Heterogeneity of antigen expression in advanced epithelial ovarian cancer

Understanding Inter-Individual Variability in Monoclonal Antibody Disposition

Monoclonal antibodies (mAbs) are currently the largest and most dominant class of therapeutic proteins. Inter-individual variability has been observed for several mAbs; however, an understanding of the underlying mechanisms and factors contributing to inter-subject differences in mAb disposition is still lacking. In this review, we analyze the mechanisms of antibody disposition and the putative mechanistic determinants of inter-individual variability. Results from in vitro, preclinical, and clinical studies were reviewed evaluate the role of the neonatal Fc receptor and Fc gamma receptors (expression and polymorphism), target properties (expression, shedding, turnover, internalization, heterogeneity, polymorphism), and the influence of anti-drug antibodies. Particular attention is given to the influence of co-administered drugs and disease, and to the physiological relevance of covariates identified by population pharmacokinetic modeling, as determinants of variability in mAb pharmacokinetics.

Role of the dynamic tumor microenvironment in controversies regarding immune checkpoint inhibitors for the treatment of non-small cell lung cancer (NSCLC) with EGFR mutations

Immunotherapy has been incorporated into the first- and second-line treatment strategies for non-small cell lung cancer (NSCLC), profoundly ushering in a new treatment landscape. However, both adaptive signaling and oncogenic (epidermal growth factor receptor (EGFR)-driven) signaling may induce PD-L1 upregulation in NSCLC. Nevertheless, the superiority of immune checkpoint inhibitors (ICIs) in advanced EGFR-mutant NSCLC is only moderate. ICIs appear to be well tolerated, but clinical activity for some advanced EGFR-mutant NSCLC patients has only been observed in a small proportion of trials. Hence, there are still several open questions about PD-L1 axis inhibitors in patients with NSCLC whose tumors harbor EGFR mutations, such as the effect of EGFR tyrosine kinase inhibitors (TKIs) or EGFR mutations in the tumor microenvironment (TME). Finding the answers to these questions requires ongoing trials and preclinical studies to identify the mechanisms explaining this possible increased susceptibility and to identify prognostic molecular and clinical markers that may predict benefits with PD-1 axis inhibition in this specific NSCLC subpopulation. The presence of multiple mechanisms, including dynamic immune TME profiles, changes in PD-L1 expression and low tumor mutational burdens, may explain the conflicting data regarding the correlation between PD-L1 axis inhibitors and EGFR mutation status. We conducted a review of this currently controversial topic in an attempt to aid in the decision-making process.

Targeting immune cells for cancer therapy

Recent years have seen a renaissance in the research linking inflammation and cancer with immune cells playing a central role in smouldering inflammation in the tumor microenvironment. Diverse immune cell types infiltrate the tumor microenvironment, and the dynamic tumor-immune cell interplay gives rise to a rich milieu of cytokines and growth factors. Fundamentally, this intricate cross-talk creates the conducive condition for tumor cell proliferation, survival and metastasis. Interestingly, the prominent impact of immune cells is expounded in their contrary pro-tumoral role, as well as their potential anti-cancer cellular weaponry. The latter is known as immunotherapy, a concept born out of evidence that tumors are susceptible to immune defence and that by manipulating the immune system, tumor growth can be successfully restrained. Naturally, a deeper understanding of the multifaceted roles of various immune cell types thus contributes toward developing innovative anti-cancer strategies. Therefore, in this review we first outline the roles played by the major immune cell types, such as macrophages, neutrophils, natural killer cells, T cells and B cells. We then explain the recently-explored strategies of immunomodulation and discuss some important approaches via an immunology perspective.

Relation between Ovarian Carcinoma-Associated Antigens in Tumor Tissue and Detached Cyst Fluid Cells of Patients with Ovarian Neoplasms

Aims

The expression and potential diagnostic value of ovarian carcinoma-associated antigens were estimated in different types of epithelial ovarian neoplasms. The comparison of antigenic expression was performed on solid tumor tissues and loose cyst fluid cells in individual cases of malignant and benign ovarian neoplasms.

Methods

All studies were performed using monoclonal antibodies (mAbs) against ovarian carcinoma-associated antigens (OC125, OV-TL3, OV632, 10B, 8C) by 3-step peroxidase-antiperoxidase test.

Results

All ovarian carcinoma-associated antigens were detected in most serous and endometrioid carcinomas. In mucinous carcinomas as well as in benign ovarian neoplasms these antigens were present only in some cases. Significant inter- and intratumoral immunological heterogeneity was evident; however, the antigens detectable in tissue sections were also found in detached cyst fluid cells.

Conclusions

Our results show that mAb show OV-TL3 is the best marker for endometrioid carcinomas and confirmed that mAbs OV632, OC125 and OV-TL3 could be good complementary markers for differentiating malignant and benign lesions in the ovary. The percentage content of all ovarian carcinoma-associated antigens in solid tumors and respective cyst fluid cells was comparable.

Cytomorphologic Characterization of Cell Subsets Isolated by Density Gradient Centrifugation from Tumor Effusions of Ovarian Endometrioid Carcinoma

Aims

Cytomorphologic characterization of tumor cell subsets, according to the stage of pathologic differentiation, and comparison of cellular composition in tumor cyst and ascitic fluids were carried out on individual patients with ovarian endometrioid carcinoma.

Methods

A density gradient centrifugation technique was applied to fractionate the cells from tumor effusions.

Results

The enrichment of cell forms representing individual stages of pathologic differentiation by gradient centrifugation facilitated their cytomorphologic characterization. According to cytomorphologic features, 5 discrete cell subpopulations were identified and catalogued. The cellular composition of tumor cyst and ascitic fluids in individual patients was similar, but the number of fractions and percentage of cell subsets differed.

Conclusions

The estimation of precise cytomorphologic criteria for cell forms in tumor effusions facilitated the cytologic diagnosis of ovarian endometrioid carcinoma. The possibility to concentrate poorly differentiated, frankly malignant cell subsets in low densities could significantly improve the diagnosis of tumor effusions.

Expression of CEA, Tag-72, and Lewis-Y antigen in primary and metastatic lesions of ovarian carcinoma

Ovarian carcinoma has a high mortality rate, because most ovarian carcinomas are detected at a late stage. Traditional therapies, such as surgical debulking and chemotherapy, have not been successful in improving the long-term survival of these patients. Alternative therapies targeting various biomarkers, such as carcinoembryonic antigen (CEA), Tag-72, and Lewis-Y antigen, have been developed to treat patients with advanced ovarian cancers. To ensure that therapies targeting these biomarkers are effective, it is imperative to determine whether there is any differential expression of these targeted biomarkers between primary and metastatic ovarian carcinomas. In the present study, primary and metastatic lesions from 68 and 58 patients, respectively, including primary and matched metastatic lesions from 31 patients, were evaluated for cytoplasmic and membranous expression of CEA (clone Col-1), Tag-72 (clone CC-49), and Lewis-Y antigen (clone BR-96) by immunohistochemistry. No significant differences were observed with cytoplasmic and membranous expression of Tag-72 (CC-49) and Lewis-Y antigen (BR-96) in the primary and metastatic, matched and unmatched lesions (Wilcoxon signed-rank test). Although there was no statistically significant difference in the scores of CEA (Col-1) between primary and metastatic lesions, 5 of 11 (45%) cases with positive staining with CEA (Col-1) demonstrated discordant results between primary and metastatic lesions. There was a moderate positive correlation of the cytoplasmic and membranous expression of Tag-72 (CC-49), as well as cytoplasmic expression of BR-96 between primary and metastatic ovarian carcinomas. There was a weak negative correlation between the membranous expression of CEA (Col-1) and that of Lewis-Y antigen (BR-96); however, the difference was not statistically significant. No correlation was observed with other combinations of biomarkers. Our findings suggest that samples from either primary or metastatic ovarian carcinomas can be used for the evaluation of the expression of Tag-72 (CC-49) and Lewis-Y antigen (BR-96) to identify targets for novel therapies in patients with disseminated ovarian carcinomas. CEA (Col-1), due to its low expression and variation in phenotypic expression between primary and metastatic lesions, should be evaluated carefully in metastatic lesions before targeting the CEA antigen with CEA (Col-1)-like antibodies.

The spectrum of immunohistochemical reactivity of monoclonal antibody DS6 in nongynecologic neoplasms

DS6 is a murine monoclonal antibody that was developed using ovarian serous adenocarcinoma as immunogen. DS6 reacts immunohistochemically with a tumor-associated antigen, CA6, which has only a limited range of expression in normal human tissues. CA6 is most characteristically expressed in type II pneumocytes, fallopian tube epithelium, and urothelium, but lacks expression in mesothelium. The authors recently reported the spectrum of reactivity of DS6 with a wide variety of neoplasms of the gynecologic tract and found DS6 to be highly characteristic of serous neoplasms. CA6 is also expressed in other müllerian-derived epithelial neoplasms of the gynecologic tissues, but is not typically expressed by ovarian intestinal-type mucinous neoplasms, mesothelioma, mesenchymal neoplasms, ovarian germ cell tumors, or sex cord-stromal neoplasms. In this study, the authors tested the monoclonal antibody DS6 with 1,202 nongynecologic neoplasms to characterize the full range of expression of antigen CA6. This study has shown that CA6 is highly expressed by many carcinomas of breast, pancreas, and urothelium, and also shows expression in some carcinomas of renal and pulmonary origin, and some neoplasms of other sites. DS6 immunoreactivity is not seen in the majority of neoplasms with hematopoietic, mesenchymal, or germ cell differentiation.

Expression profiles of 290 ESTs mapped to chromosome 3 in human epithelial ovarian cancer cell lines using DNA expression oligonucleotide microarrays

We have investigated previously the utility of oligonucleotide expression microarray technology in an analysis of four spontaneously transformed epithelial ovarian cancer (EOC) cell lines, TOV-21G, TOV-81D, OV-90, and TOV-112D. Here, we examine the expression of 290 expressed sequence tags (ESTs) that map to human chromosome 3 in a primary culture derived from normal ovarian surface epithelium (NOSE), NOV-31, and the four spontaneously transformed EOC cell lines. One of these cell lines, OV-90, harbors a deletion of an entire chromosome 3p arm. Whereas the most aggressive cell lines (OV-90, TOV-112D, and TOV-21G) exhibited the highest levels of expression, assessed by the mean of expression values of all ESTs, OV-90 showed the lowest mean of expression of ESTs that map to the 3p arm in comparison with TOV-112D and TOV-21G. This difference in expression profile of 3p ESTs in OV-90 is also reflected in the ratio of expression of ESTs on 3p versus the 3q arm and in that the expression values of ESTs that map to 3p were more often lower than higher in OV-90 in two-way comparisons with NOV-31, TOV-21G, and TOV-112D. The loss of a 3p arm does not affect the pattern of differential expression in analyses based on the range of numeric expression values of each EST or fold differences in expression for each EST in comparison with NOV-31. However, 25 differentially expressed ESTs were identified on the basis of threefold differences in expression values between NOV-31 and any EOC cell line; and six of these ESTs were differentially expressed uniquely in OV-90. The investigation of these ESTs could facilitate the identification of novel chromosome 3 genes implicated in ovarian tumorigenesis.

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.

Distribution of OV-TL 3 and MOv18 in normal and malignant ovarian tissue

AIMS

To analyse the distribution of OV-TL 3 and MOv18 in normal ovarian tissue to determine which antibody is most suitable for (radio)immunotherapy of ovarian carcinoma.

METHODS

The distribution of OV-TL 3 and MOv18 was determined using immunohistochemistry and flow cytometry.

RESULTS

Epithelial and other cells in many tissues, and leucocytes in peripheral blood, bone marrow and spleen stained positively with OV-TL 3. The staining pattern of MOv18 in normal tissues was more restricted and was confined to epithelial cells in the lung, kidney, pancreas, salivary gland, ovary, Fallopian tubes, and cervix. Reactivity was also observed with pneumocytes in the lung, tubuli in the kidney, acinar cells in the salivary gland and pancreas, in the placenta, and with Kupffer cells in the liver. The staining pattern of chimeric MOv18 was identical with the murine form. OV-TL 3 and MOv18 reacted with 100% and 98% (45/46) of the 46 tested epithelial ovarian cancers, respectively. In ovarian carcinoma tissue homogeneous staining of epithelial cells was observed with OV-TL 3 and more heterogeneous staining with MOv18. In 12 and nine patients, respectively, a difference in staining intensity for OV-TL 3 and MOv18 was observed between various tumour samples from the same patient.

CONCLUSION

MOv18 has greater therapeutic potential because of its restricted reactivity with normal tissues and especially, in contrast to OV-TL 3, its lack of reactivity with haematopoietic cells.

Monoclonal antibodies in the management of ovarian cancer. A clinical perspective

Despite recent advances in the conventional management of ovarian cancer, this disease remains the leading cause of death among the gynecologic malignancies, killing more American women each year than all other gynecologic cancers combined. As a tumor arising from a nonessential organ that remains primarily confined to the peritoneal cavity, ovarian cancer makes an attractive target for monoclonal antibodies (MoAb). Several MoAb have been developed that have actual or potential clinical use in the management of ovarian cancer. Serum assays using a MoAb against an ovarian cancer-associated antigen (CA 125) are currently in routine clinical use for monitoring the course of disease in women with known ovarian cancer. Such assays may play a role in multitechnique screening programs. Radiolabeled antibodies are under study for use in external imaging or intraoperative detection of ovarian cancer. Isotope-labeled antibodies also are being evaluated in the treatment of ovarian cancer as are antibodies coupled to drugs or biologic toxins. Some antibodies may have direct antitumor effects through binding to biologically active receptors or through immune effector functions. The use of antibody fragments, chimeric antibodies, human antibodies, and genetically engineered antibodies is under active investigation. MoAb have important potential for improving the diagnosis, monitoring of response to therapy, and treatment of ovarian cancer.

DNA-cytophotometry and immunocytochemistry in ovarian tumours of borderline malignancy and related peritoneal lesions

A total of 34 surgical specimens, obtained from 13 patients with ovarian tumours of borderline malignancy (OTBM), were investigated by conventional histology, immunocytochemistry and DNA cytophotometry. The lesions were obtained by primary ovarian surgery or second-look procedures and altogether comprised 19 (single and bilateral) OTBM, 8 cases of endosalpingiosis, 4 in situ and 2 invasive peritoneal implants and 1 overt adenocarcinoma. The morphological findings were related to follow-up data, which showed neoplasms with clinically malignant behaviour in 2 patients. The histology of the extra-ovarian manifestations was not associated with their immunocytochemical properties or with their DNA content. There were no correlations between the evolution of disease and microscopical features but the clinical course appeared to be linked to the DNA content of the extra-ovarian lesions, which was of greater prognostic importance than DNA ploidy of the ovarian tumours. Recurrence-free survival was noted in all 5 patients with diploid or euploid extra-ovarian proliferations, while the 2 clinically malignant cases fell into the group of 3 patients with noneuploid or aneuploid specimens. DNA estimations may be a methodology which increases the prognostic value of second-look procedures in OTBM patients.

Effect of differentiation agents on expression of CA 125, alkaline phosphatase, and cytokeratins in human ovarian adenocarcinoma cells (OVCA 433)

A number of chemical agents have been found to influence the proliferation, morphology, enzymatic activity, and antigen expression of neoplastic cells toward a more differentiated phenotype. We studied the effects of differentiating agents retinoic acid, sodium butyrate, and dibutyryl cyclic AMP on the expression of the tumor-associated antigen CA 125 and several biochemical markers of differentiation in cultured OVCA 433 ovarian cancer cells. Treatment of OVCA 433 cells with these agents for 96 hr reduced cellular proliferation and altered cellular morphology. Quantitation of cell surface CA 125 using flow cytometry revealed that CA 125 expression was reduced by 35-50%. The amount of CA 125 antigen shed into the culture media was reduced to a similar degree. In addition, differentiation inducers markedly enhanced cellular alkaline phosphatase activity and induced the expression of a 65-67-kDa cytokeratin. These findings provide support for the induction of a more differentiated phenotype by these agents.

Analysis of antigen expression at multiple tumor sites in epithelial ovarian cancer

The question of whether the antigenic phenotype of human epithelial ovarian cancer varies in a given patient between the primary tumor and metastatic sites or among metastatic sites themselves is an important issue in planning potential therapeutic strategies for ovarian cancer. We have obtained tumor specimens from at least two separate sites during operations on 12 patients with epithelial ovarian cancer, and we have typed these specimens with a group of 18 monoclonal antibodies that react with cell-surface glycoprotein and carbohydrate antigens, including blood group antigens. Antibodies with relative specificity for malignant cells as well as those that detect more widely distributed epithelial antigens were used. A total of 31 specimens from 12 patients with advanced adenocarcinoma (8 serous, 3 undifferentiated, 1 endometrioid) of the ovary were studied, including fresh ascites cells in two patients. Frozen sections of tumor specimens were stained with the antibodies by the indirect immunoperoxidase technique and graded semiquantitatively. Little difference was seen in antigenic expression of tumors that were obtained from various sites in the same patient for either the epithelial cell markers or blood group markers. Intratumoral antigenic heterogeneity was seen, but this was generally quite consistent within a given patient's specimens. As anticipated, variations in antigen expression were seen among specimens from different patients. The antigenic phenotype of the tumor specimens in a given patient, as determined immunohistochemically by our group of antibodies, showed only minor variation among primary and metastatic sites.

Gynecologic tumor markers

The advent of monoclonal technology has increased the potential utility of antibody-dependent tumor marker assays in gynecologic oncology. The availability of unlimited quantities of several pure monoclonal antibodies directed against novel epitopes on tumor-associated antigens has permitted development of highly sensitive assays for serum markers. Traditional assays for human chorionic gonadotropin (hCG), NB/70K and TA-4 have been improved. CA 125 has provided a useful first-generation marker for monitoring ovarian cancer and triaging patients with pelvic masses, despite limitations in sensitivity and specificity. In the next decade, the challenge is to identify new markers that will complement CA 125 in monitoring ovarian cancer and facilitate screening for occult early-stage disease. Strategies involving multiple markers and modalities may be required. Some markers may emerge through a more fundamental knowledge of the biology of gynecologic neoplasms, including the expression of growth factors and their receptors. Finally, the application of monoclonal antibodies to immunohistochemistry and radionuclide imaging also may provide new areas of diagnostic application for monoclonal antibodies in gynecologic oncology.