Introduction
Renal cell carcinoma (RCC) is a lethal urological malignancy; consist of approximately 3% of all human cancer and affecting generally men above 50 years of age (Ljungberg et al., 2010). There are several types of kidney cancer like Wilms tumors, transitional cell carcinomas and renal sarcomas, but most research has been focused on RCC. On the basis of morphology, genetic characteristics and clinical behavior RCC is classified as clear cell RCC (80-90%), papillary RCC (10-15%) and chromophobe RCC (4-5%). These are the most common and very well characterized (Ather et al.
, 2010), (Moch, 2013), (Algaba et al., 2011), (Basso et al., 2010). The clinical staging of renal tumors is classified on the basis of size, spreading tendency, presence of metastases and nodal involvement (Ljungberg et al., 2010), (Adam et al., 2014). If RCC is detected earlier in localized stage than it is curable through nephrectomy but if it is in advance and metastasized stage than there is lack of efficient therapeutic options (Cairns, 2010), (Vasudev et al., 2011). Changes in metabolism indicate early perturbations in physiology due to disease, which plays decisive role in cancer development.
Kidney is an organ after the brain that has been mostly exposed to NMR and MRI studies. Still specific biomarkers are not distinguished to detect cancer. In the arena of cancer detection and characterization, MRI is digital radiological tool, with arguable successful outcomes for more than adecade (Oliva et al., 2009), (Rosenkrantz et al., 2010). Despite the advantage, MRI is more expansive and not suitable for patients with medical implants are unsuited for MRI. Present indexes cannot identify RCC accurately and specifically therefore it is necessary to develop new approach to treat early detection of RCC to improve therapy of disease. Hence, early detection of the disease is most promising way to reduce RCC transience.
Metabolomics, the global quantitative assessment of endogenous small molecule metabolites within a biological system (Nicholson & Lindon, 2008) has been successfully utilized in biomarker discovery of cancer (Spratlin et al., 2009) such as breast cancer (Claudino et al., 2007) colon cancer (Qiu et al., 2009), oral cancer (Zhou et al., 2009), and prostate cancer (Kumar et al., 2016), Metabolites are the small chemical compounds or products involved in various metabolic pathways, and the changes of their levels might be responded to the changes of pathology or physiology (Nicholson & Lindon, 2008). Recently, Renal cancer was the focus of several studies (Gao et al., 2008), (Gao et al., 2012), (Ragone et al., 2016). Researchers tried to discover metabolic biomarkers for differentiating RCC patients from healthy persons. This may provide complete information of small molecules intermediates and can help in revolutionize disease detection and characterization. In this review, we will begin with the metabolic variations in biological matrix (tissue, urine and serum) during RCC, and later we will discuss briefly a summary of normal kidney function along with cellular bioenergitic pathways which will follow the metabolism of glucose, lipid, fatty acids and amino acid in renal cells of the specific location/areas of nephron. Purpose of the following review is threefold: 1. To persuade the reader that each part of the nephron plays an vital role in controlling renal filteration and reabsorption mechanism in normal and RCC patients. 2. Discuss about recent observations on metabolomics study, how metabolism alters during RCC within the proximal tubule and 3. To indicate some unresolved issues which should be discussed in future.