A Case Report of Sequential Use of a Yeast-CEA Therapeutic Cancer Vaccine and Anti-PD-L1 Inhibitor in Metastatic Medullary Thyroid Cancer

Medullary thyroid cancer (MTC) accounts for ~4% of all thyroid malignancies. MTC derives from the neural crest and secretes calcitonin (CTN) and carcinoembryonic antigen (CEA). Unlike differentiated thyroid cancer, MTC does not uptake iodine and I-131 RAI (radioactive iodine) treatment is ineffective. Patients with metastatic disease are candidates for FDA-approved agents with either vandetanib or cabozantinib; however, adverse effects limit their use. There are ongoing trials exploring the role of less toxic immunotherapies in patients with MTC. We present a 61-year-old male with the diagnosis of MTC and persistent local recurrence despite multiple surgeries. He was started on sunitinib, but ultimately its use was limited by toxicity. He then presented to the National Cancer Institute (NCI) and was enrolled on a clinical trial with heat-killed yeast-CEA vaccine (NCT01856920) and his calcitonin doubling time improved in 3 months. He then came off vaccine for elective surgery. After surgery, his calcitonin was rising and he enrolled on a phase I trial of avelumab, a programmed death-ligand 1 (PD-L1) inhibitor (NCT01772004). Thereafter, his calcitonin decreased > 40% on 5 consecutive evaluations. His tumor was subsequently found to express PD-L1. CEA-specific T cells were increased following vaccination, and a number of potential immune-enhancing changes were noted in the peripheral immunome over the course of sequential immunotherapy treatment. Although calcitonin declines do not always directly correlate with clinical responses, this response is noteworthy and highlights the potential for immunotherapy or sequential immunotherapy in metastatic or unresectable MTC.

Induction of type 1 cytokines during neem leaf glycoprotein assisted carcinoembryonic antigen vaccination is associated with nitric oxide production

Involvement of the nitric oxide (NO) release in CEAM phi NLGP (carcinoembryonic antigen pulsed macrophages with neem leaf glycoprotein) vaccination and its relationship with vaccine induced type 1 immune response were aimed to study in the present communication. Vaccination with CEAM phi NLGP resulted in macrophage activation as evidenced by its increased number and expression of CD69 marker. Activated macrophages demonstrated upregulation in synthesis of IL-12 and downregulation in IL-10, along with excess IFN gamma production in splenic cells, as evidenced from mRNA analysis. Induction of such type 1 immunity was further confirmed by expression of type 1 specific transcription factor, T-bet and enhancement of intracellular glutathione content. Such vaccination also induced greater nitric oxide (NO) production from macrophages. Dependence of induced type 1 immune response on the NO release and vice versa was studied by in vitro neutralization of IFN gamma/IL-12 and in vivo inhibition of NO production by methylene blue. Obtained results clearly demonstrated the interdependence of two anti-tumor immune functions, namely, NO production and generation of type 1 immune response. Understanding of the mechanism of this NO related immune modulation would have great impact in proposing CEAM phi NLGP vaccine in clinic for the treatment of CEA+ tumors.

Randomised Phase I/II trial assessing the safety and efficacy of radiolabelled anti-carcinoembryonic antigen I(131) KAb201 antibodies given intra-arterially or intravenously in patients with unresectable pancreatic adenocarcinoma

BACKGROUND

Advanced pancreatic cancer has a poor prognosis, and the current standard of care (gemcitabine based chemotherapy) provides a small survival advantage. However the drawback is the accompanying systemic toxicity, which targeted treatments may overcome. This study aimed to evaluate the safety and tolerability of KAb201, an anti-carcinoembryonic antigen monoclonal antibody, labelled with I(131) in pancreatic cancer (ISRCTN 16857581).

METHODS

Patients with histological/cytological proven inoperable adenocarcinoma of the head of pancreas were randomised to receive KAb 201 via either the intra-arterial or intravenous delivery route. The dose limiting toxicities within each group were determined. Patients were assessed for safety and efficacy and followed up until death.

RESULTS

Between February 2003 and July 2005, 25 patients were enrolled. Nineteen patients were randomised, 9 to the intravenous and 10 to the intra-arterial arms. In the intra-arterial arm, dose limiting toxicity was seen in 2/6 (33%) patients at 50 mCi whereas in the intravenous arm, dose limiting toxicity was noted in 1/6 patients at 50 mCi, but did not occur at 75 mCi (0/3).The overall response rate was 6% (1/18). Median overall survival was 5.2 months (95% confidence interval = 3.3 to 9 months), with no significant difference between the intravenous and intra-arterial arms (log rank test p = 0.79). One patient was still alive at the time of this analysis.

CONCLUSION

Dose limiting toxicity for KAb201 with I(131) by the intra-arterial route was 50 mCi, while dose limiting toxicity was not reached in the intravenous arm.

Multiple costimulatory modalities enhance CTL avidity

Recent studies in both animal models and clinical trials have demonstrated that the avidity of T cells is a major determinant of antitumor and antiviral immunity. In this study, we evaluated several different vaccine strategies for their ability to enhance both the quantity and avidity of CTL responses. CD8(+) T cell quantity was measured by tetramer binding precursor frequency, and avidity was measured by both tetramer dissociation and quantitative cytolytic function. We have evaluated a peptide, a viral vector expressing the Ag transgene alone, with one costimulatory molecule (B7-1), and with three costimulatory molecules (B7-1, ICAM-1, and LFA-3), with anti-CTLA-4 mAb, with GM-CSF, and combinations of the above. We have evaluated these strategies in both a foreign Ag model using beta-galactosidase as immunogen, and in a "self" Ag model, using carcinoembryonic Ag as immunogen in carcinoembryonic Ag transgenic mice. The combined use of several of these strategies was shown to enhance not only the quantity, but, to a greater magnitude, the avidity of T cells generated; a combination strategy is also shown to enhance antitumor effects. The results reported in this study thus demonstrate multiple strategies that can be used in both antitumor and antiviral vaccine settings to generate higher avidity host T cell responses.

Tumor immunity and prolonged survival following combined adenovirus-HSP72 and CEA-plasmid vaccination

We have studied the effects of recombinant adenoviruses as immune adjuvants for DNA vaccination. In a mouse model, using the weak immunogen carcinoembryonic antigen (CEA), anti-CEA IgG production was significantly higher and occurred earlier when immunization included a recombinant adenovirus together with CEA-plasmid DNA. Combined immunization with a recombinant adenovirus expressing the immunomodulatory molecule heat shock protein 72 (ADHSP72) and CEA-plasmid DNA resulted in CEA-specific T-cell activation capable of protecting mice from tumor formation with CEA expressing cells. Additionally, animals with CEA expressing tumors showed diminished tumor growth and prolonged survival when immunized with ADHSP72 and CEA-plasmid DNA compared to controls. Recombinant adenoviruses expressing immunomodulatory molecules such as HSP72 may be useful adjuvants for DNA vaccination.

In vivo manipulation of dendritic cells overcomes tolerance to unmodified tumor-associated self antigens and induces potent antitumor immunity

Most tumor-associated Ags are self proteins that fail to elicit a T cell response as a consequence of immune tolerance. Dendritic cells (DCs) generated ex vivo have been used to break tolerance against such self Ags; however, in vitro manipulation of DCs is cumbersome and difficult to control, resulting in vaccines of variable potency. To address this problem we developed a method for loading and activating DCs, in situ, by first directing sufficient numbers of DCs to peripheral tissues using Flt3 ligand and then delivering a tumor-associated Ag and oligonucleotide containing unmethylated CG motifs to these tissues. In this study, we show in three different tumor models that this method can overcome tolerance and induce effective antitumor immunity. Vaccination resulted in the generation of CD8(+) T and NK cell effectors that mediated durable tumor responses without attacking normal tissues. These findings demonstrate that unmodified tumor-associated self Ags can be targeted to DCs in vivo to induce potent systemic antitumor immunity.

Tumor-directed lymphocyte-activating cytokines: refolding-based preparation of recombinant human interleukin-12 and an antibody variable domain-fused protein by additive-introduced stepwise dialysis

Integration of lymphocyte-activating cytokines (e.g., interleukin-12: IL-12) to tumor cells offers promise for cancer immunotherapy, but the preparation of such heterodimeric proteins by refolding is difficult because of subunit instability. We achieved the refolding of Escherichia coli-expressed human IL-12 by a stepwise dialysis method, preventing the formation of insoluble aggregates by adding a redox reagent and an aggregation suppressor. We also constructed a tumor-specific IL-12 protein, each subunit of which was fused with one chain of variable domain fragment (Fv) of anticarcinoembryonic antigen (CEA) antibody T84.66 (aCEA-IL12). Fusion of IL-12 with Fv greatly increased the yield of functional heterodimer. Several assays have indicated that the Fv domain and IL-12 domain of the fused protein had cognate biological activities, and it enhanced the cytotoxicity of T-LAK cells for the cancer cell line.

Rejection of syngeneic colon carcinoma by CTLs expressing single-chain antibody receptors codelivering CD28 costimulation

A new strategy to improve the therapeutic utility of redirected T cells for cancer involves the development of novel Ag-specific chimeric receptors capable of stimulating optimal and sustained T cell antitumor activity in vivo. Given that T cells require both primary and costimulatory signals for optimal activation and that many tumors do not express critical costimulatory ligands, modified single-chain Ab receptors have been engineered to codeliver CD28 costimulation. In this study, we have compared the antitumor potency of primary T lymphocytes expressing carcinoembryonic Ag (CEA)-reactive chimeric receptors that incorporate either TCR-zeta or CD28/TCR-zeta signaling. Although both receptor-transduced T cell effector populations demonstrated cytolysis of CEA(+) tumors in vitro, T cells expressing the single-chain variable fragment of Ig (scFv)-CD28-zeta chimera had a far greater capacity to control the growth of CEA(+) xenogeneic and syngeneic colon carcinomas in vivo. The observed enhanced antitumor activity of T cells expressing the scFv-CD28-zeta receptor was critically dependent on perforin and the production of IFN-gamma. Overall, this study has illustrated the ability of a chimeric scFv receptor capable of harnessing the signaling machinery of both TCR-zeta and CD28 to augment T cell immunity against tumors that have lost expression of both MHC/peptide and costimulatory ligands in vivo.

Phase I trial of a recombinant vaccinia virus encoding carcinoembryonic antigen in metastatic adenocarcinoma: comparison of intradermal versus subcutaneous administration

The principal objectives of this trial were twofold: (a) to examine the safety and relative efficacy of intradermal needle injection versus s.c. jet administration of a carcinoembryonic antigen (CEA)-encoding recombinant vaccinia virus (rV-CEA) over a limited dose range and (b) to evaluate CEA-specific immune responses or antitumor effects induced by rV-CEA vaccination. Patients were randomly assigned to one of two groups, depending upon the technique of vaccine administration. All 20 patients received two doses of 10(7) or 10(8) pfu of rV-CEA at a 4-week interval. Toxicity was limited to modest local inflammation at the inoculation site as well as low-grade fever and increased fatigue, each affecting fewer than 20% of the patients. No evidence of CEA-specific lymphoproliferation, interleukin 2 release, delayed-type hypersensitivity, or antibody response was observed. Thus, the efficacy comparison between the two administration techniques was based upon the induction of immune responses to the vaccinia virus vector. Both techniques induced vaccinia-specific lymphoproliferation, interleukin 2 release, and antibody responses of comparable magnitude and frequency as well as protected 80% of patients against pustule formation following vaccinia scarification. Thus, there is no compelling reason to recommend one administration technique over the other based upon toxicity or efficacy. We have selected s.c. jet injection for subsequent trials of rV-CEA based on the ability to accommodate larger injection volumes, enhanced standardization between clinicians, and avoidance of needles that could transmit the vaccine or blood-borne pathogens to health care workers. We recommend use of 10(8) pfu doses for subsequent trials of recombinant vaccinia virus vaccines based upon the favorable toxicity profile and more consistent local pustule formation indicative of an adequate inoculation of live virus. No objective clinical responses to the rV-CEA vaccine were observed among this population of patients with widely metastatic adenocarcinoma.

Chronotolerance of experimental radioimmunotherapy: clearance, toxicity, and maximal tolerated dose of 131I-anti-carcinoembryonic antigen (CEA) IgG as a function of time of day of dosing in a murine model

The temporal variation in bone marrow proliferation has been used to help define the optimal time of day to dose with approximately 30 chemotherapeutic agents, so that treatment efficacy is maximised and toxicity is minimised. Since myelosuppression is also the dose-limiting toxicity for most forms of radioimmunotherapy, we hypothesised that time of day of administration might also influence tolerance for radioantibody therapy. Bone marrow proliferative activity in BALB/c mice was determined using cell cycle analysis of propidium iodide-stained bone marrow samples collected at 3 h intervals. Myelosuppression was determined at weekly intervals after a therapeutic dose of 131I-NP-4 anti-CEA (carcinoembryonic antigen) intact IgG at either 0900 h (2 h after light onset [HALO]), 1300 h (6 HALO) or 1600 h (9 HALO). The highest bone marrow proliferative activity was noted between 20 HALO (0300 h) and 4 HALO (1100 h), and the lowest activity could be measured at 10-13 HALO (1700-2000 h). Seven days after a maximal tolerated dose (MTD) of radioantibody, granulocyte reduction was 50% at both 2 and 6 HALO and only 32% at 9 HALO (P < 0.003). Fourteen days after radioantibody therapy, an 87% granulocyte suppression was observed in mice treated at 2 HALO and only a 64% granulocyte loss was noted in the 9 HALO treated group (P < 0.001). The 2 HALO group recovered earlier than the 9 HALO group (P < 0.013; 22% loss from the 2 HALO dose and 40% loss from the 9 HALO dose) on day 28 post-radioimmunotherapy. The difference in magnitude of neutropenia, rather than duration, was critical for establishing the MTD. A 30% increase in the MTD was possible if mice were dosed at 9 HALO (320 microCi) versus 2 HALO (240 microCi). These studies suggest that principles of chronobiology may govern the magnitude of toxicity and the highest dose tolerated in radioantibody therapy in the same way that it does for cytotoxic drug therapy.

Virus-directed enzyme/prodrug therapy (VDEPT). Selectively engineering drug sensitivity into tumors

A gene therapy approach has been described that generates a tumor-selective qualitative difference in the metabolic capability in tumor cells. This is the result of the selective expression of a nonmammalian enzyme in tumor cells. Selective expression is achieved by utilization of a chimeric gene composed of the TRS from a tumor-associated marker gene linked to the coding domain of a gene encoding a nonmammalian enzyme. We have described the application of this approach for the treatment of metastatic CRC. This approach involves creation of a chimeric gene composed of the CEA TRS linked to the coding domain of the CD gene. Selective expression of CD in the tumor cells will allow the selective conversion of the prodrug 5-FCyt to 5-FCyt in the tumor while sparing normal cells. Most importantly, delivery and expression of CD into a small fraction of tumor cells may be sufficient to achieve a significant antitumor effect.

Carcinoembryonic antigen: enhancement of liver colonisation through retention of human colorectal carcinoma cells

Carcinoembryonic antigen (CEA) is an oncofetal antigen whose function in the progression of colorectal carcinoma remains unclear although recent studies suggest it participates in homotypic cellular adhesion. We have previously shown that 40 micrograms of CEA injected intravenously into athymic nude mice enhances experimental metastasis in liver and lung by two human colorectal carcinoma cell lines that are injected intrasplenically 30 min later. The metastatic potential of another three moderately to highly metastatic colorectal carcinoma cell lines and of one weakly metastatic line has now been analysed in this model. CEA pretreatment only enhanced colony formation by cell lines that were weakly metastatic in untreated nude mice; it did not affect experimental metastasis by highly metastatic lines. CEA pretreatment enhanced the retention of 125I Idudr-labelled weakly metastatic tumour cells within the liver and lungs 4 h after intrasplenic injection but not the retention of highly metastatic tumour cells or inert latex beads. A significant correlation existed between the formation of experimental metastases and the early retention of tumour cells within the liver after intrasplenic injection. Aggregation did not appear to be important for retention in liver because CEA did not aggregate colorectal carcinoma cells in vitro. Also CEA did not alter natural host effector cell function in a cytolysis assay in vitro. We suggest that CEA facilitates liver colonisation by three of eight human colorectal carcinomas in athymic nude mice by increasing the hepatic retention of tumour cells. The potential mechanisms by which CEA may increase the retention of tumour cells in the liver are discussed.

Enhanced antibody response to liposome-associated protein antigens: preferential stimulation of IgG2a/b production

The effect of liposome encapsulation on the antibody response to bovine serum albumin (BSA), human carcinoembryonic antigen (CEA) and sheep IgG (sIgG) has been determined in the mouse. Dipalmitoylphosphatidylcholine/dimyristolylphosphatidylglycerol liposomes (10:1 molar ratio; 1 mumol) containing BSA, CEA or sIgG induced significant levels of IgG antibodies after one injection, and enhanced the proportion of IgG2a/2b to IgG1 on subsequent boost injection. The IgG antibody titre induced by liposomal antigen was 100-400-fold greater than immunization with antigen alone. Immunization with antigen and the water-soluble adjuvant N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP; 50 micrograms) resulted in antibody titres intermediate between free and liposomal antigen. MDP did not enhance the proportion of IgG2a/2b to IgG1. Incorporation of the lipid soluble MDP derivative MDP-glycerol dipalmitate (MDP-GDP; 10 micrograms) liposomes containing protein antigens resulted in higher titres and enhanced IgG2b isotype expression. Analysis of serum IgG antibody-isotype levels after immunization and boost with BSA/MDP showed that the half-life of IgG2a/2b and IgG3 was significantly less than that of IgG1. Liposomal encapsulation resulted in longer IgG2a/2b and IgG3 half-lives, especially when MDP-GDP was present in the liposome. These results demonstrate that, whereas MDP preferentially stimulates IgG1 antibodies, liposomes elicit high levels of IgG2a/2b isotypes with significantly longer serum half-lives.

Serological relationship between rat and human carcinoembryonic antigen

Enzyme immunoassays showed that a rabbit antiserum to rat carcinoembryonic antigen (CEA) had high activity with extracts containing human CEA, which was almost completely inhibited by extracts containing human or rat CEA. Little or no inhibition was obtained with extracts of normal human or rat tissues or by human blood group A or B substances. A monkey antiserum to human CEA had strong activity against extracts containing rat CEA, and little or no activity against extracts of normal rat liver or kidney or a CEA-negative rat colon tumor. Activity of the monkey antiserum against rat CEA was almost completely inhibited by extracts containing rat or human CEA. Little or no inhibition was obtained with extracts of normal rat or human tissues. These results suggest that human and rat CEA share antigenic determinants and that they may be analogous moieties.

Liposomal incorporation and immunogenicity of carcinoembryonic antigen

The ability of liposomal carriers to act as immuno-adjuvants for carcinoembryonic antigen (CEA) has been evaluated. Liposomal incorporation was consistent with association with the aqueous phase of the liposome, little if any of the protein being associated with the phospholipid bilayer. The incorporation of CEA within liposomal carriers resulted in immunological recognition in mice at doses (0.1 microgram) significantly less than required in Freund's complete adjuvant (25 micrograms), maximal responsiveness being found with liposomal-CEA preparations containing a lipophilic immunoadjuvant, N-acetyl-muramyl-L-alanyl-D-isoglutamyl-glyceryl-dipalmitate. Such liposomal formulations may have utility as immunoadjuvants for cancer immunotherapy.

Acid-treated, naked bacteria as immune carriers for protein antigens

Salmonella minnesota R595 bacteria were stripped of their natural antigenic determinants to yield acid-treated, naked bacteria. The proteins, human apolipoprotein A1 and carcino-embryonic antigen, were adsorbed to naked bacteria and these complexes were used to immunise rabbits. Although the antibody titres obtained were comparable to those achieved using Freund's adjuvant emulsions, much less antigen was needed for immunisation. This technique could be of great value where the amount of protein available for immunisation is very small.

Tumor immunity in rats immunized with rat carcinoembryonic antigen

Active immunization of rats with an emulsion consisting of Freund's complete adjuvant (FCA) and an extract of rat tumor containing carcinoembryonic antigen (CEA) induced clear-cut protection from growth of the syngeneic CEA-positive tumor, RCA-1. No protection was observed in rats treated with FCA alone nor was there protection against a tumor that no serologically detectable CEA. The results suggested that the tumor immunity exhibited by the immunized rats was mediated by an immune response specific for rat CEA. It was shown further that multiparous rats were more resistant to growth of RCA-1 tumor than nulliparous rats. This suggested that immunization against rat CEA, which is an oncofetal antigen, may occur during pregnancy.

Production of antibody for alpha 1-acid glycoprotein using carcinoembryonic antigen and normal fecal antigen

The structural characteristics of carcinoembryonic antigen (CEA) and CEA-like antigen in feces and meconium were examined using antibody raised against 2 antigens. When antibody to CEA was made, anti-alpha 1-acid glycoprotein (AG) (nonprecipitating antibody) besides the precipitating antibody for CEA was made. When antibodies against each CEA-like antigen (mol. wt. 180,000) purified from feces and meconium were tested, each antibody showed a fused precipitin line for 2 antigens. Some antibodies showed the non-precipitating antibody for AG. CEA and CEA-like antigen in feces and meconium may be composed of 2 portions (AG portion and non-AG portion). Antibody specific to these antigens may be the antibody directed to the non-AG portion.

Axillary lymphoscintigraphy by radioimmunodetection of carcinoembryonic antigen in breast cancer

In seven women with carcinoma of the breast I-131-labeled antibodies to carcinoembryonic antigen (CEA) were administered subcutaneously in the finger webs. Subsequent scintigraphic immages demonstrated localization of radioactivity in the ipsilateral axillary metastases of all patients and in the contralateral axillae of three. Fifteen patients with either gastrointestinal or genitourinary cancers were studied as controls; in 12 both the hands and feet were injected with antibodies to CEA and in the other three either the hands or feet. Radioactivity was observed in the inquinal nodes of four control patients with tumors below the diaphragm and in the axillary nodes of one patient with a tumor above the diaphragm. The concentration of antibody in lymph node metastases from breast carcinoma was 100% specific. In those lymph nodes that presumably contained no metastatic tumor but demonstrated localization of labeled antibody, retention of CEA in the nodes from tumor drainage is postulated as the receptor site for the antibody.

Detection of carcinoembryonic antigen in tissue sections by immunoperoxidase

A triple-bridge, indirect, immunoperoxidase method for detecting and localizing carcinoembryonic antigen (CEA) in tissue sections is described. By this technique, a cell-surface localization of CEA in colonic carcinoma and ovarian mucinous cystadenocarcinoma cells could be visualized. In the case of the colonic cancer, both the tumor from the descending colon and a metastasis to the skin gave positive peroxidase reactions for CEA. This immunocytochemical method for demonstrating the presence of CEA functioned in both frozen, ethanol-fixed and formalin-fixed, paraffin-embedded tissues, thus making it applicable for use with tissue sections conventionally prepared for light microscopy.