Trastuzumab--mechanism of action and use

Mechanism of cooperative N-glycan processing by the multi-modular endoglycosidase EndoE

Bacteria produce a remarkably diverse range of glycoside hydrolases to metabolize glycans from the environment as a primary source of nutrients, and to promote the colonization and infection of a host. Here we focus on EndoE, a multi-modular glycoside hydrolase secreted by Enterococcus faecalis, one of the leading causes of healthcare-associated infections. We provide X-ray crystal structures of EndoE, which show an architecture composed of four domains, including GH18 and GH20 glycoside hydrolases connected by two consecutive three α-helical bundles. We determine that the GH20 domain is an exo-β-1,2-N-acetylglucosaminidase, whereas the GH18 domain is an endo-β-1,4-N-acetylglucosaminidase that exclusively processes the central core of complex-type or high-mannose-type N-glycans. Both glycoside hydrolase domains act in a concerted manner to process diverse N-glycans on glycoproteins, including therapeutic IgG antibodies. EndoE combines two enzyme domains with distinct functions and glycan specificities to play a dual role in glycan metabolism and immune evasion.

EndoE is a multi-domain glycoside hydrolase of the human pathogen Enterococcus faecalis. Here, the authors present crystal structures of EndoE and provide biochemical insights into the molecular basis of EndoE’s substrate specificity and catalytic mechanism.

Histone deacetylase inhibitors valproic acid and vorinostat enhance trastuzumab-mediated antibody-dependent cell-mediated phagocytosis

Background

The monoclonal antibody (mAb) trastuzumab is part of the standard of care for patients with human epidermal growth factor receptor 2 (HER2)-overexpressing breast cancer. Antibody-dependent cell-mediated phagocytosis (ADCP) and cytotoxicity (ADCC) are major mechanisms of action of the mAb trastuzumab. Histone deacetylase inhibitors (HDACi), such as valproic acid (VPA) or vorinostat (SAHA), exert several immunostimulatory properties, which contribute at least in part to their anticancer effect. However, the impact of HDACi-induced immunostimulatory effects on trastuzumab-mediated anti-tumor immune response is not well characterized.

Methods

We analyzed the ADCP and ADCC activity of peripheral blood mononuclear cells (PBMCs) from age and gender-matched healthy volunteers (n=5) against HDACi-treated HER2-overexpressing breast cancer cells (SKBR3), using a well-established in vitro three-color imaging flow cytometry and flow cytometry approach.

Results

VPA and SAHA enhanced trastuzumab-mediated ADCP and trastuzumab-independent cytotoxicity. Mechanistically, VPA upregulated the activating antibody-binding receptor Fc-gamma receptor (FcγR) IIA (CD32A) on monocytes (CD14+). Moreover, VPA and SAHA downregulated the anti-apoptotic protein myeloid leukemia cell differentiation 1 (MCL1) in breast cancer cells. Additionally, VPA and SAHA induced an immunogenic cell death, characterized by the exposure of calreticulin (CALR), as well as decreased the “do not eat me” signal CD47 on tumor cells.

Conclusions

HDACi VPA and SAHA increase trastuzumab-mediated phagocytosis and trastuzumab-independent cytotoxicity. The immunomodulatory activities of those HDACi support a rationale combined treatment approach with mAb for cancer treatment.

A next-generation tumor-targeting IL-2 preferentially promotes tumor-infiltrating CD8+ T-cell response and effective tumor control

While IL-2 can potently activate both NK and T cells, its short in vivo half-life, severe toxicity, and propensity to amplify Treg cells are major barriers that prevent IL-2 from being widely used for cancer therapy. In this study, we construct a recombinant IL-2 immunocytokine comprising a tumor-targeting antibody (Ab) and a super mutant IL-2 (sumIL-2) with decreased CD25 binding and increased CD122 binding. The Ab-sumIL2 significantly enhances antitumor activity through tumor targeting and specific binding to cytotoxic T lymphocytes (CTLs). We also observe that pre-existing CTLs within the tumor are sufficient and essential for sumIL-2 therapy. This next-generation IL-2 can also overcome targeted therapy-associated resistance. In addition, preoperative sumIL-2 treatment extends survival much longer than standard adjuvant therapy. Finally, Ab-sumIL2 overcomes resistance to immune checkpoint blockade through concurrent immunotherapies. Therefore, this next-generation IL-2 reduces toxicity while increasing TILs that potentiate combined cancer therapies.

Interleukin-2 (IL-2) based cancer therapy is limited by severe toxicity and strong Treg amplification at the therapeutic dosage. Here, the authors develop a recombinant IL-2 immunocytokine which is comprised of a tumor-targeting antibody fused to a super mutant IL-2 and show in mouse models that this next-generation IL2 has reduced toxicity and enhanced antitumor activity.

Rethinking Causation in Cancer with Evolutionary Developmental Biology

Despite the productivity of basic cancer research, cancer continues to be a health burden to society because this research has not yielded corresponding clinical applications. Many proposed solutions to this dilemma have revolved around implementing organizational and policy changes related to cancer research. Here I argue for a different solution: a new conceptualization of causation in cancer. Neither the standard molecular biomarker approaches nor evolutionary biology approaches to cancer fully capture its complex causal dynamics, even when considered jointly. These approaches map on to Ernst Mayr's proximate-ultimate distinction, which is an inadequate conceptualization of causation in biological systems and makes it difficult to connect developmental and evolutionary viewpoints. I propose looking to evolutionary developmental biology (EvoDevo) to overcome the distinction and integrate the proximate and ultimate causal frameworks. I use the concepts of modularity and evolvability to show how an EvoDevo perspective can be manifested in cancer translational research. This perspective on causation in cancer is better suited for integrating the complexity of current empirical results and can facilitate novel developments in the investigation and clinical treatment of cancer.

Glycoengineering of antibody (Herceptin) through yeast expression and in vitro enzymatic glycosylation

Monoclonal antibodies (mAbs) have been developed as therapeutics, especially for the treatment of cancer, inflammation, and infectious diseases. Because the glycosylation of mAbs in the Fc region influences their interaction with effector cells that kill antibody-targeted cells, and the current method of antibody production is relatively expensive, efforts have been directed toward the development of alternative expressing systems capable of large-scale production of mAbs with desirable glycoforms. In this study, we demonstrate that the mAb trastuzumab expressed in glycoengineered P. pastoris can be remodeled through deglycosylation by endoglycosidases identified from the Carbohydrate Active Enzymes database and through transglycosylation using glycans with a stable leaving group to generate a homogeneous antibody designed to optimize the effector functions. The 10 newly identified recombinant bacterial endoglycosidases are complementary to existing endoglycosidases (EndoA, EndoH, EndoS), two of which can even accept sialylated tri- and tetraantennary glycans as substrates.

Functionally Active Fc Mutant Antibodies Recognizing Cancer Antigens Generated Rapidly at High Yields

Monoclonal antibodies find broad application as therapy for various types of cancer by employing multiple mechanisms of action against tumors. Manipulating the Fc-mediated functions of antibodies that engage immune effector cells, such as NK cells, represents a strategy to influence effector cell activation and to enhance antibody potency and potentially efficacy. We developed a novel approach to generate and ascertain the functional attributes of Fc mutant monoclonal antibodies. This entailed coupling single expression vector (pVitro1) antibody cloning, using polymerase incomplete primer extension (PIPE) polymerase chain reaction, together with simultaneous Fc region point mutagenesis and high yield transient expression in human mammalian cells. Employing this, we engineered wild type, low (N297Q, NQ), and high (S239D/I332E, DE) FcR-binding Fc mutant monoclonal antibody panels recognizing two cancer antigens, HER2/neu and chondroitin sulfate proteoglycan 4. Antibodies were generated with universal mutagenic primers applicable to any IgG1 pVitro1 constructs, with high mutagenesis and transfection efficiency, in small culture volumes, at high yields and within 12 days from design to purified material. Antibody variants conserved their Fab-mediated recognition of target antigens and their direct anti-proliferative effects against cancer cells. Fc mutations had a significant impact on antibody interactions with Fc receptors (FcRs) on human NK cells, and consequently on the potency of NK cell activation, quantified by immune complex-mediated calcium mobilization and by antibody-dependent cellular cytotoxicity (ADCC) of tumor cells. This strategy for manipulation and testing of Fc region engagement with cognate FcRs can facilitate the design of antibodies with defined effector functions and potentially enhanced efficacy against tumor cells.

HER-3 targeting alters the dimerization pattern of ErbB protein family members in breast carcinomas

Breast carcinogenesis is a multi-step process in which membrane receptor tyrosine kinases are crucial participants. Lots of research has been done on epidermal growth factor receptor (EGFR) and HER-2 with important clinical results. However, breast cancer patients present intrinsic or acquired resistance to available HER-2-directed therapies, mainly due to HER-3. Using new techniques, such as proximity ligation assay, herein we evaluate the dimerization pattern of HER-3 and the importance of context-dependent dimer formation between HER-3 and other HER protein family members. Additionally, we show that the efficacy of novel HER-3 targeting agents can be better predicted in certain breast cancer patient sub-groups based on the dimerization pattern of HER protein family members. Moreover, this model was also evaluated and reproduced in human paraffin-embedded breast cancer tissues.

Bispecific anti-CD3 x anti-HER2 antibody mediates T cell cytolytic activity to HER2-positive colorectal cancer in vitro and in vivo

Targeting HER2 overexpressed breast cancer cells with anti‑HER2 monoclonal antibodies inhibits tumor growth. Here we investigated whether HER2 can serve as a target for T cell-mediated immunotherapy of human colorectal carcinoma. Specific cytolytic activity of activated T cells (ATCs) armed with anti‑CD3 x anti‑HER2 bispecific antibody (HER2Bi-Ab) against HER2+ tumor cells was evaluated by bioluminescent signal generated by luciferase reporter on tumor cells in vitro and in vivo. In contrast to unarmed ATCs, increased cytotoxic activity of HER2Bi-armed ATCs against HER2+ tumor cells was observed. Moreover, HER2Bi-armed ATCs expressed higher level of activation marker CD69 and secreted significantly higher levels of IFN-γ than the unarmed ATC counterpart. In addition, compared with anti‑HER2 mAb (Herceptin®) or unarmed ATC, HER2Bi-armed ATCs showed significant suppression against colorectal carcinoma cells. In colorectal tumor cell xenograft mice, infusion of HER2Bi-armed ATCs successfully inhibited the growth of Colo205-luc cells. The HER2Bi-armed ATCs with anti-tumor effects may provide a promising immunotherapy for colorectal carcinoma in the future.

In vivo fluorescence lifetime imaging for monitoring the efficacy of the cancer treatment

PURPOSE

Advances in tumor biology created a foundation for targeted therapy aimed at inactivation of specific molecular mechanisms responsible for cell malignancy. In this paper, we used in vivo fluorescence lifetime imaging with HER2-targeted fluorescent probes as an alternative imaging method to investigate the efficacy of targeted therapy with 17-DMAG (an HSP90 inhibitor) on tumors with high expression of HER2 receptors.

EXPERIMENTAL DESIGN

HER2-specific Affibody, conjugated to Alexafluor 750, was injected into nude mice bearing HER2-positive tumor xenograft. The fluorescence lifetime was measured before treatment and monitored after the probe injections at 12 hours after the last treatment dose, when the response to the 17-DMAG therapy was the most pronounced as well as a week after the last treatment when the tumors grew back almost to their pretreatment size.

RESULTS

Imaging results showed significant difference between the fluorescence lifetimes at the tumor and the contralateral site (∼0.13 ns) in the control group (before treatment) and 7 days after the last treatment when the tumors grew back to their pretreatment dimensions. However, at the time frame that the treatment had its maximum effect (12 hours after the last treatment), the difference between the fluorescence lifetime at the tumor and contralateral site decreased to 0.03 ns.

CONCLUSIONS

The results showed a good correlation between fluorescence lifetime and the efficacy of the treatment. These findings show that in vivo fluorescence lifetime imaging can be used as a promising molecular imaging tool for monitoring the treatment outcome in preclinical models and potentially in patients.

Polyclonal and monoclonal antibodies in clinic

Immunoglobulins (Ig) or antibodies are heavy plasma proteins, with sugar chains added to amino-acid residues by N-linked glycosylation and occasionally by O-linked glycosylation. The versatility of antibodies is demonstrated by the various functions that they mediate such as neutralization, agglutination, fixation with activation of complement and activation of effector cells. Naturally occurring antibodies protect the organism against harmful pathogens, viruses and infections. In addition, almost any organic chemical induces antibody production of antibodies that would bind specifically to the chemical. These antibodies are often produced from multiple B cell clones and referred to as polyclonal antibodies. In recent years, scientists have exploited the highly evolved machinery of the immune system to produce structurally and functionally complex molecules such as antibodies from a single B clone, heralding the era of monoclonal antibodies. Most of the antibodies currently in the clinic, target components of the immune system, are not curative and seek to alleviate symptoms rather than cure disease. Our group used a novel strategy to identify reparative human monoclonal antibodies distinct from conventional antibodies. In this chapter, we discuss the therapeutic relevance of both polyclonal and monoclonal antibodies in clinic.

V-ATPase inhibition overcomes trastuzumab resistance in breast cancer

The HER2 oncogene targeting drug trastuzumab shows remarkable efficacy in patients overexpressing HER2. However acquired or primary resistance develops in most of the treated patients why alternative treatment strategies are strongly needed. As endosomal sorting and recycling are crucial steps for HER2 activity and the vacuolar H⁺-ATPase (V-ATPase) is an important regulator of endocytotic trafficking, we proposed that targeting V-ATPase opens a new therapeutic strategy against trastuzumab-resistant tumor cells in vitro and in vivo. V-ATPase inhibition with archazolid, a novel inhibitor of myxobacterial origin, results in growth inhibition, apoptosis and impaired HER2 pro-survival signaling of the trastuzumab-resistant cell line JIMT-1. This is accompanied by a decreased expression on the plasma membrane and accumulation of HER2 in the cytosol, where it colocalizes with endosomes, lysosomes and autophagosomes. Importantly, microscopic analysis of JIMT-1 xenograft tumor tissue of archazolid treated mice confirms the defect in HER2-recycling which leads to reduced tumor growth. These results suggest that V-ATPase inhibition by archazolid induces apoptosis and inhibits growth of trastuzumab-resistant tumor cells by retaining HER2 in dysfunctional vesicles of the recycling pathway and consequently abrogates HER2-signaling in vitro as well as in vivo. V-ATPase inhibition is thus suggested as a promising strategy for treatment of trastuzumab-resistant tumors.

HER2 as a promising target for cytotoxicity T cells in human melanoma therapy

Anti-HER2/neu antibody therapy has been reported to mediate tumor regression of HER2/ neu(+) tumors. Here we demonstrated the expression of HER2 in a wide range of human melanoma cells including a primary culture and seven cell lines, and we further investigated whether HER2 could be served as a target for T cell mediated immunotherapy of human melanoma. Specific cytolytic activity of activated T cells (ATC) armed with anti-CD3 x anti-HER2 bispecific antibody (HER2Bi-Ab) against Malme-3M-luc cells was evaluated by bioluminescent signal generated by luciferase reporter which did not alter HER2 expression or proliferation ability of Malme-3M cells. Contrast with unarmed ATC, increased cytotoxic activity of HER2Bi-armed ATC against Malme-3M-luc cells was observed at effector/target (E/T) ratios of 1:1, 5:1, and 20:1. Moreover, HER2Bi-armed ATC expressed higher level of activation marker CD69 and secreted significantly higher level of IFN-γ than unarmed ATC counterpart at the E/T ratio of 20:1. In addition, compared with anti-HER2 mAb (Herceptin®) or unarmed ATC, HER2Bi-armed ATC showed remarkable suppression effect on Malme-3M-luc tumor cells. Furthermore, in melanoma tumor cell xenograft mice, infusion of HER2Bi-armed ATC successfully inhibited the growth of melanoma tumors. The anti-tumor effect of HER2Bi-armed ATC may provide a promising immunotherapy for melanoma in the future.

Native MAG-1 antibody almost destroys human breast cancer xenografts

A native form of mouse monoclonal IgG1 antibody called MAG-1, which recognizes an epitope on provasopressin, has been found to shrink and produce extensive necrosis of human breast tumor xenografts in nu/nu mice. We examined the ability of (90)Yttrium-labeled and native MAG-1 to affect the growth in nu/nu mice of cancer xenografts that were estrogen-responsive (from MCF-7 cells) and triple-negative (from MDA-MB231 cells). The growth rates of treated cells were compared to those receiving saline vehicle and those receiving (90)Yttrium-labeled and native forms of the ubiquitous antibody, MOPC21. Short-term treatments (4 doses over 6 days) not only with (90)Yttrium-MAG-1 but also native MAG-1 produced large reductions in size of rapidly growing tumors of both types, while both (90)Yttrium- MOPC21 and native MOPC21 had no effect. Native and (90)Yttrium-MAG-1 effects were similar, and arrested tumors recommenced growing soon after treatments stopped. Increasing native MAG-1 treatment to single dosing for 16 consecutive days shrank tumors of both types with no regrowth apparent over a 20-day post-treatment period of observation. Pathological examination of such tumors revealed they had undergone very extensive (>66%) necrosis.

The fate and function of therapeutic antiaddiction monoclonal antibodies across the reproductive cycle of rats

During preclinical development of neuroprotective antiaddiction therapeutic monoclonal antibodies (mAbs) against phencyclidine (PCP) and (+)-methamphetamine, we discovered novel, gestation stage-specific changes in mAb disposition spanning the entire reproductive cycle of female rats. Each pharmacological change was independent of mAb dose and antigen target but was precisely coincident with transitions between the gestational trimesters, parturition, and lactation periods of the female reproductive cycle. Whereas anti-PCP mAb6B5 terminal elimination half-life (t(1/2λz)) in nonpregnant females was 6.6 ± 1.6 days, the mAb6B5 t(1/2λz) significantly changed to 3.7 ± 0.4 days, then 1.4 ± 0.1 days, then 3.0 ± 0.4 days in the second trimester, third trimester, and postpartum periods, respectively (p < 0.05 for each change). Initially, these evolving changes in mAb6B5 clearance (3.3-fold), distribution volume (1.8-fold), and elimination half-life (4.7-fold) affected our ability to sustain sufficient mAb6B5 levels to sequester PCP in the bloodstream. However, understanding the mechanisms underlying each transition allowed development of an adaptive mAb-dosing paradigm, which substantially reduced PCP levels in dam brains and fetuses throughout pregnancy. These mAb functional studies also revealed that antidrug mAbs readily cross the placenta before syncytiotrophoblast barrier maturation, demonstrating the dynamic nature of mAb pharmacokinetics in pregnancy and the importance of maintaining maternal mAb levels. These studies provide the first preclinical pregnancy model in any species for chronic mAb dosing and could have important implications for the use of antibody therapies involving blood organ barriers (such as addiction) or other chronic diseases in women of childbearing age (e.g., irritable bowel diseases, multiple sclerosis, breast cancer, rheumatoid arthritis).

Targeting the MET oncogene in cancer and metastases

IMPORTANCE OF THE FIELD

'Invasive growth' is a genetic program involved in embryonic development and adult organ regeneration and usurped by cancer cells. Although its control is complex, tumor- and context-specific and regulated by several cytokines and growth factors, the role played by the MET oncogene is well documented. In human cancers the contribution of MET to invasive growth is mainly through overexpression, driven by unfavorable microenvironmental conditions. MET activation confers a selective advantage to neoplastic cells in tumor progression and drug resistance. A subset of tumors feature alterations of the MET gene and a consequent MET-addicted phenotype.

AREAS COVERED IN THIS REVIEW

The molecular basis and rationale of MET inhibition in cancer and metastases are discussed. A number of molecules designed to block MET signaling are under development and several Phase II trials are ongoing.

WHAT THE READER WILL GAIN

Knowledge of the state of the art of anti-MET targeted approaches and the molecular basis and strategies to select patients eligible for treatment with MET inhibitors.

TAKE HOME MESSAGE

Due to its versatile functions MET is a promising candidate for cancer therapy. Understanding molecular mechanisms of sensitization and resistance to MET inhibitors is a priority to guide tailored therapies and select patients that are most likely to achieve a clinical benefit.

Generation of monoclonal antibody targeting fibroblast growth factor receptor 3

Fibroblast growth factor receptor 3 (FGFR3) is a member of the FGFR family of receptor tyrosine kinases, whose function has been implicated in diverse biological processes, including cell proliferation, differentiation, survival, and tumorigenesis. Deregulation of FGFR3 signaling has been implicated with human pathologies, including cancer. Activating mutations in FGFR3 gene are frequently detected in bladder cancer, multiple myeloma, and noninvasive papillary urothelial cell carcinomas, while the overexpression of the receptor is observed in thyroid lymphoma and bladder cancer. The main aim of this study was to generate hybridoma clones producing antibody that could specifically recognize FGFR3/S249C mutant, but not the wild-type FGFR. To achieve this, we used for immunization bacterially expressed fragment of FGFR3 corresponding to loops II-III of the extracellular domain (GST-His/FGFR3/S249C-LII-III), which possesses oncogenic mutation at Ser249 detected in at least 50% of bladder cancers. Primary ELISA screening allowed us to isolate several hybridoma clones that showed specificity towards FGFR3/S249C, but not FGFR3wt protein. Unfortunately, these clones were not stable during single-cell cloning and expansion and lost the ability to recognize specifically FGFR3/S249C. However, this study allowed us to generate several monoclonal antibodies specific towards both FGFR3wt and FGFR3/S249C recombinant proteins. Produced hybridomas secreted MAbs that were specific in Western blotting towards bacterially expressed FGFR3wt and FGFR3/S249C, as well as the full-length receptors ectopically expressed in Sf21 and HEK293 cells. Moreover, transiently expressed wild-type and oncogenic forms of FGFR were efficiently immunoprecipitated with selected antibodies from the lysates of infected Sf21 and transiently transfected HEK293. In summary, generated antibodies should be useful as tools for examining the expression pattern and biological functions of FGFR3 in normal and pathological cells and tissues.

Targeting MET as a strategy to overcome crosstalk-related resistance to EGFR inhibitors

The hepatocyte growth factor (HGF)-mesenchymal-epithelial transition factor (MET) pathway has a key role in carcinogenesis; it is implicated in proliferation, inhibition of apoptosis, angiogenesis, migration, invasiveness, and metastasis. All of these molecular events are driven through membrane and intracellular coplayers and several downstream effector proteins. MET has been shown to cross react with epithelial growth factor receptor (EGFR) proteins and possibly substitutes their activity, thus conferring resistance to EGFR-targeting drugs. Therefore, identification of MET inhibitors might lead to new treatments for MET-triggered neoplasia and improve the sensitivity of molecularly targeted antineoplastic compounds that are currently in use. In this Review, we outline current data regarding the HGF-MET pathway during carcinogenesis and the strategies for therapeutic targeting of this pathway. We also discuss the rationale and future perspectives of the combinatorial blockade of HGF-MET and EGFR signalling cascades in cancer treatment.