Global Journal of Medical Research, F: Diseases, Volume 23 Issue 2

relationship to the embryo. The immunology of pregnancy and cancer is similar [11]. Embryo and cancer cells exploit the mechanisms that allow them to grow despite the host’s immune system attacks. During pregnancy, the mother’s anti-embryo immune response is neutralized by the oncofetal proteins that re-appear during cancer development. Some of the oncofetal proteins are AFP, AFP receptor (AFPR), human chorionic gonadotropin (HCG), carcinoembryonic antigen (CAE), and pregnancy- associated protein A. A few molecules regulate the immune tolerance of the mother – AFP, HCG, glycodelin, and pregnancy-specific β 1-glycoprotein [12]. Cancers express oncofetal proteins at “a wrong time in a wrong place” to withstand immune system attacks. Forty years ago, oncofetal proteins were used for cancer patients’ vaccination. The placenta is the first organ that forms after conceiving—before any baby's organs even take shape. Immunotherapy with placental proteins has demonstrated a 77.1% 5-year survival rate and a 65.4% 10-year in 35 terminal patients [11]. (The handful of cancer immunotherapy drugs available today have demonstrated robust and durable results only in a minority of patients). AFP is the major oncofetal protein secreted in early post-implantation embryos of mammals; the ability to synthesize AFP is restricted to the visceral endoderm cells around the embryonic region of the egg cylinder [13]. Later in development, AFP is produced by the yolk sac, liver, and gastrointestinal tract and penetrates the mother’s blood (<200 ng/ml)(Fig. 1). Figure 1: AFP generated by embryo cells penetrates the mother’s blood. 8 Year 2023 Global Journal of Medical Research Volume XXIII Issue II Version I ( D ) F © 2023 Global Journals A Cancer Prevention and Treatment Opportunity AFP can be re-expressed in adult life in a few cancers: hepatomas, germ cell tumors, yolk sac tumors of the ovary, and gastrointestinal cancers. The AFP structure, functions, and clinical applications are well covered in the literature [14-18]. AFP and its peptides have immunomodulatory properties [19-21]. For example, AFP selectively induced a rapid downregulation of surface MHC class II antigens in their expression on human monocytes, thereby making embryo/tumor cells “invisible” to the immune system. MHC class II antigens on monocytes are the key molecules in antigen presentation. They differentiate between a self-cell and an “alien” embryo or cancer cell. AFP neither alters the expression of MHC I, CD4, CD18, CD45, and Fc receptors for IgG on the surface of monocytes/macrophages nor affects the functional maturation of the macrophages Fc receptors or the ability to express antibody-dependent cell- mediated cytolytic activity. AFP may, by reducing the antigen-presenting capacity of monocytes/ macrophages, function as an essential factor in maintaining a fetal allograft, as well as participate in the downregulation of the entire immune system in cancer [22]. Nevertheless, the primary immune regulatory impact is AFP ligands because AFP delivers dozens of molecules within 3-5 days of its half-life. Moreover, the AFP-binding monocytes play a fundamental role in regulating the immune response. The AFP's primary function is nutrient delivery in a shuttle manner (like oxygen delivery by hemoglobin). AFP binds different ligands, delivers them to the AFPR- positive cells, and releases them inside the cell compartment with an acidic pH. The 69 kDa AFP can hide 1-2 molecules (<2 kDa) in its hydrophobic cavity [23]. For example, docosahexaenoic acid (DHA) is not synthesized by the mother, who should take essential nutrients with food. AFP grabs DHA from albumin and transports it through the placenta [24]. Polyunsaturated fatty acids are necessary for many purposes, for