Philip W. Noble

DNA-damaging autoantibodies and cancer: the lupus butterfly theory.

Autoantibodies reactive against host DNA are detectable in the circulation of most people with systemic lupus erythematosus (SLE). The long-held view that antibodies cannot penetrate live cells has been disproved. A subset of lupus autoantibodies penetrate cells, translocate to nuclei, and inhibit DNA repair or directly damages DNA. The result of these effects depends on the microenvironment and genetic traits of the cell. Some DNA-damaging antibodies alone have little impact on normal cells, but in the presence of other conditions, such as pre-existing DNA-repair defects, can become highly toxic. These findings raise new questions about autoimmunity and DNA damage, and reveal opportunities for new targeted therapies against malignancies particularly vulnerable to DNA damage. In this Perspectives article, we review the known associations between SLE, DNA damage and cancer, and propose a theory for the effects of DNA-damaging autoantibodies on SLE pathophysiology and cancer risk.

DNA-dependent targeting of cell nuclei by a lupus autoantibody.

A nuclear-penetrating lupus anti-DNA autoantibody, 3E10, has been found to inhibit DNA repair and selectively kill certain cancer cells that are highly vulnerable to DNA damage. In addition, a 3E10 single chain variable fragment (scFv) has been developed for use as a delivery vehicle to carry therapeutic cargo proteins into cell nuclei. A greater understanding of the mechanism by which 3E10 penetrates cell nuclei is needed to help determine the scope of its potential therapeutic applications. Here we show that the presence of extracellular DNA significantly enhances the nuclear uptake of 3E10 scFv. In addition, we find that 3E10 scFv preferentially localizes into tumor cell nuclei in vivo, likely due to increased DNA in the local environment released from ischemic and necrotic regions of tumor. These data provide insight into the mechanism of nuclear penetration by 3E10 and demonstrate the potential for use of 3E10 in therapeutic approaches to diseases ranging from malignancy to ischemic conditions such as stroke.

A nucleolytic lupus autoantibody is toxic to BRCA2-deficient cancer cells

Cancer cells with defects in DNA repair are highly susceptible to DNA-damaging agents, but delivery of therapeutic agents into cell nuclei can be challenging. A subset of lupus autoantibodies is associated with nucleolytic activity, and some of these antibodies are capable of nuclear penetration. We hypothesized that such antibodies might have potential as therapeutic agents targeted towards DNA repair-deficient malignancies. We identified the lupus autoantibody 5C6 as a cell-penetrating nucleolytic antibody and found that 5C6 has a differential effect on a matched pair of BRCA2-proficient and deficient DLD1 colon cancer cells. 5C6 selectively induced γH2AX in, and suppressed the growth of, the BRCA2-deficient cells. These findings demonstrate the potential utility of 5C6 in targeted therapy for DNA repair-deficient malignancies and strengthen the rationale for studies of additional lupus autoantibodies in order to identify the best candidates for development as therapeutic agents. In addition, the toxic effect of 5C6 on BRCA2-deficient cells provides further support for the hypothesis that some lupus autoantibodies contribute to the lower risk of specific cancers associated with systemic lupus erythematosus.

Optimizing a Lupus Autoantibody for Targeted Cancer Therapy

The specificity of binding by antibodies to target antigens is a compelling advantage to antibody-based cancer therapy, but most antibodies cannot penetrate cells to affect intracellular processes. Select lupus autoantibodies penetrate into cell nuclei, and the potential for application of these antibodies in cancer therapy is an emerging concept. Here, we show that a divalent lupus anti-DNA autoantibody fragment with enhancing mutations that increase its ability to penetrate cell nuclei and bind DNA causes accumulation of DNA double-strand breaks in and is highly and selectively toxic to cancer cells and tumors with defective homology-directed repair of DNA double-strand breaks. These findings provide proof of principle for the use of optimized lupus autoantibodies in targeted cancer therapy.

A lupus anti-DNA autoantibody mediates autocatalytic, targeted delivery of nanoparticles to tumors.

Strategies to target nanoparticles to tumors that rely on surface modification with ligands that bind molecules overexpressed on cancer cells or the tumor neovasculature suffer from a major limitation: with delivery of toxic agents the amount of molecules available for targeting decreases with time; consequently, the efficiency of nanoparticle delivery is reduced. To overcome this limitation, here we propose an autocatalytic tumor-targeting mechanism based on targeting extracellular DNA (exDNA). exDNA is enriched in the tumor microenviroment and increases with treatment with cytotoxic agents, such as doxorubicin (DOX), due to release of DNA by dying tumor cells. We tested this approach using poly(lactic-co-glycolic acid) (PLGA) nanoparticles surface-conjugated with fragments of 3E10 (3E10EN), a lupus anti-DNA autoantibody. We demonstrated that 3E10EN-conjugated nanoparticles bound to DNA and preferentially localized to tumors in vivo. The efficiency of tumor localization of 3E10EN-conjugated, DOX-loaded nanoparticles increased with time and subsequent treatments, demonstrating an autocatalytic effect. 3E10EN-conjugated DOX-loaded nanoparticles exhibited a significant anti-tumor effect that was superior to all controls. This work demonstrates the promise of autocatalytic drug delivery mechanisms and establishes proof of concept for a new anti-DNA autoantibody-based approach for enhancing delivery of nanoparticles to tumors.

Abstract 2773: A DNA-damaging lupus autoantibody synergizes with PARP inhibitors against DNA repair-deficient tumor cells

The lupus anti-DNA autoantibody 3E10 is a compelling candidate for development as a targeted therapy for DNA repair-deficient malignancies. 3E10 has previously been shown to localize to tumors due to its attraction to DNA released by dying cancer cells, penetrate into cell nuclei, inhibit DNA repair, and kill cancer cells with defects in homology-directed repair (HDR) of DNA double-strand breaks. A more potent derivative of 3E10 with increased affinity for DNA has been developed (referred to here as 3E10 EN ), and identification of optimal combination therapies with 3E10 EN is needed to facilitate planning for upcoming clinical trials. In the present study, we found that 3E10 EN increases the activity of the DNA repair enzyme poly (ADP-ribose) polymerase (PARP) in HDR-deficient cells and hypothesized that combination treatment with 3E10 EN and PARP inhibitors (PARPi) would yield synergistic effects on HDR-deficient cancer cell survival. PARP content and activity in HDR-deficient and proficient cells prior to and following treatment with 3E10 EN was evaluated. 3E10 EN did not impact PARP protein content but yielded a significant increase in pADPr signal in HDR-deficient cells, which suggests a compensatory increase in PARP activity in response to DNA damage accumulation in HDR-deficient cells. Combinations of 3E10 EN and the PARPi olaparib were tested on a panel of HDR-deficient cells, and a matched pair of BRCA2-deficient and proficient DLD1 cells. Olaparib inhibited the increase in pADPr caused by 3E10 EN , and colony formation assays analyzed by the Chou-Talalay method confirmed that 3E10 EN and olaparib synergized against HDR-deficient cancer cells. Conversely, HDR-proficient cells were resistant to 3E10 EN and olaparib combination treatment. The original 3E10 is a murine antibody isolated from a lupus mouse model, and in preparation for its further development as a new drug we have recently designed Deoxymab 1 (DX1), a humanized version of 3E10 EN . DX1 exhibits improved activity relative to the 3E10 EN prototype, and when tested on a panel of HDR-deficient and proficient cells, DX1 and olaparib exhibited synergistic effects similar to that observed with the 3E10 EN prototype. In conclusion, we have found that both the prototype 3E10 EN and humanized DX1 synergize with PARPi against HDR-deficient tumor cells. These findings provide the rationale for further studies to determine the potential for this approach to be translated into a clinically relevant therapeutic strategy. Citation Format: Zahra Rattray, Jaymin M. Patel, Philip W. Noble, Valentina Dubljevic, Deanne L. Greenwood, James A. Campbell, James E. Hansen. A DNA-damaging lupus autoantibody synergizes with PARP inhibitors against DNA repair-deficient tumor cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2773.

Abstract 654: Targeting K-ras mutant cancer cells with a lupus anti-guanosine antibody

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Aberrant G-protein signaling due to mutations in genes encoding the Ras family of small GTPases is associated with approximately 30% of human cancers, and K-ras is one of the most commonly mutated Ras proteins. Development of targeted therapies that are preferentially toxic to cancer cells harboring K-ras mutations is therefore an important goal in cancer research. We have identified an unusual cell-penetrating lupus autoantibody, 4H2, as a potential candidate for development as a targeted therapy for tumors with activating K-ras mutations. 4H2 is an anti-guanosine antibody that has previously been shown to penetrate living cells and inhibit cAMP formation. Taken together, the ability of 4H2 to bind guanosine (a component of GDP/GTP) and to inhibit cAMP formation suggests that 4H2 perturbs G-protein signaling. We therefore hypothesized that 4H2 would be selectively toxic to cancer cells with aberrant G-protein signaling due to activating K-ras mutations compared to cells without mutations in K-ras. To test this hypothesis, we evaluated the effects of 4H2 on a panel of isogenic pairs of cells with and without activating K-ras mutations, including Cal12T lung cancer cells (with and without a G12C activating K-ras mutation), NCI-H1975 lung cancer cells (with and without a G12D activating K-ras mutation), and SW48 colon cancer cells (with and without a G12A activating K-ras mutation). Immunofluorescence experiments confirmed that 4H2 penetrates into and localizes to the cytoplasm of cells with and without an activating K-ras mutation. In cell proliferation assays the matched pairs of cells were treated with 4H2 while growing as subconfluent monolayers, and 4H2 was observed to significantly inhibit the proliferation of the cells with activating K-ras mutations but not the cells without K-ras mutations. Next, colony formation assays confirmed that treatment with 4H2 was significantly more toxic to cells with activating K-ras mutations compared to cells without K-ras mutations. Mechanistically, Western blot analyses suggest a differential effect of 4H2 on the MAP kinase and Akt signaling pathways in K-ras mutant and wild type cells, consistent with the hypothesis that 4H2 interferes with G-protein associated intracellular signaling pathways. In summary, this work has demonstrated that 4H2 is an intriguing candidate for further study and development as a potential targeted therapy for tumors with activating mutations in K-ras. Citation Format: Melissa R. Young, Philip W. Noble, Richard H. Weisbart, James E. Hansen. Targeting K-ras mutant cancer cells with a lupus anti-guanosine antibody. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 654. doi:10.1158/1538-7445.AM2014-654

Abstract 4220: A cell-penetrating nucleolytic lupus autoantibody damages DNA and is toxic to BRCA2-deficient cancer cells

Identification of therapeutic agents that are more toxic to malignant cells than normal cells is a key goal in cancer research. Many tumor cells harbor genetic defects that distinguish them from normal cells, and some of these defects have the potential to be exploited in the development of targeted therapies for cancer. Cancer cells with defects in DNA repair are highly susceptible to DNA-damaging agents, but delivery of therapeutic agents into cell nuclei can be challenging. A subset of lupus autoantibodies is associated with nucleolytic activity, and some of these antibodies are capable of nuclear penetration. We hypothesized that such antibodies might be capable of damaging DNA in cell nuclei and therefore have potential as therapeutic agents targeted towards DNA repair-deficient malignancies, such as tumors that are BRCA2-deficient. To test this hypothesis we screened a panel of cell-penetrating lupus autoantibodies for nucleolytic activity, and we identified 5C6 as an antibody of interest. 5C6 catalyzes degradation of single and double-stranded DNA in vitro and induces phospho-H2AX formation in BRCA2-deficient cells. When tested on a matched pair of BRCA2-proficient and deficient cancer cells, 5C6 selectively suppressed the growth of and was significantly more toxic to the BRCA2-deficient cells. These findings demonstrate the potential utility of 5C6 in targeted therapy for DNA repair-deficient malignancies and strengthen the rationale for studies of additional lupus autoantibodies in order to identify the best candidates for development as therapeutic agents. In addition, the toxicity of 5C6 for BRCA2-deficient cells provides further support for the hypothesis that some lupus autoantibodies contribute to the unusual cancer risk profile associated with systemic lupus erythematosus. Citation Format: Philip W. Noble, Melissa R. Young, Richard H. Weisbart, James E. Hansen. A cell-penetrating nucleolytic lupus autoantibody damages DNA and is toxic to BRCA2-deficient cancer cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4220. doi:10.1158/1538-7445.AM2014-4220