TAG-72 Expression in Primary, Metastatic and Hormonally Treated Prostate Cancer as Defined by Monoclonal Antibody CC49

Micro-hydrogel injectables that deliver effective CAR-T immunotherapy against 3D solid tumor spheroids

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CAR-T cells are encapsulated in injectable, gelatin-based microgels.

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Encapsulated CAR-T cells possessed high viability and retained T cell phenotype.

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CAR-T cells displayed potent on-target cytotoxicity to 3D solid tumor spheroids.

Chimeric antigen receptor (CAR-) T cells are revolutionizing cancer treatment, as a direct result of their clinical impact on the treatment of hematological malignancies. However for solid tumors, CAR-T cell therapeutic efficacy remains limited, primarily due to the complex immunosuppressive tumor microenvironment, inefficient access to tumor cells and poor persistence of the killer cells. In this in vitro study, an injectable, gelatin-based micro-hydrogel system that can encapsulate and deliver effective CAR-T therapy is investigated. CAR-T cells targeting TAG-72, encapsulated in these microgels possessed high viability (> 87%) after 7 days, equivalent to those grown under normal expansion conditions, with retention of the T cell phenotype and functionality. Microgel recovered CAR-T cells demonstrated potent on-target cytotoxicity against human ovarian cancer in vitro and on three-dimensional tumor spheroids, by completely eliminating tumor cells. The gelatin-based micro-hydrogels have the potential to serve as carrier systems to augment CAR-T immunotherapeutic treatment of solid tumors.

Improved targeting of an anti-TAG-72 antibody drug conjugate for the treatment of ovarian cancer

INTRODUCTION

Ovarian cancer has only a 17% 5-year survival rate in patients diagnosed with late stage disease. Tumor-associated glycoprotein-72 (TAG72), expressed in 88% of all stages of ovarian cancer, is an excellent candidate for antibody-targeted therapy, as it is not expressed in normal human adult tissues, except in the secretory endometrium.

METHODS

Using the clinically relevant anti-TAG72 murine monoclonal antibody CC49, we evaluated antibody drug conjugates (ADCs) incorporating the highly potent, synthetic antimitotic agent monomethylauristatin E (MMAE). MMAE was conjugated to CC49 via reduced disulfides in the hinge region, using three different types of linker chemistry, vinylsulfone (VS-MMAE), bromoacetamido (Br-MMAE), and maleimido (mal-MMAE).

RESULTS

The drug antibody ratios (DARs) of the three ADCs were 2.3 for VS-MMAE, 10 for Br-MMAE, and 9.5 for mal-MMAE. All three ADCs exhibited excellent tumor to blood ratios on PET imaging, but the absolute uptake of CC49-mal-MMAE (3.3%ID/g) was low compared to CC49-Br-MMAE (6.43%ID/g), at 142 hours. Blood clearance at 43 hours was 38% for intact CC49, about 24% for both CC49-VS-MMAE and CC49-Br-MMAE, and 7% for CC49-mal-MMAE. CC49-VS-MMAE was not further studied due to its low DAR, while CC49-mal-MMAE was ineffective in the OVCAR3 xenograft likely due to its rapid blood clearance. In contrast, CC49-Br-MMAE treated mice exhibited an average of a 15.6 day tumor growth delay and a 40% increase in survival vs controls with four doses of 7.5 or 15 mg/kg of CC49-Br-MMAE.

CONCLUSION

We conclude that CC49-Br-MMAE with a high DAR and stable linker performs well in a difficult to treat solid tumor model.

The expansion of targetable biomarkers for CAR T cell therapy

Biomarkers are an integral part of cancer management due to their use in risk assessment, screening, differential diagnosis, prognosis, prediction of response to treatment, and monitoring progress of disease. Recently, with the advent of Chimeric Antigen Receptor (CAR) T cell therapy, a new category of targetable biomarkers has emerged. These biomarkers are associated with the surface of malignant cells and serve as targets for directing cytotoxic T cells. The first biomarker target used for CAR T cell therapy was CD19, a B cell marker expressed highly on malignant B cells. With the success of CD19, the last decade has shown an explosion of new targetable biomarkers on a range of human malignancies. These surface targets have made it possible to provide directed, specific therapy that reduces healthy tissue destruction and preserves the patient's immune system during treatment. As of May 2018, there are over 100 clinical trials underway that target over 25 different surface biomarkers in almost every human tissue. This expansion has led to not only promising results in terms of patient outcome, but has also led to an exponential growth in the investigation of new biomarkers that could potentially be utilized in CAR T cell therapy for treating patients. In this review, we discuss the biomarkers currently under investigation and point out several promising biomarkers in the preclinical stage of development that may be useful as targets.

Oncolytic virotherapy for urological cancers

Oncolytic virotherapy is a cancer treatment in which replication-competent viruses are used that specifically infect, replicate in and lyse malignant tumour cells, while minimizing harm to normal cells. Anecdotal evidence of the effectiveness of this strategy has existed since the late nineteenth century, but advances and innovations in biotechnological methods in the 1980s and 1990s led to a renewed interest in this type of therapy. Multiple clinical trials investigating the use of agents constructed from a wide range of viruses have since been performed, and several of these enrolled patients with urological malignancies. Data from these clinical trials and from preclinical studies revealed a number of challenges to the effectiveness of oncolytic virotherapy that have prompted the development of further sophisticated strategies. Urological cancers have a range of distinctive features, such as specific genetic mutations and cell surface markers, which enable improving both effectiveness and safety of oncolytic virus treatments. The strategies employed in creating advanced oncolytic agents include alteration of the virus tropism, regulating transcription and translation of viral genes, combination with chemotherapy, radiotherapy or gene therapy, arming viruses with factors that stimulate the immune response against tumour cells and delivery technologies to ensure that the viral agent reaches its target tissue.

Pretargeting CWR22 prostate tumor in mice with MORF-B72.3 antibody and radiolabeled cMORF

PURPOSE

We have now applied our MORF/cMORF pretargeting technology to the targeting of CWR22 prostate tumor in nude mice.

METHODS

The antiTAG-72 antibody B72.3 was conjugated with an 18 mer MORF while the cMORF was radiolabeled with (99m)Tc. The specific binding of the antibody to the CWR22 cells was first confirmed in an assay placing the radiolabeled B72.3 antibody in competition with increasing concentrations of native B72.3. Thereafter, a group of four CWR22 tumored mice intravenously received the MORF-B72.3 and, 3 days later, the (99m)Tc-cMORF, and were killed at 3 h postradioactivity injection. The dosage of the labeled cMORF was selected on the basis of previous experience in LS174T tumored mice. As controls, four animals received only the radiolabeled cMORF and another four received only the (111)In-B72.3. The maximum percent tumor accumulation (MPTA) of the labeled cMORF was subsequently determined by a dosage study of labeled cMORF. Both a multipinhole SPECT image and a planar gamma camera image were obtained of a representative mouse.

RESULTS

The CWR22 tumor was confirmed to be TAG-72-positive. The MPTA of the labeled cMORF in the CWR22 tumor was 2.22%ID/g compared to only 0.12%ID/g in control mice without pretargeting. Both the planar and tomographic images confirmed the success of the CWR22 pretargeting.

CONCLUSIONS

The MORF/cMORF pretargeting approach has been successfully applied to tumor targeting of the prostate xenograft CWR22. However, the MPTA in this tumor model is lower than that in the LS174T tumor model investigated earlier, possibly due to a lower tumor blood supply.

Targeting osseous metastases: rationale and development of radio-immunotherapy for prostate cancer

For patients with metastatic prostate cancer, bone is the primary site of tumor localization and the major cause of disease-related morbidity and mortality. Hormonal therapy and chemotherapy alone cannot eradicate disease harbored in bone. The delivery of radiotherapy to the reservoir of disease is an approach previously only achievable using bone-seeking radiopharmaceuticals. Now, however, with the identification of tumor-specific targets, antibodies are being used to deliver radiotherapy to these sites. In this article, we review the rationale behind this approach, the targets being explored, the radiation sources available, and the antibodies currently under clinical development.

Targeting osseous metastases: rationale and development of radio-immunotherapy for prostate cancer

For patients with metastatic prostate cancer, bone is the primary site of tumor localization and the major cause of disease-related morbidity and mortality. Hormonal therapy and chemotherapy alone cannot eradicate disease harbored in bone. The delivery of radiotherapy to the reservoir of disease is an approach previously only achievable using bone-seeking radiopharmaceuticals. Now, however, with the identification of tumor-specific targets, antibodies are being used to deliver radiotherapy to these sites. In this article, we review the rationale behind this approach, the targets being explored, the radiation sources available, and the antibodies currently under clinical development.

DC therapy for prostate cancer

The wide range of currently available treatments for metastatic prostate cancer have demonstrated a modest palliative effect, but none to date has shown an increase in overall survival. The immune system has evolved to protect against infection, however, the modulation of this system represents the possibility of allowing it to identify and destroy cancer cells. The immune system is capable of inciting a powerful immune response against tissues, in the form of transplant rejection, and the potential exists to harness these powers to fight against tumors. Modest clinical responses have been seen in patients with metastatic prostate cancer treated with DC therapies; however, no increase in overall survival has been demonstrated. The current state of DC immunotherapy for prostate cancer is reviewed.

Fully synthetic carbohydrate-based vaccines in biochemically relapsed prostate cancer: clinical trial results with alpha-N-acetylgalactosamine-O-serine/threonine conjugate vaccine

PURPOSE

We report the synthesis of a mucin-related O-linked glycopeptide, alpha-N-acetylgalactosamine-O-serine/threonine (Tn), which is highly simplistic in its structure and can induce a relevant humoral response when given in a trimer or clustered (c) formation. We tested for an antitumor effect, in the form of a change in the posttreatment versus pretreatment prostate-specific antigen (PSA) slopes, that might serve as a surrogate for effectiveness of vaccines in delaying the time to radiographic progression.

METHODS

We compared the antibody response to immunization with two conjugates, Tn(c)-keyhole limpet hemocyanin (KLH) and Tn(c)-palmitic acid (PAM) with the saponin immunologic adjuvant QS21, in a phase I clinical trial in patients with biochemically relapsed prostate cancer. Patients received Tn(c)-KLH vaccine containing either 3, 7, or 15 microg of Tn(c) per vaccination. Ten patients received 100 microg of Tn(c)-PAM. QS21 was included in all vaccines. Five vaccinations were administered subcutaneously during 26 weeks with an additional booster vaccine at week 50.

RESULTS

Tn(c), when given with the carrier molecule KLH and QS21, stimulated the production of high-titer immunoglobulin M (IgM) and IgG antibodies. Inferior antibody responses were seen with T(c)-PAM. There was no evidence of enhanced immunogenicity with increasing doses of vaccine. An antitumor effect in the form of a decline in posttreatment versus pretreatment PSA slopes was also observed.

CONCLUSION

A safe synthetic conjugate vaccine in a trimer formation was developed that can break immunologic tolerance by inducing specific humoral responses. It seemed to affect the biochemical progression of the disease as determined by a change in PSA log slope.

Advances in prostate cancer immunotherapy

Metastatic prostate cancer remains incurable. Harnessing the body's own immune system to control or eradicate tumours has long been an attractive concept. Only recently has the field of tumour immunology provided the basic science behind the mechanisms of tumour genesis, molecular basis of the recognition of tumour associated antigens and the interactions of the antigen-presenting cells with effector cells. This research has been translated into numerous clinical immunotherapy strategies, which have reached the oncology clinic and which should provide options for our patients.

Immunohistochemical distribution of tumor-associated antigen CA6 in gynecological neoplasms as detected by monoclonal antibody DS6

DS6 is a murine monoclonal antibody developed using ovarian papillary serous adenocarcinoma as the immunogen. DS6 immunohistochemically reacts with a tumor-associated antigen, CA6, which has a limited range of expression in normal human tissues and is not expressed by benign mesothelium. We have studied the spectrum of immunohistochemical reactivity of antibody DS6 in 293 formalin-fixed, paraffin-embedded human gynecological neoplasms. The CA6 antigen shows strong expression in serous adenocarcinomas of the ovary (56/58 cases) and endometrium (6/6). CA6 is also expressed by the majority of ovarian endometrioid adenocarcinomas and Brenner tumors and by the majority of endometrioid adenocarcinomas, mucinous adenocarcinomas, and clear cell adenocarcinomas of the endometrium. CA6 is detected in 14% of ovarian clear cell carcinomas and is not detected in ovarian mucinous cystadenomas (0/7), mucinous intestinal-type borderline tumors (0/8), mucinous adenocarcinomas (0/10), or in malignant mesotheliomas (0/8). In neoplasms with papillary or glandular growth patterns, CA6 is detected along luminal cell membranes. CA6 is also seen along peripheral cell membranes and focally in the cytoplasm in some epithelial neoplasms. There is heterogeneity in immunohistochemical staining for DS6 both within an individual neoplasm and between neoplasms. Reactivity is not detected in neoplasms of sex cord-stromal, mesenchymal or germ cell origin.

Immunophenotype of high-grade prostatic adenocarcinoma and urothelial carcinoma

Morphologic features alone can usually be used to distinguish prostatic adenocarcinoma and urothelial carcinoma of the urinary bladder. Poorly differentiated tumors, however, can occasionally have features of both neoplasms, making determination of site of origin difficult. No study has provided a panel of antibodies to assist in the distinction of these two tumors. For this study, 73 examples of moderately and poorly differentiated prostatic adenocarcinoma and 46 examples of high-grade urothelial carcinoma were obtained from radical resection specimens. Immunohistochemical studies were performed using the following panel of antibodies: cytokeratin (CK) 7, CK 20, 34betaE12, Leu M1, carcinoembryonic antigen (CEA)m, CEAp, p53, Leu 7, prostate-specific acid phosphatase (PSAP), prostate-specific antigen (PSA), and B72.3. Mucicarmine was also performed. Intermediate and high-grade prostatic carcinoma were compared and then high-grade prostatic carcinoma was compared with high-grade urothelial carcinoma. PSA and PSAP each stained 94% of prostatic adenocarcinomas, but no urothelial carcinomas. Leu 7 stained 94% of prostate and 17% of urothelial carcinomas. Over half of the urothelial carcinomas showed positivity for 34betaE12 (65%), as did two cases of prostatic carcinoma (6%). Eighty-three percent of urothelial carcinomas and 12% of prostatic adenocarcinomas stained with CK 7. Forty-one percent of urothelial carcinomas and 12% of prostatic carcinomas were reactive for CEAm, and p53 stained 33% and 3% of urothelial and prostatic adenocarcinomas, respectively. No significant difference was seen in the expression of CEAp, CK 20, B72.3, Leu M1, or mucicarmine between prostate and urothelial carcinoma. We propose a panel of six antibodies to assist in the distinction of high-grade prostatic adenocarcinoma from high grade urothelial carcinoma: PSA, PSAP, 34betaE12, Leu 7, CK 7, and p53. The first three antibodies should be used initially; if results are negative, the remaining antibodies may be employed.

Prospects for vaccination in prostate cancer

Prostate cancer continues to be a major cause of morbidity and mortality. Surgical and medical management of the disease has improved but there is little effect upon overall survival. Novel therapies such as immunotherapy offer the potential of treating the disease by stimulating the immune system to mount a response to the cancer systemically. This review highlights the pitfalls and progress in the understanding of the role of the immune system in malignancy and also explains the theory behind prostate cancer vaccine trials.

Risk of concurrent prostate cancer in cystoprostatectomy specimens is related to volume of high-grade prostatic intraepithelial neoplasia

OBJECTIVES

To assess the relationship of prostatic intraepithelial neoplasia (PIN) with both incidental and clinical carcinoma of the prostate.

METHODS

We retrospectively reviewed prostate histology in 48 men (group 1) who underwent surgical removal of the prostate for diagnoses other than prostate cancer, as well as in 64 men (group 2) who underwent radical prostatectomies. Both groups were assessed for the presence and extent of high-grade (HG-) PIN and compared with respect to patient age, Gleason score, and volume of prostate cancer.

RESULTS

HG-PIN was present in 40 of 48 (83%) group 1 cases. Forty-six percent of these cases (22 of 48) had incidental prostate cancer. Twenty-nine of 48 (60%) group 1 patients with HG-PIN had multifocal or extensive disease. Twenty of 22 (91%) incidental prostate cancers were present in 29 prostates with multifocal or extensive HG-PIN. In contrast, only 2 of 19 (11%) cases with absent to focal HG-PIN had prostate cancer. The association of multifocal or extensive HG-PIN with incidental prostate cancer was significant (P = 0.001); the relationships of extent of HG-PIN and cancer volume (P = 0.06) or high Gleason score (P = 0.017) were not significant. HG-PIN was present in 61 of 64 (95%) group 2 cases. The associations of extent of HG-PIN and cancer volume (P = 0.169) or high Gleason score (P = 0.156) were not significant.

CONCLUSIONS

Both the low rate of incidental prostate cancer in specimens with absent to focal HG-PIN and the high rate of cancer in specimens with multifocal or extensive HG-PIN suggest that HG-PIN is a marker for concurrent prostate cancer and that the risk of concurrent prostate cancer is related to the volume of HG-PIN in the prostate gland.

Changes in biomarker expression in the development of prostatic adenocarcinoma

In spite of the prevalence of prostatic adenocarcinoma, the development and natural history of this malignancy is poorly understood. This paper reviews the current knowledge of biomarker expression during the development and progression of prostatic adenocarcinoma. Emphasis is placed on the comparison of biomarker expression in benign prostatic epithelium, intraepithelial neoplasia (PIN), a putative preinvasive lesion, and prostatic adenocarcinoma. Within the benign epithelium, the proliferative potential is restricted to the basal cells as demonstrated by the expression of proliferating cellular nuclear antigen (PCNA). The strong expression of the bcl-2 protein, an inhibitor of a apoptosis, supports the concept that the basal cells or a subpopulation of the basal cells represent the stem cell of the epithelium. In addition, the strong expression of growth factor receptors such as the epidermal growth factor receptor (EGFr), p185erbB-2, p180erbB-3, and c-met suggests that the growth of the basal cells is regulated by autocrine or paracrine factors. The luminal cells express secretory products such as prostate specific antigen and prostatic acid phosphatase, but demonstrate little expression of PCNA as well as growth factor receptors and proto-oncogene products. These observations are consistent with the theory that the luminal cell population is derived from the differentiation of the basal cells. In contrast to the normal epithelium, PCNA expression is frequently detected in the dysplastic luminal cells of the PIN lesion. Likewise, strong expression of p185erbB-2, p180erbB-3 and the c-met proto-oncogene product is also detected in the luminal cells of PIN lesions. Other factors which are strongly expressed by the dysplastic luminal cells include the nm23-H1 gene product, tumor associated glycoprotein-72 (TAG-72), fatty acid synthetase (FASE) and proteolytic enzymes. These findings suggest that PIN lesions are derived from an impairment of the differentiation of basal cells. The majority of biomarkers such as PCNA, p185erbB-2, P180erbB-3, TAG-72, nm23-H1 and FASE which are strongly expressed in PIN lesions are also expressed in prostatic adenocarcinoma supporting the concept that PIN is a preinvasive lesion. Mutations of the p53 tumor suppressor gene, as well as strong expression of transforming growth factor alpha and bcl-2 typically occur in advanced stage prostatic adenocarcinomas and therefore likely represent late events in the development of prostatic adenocarcinoma.

Molecular biology of prostatic intraepithelial neoplasia

High-grade PIN is the most likely precursor of prostatic adenocarcinoma, according to virtually all available evidence to date. The clinical importance of recognizing PIN is based on its strong association with prostatic carcinoma. PIN has a high predictive value as a marker for adenocarcinoma. Its identification in biopsy specimens of the prostate warrants further search for concurrent invasive carcinoma. PIN is associated with progressive abnormalities of phenotype and genotype intermediate between normal prostatic epithelium and cancer, indicating impairment of cell differentiation and regulatory control with advancing stages of prostatic carcinogenesis. There is progressive gain or loss of a wide variety of biomarkers, including morphometric markers, differentiation markers, stromal markers, growth factors and associated receptors, oncogenes, tumor suppressor genes, and chromosomes. Abnormalities in expression of most biomarkers are amplified in the progression from high-grade PIN to localized cancer, metastatic cancer, and hormone-refractory cancer. Oncogenesis of prostatic carcinoma probably occurs through the selection of several genetic changes, each modifying the expression or function of genes controlling cell growth and differentiation. Further studies are needed to evaluate the function and prognostic value of oncogene expression in the normal, preneoplastic, and neoplastic prostate.