Combination assay of urinary beta-core fragment of human chorionic gonadotropin with serum tumor markers in gynecologic cancers

Biomarkers in Gynecologic Tumors

Gynecologic malignancies are one of the most frequent cancers amongst women. Biomarkers are crucial for the differential diagnosis of adnexal masses; however, their potential for diagnosis is limited. In the era of difficulty in ovarian cancer screening, novel biomarkers are defined, but CA125 still remains the most valuable one. Circulating tumor DNAs, DNA hypermethylation, metabolites, microRNAs, and kallikreins have recently turned out as ovarian cancer biomarkers and are being applied to clinical practice. For uterine cancer, genomic classification has now been described, it will be used as a prognostic tool. In this chapter, we describe ovarian, endometrial, and cervical cancer biomarkers in detail.

Urinary Biomarkers and Their Potential for the Non-Invasive Detection of Endometrial Cancer

Endometrial cancer is the most common malignancy of the female genital tract and its incidence is rising in parallel with the mounting prevalence of obesity. Early diagnosis has great potential to improve outcomes as treatment can be curative, especially for early stage disease. Current tests and procedures for diagnosis are limited by insufficient accuracy in some and unacceptable levels of invasiveness and discomfort in others. There has, therefore, been a growing interest in the search for sensitive and specific biomarkers for endometrial cancer detection based on non-invasive sampling methodologies. Urine, the prototype non-invasive sample, is attractive for biomarker discovery as it is easily accessible and can be collected repeatedly and in quantity. Identification of urinary biomarkers for endometrial cancer detection relies on the excretion of systemic biomarkers by the kidneys or urinary contamination by biomarkers shed from the uterus. In this review, we present the current standing of the search for endometrial cancer urinary biomarkers based on cytology, genomic, transcriptomic, proteomic, and metabolomic platforms. We summarize the biomarker candidates and highlight the challenges inherent in urinary biomarker discovery. We review the various technologies with promise for biomarker detection and assess these novel approaches for endometrial cancer biomarker research.

The Role of Human Chorionic Gonadotropin as Tumor Marker: Biochemical and Clinical Aspects

Tumor markers are biological substances that are produced/released mainly by malignant tumor cells, enter the circulation in detectable amounts and are potential indicators of the presence of a tumor. The most useful biochemical markers are the tumor-specific molecules, i.e., receptors, enzymes, hormones, growth factors or biological response modifiers that are specifically produced by tumor cells and not, or minimally, by the normal counterpart (Richard et al. Principles and practice of gynecologic oncology. Wolters Kluwer Health, Philadelphia, 2009). Based on their specificity and sensitivity in each malignancy, biomarkers are used for screening, diagnosis, disease monitoring and therapeutic response assessment in clinical management of cancer patients.This chapter is focused on human chorionic gonadotropin (hCG), a hormone with a variety of functions and widely used as a tumor biomarker in selected tumors. Indeed, hCG is expressed by both trophoblastic and non-trophoblastic human malignancies and plays a role in cell transformation, angiogenesis, metastatization, and immune escape, all process central to cancer progression. Of note, hCG testing is crucial for the clinical management of placental trophoblastic malignancies and germ cell tumors of the testis and the ovary. Furthermore, the production of hCG by tumor cells is accompanied by varying degrees of release of the free subunits into the circulation, and this is relevant for the management of cancer patients (Triozzi PL, Stevens VC, Oncol Rep 6(1):7-17, 1999).The name chorionic gonadotropin was conceived: chorion derives from the latin chordate meaning afterbirth, gonadotropin indicates that the hormone is a gonadotropic molecule, acting on the ovaries and promoting steroid production (Cole LA, Int J Endocrinol Metab 9(2):335-352, 2011). The function, the mechanism of action and the interaction between hCG and its receptor continue to be the subject of intensive investigation, even though many issues about hCG have been well documented (Tegoni M et al., J Mol Biol 289(5):1375-1385, 1999).

HCG variants, the growth factors which drive human malignancies

The term human chorionic gonadotropin (hCG) refers to a group of 5 molecules, each sharing the common amino acid sequence but each differing in meric structure and carbohydrate side chain structure. The 5 molecules are each produced by separate cells and each having separate biological functions. hCG and sulfated hCG are hormones produced by placental syncytiotrophoblast cells and pituitary gonadotrope cells. Hyperglycosylated hCG is an autocrine produced by placental cytotrophoblast cells. Hyperglycosylated hCG drives malignancy in placental cancers, and in testicular and ovarian germ cell malignancies. hCGβ and hyperglycosylated hCGβ are autocrines produce by most advanced malignancies. These molecules, particularly the malignancy promoters are presented in this review on hCG and cancer. hCGβ and hyperglycosylated hCGβ are critical to the growth and invasion, or malignancy of most advanced cancers. In many ways, while hCG may appear like a nothing, a hormone associated with pregnancy, it is not, and may be at the center of cancer research.

hCG, five independent molecules

INTRODUCTION

The hCG amino acid sequence supports 5 glycoproteins. All are called hCG forms. This review examines all 5 molecules, the hormone as produced by the placental syncytiotrophoblast cells, the sulfated hormone produced by the pituitary gonadotrope cells, the hyperglycosylated hCG autocrine made by placental cytotrophoblast cells, and the autocrine cancer promoters hyperglycosylated hCG, hCGß and hyperglycosylated hCGß as made by all malignancies. This review examines all the molecules and multiple proven functions, ranging from evolution to cancer promotion to hormone action.

RESULTS AND DISCUSSION

hCG forms are critical super-growth factors in humans, with an exceptional wide range of functions.

Human chorionic gonadotropin in cancer

Human chorionic gonadotropin (hCG) is mainly used for detection and monitoring of pregnancy and pregnancy-related disorders but it is also an extremely sensitive and specific marker for trophoblastic tumors of placental and germ cell origin. Thus treatment of relapsing choriocarcinomas and testicular germ cell tumors is often initiated on the basis of rising hCG levels even in the absence of clinical or histological evidence of a relapse. While these tumors mostly produce the intact heterodimeric hormone consisting of an alpha (hCGalpha), and a beta subunit (hCGbeta), many nontrophoblastic tumors produce only hCGbeta This is usually a sign of aggressive disease and elevated serum levels of hCGbeta are strongly associated with poor prognosis. Elevated serum levels are observed in 45-60% of patients with biliary and pancreatic cancer and in 10-30% of most other cancers. Methods that detect hCG and hCGbeta together are mainly used for measurement of hCG-like immunoreactivity in serum. However, the reference range for hCG is 5-8 fold higher than that for hCGbeta and thus moderately elevated levels can be identified only with a specific and sensitive hCGbeta assay.

Human chorionic gonadotropin beta-core fragment is present in the human placenta

The presence of hCG beta-core fragment (beta-core) in the human placenta has been controversial. To clarify its presence in the villous tissue, first, we developed an enzyme immunoassay which is highly specific for beta-core. Then, we investigated the presence of beta-core immunoreactivity in the supernatants of placental organ culture and those of primary culture of trophoblasts as well as in the placental extracts at different stages of gestation. The immunoreactivity of beta-core was demonstrated in each sample, and the amount was at least 5% of intact hCG immunoreactivity. Immunohistochemical analysis of the placental tissue showed localization of beta-core immunoreactivity to the syncytiotrophoblast. Western blot analysis of the supernatants of organ culture as well as urine samples of pregnant women showed two major bands with molecular weight of approximately 15000. On the other hand, beta-core immunoreactivity in the pregnant sera ranged from 0.1 to 0.19% of intact hCG immunoreactivity. These results suggest the presence and possible secretion of beta-core fragment in the human placenta, and its immunoreactivity in the serum is likely to be reduced due to its short half life in the maternal blood.

Rising serum values of beta-subunit human chorionic gonadotrophin (hCG) in patients with progressive vulvar carcinomas

Elevated serum levels of the beta-subunit of human chorionic gonadotrophin (hCG) were measured in 50% of patients with locoregional recurrences or progressive vulvar carcinoma (n = 14). At diagnosis of vulvar cancer, however, the incidence of elevated serum levels was low (5%) in 104 patients. The rising serum levels during progression of disease indicate that the synthesis of the beta-subunit hCG can be increased in vulvar carcinoma.

Metabolism of hCG and hLH to multiple urinary forms

Human chorionic gonadotropin (hCG) is synthesized primarily in the placenta while human luteinizing hormone (hLH) is produced in the pituitary. Both hormones are highly homologous in structure and both appear to be altered to analogous molecular forms as the hormones are proteolytically processed, or metabolized, from tissue of origin, through the circulation, and finally to the urine. Placental hCG is excreted into urine as heterodimeric hormone, heterodimeric nicked hCG, free subunits (some nicked), and predominantly as the hCG beta core fragment. A pituitary form of heterodimeric hCG, which is partly sulfated as is pituitary hLH, was recently isolated and is likely the form of hCG observed in the urine of healthy postmenopausal women and nonpregnant premenopausal women as well. A pituitary form of the hLH beta core fragment, highly analogous in structure to that of urinary hCG beta core fragment, has been used to develop specific monoclonal antibody assays to measure urinary hLH beta core fragment which is excreted at significantly higher molar concentrations than is hLH in the urine of ovulating women 1 or 2 days after the LH surge. This fragment of LH appears in the urine of postmenopausal women as well. The development of the capability to distinguish the hCG beta core fragment from the hLH beta core fragment in urine may have useful applications in tumor marker assays, pregnancy tests, and menopause. While hCG urinary assays have been widely employed, urinary assays for hCG and hLH metabolites are much less used since the urinary molecular forms are only partly known. Our studies of hCG and hLH urinary metabolites are directed towards improvement of the utility of urinary measurements of molecules derived from these hormones. Since many of the molecular forms of these two hormones in urine differ from their forms in blood, it may be necessary to produce new immunoassays as well as novel urinary reference preparations to accurately measure these molecules within their urinary matrix.