S-S diabody significantly prolonged the survival of severe combined immunodeficiency (SCID) mice inoculated with JOK-1 cells. In gene expression profiling of the S-S diabody-treated MOLT-4 cells, hypoxia inducible factor (HIF)-1α downstream genes (RTP801 and BNIP3) were upregulated, and the mRNA expression levels of HIF-1α, RTP801 and BNIP3 were increased. Knockdown of HIF-1α by siRNA repressed S-S diabody-induced apoptosis in MOLT4 cells. In conclusion, CD47 will be a molecular target for the treatment of lymphoid malignancies, and S-S diabody might have potential as a novel therapeutic agent for B-CLL.

Thiochroman derivative CH4986399, a new nonsteroidal estrogen receptor down-regulator, is effective in breast cancer models.

BACKGROUND: Tamoxifen, a selective estrogen receptor modulator, and fulvestrant, a selective estrogen receptor down-regulator (SERD), are now available for estrogen receptor-positive breast cancer patients. However, these patients acquire drug-resistance during the treatments. We identified a new orally active nonsteroidal SERD, CH4986399, which is structurally unrelated to fulvestrant and tamoxifen. MATERIALS AND METHODS: We examined the oral antitumor activity and down-regulation of ER by CH4986399 in human breast cancer Br-10 and ZR-75-1 xenografts. RESULTS: In the Br-10 xenografts, CH4986399 (100 mg/kg p.o.) as well as fulvestrant (3 mg/body s.c.) strongly reduced tumor weight. In the ZR-75-1 xenografts, CH4986399 (100 mg/kg p.o.) strongly reduced tumor weight and ER content without agonistic activity. In contrast, tamoxifen (100 mg/kg p.o.) showed only moderate antitumor activity and no ER down-regulation. CONCLUSION: With a chemical structure different from both fulvestrant and tamoxifen, CH4986399, may help overcome drug resistance from the endocrine treatment sequence for breast cancer patients.

Anti-glypican 3 antibodies cause ADCC against human hepatocellular carcinoma cells.

Glypican 3 (GPC3), a GPI-anchored heparan sulfate proteoglycan, is expressed in the majority of hepatocellular carcinoma (HCC) tissues. Using MRL/lpr mice, we successfully generated a series of anti-GPC3 monoclonal antibodies (mAbs). GPC3 was partially cleaved between Arg358 and Ser359, generating a C-terminal 30-kDa fragment and an N-terminal 40-kDa fragment. All mAbs that induced antibody-dependent cellular cytotoxicity (ADCC) and/or complement-dependent cytotoxicity (CDC) against cells expressing GPC3 recognized the 30-kDa fragment, indicating that the C-terminal region of GPC3 serves as an epitope for mAb with ADCC and/or CDC inducing activities. Chimeric mAbs with Fc replaced by human IgG1 were created from GC33, one of the mAbs that reacted with the C-terminal 30-kDa fragment. Chimeric GC33 induced not only ADCC against GPC3-positive human HCC cells but also was efficacious against the Huh-7 human HCC xenograft. Thus, mAbs against the C-terminal 30-kDa fragment such as GC33 are useful in therapy targeting HCC.

Anti-glypican 3 antibody as a potential antitumor agent for human liver cancer.

Human glypican 3 (GPC3) is preferentially expressed in the tumor tissues of liver cancer patients. In this study, we obtained a monoclonal antibody (mAb) against the COOH-terminal part of GPC3, which induced antibody-dependent cellular cytotoxicity (ADCC). The mAb, designated GC33, exhibited marked tumor growth inhibition of s.c. transplanted Hep G2 and HuH-7 xenografts that expressed GPC3 but did not inhibit growth of the SK-HEP-1 that was negative for GPC3. GC33 was efficacious even in an orthotopic model; it markedly reduced the blood alpha-fetoprotein levels of mice intrahepatically transplanted with Hep G2 cells. Humanized GC33 (hGC33) was as efficacious as GC33 against the Hep G2 xenograft, but hGC33 lacking carbohydrate moieties caused neither ADCC nor tumor growth inhibition. Depletion of CD56+ cells from human peripheral blood mononuclear cells markedly abrogated the ADCC caused by hGC33. The results show that the antitumor activity of hGC33 is mainly attributable to ADCC, and in human, natural killer cell-mediated ADCC is one possible mechanism of the antitumor effects by GC33. hGC33 will provide a novel treatment option for liver cancer patients with GPC3-positive tumors.

Viral envelope protein gp64 transgenic mouse facilitates the generation of monoclonal antibodies against exogenous membrane proteins displayed on baculovirus.

We have been investigating the functional display of multipass membrane protein such as transporter or G-protein coupled receptor on the budded baculovirus (BV). We tested the use of a viral envelope protein gp64 transgenic mouse for the direct immunization of these membrane proteins displayed on BVs. The gp64 transgenic mice showed only a weak response to virus compared to wild type BALB/c mice. Immunizing gp64 transgenic mice with the BV expressing peptide transporter PepT1, we obtained 47 monoclonal antibodies (mAbs). These mAbs were specific to the PepT1 on the pancreatic cancer cells AsPC-1 by fluorocytometric analysis and exhibited antibody-dependent cellular cytotoxicity or complement-dependent cytotoxicity to AsPC-1. We also generated 7 mAbs by immunizing gp64 transgenic mice on a CCR2-deficient background with the BV expressing chemokine receptor CCR2 together with partially purified CCR2. These mAbs possessed specific binding to CCR2 in CHO cells on fluorocytometric analysis, and exhibited neutralizing activities for ligand-dependent inhibition of cyclic AMP production. This method provides a powerful tool for the generation of therapeutic/diagnostic mAbs against membrane proteins.

Newly discovered orally active pure antiestrogens.

In order to develop orally active pure antiestrogens, we incorporated the carboxy-containing side chains into the 7alpha-position of the steroid scaffold and found that 17-keto derivative CH4893237 (12b) functioned as a pure antiestrogen with its oral activity much superior to clinically used pure antiestrogen, ICI182,780. Results from the pharmacokinetic evaluation indicated that the potent antiestrogen activity at oral dosing in mice attributed to both improved absorption from the intestinal wall and metabolic stability in liver.

Discovery of thiochroman derivatives bearing a carboxy-containing side chain as orally active pure antiestrogens.

In order to search for alternatives to the sulfoxide moiety in the long side chain of pure antiestrogens, several molecules that may interact with water in a fashion similar to ICI164,384 were designed and it was found that compounds with the carboxy, the sulfamide, or the sulfonamide instead of the sulfoxide moiety also functioned as pure antiestrogens. Interestingly, the compound possessing the carboxy moiety showed superior antiestrogen activity compared to ICI182,780 when dosed orally. Results of the pharmacokinetic evaluation indicated that the potent antiestrogen activity at oral dosing attributed to both the improved absorption from the intestinal wall and the metabolic stability of the compound in liver.

Discovery of thiochroman and chroman derivatives as pure antiestrogens and their structure-activity relationship.

In order to develop pure antiestrogens, a series of 7-hydroxy-3-(4-hydroxyphenyl)-3-methylchroman and 7-hydroxy-3-(4-hydroxyphenyl)-3-methylthiochroman derivatives with sulfoxide containing side chains at the 4-position were designed, synthesized, and evaluated. Among them, compounds 14b and 24b functioned as pure antiestrogens with the ability to downregulate ER, and their in vitro and in vivo antiestrogen activities were similar to those of ICI182,780. In addition, the structure-activity relationship indicated that the (3RS,4RS)-configuration between the 3- and 4-position, the methyl group at the 3-position, the 9-methylene chain between the scaffold and the sulfoxide moiety, and the terminal perfluoroalkyl moiety play an important role in increasing estrogen receptor binding and oral antiestrogen activities.

Recovery of functional peptide transporter PepT1 in budded baculovirus fraction.

Transporters play a critical role in many physiological and pathological states and expression of the functional transporter protein is essential in exploring its kinetics and developing effective drugs. We describe here the recovery of functional transporter protein in the baculovirus fraction. We introduced a gene encoding human peptide transporter PepT1, important for the absorption of protein hydrolytic products or peptide-mimetic drugs, into a baculovirus vector. After infection, a large amount of PepT1 appeared in the budded virus fraction compared with Sf9 cells. Uptake of [14C]glycylsarcosine was markedly increased in an acidic condition and showed a clear overshoot in PepT1-expressing virus fraction. The apparent Michaelis constant for [14C]glycylsarcosine was 0.55 +/- 0.06 mM. [14C]Glycylsarcosine uptake was inhibited by di- and tripeptides and orally active beta-lactam antibiotics. These results suggest that functional PepT1 recovers efficiently in a budded virus fraction, and, thus, this expression system will be a useful tool for characterization and screening of peptide-mimetic drugs in drug discovery.

Identification of soluble NH2-terminal fragment of glypican-3 as a serological marker for early-stage hepatocellular carcinoma.

For detection of hepatocellular carcinoma (HCC) in patients with liver cirrhosis, serum alpha-fetoprotein has been widely used, but its sensitivity has not been satisfactory, especially in small, well-differentiated HCC, and complementary serum marker has been clinically required. Glypican-3 (GPC3), a heparan sulfate proteoglycan anchored to the plasma membrane, is a good candidate marker of HCC because it is an oncofetal protein overexpressed in HCC at both the mRNA and protein levels. In this study, we demonstrated that its NH(2)-terminal portion [soluble GPC3 (sGPC3)] is cleaved between Arg(358) and Ser(359) of GPC3 and that sGPC3 can be specifically detected in the sera of patients with HCC. Serum levels of sGPC3 were 4.84 +/- 8.91 ng/ml in HCC, significantly higher than the levels seen in liver cirrhosis (1.09 +/- 0.74 ng/ml; P < 0.01) and healthy controls (0.65 +/- 0.32 ng/ml; P < 0.001). In well- or moderately-differentiated HCC, sGPC3 was superior to alpha-fetoprotein in sensitivity, and a combination measurement of both markers improved overall sensitivity from 50% to 72%. These results indicate that sGPC3 is a novel serological marker essential for the early detection of HCC.