L6 monoclonal antibody binds prostate cancer

MicroRNA-206 inhibits metastasis of triple-negative breast cancer by targeting transmembrane 4 L6 family member 1

Purpose: Breast cancer (BC) is a common malignancy in women, but the survival rate for BC is not very encouraging. Especially for triple-negative breast cancer (TNBC), a kind of breast cancer that does not have any of the receptors that are commonly found in BC. We investigated the impact of microRNA-206 (miR-206) on transmembrane 4 L6 family member 1 (TM4SF1) in TNBC for therapeutic purpose. Patients and methods: Twenty BC tissues from diagnosed BC patients were analyzed via real-time PCR and Western blotting for expression of TM4SF1 and miR-206. The expression of TM4SF1 was studied in relationship with miR-206 in MDA-MB-231 cells. The biological impact of TM4SF1 and miR-206 on MDA-MB-231 cells and BALB/c nude mice model was studied using proliferation, transwell migration, and invasion assays both in vitro and in vivo. Results: The expression of TM4SF1 in BC tissues was significantly higher than that in adjacent normal breast tissues. In contrast, miR-206 showed a decreased expression level in BC tissues, especially for subtype basal like. Overexpression of miR-206 in MDA-MB-231 cells by transfecting miR-206 resulted in downregulation of TM4SF1. In contrast, knockdown miR-206 expression reversed miR-206-mediated phenotype in MDA-MB-231 cells. Expression level of TM4SF1 in MDA-MB-231 cells was associated with cell migration and invasion capabilities in vitro. Breast tumor burden was correlated with the expression level of TM4SF1 in vivo. Conclusion: Taken together, our results showed the involvement of TM4SF1 in TNBC migration and invasion. miR-206 negatively regulated gene expression of TM4SF1. These findings indicate that miR-206 could be used as a potential therapeutic agent for TNBC.

TM4SF1 is a potential target for anti-invasion and metastasis in ovarian cancer

BACKGROUND

Patients with ovarian cancer commonly have a poor prognosis, owing to its invasiveness and distant metastasis. Studies have found TM4SF1 participates in regulating tumor cell invasion and migration. Therefore, it is expected to become a target for anti-invasion and metastasis in ovarian cancer.

METHODS

The expression of TM4SF1 in normal ovarian epithelial tissues, benign ovarian tumor tissues, primary foci of epithelial ovarian cancer and the matched lymph mode metastatic foci was detected using immunohistochemistry to analyze its association with prognosis. The expression of TM4SF1 in HO8910PM, SKOV3 was inhibited using RNAi, and the growth, proliferation, migration, invasion abilities of HO8910PM and SKOV3 cells and the growth of xenograft tumors in nude mice were examined.

RESULTS

(1) The positive expression rate of TM4SF1 protein in epithelial ovarian cancer tissues (90.90%) was higher than that in benign ovarian tumor tissues (65.22%) and normal ovarian epithelial tissues (31.25%), and both differences were significant (P < 0.05). The expression of TM4SF1 protein was positive in all metastatic lymph node foci and matched primary foci (100%). (2) The level of TM4SF1 protein expression was positively correlated with the International Federation of Gynecology and Obstetrics (FIGO) stage and histological grade. However, The positive TM4SF1 protein expression was not an independent factor of prognosis (P > 0.05). (3) Silencing TM4SF1 expression did not affect growth, proliferation, or cell cycle distribution but inhibited the migration and invasion abilities of HO8910PM and SKOV3 cells. Silencing TM4SF1 expression inhibited the growth of xenograft tumors in nude mice.

CONCLUSION

TM4SF1 is a potential target for anti-invasion and metastasis in ovarian cancer.

MicroRNA-9 suppresses cell migration and invasion through downregulation of TM4SF1 in colorectal cancer

Transmembrane-4-L6 family 1 (TM4SF1) is upregulated in colorectal carcinoma (CRC). However, the mechanism leading to inhibition of the TM4SF1 is not known. In the present study, we investigated the regulation of TM4SF1 and function of microRNAs (miRNAs) in CRC invasion and metastasis. We analyzed 60 colon cancers and paired normal specimens for TM4SF1 and miRNA-9 (miR-9) expression using quantitative real-time PCR. A bioinformatics analysis identified a putative miR-9 binding site within the 3'-UTR of TM4SF1. We also found that TM4SF1 was upregulated in CRC tissues and CRC cell lines. The expression of TM4SF1 was positively correlated with clinical advanced stage and lymph node metastasis. Moreover, a luciferase assay revealed that miR-9 directly targeted 3'-UTR-TM4SF1. Overexpression of miR-9 inhibited expression of TM4SF1 mRNA and protein, wound healing, transwell migration and invasion of SW480 cells, whereas, overexpression of anti-miR-9 and siRNA-TM4SF1 inversely regulated the TM4SF1 mRNA and protein level in HCT116 cells. Furthermore, miR-9 suppressed not only TM4SF1 expression but also MMP-2, MMP-9 and VEGF expression. In clinical specimens, miR-9 was generally down-regulated in CRC and inversely correlated with TM4SF1 expression. These results suggest that miR-9 functions as a tumor-suppressor in CRC, and that its suppressive effects mediate invasion and metastasis by inhibition of TM4SF1 expression. Our results also indicate that miR-9 might be a novel target for the treatment of CRC invasion and metastasis.

Novel Anti-TM4SF1 Antibody-Drug Conjugates with Activity against Tumor Cells and Tumor Vasculature

Antibody-drug conjugates (ADC) represent a promising therapeutic modality for managing cancer. Here, we report a novel humanized ADC that targets the tetraspanin-like protein TM4SF1. TM4SF1 is highly expressed on the plasma membranes of many human cancer cells and also on the endothelial cells lining tumor blood vessels. TM4SF1 is internalized upon interaction with antibodies. We hypothesized that an ADC against TM4SF1 would inhibit cancer growth directly by killing cancer cells and indirectly by attacking the tumor vasculature. We generated a humanized anti-human TM4SF1 monoclonal antibody, v1.10, and armed it with an auristatin cytotoxic agent LP2 (chemical name mc-3377). v1.10-LP2 selectively killed cultured human tumor cell lines and human endothelial cells that express TM4SF1. Acting as a single agent, v1.10-LP2 induced complete regression of several TM4SF1-expressing tumor xenografts in nude mice, including non-small cell lung cancer and pancreas, prostate, and colon cancers. As v1.10 did not react with mouse TM4SF1, it could not target the mouse tumor vasculature. Therefore, we generated a surrogate anti-mouse TM4SF1 antibody, 2A7A, and conjugated it to LP2. At 3 mpk, 2A7A-LP2 regressed several tumor xenografts without noticeable toxicity. Combination therapy with v1.10-LP2 and 2A7A-LP2 together was more effective than either ADC alone. These data provide proof-of-concept that TM4SF1-targeting ADCs have potential as anticancer agents with dual action against tumor cells and the tumor vasculature. Such agents could offer exceptional therapeutic value and warrant further investigation. Mol Cancer Ther; 14(8); 1868-76. ©2015 AACR.

TM4SF1: a new vascular therapeutic target in cancer

Transmembrane-4 L-six family member-1 (TM4SF1) is a small plasma membrane glycoprotein that regulates cell motility and proliferation. TM4SF1 is an attractive cancer target because of its high expression in both tumor cells and on the vascular endothelial cells lining tumor blood vessels. We generated mouse monoclonal antibodies against human TM4SF1 in order to evaluate their therapeutic potential; 13 of the antibodies we generated reacted with extracellular loop-2 (EL2), TM4SF1's larger extracellular, lumen-facing domain. However, none of these antibodies reacted with mouse TM4SF1, likely because the EL2 of mouse TM4SF1 differs significantly from that of its human counterpart. Therefore, to test our antibodies in vivo, we employed an established model of engineered human vessels in which human endothelial colony-forming cells (ECFC) and human mesenchymal stem cells (MSC) are incorporated into Matrigel plugs that are implanted subcutaneously in immunodeficient nude mice. We modified the original protocol by (1) preculturing human ECFC on laminin, fibronectin, and collagen-coated plates, and (2) increasing the ECFC/MSC ratio. These modifications significantly increased the human vascular network in Matrigel implants. Two injections of one of our anti-TM4SF1 EL2 monoclonal antibodies, 8G4, effectively eliminated the human vascular component present in these plugs; they also abrogated human PC3 prostate cancer cells that were incorporated into the ECFC/MSC Matrigel mix. Together, these studies provide a mouse model for assessing tumor xenografts that are supplied by a human vascular network and demonstrate that anti-TM4SF1 antibodies such as 8G4 hold promise for cancer therapy.

Have we overestimated the benefit of human(ized) antibodies?

The infusion of animal-derived antibodies has been known for some time to trigger the generation of antibodies directed at the foreign protein as well as adverse events including cytokine release syndrome. These immunological phenomena drove the development of humanized and fully human monoclonal antibodies. The ability to generate human(ized) antibodies has been both a blessing and a curse. While incremental gains in the clinical efficacy and safety for some agents have been realized, a positive effect has not been observed for all human(ized) antibodies. Many human(ized) antibodies trigger the development of anti-drug antibody responses and infusion reactions. The current belief that antibodies need to be human(ized) to have enhanced therapeutic utility may slow the development of novel animal-derived monoclonal antibody therapeutics for use in clinical indications. In the case of murine antibodies, greater than 20% induce tolerable/negligible immunogenicity, suggesting that in these cases humanization may not offer significant gains in therapeutic utility. Furthermore, humanization of some murine antibodies may reduce their clinical effectiveness. The available data suggest that the utility of human(ized) antibodies needs to be evaluated on a case-by-case basis, taking a cost-benefit approach, taking both biochemical characteristics and the targeted therapeutic indication into account.

Hexa-arginine enhanced uptake and residualization of selective high affinity ligands by Raji lymphoma cells

Background

A variety of arginine-rich peptide sequences similar to those found in viral proteins have been conjugated to other molecules to facilitate their transport into the cytoplasm and nucleus of targeted cells. The selective high affinity ligand (SHAL) (DvLPBaPPP)₂LLDo, which was developed to bind only to cells expressing HLA-DR10, has been conjugated to one of these peptide transduction domains, hexa-arginine, to assess the impact of the peptide on SHAL uptake and internalization by Raji cells, a B-cell lymphoma.

Results

An analog of the SHAL (DvLPBaPPP)₂LLDo containing a hexa-arginine peptide was created by adding six D-arginine residues sequentially to a lysine inserted in the SHAL's linker. SHAL binding, internalization and residualization by Raji cells expressing HLA-DR10 were examined using whole cell binding assays and confocal microscopy. Raji cells were observed to bind two fold more ¹¹¹In-labeled hexa-arginine SHAL analog than Raji cells treated with the parent SHAL. Three fold more hexa-arginine SHAL remained associated with the Raji cells after washing, suggesting that the peptide also enhanced residualization of the ¹¹¹In transported into cells. Confocal microscopy showed both SHALs localized in the cytoplasm of Raji cells, whereas a fraction of the hexa-arginine SHAL localized in the nucleus.

Conclusion

The incorporation of a hexa-D-arginine peptide into the linker of the SHAL (DvLPBaPPP)₂LLDo enhanced both the uptake and residualization of the SHAL analog by Raji cells. In contrast to the abundant cell surface binding observed with Lym-1 antibody, the majority of (DvLPBaPPP)₂LArg6AcLLDo and the parent SHAL were internalized. Some of the internalized hexa-arginine SHAL analog was also associated with the nucleus. These results demonstrate that several important SHAL properties, including uptake, internalization, retention and possibly intracellular distribution, can be enhanced or modified by conjugating the SHALs to a short polypeptide.

The L6 protein TM4SF1 is critical for endothelial cell function and tumor angiogenesis

Transmembrane-4-L-six-family-1 (TM4SF1) was originally described as a cancer cell protein. Here, we show that it is highly expressed in the vascular endothelium of human cancers and in a banded pattern in the filopodia of cultured endothelial cells (EC). TM4SF1 knockdown prevented filopodia formation, inhibited cell mobility, blocked cytokinesis, and rendered EC senescent. Integrin-alpha5 and integrin-beta1 subunits gave a similar staining pattern and interacted constitutively with TM4SF1, whereas integrin subunits often associated with angiogenesis (alphaV, beta3, beta5) interacted with TM4SF1 only after vascular endothelial growth factor (VEGF)-A or thrombin stimulation. TM4SF1 knockdown substantially inhibited maturation of VEGF-A(164)-induced angiogenesis. Thus, TM4SF1 is a key regulator of EC function in vitro and of pathologic angiogenesis in vivo and is potentially an attractive target for antiangiogenesis therapy.

Diethylstilbestrol glutamate as a potential substrate for ADEPT

The combination of systemic toxicity, water insolubility and a labile chemical structure has limited the clinical use of diethylstilbestrol (DES) 1 for the treatment of prostate cancer. To determine if DES could potentially be a prodrug substrate for the pre-targeting strategy known as antibody directed enzyme prodrug therapy (ADEPT), the DES-glutamate 5 was prepared. The synthesis required the activation of the bis-t-butyl glutamate ester 2 to the isocyanate 3 followed by addition of DES 1. The desired DES-glutamate 5 was water-soluble and upon incubation with carboxypeptidase G2 (CPG2) underwent carbamate cleavage to give DES 1. A control reaction in the absence of CPG2 demonstrated that the enzyme was necessary for rapid glutamate cleavage to give DES 1. HPLC analysis was required to follow the reaction of DES-glutamate 5 with CPG2. These preliminary results suggest that it may be possible to examine an ADEPT strategy for DES provided enzymatic kinetics can be measured.

CD13 (aminopeptidase N) can associate with tumor-associated antigen L6 and enhance the motility of human lung cancer cells

Cancer metastasis is a multiple-step process that involves the regulated interaction of diverse cellular proteins. We recently reported that the expression of tumor-associated antigen L6 (TAL6) promoted the invasiveness of lung cancer cells and was inversely correlated with disease-free survival of squamous lung carcinoma patients. We now report that CD13 (aminopeptidase N) can associate with TAL6 and can enhance cancer cell migration. CD13 was shown by coimmunoprecipitation to associate in vitro with TAL6 on several cancer cell lines and to associate in vivo by antibody-mediated copatching immunofluorescence. CD13 was selectively expressed on highly invasive CL1-5 lung cancer cells as compared to poorly invasive CL1-0 lung cancer cells. The role of CD13 aminopeptidase activity in regulating cell motility was investigated with chemical inhibitors, specific antibodies and a catalytically inactive CD13 protein. Inhibition of CD13 aminopeptidase activity by nontoxic concentrations of leuhistin modestly decreased the migration of CL1-5 cells. In contrast, binding of CD13 by specific antibodies significantly reduced both the migration and the invasion of CL1-5 cells. Poorly invasive CL1-0 cells that stably expressed CD13 displayed significantly (p < or = 0.0005) enhanced cell migration (300% of control). Expression of an enzymatically inactive CD13 mutant on CL1-0 cells also significantly (p < or = 0.0005) enhanced cell migration (200% of control). Our results show that TAL6 and CD13 can form a complex on lung cancer cells, that these molecules can modulate cell migration and invasion and that the influence of CD13 on cell motility did not strictly depend on its aminopeptidase activity.

Combined modality radioimmunotherapy for human prostate cancer xenografts with taxanes and 90yttrium-DOTA-peptide-ChL6

BACKGROUND

Therapy for prostate cancer in the PC3 tumor-nude mouse model with 90yttrium-(90Y)-DOTA-peptide-ChL6 (5.55 MBq;150 microCi) has resulted in durable responses. To make radioimmunotherapy (RIT) more effective, the radiation-enhancing drugs Taxol (paclitaxel) and Taxotere (docetaxel) were tested for synergy with 90Y-DOTA-peptide-ChL6.

METHODS

Nude mice bearing human prostate cancer PC3 xenografts were treated with 90Y-DOTA-peptide-ChL6 (2.78 MBq; 75 microCi) and after 24 hr, paclitaxel (300 or 600 microg), or docetaxel (300 microg). Tumor size, survival, blood counts, and pharmacokinetics were monitored to assess efficacy and toxicity.

RESULTS

Docetaxel plus RIT had a 67% cure rate, whereas no mice were cured among the RIT alone, chemotherapy alone, or untreated controls. Paclitaxel (600 microg) plus RIT produced a 100% response rate with 20% cures. Average tumor volume was reduced to a greater degree in the combined modality radioimmunotherapy (CMRIT) groups compared to controls and the anti-tumor response was durable. Myelotoxicity in the combined modality groups (RIT plus paclitaxel or RIT plus docetaxel) were similar to groups receiving the same dose of RIT alone.

CONCLUSION

In the PC3-tumor nude mouse model, addition of paclitaxel or docetaxel to 90Y-DOTA-peptide-ChL6, in doses clinically achievable in humans, provided therapeutic synergy without increased or excessive toxicity.

Efficacy and toxicity of radioimmunotherapy with (90)Y-DOTA-peptide-ChL6 for PC3-tumored mice

BACKGROUND

Radioimmunotherapy (RIT) is a new therapeutic modality capable of systemic delivery of radionuclides specifically to sites of metastatic cancer. The L6 monoclonal antibody has been shown to target prostate cancer in preclinical studies and, along with chimeric L6 (ChL6), has been used for RIT in breast cancer patients.

METHODS

Pharmacokinetics, blood counts, body weight, and antitumor activity of RIT with (90)yttrium-((90)Y)-DOTA-peptide-ChL6 (75-260 microCi) were determined in nude mice bearing human prostate cancer (PC3) xenografts.

RESULTS

RIT produced durable, dose-dependent antitumor effects with a 100% response rate using 112 microCi and 150 microCi (the maximum tolerated dose) of (90)Y-DOTA-peptide-ChL6. Myelotoxicity was reversible, dose-limiting, and dose-related. RIT was associated with improved survival (P = 0.05). All 5 mice in the 150-microCi group survived the 84-day study period vs. 1/8 (13%) for untreated, tumored control mice.

CONCLUSIONS

(90)Y-DOTA-peptide-ChL6 targets PC3 human prostate cancer xenografts in nude mice and has an antitumor effect. These results provide a basis for future RIT trials for patients with metastatic prostate cancer.

Monoclonal antibodies: will they become an integral part of the evaluation and treatment of prostate cancer--focus on prostate-specific membrane antigen?

Over the past two decades, monoclonal antibody technology has had an increasing impact on clinical diagnostic and therapeutic options, and this is true in the realm of managing prostate cancer. Several targets such as prostate-specific antigen and prostatic acid phosphatase as well as, more recently, angiogenic antigens such as vascular endothelial growth factor have been examined for therapy. Prostate-specific membrane antigen, a type II integral membrane glycoprotein initially characterized by the monoclonal antibody 7E11, has shown promise. Recent evidence suggests that prostate-specific membrane antigen is also expressed in tumor-associated neovasculature of a wide variety of malignant neoplasms. With its expression in prostate secretory-acinar epithelium and the prostate and in the neovasculature associated with tumors, prostate-specific membrane antigen represents an excellent antigenic target for monoclonal antibody diagnostic and therapeutic options. As research continues, the role of monoclonal antibody imaging and therapy will become increasingly important in the management of prostate cancer.