Role of LncRNA H19 in The Regulation of IGF-1R Expression: A Possible Association Between Type 2 Diabetes and Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a common cancer that poses a heavy economic burden on the healthcare system. It represents the fourth and sixth most common cancer in Egypt and worldwide respectively. Globally, HCC is the fourth most common cause of death from cancer. It was estimated to be responsible for nearly 9.1% of the total deaths in 2012 (746,000 deaths). In Egypt, it is the most common cause of cancer-related mortality, and morbidity (32.35% of the total cancer deaths, mortality data were derived from the World Health Organization (WHO)). The leading risk factor in developing HCC in Egypt is hepatitis C virus (HCV).

Diabetes mellitus (DM) is a metabolic disorder characterized by hyperglycemia, which may be caused by insufficient insulin secretion, insulin resistance, or augmented glucagon production. Cancer and type II diabetes (T2DM), The world's two most prevalent diseases, share many overlapping risk factors and predisposing pathological conditions. Although the T2DM-cancer co-existence has been noted for many decades, the exact mechanisms linking these diseases are yet to be fully understood.

Insulin-Like Growth Factor-1 Receptor (IGF-1R) is a member of the insulin and IGF family. It coordinates a complex downstream signaling network through which it plays essential roles in the regulation of cell growth, proliferation, and survival as well as in glucose homeostasis. IGF-1R plays a crucial role in many tumor-related courses, such as tumor growth and metastasis in addition to drug resistance. The IGF-1R dysregulated signaling pathways in cancer and DM have been reported to be controlled at different levels by non-coding RNAs.

Non-coding RNAs (ncRNAs) are a large category of RNAs that usually do not participate in protein encoding but have a wide range of biological functions through regulation of protein expression and functions. The two most researched classes of ncRNAs are microRNAs (miRNAs) and the long non-coding RNAs (lncRNAs). H19 is a lncRNA that is found to be overexpressed in many solid tumors including HCC. The relationship between H19 and IGF-1R expression levels in addition to the dysregulation of H19 in DM are still inconsistent in literature, warranting further investigations. Ghazal et al. noted that H19 levels are directly proportional to IGF-1R expression levels in women with endometriosis (Ghazal et al., 2015). This is conflicting with Farzi-Molan et al. who remarked the reverse relation between IGF-1R & H19 during the differentiation of Bone Marrow Mesenchymal Stem Cells (BMSCs) to neural cells