Visible Light Control over the Cytolytic Activity of a Toxic Pore-Forming Protein

Enabling control over the bioactivity of proteins with light, along with the principles of photopharmacology, has the potential to generate safe and targeted medical treatments. Installing light sensitivity in a protein can be achieved through its covalent modification with a molecular photoswitch. The general challenge in this approach is the need for the use of low energy visible light for the regulation of bioactivity. In this study, we report visible light control over the cytolytic activity of a protein. A water-soluble visible-light-operated tetra-ortho-fluoro-azobenzene photoswitch was synthesized by utilizing the nucleophilic aromatic substitution reaction for installing a solubilizing sulfonate group onto the electron-poor photoswitch structure. The azobenzene was attached to two cysteine mutants of the pore-forming protein fragaceatoxin C (FraC), and their respective activities were evaluated on red blood cells. For both mutants, the green-light-irradiated sample, containing predominantly the cis-azobenzene isomer, was more active compared to the blue-light-irradiated sample. Ultimately, the same modulation of the cytolytic activity pattern was observed toward a hypopharyngeal squamous cell carcinoma. These results constitute the first case of using low energy visible light to control the biological activity of a toxic protein.

Bispecific antibody CD73xEGFR more selectively inhibits the CD73/adenosine immune checkpoint on cancer cells and concurrently counteracts pro-oncogenic activities of CD73 and EGFR

BACKGROUND

CD73 is an ecto-enzyme that is involved in the conversion of pro-inflammatory extracellular ATP (eATP) excreted by cancer cells under stress to anti-inflammatory adenosine (ADO). A broad variety of solid cancer types was shown to exploit CD73 overexpression as a suppressive immune checkpoint. Consequently, CD73-antagonistic antibodies, most notably oleclumab, are currently evaluated in several multicenter trials for clinical applicability. However, the efficacy of conventional monospecific CD73-inhibiting antibodies may be limited due to on-target/off-tumor binding to CD73 on normal cells. Therefore, a novel approach that more selectively directs CD73 immune checkpoint inhibition towards cancer cells is warranted.

METHODS

To address this issue, we constructed a novel tetravalent bispecific antibody (bsAb), designated bsAb CD73xEGFR. Subsequently, the anticancer activities of bsAb CD73xEGFR were evaluated using in vitro and in vivo tumor models.

RESULTS

In vitro treatment of various carcinoma cell types with bsAb CD73xEGFR potently inhibited the enzyme activity of CD73 (~71%) in an EGFR-directed manner. In this process, bsAb CD73xEGFR induced rapid internalization of antigen/antibody complexes, which resulted in a prolonged concurrent displacement of both CD73 and EGFR from the cancer cell surface. In addition, bsAb CD73xEGFR sensitized cancer to the cytotoxic activity of various chemotherapeutic agents and potently inhibited the proliferative/migratory capacity (~40%) of cancer cells. Unexpectedly, we uncovered that treatment of carcinoma cells with oleclumab appeared to enhance several pro-oncogenic features, including upregulation and phosphorylation of EGFR, tumor cell proliferation (~20%), and resistance towards cytotoxic agents and ionizing radiation (~39%). Importantly, in a tumor model using immunocompetent BALB/c mice inoculated with syngeneic CD73pos/EGFRpos CT26 cancer cells, treatment with bsAb CD73xEGFR outperformed oleclumab (65% vs 31% tumor volume reduction). Compared with oleclumab, treatment with bsAb CD73xEGFR enhanced the intratumoral presence of CD8pos T cells and M1 macrophages.

CONCLUSIONS

BsAb CD73xEGFR outperforms oleclumab as it inhibits the CD73/ADO immune checkpoint in an EGFR-directed manner and concurrently counteracts several oncogenic activities of EGFR and CD73. Therefore, bsAb CD73xEGFR may be of significant clinical potential for various forms of difficult-to-treat solid cancer types.

Applications of Anti-Cytomegalovirus T Cells for Cancer (Immuno)Therapy

Infection with cytomegalovirus (CMV) is highly prevalent in the general population and largely controlled by CD8pos T cells. Intriguingly, anti-CMV T cells accumulate over time to extraordinarily high numbers, are frequently present as tumor-resident 'bystander' T cells, and remain functional in cancer patients. Consequently, various strategies for redirecting anti-CMV CD8pos T cells to eliminate cancer cells are currently being developed. Here, we provide an overview of these strategies including immunogenic CMV peptide-loading onto endogenous HLA complexes on cancer cells and the use of tumor-directed fusion proteins containing a preassembled CMV peptide/HLA-I complex. Additionally, we discuss conveying the advantageous characteristics of anti-CMV T cells in adoptive cell therapy. Utilization of anti-CMV CD8pos T cells to generate CAR T cells promotes their in vivo persistence and expansion due to appropriate co-stimulation through the endogenous (CMV-)TCR signaling complex. Designing TCR-engineered T cells is more challenging, as the artificial and endogenous TCR compete for expression. Moreover, the use of expanded/reactivated anti-CMV T cells to target CMV peptide-expressing glioblastomas is discussed. This review highlights the most important findings and compares the benefits, disadvantages, and challenges of each strategy. Finally, we discuss how anti-CMV T cell therapies can be further improved to enhance treatment efficacy.

A Novel Bispecific Antibody for EpCAM-Directed Inhibition of the CD73/Adenosine Immune Checkpoint in Ovarian Cancer

PD-1/PD-L1-inhibiting antibodies have shown disappointing efficacy in patients with refractory ovarian cancer (OC). Apparently, OC cells exploit nonoverlapping immunosuppressive mechanisms to evade the immune system. In this respect, the CD73-adenosine inhibitory immune checkpoint is of particular interest, as it rapidly converts pro-inflammatory ATP released from cancer cells to immunosuppressive adenosine (ADO). Moreover, cancer-cell-produced ADO is known to form a highly immunosuppressive extra-tumoral 'halo' that chronically inhibits the anticancer activity of various immune effector cells. Thus far, conventional CD73-blocking antibodies such as oleclumab show limited clinical efficacy, probably due to the fact that it indiscriminately binds to and blocks CD73 on a massive surplus of normal cells. To address this issue, we constructed a novel bispecific antibody (bsAb) CD73xEpCAM that inhibits CD73 expressed on the OC cell surface in an EpCAM-directed manner. Importantly, bsAb CD73xEpCAM showed potent capacity to inhibit the CD73 enzyme activity in an EpCAM-directed manner and restore the cytotoxic activity of ADO-suppressed anticancer T cells. Additionally, treatment with bsAb CD73xEpCAM potently inhibited the proliferative capacity of OC cells and enhanced their sensitivity to cisplatin, doxorubicin, 5FU, and ionizing radiation. BsAb CD73xEpCAM may be useful in the development of tumor-directed immunotherapeutic approaches to overcome the CD73-mediated immunosuppression in patients with refractory OC.

Novel Fab-peptide-HLA-I fusion proteins for redirecting pre-existing anti-CMV T cell immunity to selective eliminate carcinoma cells

Typically, anticancer CD8pos T cells occur at low frequencies and become increasingly impaired in the tumor micro environment. In contrast, antiviral CD8pos T cells display a much higher polyclonality, frequency, and functionality. In particular, cytomegalovirus (CMV) infection induces high numbers of 'inflationary' CD8pos T cells that remain lifelong abundantly present in CMV-seropositive subjects. Importantly, these so-called inflationary anti-CMV T cells increase with age, maintain a ready-to-go state, populate tumors, and do not become exhausted or senescent. Given these favorable attributes, we devised a novel series of recombinant Fab-peptide-HLA-I fusion proteins and coined them 'ReTARGs'. A ReTARG fusion protein consists of a high-affinity Fab antibody fragment directed to carcinoma-associated cell surface antigen EpCAM (or EGFR), fused in tandem with soluble HLA-I molecule/β2-microglobulin, genetically equipped with an immunodominant peptide derived from CMV proteins pp65 (or IE-1). Decoration with EpCAM-ReTARGpp65 rendered EpCAM-expressing primary patient-derived carcinoma cells highly sensitive to selective elimination by cognate anti-CMV CD8pos T cells. Importantly, this treatment did not induce excessive levels of proinflammatory T cell-secreted IFNγ. In contrast, analogous treatment with equimolar amounts of EpCAM/CD3-directed bispecific T-cell engager solitomab resulted in a massive release of IFNγ, a feature commonly associated with adverse cytokine-release syndrome. Combinatorial treatment with EpCAM-ReTARGpp65 and EGFR-ReTARGIE-1 strongly potentiated selective cancer cell elimination owing to the concerted action of the corresponding cognate anti-CMV CD8pos T cell clones. In conclusion, ReTARG fusion proteins may be useful as an alternative or complementary form of targeted cancer immunotherapy for 'cold' solid cancers.

Impact of cumulative complications on 1-year treatment-related healthcare costs in patients with colorectal peritoneal metastases undergoing cytoreductive surgery with hyperthermic intraperitoneal chemotherapy

Background

The aim of this study was to evaluate the impact of all minor and major complications on treatment-related healthcare costs in patients who undergo cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC) for the treatment of colorectal peritoneal metastases (PMs).

Method

Patients with histologically proven colorectal PMs who underwent CRS + HIPEC from March 2006 to October 2019 in a tertiary referral centre were retrospectively identified from a prospectively maintained database. Patients were divided into six subgroups according to the severity of the complications, which were scored using the comprehensive complication index (CCI) (CCI 0–9.9, CCI 10–19.9, CCI 20–29.9, CCI 30–39.9, CCI 40–49.9, and CCI 50 or higher). Treatment-related healthcare costs up to 1 year after CRS + HIPEC were obtained from the financial department. Differences in costs and survival outcomes were compared using the chi-squared test and Kruskal–Wallis H test.

Results

A total of 142 patients were included (CCI 0–9.9, 53 patients; CCI 10–19.9, 0 patients; CCI 20–29.9, 45 patients; CCI 30–39.9, 14 patients; CCI 40–49, 9 patients; and CCI 50 or higher, 21 patients). Median (interquartile range) treatment-related healthcare costs increased significantly and exponentially for the CCI 30–39, CCI 40–49, and CCI 50 or higher groups (€48 993 (€44 262–€84 805); €57 167 (€43 047–€67 591); and €82 219 (€55 487–€145 314) respectively) compared with those for the CCI 0–9.9 and CCI 20–29.9 groups (€33 856 (€24 433–€40 779) and €40 621 (€31 501–€58 761) respectively, P < 0.010).

Conclusion

Treatment-related healthcare costs increase exponentially as more complications develop among patients who undergo CRS + HIPEC for the treatment of colorectal PMs. Anastomotic leakages after CRS + HIPEC lead to an increase of 295 per cent of treatment-related healthcare costs.

Neoantigen-based cancer vaccination using chimeric RNA-loaded dendritic cell-derived extracellular vesicles

Cancer vaccines critically rely on the availability of targetable immunogenic cancer-specific neoepitopes. However, mutation-based immunogenic neoantigens are rare or even non-existent in subgroups of cancer types. To address this issue, we exploited a cancer-specific aberrant transcription-induced chimeric RNA, designated A-P_as chiRNA, as a possible source of clinically relevant and targetable neoantigens. A-P_as chiRNA encodes a recently discovered cancer-specific chimeric protein that comprises full-length astrotactin-2 (ASTN2) C-terminally fused in-frame to the antisense sequence of the 18^th intron of pregnancy-associated plasma protein-A (PAPPA). We used extracellular vesicles (EVs) from A-P_as chiRNA-transfected dendritic cells (DCs) to produce the cell-free anticancer vaccine DEX_A-P . Treatment of immunocompetent cancer-bearing mice with DEX_A-P inhibited tumour growth and prolonged animal survival. In summary, we demonstrate for the first time that cancer-specific transcription-induced chimeric RNAs can be exploited to produce a cell-free cancer vaccine that induces potent CD8⁺ T cell-mediated anticancer immunity. Our novel approach may be particularly useful for developing cancer vaccines to treat malignancies with low mutational burden or without mutation-based antigens. Moreover, this cell-free anticancer vaccine approach may offer several practical advantages over cell-based vaccines, such as ease of scalability and genetic modifiability as well as enhanced shelf life.

A proof-of-concept study on the use of a fluorescein-based 18F-tracer for pretargeted PET

Background

Pretargeted immuno-PET tumor imaging has emerged as a valuable diagnostic strategy that combines the high specificity of antibody-antigen interaction with the high signal and image resolution offered by short-lived PET isotopes, while reducing the irradiation dose caused by traditional ⁸⁹Zr-labelled antibodies. In this work, we demonstrate proof of concept of a novel ‘two-step’ immuno-PET pretargeting approach, based on bispecific antibodies (bsAbs) engineered to feature dual high-affinity binding activity for a fluorescein-based ¹⁸F-PET tracer and tumor markers.

Results

A copper(I)-catalysed click reaction-based radiolabeling protocol was developed for the synthesis of fluorescein-derived molecule [¹⁸F]TPF. Binding of [¹⁸F]TPF on FITC-bearing bsAbs was confirmed. An in vitro autoradiography assay demonstrated that [¹⁸F]TPF could be used for selective imaging of EpCAM-expressing OVCAR3 cells, when pretargeted with EpCAMxFITC bsAb. The versatility of the pretargeting approach was showcased in vitro using a series of fluorescein-binding bsAbs directed at various established cancer-associated targets, including the pan-carcinoma cell surface marker EpCAM, EGFR, melanoma marker MCSP (aka CSPG4), and immune checkpoint PD-L1, offering a range of potential future applications for this pretargeting platform.

Conclusion

A versatile pretargeting platform for PET imaging, which combines bispecific antibodies and a fluorescein-based ¹⁸F-tracer, is presented. It is shown to selectively target EpCAM-expressing cells in vitro and its further evaluation with different bispecific antibodies demonstrates the versatility of the approach.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41181-022-00155-2.

Cancer cells under immune attack acquire CD47-mediated adaptive immune resistance independent of the myeloid CD47-SIRPα axis

Cancer cells exploit CD47 overexpression to inhibit phagocytic elimination and neoantigen processing via the myeloid CD47-SIRPα axis and thereby indirectly evade adaptive T cell immunity. Here, we report on a hitherto unrecognized direct immunoinhibitory feature of cancer cell-expressed CD47. We uncovered that in response to IFNγ released during cognate T cell immune attack, cancer cells dynamically enhance CD47 cell surface expression, which coincides with acquiring adaptive immune resistance toward pro-apoptotic effector T cell mechanisms. Indeed, CRISPR/Cas9-mediated CD47-knockout rendered cancer cells more sensitive to cognate T cell immune attack. Subsequently, we developed a cancer-directed strategy to selectively overcome CD47-mediated adaptive immune resistance using bispecific antibody (bsAb) CD47xEGFR-IgG2s that was engineered to induce rapid and prolonged cancer cell surface displacement of CD47 by internalization. Treatment of CD47^pos cancer cells with bsAb CD47xEGFR-IgG2s potently enhanced susceptibility to cognate CD8^pos T cells. Targeting CD47-mediated adaptive immune resistance may open up new avenues in cancer immunotherapy.

Bispecific antibody CD73xEpCAM selectively inhibits the adenosine-mediated immunosuppressive activity of carcinoma-derived extracellular vesicles

Tumor-derived extracellular vesicles (EVs) carry potent immunosuppressive factors that affect the antitumor activities of immune cells. A significant part of the immunoinhibitory activity of EVs is attributable to CD73, a GPI-anchored ecto-5'-nucleotidase involved in the conversion of tumor-derived proinflammatory extracellular ATP (eATP) to immunosuppressive adenosine (ADO). The CD73-antagonist antibody oleclumab inhibits cell surface-exposed CD73 and is currently undergoing clinical testing for cancer immunotherapy. However, a strategy to selectively inhibit CD73 exposed on EVs is not available. Here, we present a novel bispecific antibody (bsAb) CD73xEpCAM designed to bind with high affinity the common EV surface marker EpCAM and concurrently inhibit CD73. Unlike oleclumab, bsAb CD73xEpCAM potently inhibited the immunosuppressive activity of EVs from CD73pos/EpCAMpos carcinoma cell lines and patient-derived colorectal cancer cells. Taken together, selective blockade of EV-exposed CD73 by bsAb CD73xEpCAM may be useful as an alternate or complementary targeted approach in cancer immunotherapy.

Synthesis and Evaluation of 18F-Enzalutamide, a New Radioligand for PET Imaging of Androgen Receptors: A Comparison with 16β-18F-Fluoro-5α-Dihydrotestosterone

16β-¹⁸F-fluoro-5α-dihydrotestosterone (¹⁸F-FDHT) is a radiopharmaceutical that has been investigated as a diagnostic agent for the assessment of androgen receptor (AR) density in prostate cancer using PET. However, ¹⁸F-FDHT is rapidly metabolized in humans and excreted via the kidneys into the urine, potentially compromising the detection of tumor lesions close to the prostate. Enzalutamide is an AR signaling inhibitor currently used in different stages of prostate cancer. Enzalutamide and its primary metabolite N-desmethylenzalutamide have an AR affinity comparable to that of FDHT but are excreted mainly via the hepatic route. Radiolabeled enzalutamide could thus be a suitable candidate PET tracer for AR imaging. Here, we describe the radiolabeling of enzalutamide with ¹⁸F. Moreover, the in vitro and in vivo behavior of ¹⁸F-enzalutamide was evaluated and compared with the current standard, ¹⁸F-FDHT. Methods: ¹⁸F-enzalutamide was obtained by fluorination of the nitro precursor. In vitro cellular uptake studies with ¹⁸F-enzalutamide and ¹⁸F-FDHT were performed in LNCaP (AR-positive) and HEK293 (AR-negative) cells. Competition assays with both tracers were conducted on the LNCaP (AR-positive) cell line. In vivo PET imaging, ex vivo biodistribution, and metabolite studies with ¹⁸F-enzalutamide and ¹⁸F-FDHT were conducted on athymic nude male mice bearing an LNCaP xenograft in the shoulder. Results: ¹⁸F-enzalutamide was obtained in 1.4% ± 0.9% radiochemical yield with an apparent molar activity of 6.2 ± 10.3 GBq/µmol. ¹⁸F-FDHT was obtained in 1.5% ± 0.8% yield with a molar activity of more than 25 GBq/µmol. Coincubation with an excess of 5α-dihydrotestosterone or enzalutamide significantly reduced the cellular uptake of ¹⁸F-enzalutamide and ¹⁸F-FDHT to about 50% in AR-positive LNCaP cells but not in AR-negative HEK293 cells. PET and biodistribution studies on male mice bearing a LnCaP xenograft showed about 3 times higher tumor uptake for ¹⁸F-enzalutamide than for ¹⁸F-FDHT. Sixty minutes after tracer injection, 93% of ¹⁸F-enzalutamide in plasma was still intact, compared with only 3% of ¹⁸F-FDHT. Conclusion: Despite its lower apparent molar activity, ¹⁸F-enzalutamide shows higher tumor uptake and better metabolic stability than ¹⁸F-FDHT and thus seems to have more favorable properties for imaging of AR with PET. However, further evaluation in other oncologic animal models and patients is warranted to confirm these results.

Bispecific antibody approach for EGFR-directed blockade of the CD47-SIRPα "don't eat me" immune checkpoint promotes neutrophil-mediated trogoptosis and enhances antigen cross-presentation

Cancer cells overexpress CD47 to subvert phagocytic elimination and evade immunogenic processing of cancer antigens. Moreover, CD47 overexpression inhibits the antibody-dependent cellular phagocytosis (ADCP) and cytotoxicity (ADCC) activities of therapeutic anticancer antibodies. Consequently, CD47-blocking antibodies have been developed to overcome the immunoevasive activities of cancer cell-expressed CD47. However, the wide-spread expression of CD47 on normal cells forms a massive "antigen sink" that potentially limits sufficient tumor accretion of these antibodies. Additionally, a generalized blockade of CD47-SIRPα interaction may ultimately lead to unintended cross-presentation of self-antigens potentially promoting autoimmunity. To address these issues, we constructed a bispecific antibody, designated bsAb CD47xEGFR-IgG1, that blocks cancer cell surface-expressed CD47 in an EGFR-directed manner. BsAb CD47xEGFR-IgG1 selectively induced phagocytic removal of EGFR^pos/CD47^pos cancer cells and endowed neutrophils with capacity to kill these cancer cells by trogoptosis; an alternate form of ADCC that disrupts the target cell membrane. Importantly, bsAb CD47xEGFR-IgG1 selectively enhanced phagocytosis and immunogenic processing of EGFR^pos/CD47^pos cancers cells ectopically expressing viral protein CMVpp65. In conclusion, bsAb CD47xEGFR-IgG1 may be useful to reduce on-target/off-tumor effects of CD47-blocking approaches, enhance cancer cell elimination by trogoptosis, and promote adaptive anticancer immune responses.

Modular Medical Imaging Agents Based on Azide-Alkyne Huisgen Cycloadditions: Synthesis and Pre-Clinical Evaluation of 18 F-Labeled PSMA-Tracers for Prostate Cancer Imaging

Since the seminal contribution of Rolf Huisgen to develop the [3+2] cycloaddition of 1,3-dipolar compounds, its azide-alkyne variant has established itself as the key step in numerous organic syntheses and bioorthogonal processes in materials science and chemical biology. In the present study, the copper(I)-catalyzed azide-alkyne cycloaddition was applied for the development of a modular molecular platform for medical imaging of the prostate-specific membrane antigen (PSMA), using positron emission tomography. This process is shown from molecular design, through synthesis automation and in vitro studies, all the way to pre-clinical in vivo evaluation of fluorine-18- labeled PSMA-targeting 'F-PSMA-MIC' radiotracers (t1/2 =109.7 min). Pre-clinical data indicate that the modular PSMA-scaffold has similar binding affinity and imaging properties to the clinically used [68 Ga]PSMA-11. Furthermore, we demonstrated that targeting the arene-binding in PSMA, facilitated through the [3+2]cycloaddition, can improve binding affinity, which was rationalized by molecular modeling. The here presented PSMA-binding scaffold potentially facilitates easy coupling to other medical imaging moieties, enabling future developments of new modular imaging agents.

Bispecific Antibody Approach for Improved Melanoma-Selective PD-L1 Immune Checkpoint Blockade

Reactivation of functionally-impaired anticancer T cells by programmed cell death protein 1 (PD-1) and programmed cell death receptor ligand-1 (PD-L1)-blocking antibodies shows prominent therapeutic benefit in advanced melanoma and patients with non-small cell lung cancer. However, current PD-L1-blocking antibodies lack intrinsic tumor selectivity. Therefore, efficacy may be reduced resulting from on-target and off-tumor binding to PD-L1-expressing normal cells. This may lead to indiscriminate activation of antigen-experienced T cells, including those implicated in autoimmune-related adverse events. To direct PD-L1 blockade to chondroitin sulfate proteoglycan 4 (CSPG4)-expressing cancers and to reactivate anticancer T cells more selectively, we constructed bispecific antibody PD-L1xCSPG4. CSPG4 is an established target antigen that is selectively overexpressed on malignant melanoma and various other difficult-to-treat cancers. PD-L1xCSPG4 showed enhanced capacity for CSPG4-directed blockade of PD-L1 on cancer cells. Importantly, treatment of mixed cultures containing primary patient-derived CSPG4-expressing melanoma cells and autologous tumor-infiltrating lymphocytes with PD-L1xCSPG4 significantly enhanced activation status, IFN-γ production, and cytolytic activity of anticancer T cells. In conclusion, tumor-directed blockade of PD-L1 by PD-L1xCSPG4 may improve efficacy and safety of PD-1/PD-L1 checkpoint blockade for treatment of melanoma and other CSPG4-overexpressing malignancies.

A light-responsive liposomal agent for MRI contrast enhancement and monitoring of cargo delivery

A liposomal MRI-probe changing relaxivity and releasing cargo upon light irradiation was developed for diagnostics and monitoring of drug delivery.

Development of Bispecific Antibody Derivatives for Cancer Immunotherapy

Development of antibody-based immunotherapeutics has progressed from direct tumor-targeting, with antibodies such as rituximab, to blocking of immune checkpoints to reactivate antitumor immunity. In addition, bispecific antibodies/antibody fragments are also of great interest in cancer therapy, as these constructs have the ability to redirect immune effector cells to cancer targets and, thereby, enhance therapeutic efficacy. A number of bispecific antibody formats have been reported, with the first FDA-approved bispecific antibody being blinatumomab, a so-called bispecific T cell engager (BiTE), which redirects and potently activates T cell immune responses. Recently, we described an additional novel bispecific antibody derivative, termed RTX-CD47, which was designed to inhibit the innate immune checkpoint CD47-SIRPα only on -positive cancer cells. RTX-CD47 contains two antibody fragments in tandem and has monovalent binding specificity for CD47 and . Only upon dual binding to and CD47 RTX-CD47 blocks CD47 "Don't eat me" signaling. Here, we provide a detailed protocol for the construction and functional evaluation of such a bispecific antibody derivative.

Quantitative proteomics analysis identifies MUC1 as an effect sensor of EGFR inhibition

Tumor responses to cancer therapeutics are generally monitored every 2-3 months based on changes in tumor size. Dynamic biomarkers that reflect effective engagement of targeted therapeutics to the targeted pathway, so-called "effect sensors", would fulfill a need for non-invasive, drug-specific indicators of early treatment effect. Using a proteomics approach to identify effect sensors, we demonstrated MUC1 upregulation in response to epidermal growth factor receptor (EGFR)-targeting treatments in breast and lung cancer models. To achieve this, using semi-quantitative mass spectrometry, we found MUC1 to be significantly and durably upregulated in response to erlotinib, an EGFR-targeting treatment. MUC1 upregulation was regulated transcriptionally, involving PI3K-signaling and STAT3. We validated these results in erlotinib-sensitive human breast and non-small lung cancer cell lines. Importantly, erlotinib treatment of mice bearing SUM149 xenografts resulted in increased MUC1 shedding into plasma. Analysis of MUC1 using serial blood sampling may therefore be a new, relatively non-invasive tool to monitor early and drug-specific effects of EGFR-targeting therapeutics.

Antigen-specific active immunotherapy for ovarian cancer

BACKGROUND

This is the second update of the review first published in the Cochrane Library (2010, Issue 2) and later updated (2014, Issue 9).Despite advances in chemotherapy, the prognosis of ovarian cancer remains poor. Antigen-specific active immunotherapy aims to induce tumour antigen-specific anti-tumour immune responses as an alternative treatment for ovarian cancer.

OBJECTIVES

Primary objective• To assess the clinical efficacy of antigen-specific active immunotherapy for the treatment of ovarian cancer as evaluated by tumour response measured by Response Evaluation Criteria In Solid Tumors (RECIST) and/or cancer antigen (CA)-125 levels, response to post-immunotherapy treatment, and survival differences◦ In addition, we recorded the numbers of observed antigen-specific humoral and cellular responsesSecondary objective• To establish which combinations of immunotherapeutic strategies with tumour antigens provide the best immunological and clinical results SEARCH METHODS: For the previous version of this review, we performed a systematic search of the Cochrane Central Register of Controlled Trials (CENTRAL; 2009, Issue 3), in the Cochrane Library, the Cochrane Gynaecological Cancer Group Specialised Register, MEDLINE and Embase databases, and clinicaltrials.gov (1966 to July 2009). We also conducted handsearches of the proceedings of relevant annual meetings (1996 to July 2009).For the first update of this review, we extended the searches to October 2013, and for this update, we extended the searches to July 2017.

SELECTION CRITERIA

We searched for randomised controlled trials (RCTs), as well as non-randomised studies (NRSs), that included participants with epithelial ovarian cancer, irrespective of disease stage, who were treated with antigen-specific active immunotherapy, irrespective of type of vaccine, antigen used, adjuvant used, route of vaccination, treatment schedule, and reported clinical or immunological outcomes.

DATA COLLECTION AND ANALYSIS

Two reviews authors independently extracted the data. We evaluated the risk of bias for RCTs according to standard methodological procedures expected by Cochrane, and for NRSs by using a selection of quality domains deemed best applicable to the NRS.

MAIN RESULTS

We included 67 studies (representing 3632 women with epithelial ovarian cancer). The most striking observations of this review address the lack of uniformity in conduct and reporting of early-phase immunotherapy studies. Response definitions show substantial variation between trials, which makes comparison of trial results unreliable. Information on adverse events is frequently limited. Furthermore, reports of both RCTs and NRSs frequently lack the relevant information necessary for risk of bias assessment. Therefore, we cannot rule out serious biases in most of the included trials. However, selection, attrition, and selective reporting biases are likely to have affected the studies included in this review. GRADE ratings were high only for survival; for other primary outcomes, GRADE ratings were very low.The largest body of evidence is currently available for CA-125-targeted antibody therapy (17 studies, 2347 participants; very low-certainty evidence). Non-randomised studies of CA-125-targeted antibody therapy suggest improved survival among humoral and/or cellular responders, with only moderate adverse events. However, four large randomised placebo-controlled trials did not show any clinical benefit, despite induction of immune responses in approximately 60% of participants. Time to relapse with CA-125 monoclonal antibody versus placebo, respectively, ranged from 10.3 to 18.9 months versus 10.3 to 13 months (six RCTs, 1882 participants; high-certainty evidence). Only one RCT provided data on overall survival, reporting rates of 80% in both treatment and placebo groups (three RCTs, 1062 participants; high-certainty evidence). Other small studies targeting many different tumour antigens have presented promising immunological results. As these strategies have not yet been tested in RCTs, no reliable inferences about clinical efficacy can be made. Given the promising immunological results and the limited side effects and toxicity reported, exploration of clinical efficacy in large well-designed RCTs may be worthwhile.

AUTHORS' CONCLUSIONS

We conclude that despite promising immunological responses, no clinically effective antigen-specific active immunotherapy is yet available for ovarian cancer. Results should be interpreted cautiously, as review authors found a significant dearth of relevant information for assessment of risk of bias in both RCTs and NRSs.

Abstract 4553: A novel bispecific antibody for EGFR-directed blockade of the PD-1/PD-L1 immune checkpoint

PD-L1-blocking antibodies produce significant clinical benefit in selected cancer patients by reactivating functionally-impaired anticancer T cells. However, their efficacy is potentially reduced by ‘on-target/off-tumor' binding to PD-L1 widely expressed on normal cells. This lack of tumor selectivity potentially induces a generalized activation of all antigen-experienced T cells as is evidenced by frequent autoimmune-related adverse events during and after treatment. To address these issues, we constructed a tetravalent bispecific antibody (bsAb), designated PD-L1xEGFR, to direct PD-L1-blockade to EGFR-expressing cancer cells and thus reactivate anticancer T cells more selectively. The IC50 of PD-L1xEGFR for binding to EGFR+ cancer cells was ~140 fold lower compared to an analogous PD-L1-blocking bsAb of irrelevant target antigen specificity (PD-L1xMock). Importantly, treatment with PD-L1xEGFR selectively enhanced activation status, INF-γ production, and activity of anti-CD3xanti-EpCAM-redirected T cells in presence of EGFR+/EpCAM+, but not EGFR-/EpCAM+ carcinoma cells. Similarly, capacity of PD-L1xEGFR to promote proliferation and IFN-γ production by CMVpp65-specific CD8+ effector T cells was enhanced in the presence of EGFR+/CMVpp65+ cancer cells. In contrast, the clinically-used PD-L1-blocking antibody MEDI4736 (durvalumab) promoted T cell activation indiscriminate of EGFR expression on cancer cells. Additionally, in tumor-bearing mice 111In-PD-L1xEGFR showed a significantly higher tumor uptake compared to 111In-PD-L1xMock. In conclusion, PD-L1xEGFR blocks the PD-1/PD-L1 immune checkpoint in an EGFR-directed manner, which promotes a more selective reactivation of anticancer T cells. This novel targeted approach may be useful to enhance efficacy and safety of PD-1/PD-L1 checkpoint blockade in EGFR-overexpressing malignancies.

Citation Format: Iris Koopmans, Douwe F. Samplonius, Robert J. van Ginkel, Peter J. Wierstra, Sandra Heskamp, Edwin Bremer, Wijnand Helfrich. A novel bispecific antibody for EGFR-directed blockade of the PD-1/PD-L1 immune checkpoint [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 4553.

A novel bispecific antibody for EGFR-directed blockade of the PD-1/PD-L1 immune checkpoint

PD-L1-blocking antibodies produce significant clinical benefit in selected cancer patients by reactivating functionally-impaired antigen-experienced anticancer T cells. However, the efficacy of current PD-L1-blocking antibodies is potentially reduced by ‘on-target/off-tumor’ binding to PD-L1 widely expressed on normal cells. This lack of tumor selectivity may induce a generalized activation of all antigen-experienced T cells which may explain the frequent occurrence of autoimmune-related adverse events during and after treatment.

To address these issues, we constructed a bispecific antibody (bsAb), designated PD-L1xEGFR, to direct PD-L1-blockade to EGFR-expressing cancer cells and to more selectively reactivate anticancer T cells. Indeed, the IC50 of PD-L1xEGFR for blocking PD-L1 on EGFR⁺ cancer cells was ∼140 fold lower compared to that of the analogous PD-L1-blocking bsAb PD-L1xMock with irrelevant target antigen specificity. Importantly, activation status, IFN-γ production, and oncolytic activity of anti-CD3xanti-EpCAM-redirected T cells was enhanced when cocultured with EGFR-expressing carcinoma cells. Similarly, the capacity of PD-L1xEGFR to promote proliferation and IFN-γ production by CMVpp65-directed CD8⁺ effector T cells was enhanced when cocultured with EGFR-expressing CMVpp65-transfected cancer cells. In contrast, the clinically-used PD-L1-blocking antibody MEDI4736 (durvalumab) promoted T cell activation indiscriminate of EGFR expression on cancer cells. Additionally, in mice xenografted with EGFR-expressing cancer cells ¹¹¹In-PD-L1xEGFR showed a significantly higher tumor uptake compared to ¹¹¹In-PD-L1xMock. In conclusion, PD-L1xEGFR blocks the PD-1/PD-L1 immune checkpoint in an EGFR-directed manner, thereby promoting the selective reactivation of anticancer T cells. This novel targeted approach may be useful to enhance efficacy and safety of PD-1/PD-L1 checkpoint blockade in EGFR-overexpressing malignancies.

CD103+ intraepithelial T cells in high-grade serous ovarian cancer are phenotypically diverse TCRαβ+ CD8αβ+ T cells that can be targeted for cancer immunotherapy

CD103+ tumor-infiltrating lymphocytes (TIL) have been linked to specific epithelial infiltration and a prolonged survival in high-grade serous epithelial ovarian cancer (HGSC). However, whether these cells are induced as part of an ongoing anti-HGSC immune response or represent non-specifically expanded resident or mucosal lymphocytes remains largely unknown. In this study, we first confirmed that CD103+ TIL from HGSC were predominantly localized in the cancer epithelium and were strongly correlated with an improved prognosis. We further demonstrate that CD103+ TIL were almost exclusively CD3+ TCRαβ+ CD8αβ+ CD4- T cells, but heterogeneously expressed T cell memory and differentiation markers. Activation of peripheral T cells in the presence of HGSC was sufficient to trigger induction of CD103 in over 90% of all CD8+ cells in a T cell receptor (TCR)- and TGFβR1-dependent manner. Finally, CD103+ TIL isolated from primary HGSC showed signs of recent activation and dominantly co-expressed key immunotherapeutic targets PD-1 and CD27. Taken together, our data indicate CD103+ TIL in HGSC are formed as the result of an adaptive anti-tumor immune response that might be reactivated by (dual) checkpoint inhibition.

CD20-selective inhibition of CD47-SIRPα "don't eat me" signaling with a bispecific antibody-derivative enhances the anticancer activity of daratumumab, alemtuzumab and obinutuzumab

Here, we report on a novel bispecific antibody-derivative, designated RTX-CD47, with unique capacity for CD20-directed inhibition of CD47-SIRPα “don't eat me” signaling. RTX-CD47 comprises a CD20-targeting scFv antibody fragment derived from rituximab fused in tandem to a CD47-blocking scFv. Single agent treatment with RTX-CD47 triggered significant phagocytic removal of CD20^pos/CD47^pos malignant B-cells, but not of CD20^neg/CD47^pos cells, and required no pro-phagocytic FcR-mediated signaling. Importantly, treatment with RTX-CD47 synergistically enhanced the phagocytic elimination of primary malignant B cells by autologous phagocytic effector cells as induced by therapeutic anticancer antibodies daratumumab (anti-CD38), alemtuzumab (anti-CD52) and obinutuzumab (anti-CD20). In conclusion, RTX-CD47 blocks CD47 “don't eat me” signaling by cancer cells in a CD20-directed manner with essentially no activity towards CD20^neg/CD47^pos cells and enhances the activity of therapeutic anticancer antibodies directed to B-cell malignancies.

Programmed Death Ligand 1 (PD-L1)-targeted TRAIL combines PD-L1-mediated checkpoint inhibition with TRAIL-mediated apoptosis induction

Antibodies that block PD-L1/PD-1 immune checkpoints restore the activity of functionally-impaired antitumor T cells. These antibodies show unprecedented clinical benefit in various advanced cancers, particularly in melanoma. However, only a subset of cancer patients responds to current PD-L1/PD-1-blocking strategies, highlighting the need for further advancements in PD-L1/PD-1-based immunotherapy. Here, we report on a novel approach designed to combine PD-L1 checkpoint inhibition with the tumor-selective induction of apoptosis by TNF-related Apoptosis Inducing Ligand (TRAIL). In brief, a new bi-functional fusion protein, designated anti-PD-L1:TRAIL, was constructed comprising a PD-L1-blocking antibody fragment genetically fused to the extracellular domain of the pro-apoptotic tumoricidal protein TRAIL. Treatment of PD-L1-expressing cancer cells with anti-PD-L1:TRAIL induced PD-L1-directed TRAIL-mediated cancer cell death. Treatment of T cells with anti-PD-L1:TRAIL augmented T cell activation, as evidenced by increased proliferation, secretion of IFNγ and enhanced killing of cancer cell lines and primary patient-derived cancer cells in mixed T cell/cancer cell culture experiments. Of note, elevated levels of IFNγ further upregulated PD-L1 on cancer cells and simultaneously sensitized cancer cells to TRAIL-mediated apoptosis by anti-PD-L1:TRAIL. Additionally, anti-PD-L1:TRAIL converted immunosuppressive PD-L1-expressing myeloid cells into pro-apoptotic effector cells that triggered TRAIL-mediated cancer cell death. In conclusion, combining PD-L1 checkpoint inhibition with TRAIL-mediated induction of apoptosis using anti-PD-L1:TRAIL yields promising multi-fold and mutually reinforcing anticancer activity that may be exploited to enhance the efficacy of therapeutic PD-L1/PD-1 checkpoint inhibition.

The epithelial polarity regulator LGALS9/galectin-9 induces fatal frustrated autophagy in KRAS mutant colon carcinoma that depends on elevated basal autophagic flux

Oncogenic mutation of KRAS (Kirsten rat sarcoma viral oncogene homolog) in colorectal cancer (CRC) confers resistance to both chemotherapy and EGFR (epidermal growth factor receptor)-targeted therapy. We uncovered that KRAS mutant (KRAS^mut) CRC is uniquely sensitive to treatment with recombinant LGALS9/Galectin-9 (rLGALS9), a recently established regulator of epithelial polarity. Upon treatment of CRC cells, rLGALS9 rapidly internalizes via early- and late-endosomes and accumulates in the lysosomal compartment. Treatment with rLGALS9 is accompanied by induction of frustrated autophagy in KRAS^mut CRC, but not in CRC with BRAF (B-Raf proto-oncogene, serine/threonine kinase) mutations (BRAF^mut). In KRAS^mut CRC, rLGALS9 acts as a lysosomal inhibitor that inhibits autophagosome-lysosome fusion, leading to autophagosome accumulation, excessive lysosomal swelling and cell death. This antitumor activity of rLGALS9 directly correlates with elevated basal autophagic flux in KRAS^mut cancer cells. Thus, rLGALS9 has potent antitumor activity toward refractory KRAS^mut CRC cells that may be exploitable for therapeutic use.

Granzyme B-based cytolytic fusion protein targeting EpCAM specifically kills triple negative breast cancer cells in vitro and inhibits tumor growth in a subcutaneous mouse tumor model

Triple-negative breast cancer (TNBC) is associated with poor prognosis and high prevalence among young premenopausal women. Unlike in other breast cancer subtypes, no targeted therapy is currently available. Overexpression of epithelial cell adhesion molecule (EpCAM) in 60% of TNBC tumors correlates with poorer prognosis and is associated with cancer stem cell phenotype. Thus, selective elimination of EpCAM(+) TNBC tumor cells is of clinical importance. Therefore, we constructed a fully human targeted cytolytic fusion protein, designated GbR201K-αEpCAM(scFv), in which an EpCAM-selective single-chain antibody fragment (scFv) is genetically fused to a granzyme B (Gb) mutant with reduced sensitivity to its natural inhibitor serpin B9. In vitro studies confirmed its specific binding, internalization and cytotoxicity toward a panel of EpCAM-expressing TNBC cells. Biodistribution kinetics and tumor-targeting efficacy using MDA-MB-468 cells in a human TNBC xenograft model in mice revealed selective accumulation of GbR201K-αEpCAM(scFv) in the tumors after i.v. injection. Moreover, treatment of tumor-bearing mice demonstrated a prominent inhibition of tumor growth of up to 50 % in this proof-of-concept study. Taken together, our results indicate that GbR201K-αEpCAM(scFv) is a promising novel targeted therapeutic for the treatment of TNBC.

C-type lectin-like molecule-1 (CLL1)-targeted TRAIL augments the tumoricidal activity of granulocytes and potentiates therapeutic antibody-dependent cell-mediated cytotoxicity

The therapeutic effect of anti-cancer monoclonal antibodies stems from their capacity to opsonize targeted cancer cells with subsequent phagocytic removal, induction of antibody-dependent cell-mediated cytotoxicity (ADCC) or induction of complement-mediated cytotoxicity (CDC). The major immune effector cells involved in these processes are natural killer (NK) cells and granulocytes. The latter and most prevalent blood cell population contributes to phagocytosis, but is not effective in inducing ADCC. Here, we report that targeted delivery of the tumoricidal protein tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) to granulocyte marker C-type lectin-like molecule-1 (CLL1), using fusion protein CLL1:TRAIL, equips granulocytes with high levels of TRAIL. Upon CLL1-selective binding of this fusion protein, granulocytes acquire additional TRAIL-mediated cytotoxic activity that, importantly, potentiates antibody-mediated cytotoxicity of clinically used therapeutic antibodies (e.g., rituximab, cetuximab). Thus, CLL1:TRAIL could be used as an adjuvant to optimize the clinical potential of anticancer antibody therapy by augmenting tumoricidal activity of granulocytes.

Targeted elimination of activated hepatic stellate cells by an anti-epidermal growth factor-receptor single chain fragment variable antibody-tumor necrosis factor-related apoptosis-inducing ligand (scFv425-sTRAIL)

BACKGROUND

Progressive liver fibrosis is the result of chronic liver injury and is characterized by the excessive accumulation of extracellular matrix that may result in liver failure. Activated hepatic stellate cells are known to play a central role in this process and their elimination is a crucial step towards the resolution and reversion of liver fibrosis. In the present study, we investigated the potential application of an anti-epidermal growth factor receptor single chain fragment variable antibody-tumor necrosis factor-related apoptosis-inducing ligand (scFv425-sTRAIL) fusion protein in the targeted elimination of activated hepatic stellate cells.

METHODS

Activated hepatic stellate cells (LX2 cells) were treated by adenovirus-derived scFv425-sTRAIL to evaluate its effect on the viability and extracellular matrix production of this type of cells.

RESULTS

In vitro treatment of activated hepatic stellate cells with scFv425-sTRAIL induced a significant reduction in viability (up to 100% reduction) and extracellular matrix production (60% reduction), yet no significant effect was observed on hepatic parenchymal cells. Blockage of the epidermal growth factor receptor (EGFR) by a monoclonal antibody significantly reduced the effectiveness of scFv425-sTRAIL in activated hepatic stellate cells, whereas a reduced effectivity was also observed after inhibition of the caspase pathway.

CONCLUSIONS

Evidence is presented for the successful application of the scFv425-sTRAIL fusion protein in the targeted elimination of activated hepatic stellate cells via EGFR and simultaneous activation of the caspase pathway. scFv425-sTRAIL may thus represent a new therapeutic compound against liver fibrosis.

GRPR-selective PET imaging of prostate cancer using [(18)F]-lanthionine-bombesin analogs

The gastrin-releasing peptide receptor (GRPR) is overexpressed in a variety of human malignancies, including prostate cancer. Bombesin (BBN) is a 14 amino acids peptide that selectively binds to GRPR. In this study, we developed two novel Al(18)F-labeled lanthionine-stabilized BBN analogs, designated Al(18)F-NOTA-4,7-lanthionine-BBN and Al(18)F-NOTA-2,6-lanthionine-BBN, for positron emission tomography (PET) imaging of GRPR expression using xenograft prostate cancer models. (Methyl)lanthionine-stabilized 4,7-lanthionine-BBN and 2,6-lanthionine-BBN analogs were conjugated with a NOTA chelator and radiolabeled with Al(18)F using the aluminum fluoride strategy. Al(18)F-NOTA-4,7-lanthionine-BBN and Al(18)F-NOTA-2,6-lanthionine-BBN was labeled with Al(18)F with good radiochemical yield and specific activity>30 GBq/μmol for both radiotracers. The logD values measured for Al(18)F-NOTA-4,7-lanthionine-BBN and Al(18)F-NOTA-2,6-lanthionine-BBN were -2.14 ± 0.14 and -2.34 ± 0.15, respectively. In athymic nude PC-3 xenografts, at 120 min post injection (p.i.), the uptake of Al(18)F-NOTA-4,7-lanthionine-BBN and Al(18)F-NOTA-2,6-lanthionine-BBN in prostate cancer (PC-3) mouse models was 0.82 ± 0.23% ID/g and 1.40 ± 0.81% ID/g, respectively. An excess of unlabeled ɛ-aminocaproic acid-BBN(7-14) (300-fold) was co-injected to assess GRPR binding specificity. Tumor uptake of Al(18)F-NOTA-4,7-lanthionine-BBN and Al(18)F-NOTA-2,6-lanthionine-BBN in PC-3 tumors was evaluated by microPET (μPET) imaging at 30, 60 and 120 min p.i. Blocking studies showed decreased uptake in PC-3 bearing mice. Stabilized 4,7-lanthionine-BBN and 2,6-lanthionine-BBN peptides were rapidly and successfully labeled with (18)F. Both tracers may have potential for GRPR-positive tumor imaging.

CD20+ T cells have a predominantly Tc1 effector memory phenotype and are expanded in the ascites of patients with ovarian cancer

Recently, a small subset of T cells that expresses the B cell marker CD20 has been identified in healthy volunteers and in patients with rheumatoid arthritis and multiple sclerosis. The origin of these CD20-positive T cells as well as their relevance in human disease remains unclear. Here, we identified that after functional B cell/T cell interaction CD20 molecules are transferred to the cell surface of T cells by trogocytosis together with the established trogocytosis marker HLA-DR. Further, the presence of CD20 on isolated CD20⁺ T cells remained stable for up to 48h of ex vivo culture. These CD20⁺ T cells almost exclusively produced IFNγ (∼70% vs. ∼20% in the CD20^- T cell population) and were predominantly (CD8⁺) effector memory T cells (∼60-70%). This IFNγ producing and effector memory phenotype was also determined for CD20⁺ T cells as detected in the peripheral blood and ascitic fluids of ovarian cancer (OC) patients. In the latter, the percentage of CD20⁺ T cells was further strongly increased (from ∼6% in peripheral blood to 23% in ascitic fluid). Taken together, the data presented here indicate that CD20 is transferred to T cells upon intimate T cell/B cell interaction. Further, CD20⁺ T cells are of memory and IFNγ producing phenotype and are present in increased amounts in ascitic fluid of OC patients.

The ever-expanding immunomodulatory role of calreticulin in cancer immunity

Calreticulin is a pleiotropic molecule that normally resides in the lumen of the endoplasmic reticulum (ER). Here, it has various functions, ranging from regulation of calcium homeostasis to ensuring proper protein folding. More recently, calreticulin gained special interest for its extracellular functions, where it has direct immunomodulatory activity. In this respect, calreticulin activates dendritic cells and macrophages. In addition, certain anti-cancer therapies induce the translocation of calreticulin from the ER to the cell surface of dying cancer cells, where calreticulin dictates the immunogenicity of these cells. Interestingly, treatment with tumor necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL) also induces membrane calreticulin exposure on cancer cells. As shown here, calreticulin directly interacts with TRAIL and its receptor-signaling complex, as well as with other TNF family members. Of note, TRAIL is a well known immunomodulatory molecule, and is expressed on the surface of natural killer T-cells. Therefore, calreticulin may have an as yet unrecognized wide(r) impact on immunity, with the TNF-ligand family modulating virtually all aspects of the immune response.

Photochemical internalization (PCI)-mediated enhancement of bleomycin cytotoxicity by liposomal mTHPC formulations in human head and neck cancer cells

BACKGROUND AND OBJECTIVE

Photodynamic therapy (PDT) with photosensitizers that locate in endocytic vesicles of cancer cells can be exploited to promote the intracellular release of anticancer drugs entrapped in endolysosomal vesicles. This new approach is commonly referred to as Photochemical Internalization (PCI). Here we report on the PCI effects of three different formulations (Foscan, Foslip, and Fospeg) of the clinically approved photosensitizer, meta-tetrahydroxyphenyl chlorin (mTHPC) on the anticancer drug bleomycin (BLM) in the head and neck cancer cell lines.

MATERIALS AND METHODS

Uptake and localization of Foscan, Foslip, and Fospeg in head and neck cancer cells were evaluated by fluorescence spectrophotometry and fluorescence microscopy. Photodynamic efficacy of Foscan, Foslip, and Fospeg were compared with cell proliferation assay. Moreover, PCI effects of Foscan, Foslip, and Fospeg on BLM were compared using protocols in which PDT was applied after or before BLM treatment.

RESULTS

Cellular uptake of Foscan, Foslip, and Fospeg increased in a dose-dependent fashion with consistent higher uptakes of Foslip and Fospeg than Foscan. Fluorescence microscopy showed diffuse intracellular localization pattern for Foscan, Foslip, and Fospeg similar to that of a specific ER probe. However, the subcellular localization pattern of the Rhodamine-labelled same type of pegylated liposomes as Fospeg was similar to that of a specific endolysosomal probe, suggesting that Fospeg uptake appeared to initially proceed via endolysosomal trafficking. Foscan, Foslip, and Fospeg showed no apparent PCI-mediated cytotoxicity when PDT was performed after BLM treatment. However, significantly increased cytotoxicity of BLM (P < 0.05) was observed for both Foslip and Fospeg when PDT was performed before BLM treatment. The observed differences of PCI-mediated cytotoxicity between these two timing protocols appears to be related to the differential intracellular trafficking and localization of Foscan, Foslip, and Fospeg.

CONCLUSION

Liposomal formulations of mTHPC may be candidates for developing mTHPC-based PCI protocols to enhance the efficacy of anticancer drugs entrapped in endolysosomal vesicles.

A CSPG4-specific immunotoxin kills rhabdomyosarcoma cells and binds to primary tumor tissues

The treatment of rhabdomyosarcoma (RMS) remains challenging, with metastatic and alveolar RMS offering a particularly poor prognosis. Therefore, the identification and evaluation of novel antigens, which are suitable targets for immunotherapy, is one attractive possibility to improve the treatment of this disease. Here we show that chondroitin sulfate proteoglycan 4 (CSPG4) is expressed on RMS cell lines and RMS patient material. We evaluated the immunotoxin (IT) αMCSP-ETA', which specifically recognizes CSPG4 on the RMS cell lines RD, FL-OH1, TE-671 and Rh30. It is internalized rapidly, induces apoptosis and thus kills RMS cells selectively. We also demonstrate the specific binding of this IT to RMS primary tumor material from three different patients.

Pretargeted dual-modality immuno-SPECT and near-infrared fluorescence imaging for image-guided surgery of prostate cancer

Radical removal of malignant lesions may be improved using tumor-targeted dual-modality probes that contain both a radiotracer and a fluorescent label to allow for enhanced intraoperative delineation of tumor resection margins. Because pretargeting strategies yield high signal-to-background ratios, we evaluated the feasibility of a pretargeting strategy for intraoperative imaging in prostate cancer using an anti-TROP-2 x anti-HSG bispecific antibody (TF12) in conjunction with the dual-labeled diHSG peptide (RDC018) equipped with both a DOTA chelate for radiolabeling purposes and a fluorophore (IRdye800CW) to allow near-infrared optical imaging. Nude mice implanted s.c. with TROP-2-expressing PC3 human prostate tumor cells or with PC3 metastases in the scapular and suprarenal region were injected i.v. with 1 mg of TF12 and, after 16 hours of tumor accumulation and blood clearance, were subsequently injected with 10 MBq, 0.2 nmol/mouse of either (111)In-RDC018 or (111)In-IMP288 as a control. Two hours after injection, both microSPECT/CT and fluorescence images were acquired, both before and after resection of the tumor nodules. After image acquisition, the biodistribution of (111)In-RDC018 and (111)In-IMP288 was determined and tumors were analyzed immunohistochemically. The biodistribution of the dual-label RDC018 showed specific accumulation in the TROP-2-expressing PC3 tumors (12.4 ± 3.7% ID/g at 2 hours postinjection), comparable with (111)In-IMP288 (9.1 ± 2.8% ID/g at 2 hours postinjection). MicroSPECT/CT and near-infrared fluorescence (NIRF) imaging confirmed this TROP-2-specific uptake of the dual-label (111)In-RDC018 in both the s.c. and metastatic growing tumor model. In addition, PC3 metastases could be visualized preoperatively with SPECT/CT and could subsequently be resected by image-guided surgery using intraoperative NIRF imaging, showing the preclinical feasibility of pretargeted dual-modality imaging approach in prostate cancer.

Antigen-specific active immunotherapy for ovarian cancer

BACKGROUND

Despite advances in chemotherapy, prognosis of ovarian cancer remains poor. Antigen-specific active immunotherapy aims to induce tumour-antigen-specific anti-tumour immune responses as an alternative treatment for ovarian cancer.

OBJECTIVES

To assess the feasibility of antigen-specific active immunotherapy for ovarian cancer. Primary outcomes are clinical efficacy and antigen-specific immunogenicity with carrier-specific immunogenicity and side effects as secondary outcomes.

SEARCH METHODS

For the previous version of this review, a systematic search of the Cochrane Central Register of Controlled Trials (CENTRAL) 2009, Issue 3, Cochrane Gynaecological Cancer Group Specialized Register, MEDLINE and EMBASE databases and clinicaltrials.gov was performed (1966 to July 2009). We conducted handsearches of the proceedings of relevant annual meetings (1996 to July 2009).For this update of the review the searches were extended to October 2013.

SELECTION CRITERIA

Randomised controlled trials (RCTs), as well as non-randomised non-controlled studies that included participants with epithelial ovarian cancer, irrespective of stage of disease, and treated with antigen-specific active immunotherapy, irrespective of type of vaccine, antigen used, adjuvant used, route of vaccination, schedule, and reported clinical or immunological outcomes.

DATA COLLECTION AND ANALYSIS

Two reviews authors independently performed the data extraction. Risk of bias was evaluated for RCTs according to standard methodological procedures expected by The Cochrane Collabororation or for non-RCTs using a selection of quality domains deemed best applicable to the non-randomised non-controlled studies.

MAIN RESULTS

Fifty-five studies were included (representing 3051 women with epithelial ovarian cancer). Response definitions showed substantial variation between trials, which makes comparison of trial results unreliable. Information on adverse events was frequently limited. Furthermore, reports of both RCTs and non-RCTs frequently lacked the relevant information necessary to assess risk of bias. Serious biases in most of the included trials can therefore not be ruled out.The largest body of evidence is currently available for CA-125 targeted antibody therapy (16 studies: 2339 participants). Non-RCTs of CA-125 targeted antibody therapy suggests increased survival in humoral and/or cellular responders. However, four large randomised placebo-controlled trials did not show any clinical benefit despite induction of immune responses in approximately 60% of participants.Other small studies targeting many different tumour antigens showed promising immunological results. As these strategies have not yet been tested in RCTs, no reliable inferences about clinical efficacy can be made. Given the promising immunological results, limited side effects and toxicity exploration of clinical efficacy in large well-designed RCTs may be worthwhile.

AUTHORS' CONCLUSIONS

We conclude that despite promising immunological responses, no clinically effective antigen-specific active immunotherapy is yet available for ovarian cancer. Results should be interpreted cautiously as there was a significant lack of relevant information for the assessment of risk of bias in both RCTs and non-RCTs.

EpCAM-selective elimination of carcinoma cells by a novel MAP-based cytolytic fusion protein

In normal epithelia, the epithelial cell adhesion molecule (EpCAM) expression is relatively low and only present at the basolateral cell surface. In contrast, EpCAM is aberrantly overexpressed in various human carcinomas. Therefore, EpCAM is considered to be a highly promising target for antibody-based cancer immunotherapy. Here, we present a new and fully human cytolytic fusion protein (CFP), designated "anti-EpCAM(scFv)-MAP," that is comprised of an EpCAM-specific antibody fragment (scFv) genetically fused to the microtubule-associated protein tau (MAP). Anti-EpCAM(scFv)-MAP shows potent EpCAM-restricted proapoptotic activity toward rapidly proliferating carcinoma cells. In vitro assays confirmed that treatment with anti-EpCAM(scFv)-MAP resulted in the colocalization and stabilization of microtubules, suggesting that this could be the potential mode of action. Dose-finding experiments indicated that anti-EpCAM(scFv)-MAP is well tolerated in mice. Using noninvasive far-red in vivo imaging in a tumor xenograft mouse model, we further demonstrated that anti-EpCAM(scFv)-MAP inhibited tumor growth in vivo. In conclusion, our data suggest that anti-EpCAM(scFv)-MAP may be of therapeutic value for the targeted elimination of EpCAM(+) carcinomas.

Alignment and Opening of Giant Lecithin Vesicles by Electric Fields

AC electric fields ware applied to suspensions of giant lecithin vesicles observed under a phase contrast microscope. Elongated vesicles were found to align parallel to the field. In sufficiently strong fields the vesicles opened at both ends and became cylinders which in some cases were immutable under further increase of the field. The cylinder parameters can be used to calculate the edge energy of the cylinder wall. For the single bilayer we obtain 2-10-6 erg cm-1.

Direct X-Ray Study of the Molecular Tilt in Dipalmitoyl Lecithin Bilayers

Direction and angle of molecular tilt in an ordered multilayer system of dipalmitoyl lecithin and water were directly determined by X-ray diffraction as a function of temperature in the gel phase with ca. 20 wt. % of water

Steric Interaction of Fluid Membranes in Multilayer Systems

The out-of-plane fluctuations of fluid membranes are sterically hindered in multilayer systems. The repulsive interaction associated with the steric or excluded-volume effect is studied theoretically by two methods. The interaction energy per unit area of membrane is derived as a function of temperature, membrane curvature elasticity and mean membrane spacing; it is inversely proportional to the square of the latter. Steric repulsion is estimated for lecithin bilayers in water. There and in other cases, it may compete with van der Waals attraction.

Passages in Lecithin-Water Systems

Large numbers of tunnel-like structures apparently connecting neighbouring bilayers were found in phase-contrast microscopy of certain preparations of egg lecithin in water. These passages either cause a pairing of the bilayers or form threedimensional lattices. They appear to originate while the lecithin swells in water. Some theoretical aspects of passage formation in fluid bilayers is shown to be 4πx̅, x̅ being the elastic modulus of Gaussian curvature.

Targeting human prostate cancer with 111In-labeled D2B IgG, F(ab')2 and Fab fragments in nude mice with PSMA-expressing xenografts

D2B is a new monoclonal antibody directed against an extracellular domain of prostate-specific membrane antigen (PSMA), which is overexpressed in prostate cancer. The potential of D2B IgG, and F(ab')2 and Fab fragments of this antibody for targeting prostate cancer was determined in mice bearing subcutaneous prostate cancer xenografts. The optimal time point for imaging was determined in biodistribution and microSPECT imaging studies with (111)In-D2B IgG, (111)In-capromab pendetide, (111)In-D2B F(ab')2 and (111)In-D2B Fab fragments in mice with PSMA-expressing LNCaP and PSMA-negative PC3 tumors at several time points after injection. All (111)In-labeled antibody formats specifically accumulated in the LNCaP tumors, with highest uptake of (111)In-D2B IgG and (111)In-capromab pendetide at 168 h p.i. (94.8 ± 19.2% injected dose per gram (ID/g) and 16.7 ± 2.2% ID/g, respectively), whereas uptake of (111)In-D2B F(ab')2 and (111)In-D2B Fab fragments peaked at 24 h p.i. (12.1 ± 3.0% ID/g and 15.1 ± 2.9% ID/g, respectively). Maximum LNCaP tumor-to-blood ratios were 13.0 ± 2.3 (168 h p.i.), 6.2 ± 0.7 (24 h p.i.), 23.0 ± 4.0 (24 h p.i.) and 4.5 ± 0.6 (168 h p.i.) for (111)In-D2B IgG, (111)In-F(ab')2, (111)In-Fab and (111)In-capromab pendetide, respectively. LNCaP tumors were clearly visualized with microSPECT with all antibody formats. This study demonstrates the feasibility of D2B IgG, F(ab')2 and Fab fragments for targeting PSMA-expressing prostate cancer xenografts.

Targeted delivery of CD40L promotes restricted activation of antigen-presenting cells and induction of cancer cell death

Background

Stimulation of CD40 can augment anti-cancer T cell immune responses by triggering effective activation and maturation of antigen-presenting cells (APCs). Although CD40 agonists have clinical activity in humans, the associated systemic activation of the immune system triggers dose-limiting side-effects.

Methods

To increase the tumor selectivity of CD40 agonist-based therapies, we developed an approach in which soluble trimeric CD40L (sCD40L) is genetically fused to tumor targeting antibody fragments, yielding scFv:CD40L fusion proteins. We hypothesized that scFv:CD40L fusion proteins would have reduced CD40 agonist activity similar to sCD40L but will be converted to a highly agonistic membrane CD40L-like form of CD40L upon anchoring to cell surface exposed antigen via the scFv domain.

Results

Targeted delivery of CD40L to the carcinoma marker EpCAM on carcinoma cells induced dose-dependent paracrine maturation of DCs ~20-fold more effective than a non-targeted control scFv:CD40L fusion protein. Similarly, targeted delivery of CD40L to the B cell leukemia marker CD20 induced effective paracrine maturation of DCs. Of note, the CD20-selective delivery of CD40L also triggered loss of cell viability in certain B cell leukemic cell lines as a result of CD20-induced apoptosis.

Conclusions

Targeted delivery of CD40L to cancer cells is a promising strategy that may help to trigger cancer-localized activation of CD40 and can be modified to exert additional anti-cancer activity via the targeting domain.

Dual-Modality Image-Guided Surgery of Prostate Cancer with a Radiolabeled Fluorescent Anti-PSMA Monoclonal Antibody

Both radionuclide imaging and near-infrared fluorescent (NIRF) imaging have a high sensitivity to detect tumors in vivo. The combination of these modalities using dual-labeled antibodies may allow both preoperative and intraoperative tumor localization and may be used in image-guided surgery to ensure complete resection of tumor tissue. Here, we evaluated the potential of dual-modality imaging of prostate cancer with the monoclonal antibody D2B, directed against an extracellular domain of prostate-specific membrane antigen (PSMA). For these studies, D2B was labeled both with (111)In and with the NIRF dye IRDye800CW.

METHODS

D2B was conjugated with N-hydroxysuccinimide-IRDye800CW and p-isothiocyanatobenzyl-diethylenetriaminepentaacetic acid (ITC-DTPA) and subsequently radiolabeled with (111)In. For biodistribution and NIRF imaging, (111)In-DTPA-D2B-IRDye800CW (2 μg, 0.55 MBq/mouse) was injected intravenously into BALB/c nude mice with subcutaneous PSMA-expressing LNCaP tumors (right flank) and PSMA-negative PC3 tumors (left flank). The biodistribution was determined at 1, 2, 3, and 7 d after injection. In addition, micro-SPECT/CT and NIRF imaging with (111)In-DTPA-D2B-IRDye800CW (3 μg, 8.5 MBq/mouse) was performed on mice with intraperitoneally growing LS174T-PSMA tumors.

RESULTS

(111)In-DTPA-D2B-IRDye800CW specifically accumulated in subcutaneous PSMA-positive LNCaP tumors (45.8 ± 8.0 percentage injected dose per gram at 168 h after injection), whereas uptake in subcutaneous PSMA-negative PC3 tumors was significantly lower (6.6 ± 1.3 percentage injected dose per gram at 168 h after injection). Intraperitoneal LS174T-PSMA tumors could be visualized specifically with both micro-SPECT/CT and NIRF imaging at 2 d after injection, and the feasibility of image-guided resection of intraperitoneal tumors was demonstrated in this model.

CONCLUSION

Dual-labeled (111)In-DTPA-D2B-IRDye800CW enables specific and sensitive detection of prostate cancer lesions in vivo with micro-SPECT/CT and NIRF imaging. In addition to preoperative micro-SPECT/CT imaging to detect tumors, NIRF imaging enables image-guided surgical resection. These preclinical findings warrant clinical studies with (111)In-DTPA-D2B-IRDye800CW to improve tumor detection and resection in prostate cancer patients.

Bifunctional antibody fragment-based fusion proteins for the targeted elimination of pathogenic T-cell subsets

Pathogenic effector T cells are key contributors to autoimmune diseases such as systemic lupus erythematosus (SLE). General inhibition of T cells using, e.g., methotrexate, prednisolone, or TNF blockers, has prominent therapeutic effects frequently at the cost of severe long-term side effects and toxicity. Therefore, targeted strategies that can selectively inhibit or eliminate pathogenic T cells are sought after as a new approach to safely block perpetual inflammatory T-cell responses and inhibit concomitant progressive tissue destruction. Of particular interest in this respect is the use of the so-called single-chain fragments of variable region (scFv) antibody fragments for the targeted reactivation of Fas-dependent activation-induced cell death (AICD). Recently, we demonstrated that a recombinant fusion protein comprising a T-cell-targeted anti-CD7 scFv antibody fragment genetically fused to soluble FasL (sFasL) can eliminate synovial fluid T cells in the absence of activity toward resting peripheral blood cells. Here, we describe a detailed protocol for construction and preclinical evaluation of such scFv:FasL fusion proteins that may be used to selectively eliminate pathogenic immune cells.

An update of radiolabeled bombesin analogs for gastrin-releasing peptide receptor targeting

Prostate cancer is a critical public health problem in USA and Europe. New non-invasive imaging methods are urgently needed, due to the low accuracy and specificity of current screen methods and the desire of localizing primary prostate cancer and bone metastasis. Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT) are the non-invasive and sensitive imaging methods which have been widely used for diagnosing diseases in the clinic. Lack of suitable radiotracers is the major issue for nuclear imaging of prostate cancer, although radiolabeled bombesin (BN) peptides targeting the Gastrin-Releasing Peptide Receptor (GRPR) on tumor cells are widely investigated. In this review we discuss the recent trends in the development of GRPR-targeted radiopharmaceuticals based on BN analogs with regard to their potential for imaging and therapy of GRPR-expressing malignancies. Following a brief introduction of GRPR and bombesin peptides, we summarize the properties of prostate cancer specific radiolabeled bombesins. New bombesin tracers published in the last five years are reviewed and compared according to their novelties in biomolecules, radionuclides, labeling methods, bifunctional chelators and linkers. Hot topics such as multimerization, application of agonists and antagonists are highlighted in the review. Lastly, a few clinical trials of cancer nuclear imaging with radiolabeled bombesin have been discussed.