Diabetes is characterised by hyperglycemia, which is also a risk factor for cancer progression. High hyperglycemia has been linked to a number of direct and indirect processes that work together to enhance CC development [24]. Although deregulation of lncRNA has been linked to the advancement of colon cancer, the consequences of high glucose levels on their deregulation and, as a result, colon cancer are unknown.
High hyperglycemia (HG) may provide a favourable molecular environment for CC tumorgenesis in T2DM patients, according to the findings of this study. The current study found substantial differences in tumour differentiation, primary tumour invasion, lymph node metastasis, and TNM stage between diabetic and non-diabetic cancer colon patients, implying that diabetic patients have a worse prognosis. When compared to patients without hyperglycemia, Ramteke et al found that hyperglycemic cancer patients have a higher rate of metastasis and poorer outcomes [25]. In comparison to the normal glucose group, Cui et al found that CC patients in the HG group had bigger tumour sizes and lesser tumour differentiation. In addition, the HG group had a greater ratio of patients and more advanced TNM staging and more ulcerative CRC gross type [26].
According to the current study, one of the mechanisms of poorer clinical outcome of CC was deregulation of ANRIL and its taget; miR 186-5p. We found an upregulation of ANRIL expression levels and downregulation of miR 186-5p in diabetic colon cancer specimens in relation to those in non-diabetic colon cancer. In the current research there were significant positive correlations between the expression levels of ANRIL with blood glucose levels and HbA1c% and negative correlation between miR 186-5p and these diabetic biomarkers indicating that a high-glucose environment can enhance the tumor-promoting effect of ANRIL.
Human cancer and metabolic disease risk are linked to the CDKN2A/B genetic locus. Despite the fact that the locus contains multiple key protein-coding genes, studies suggest that a lesser-known antisense lncRNA encoded at this locus, dubbed ANRIL, may play a role in illness [10]. Because of its frequent overexpression in various malignancies and associated with a poor prognosis, ANRIL is considered an oncogene [27]. ANRIL RNA expression was considerably higher in tumour tissues of colon cancer patients with or without DM than in the distal normal intestinal mucosa in the current investigation. In addition, when compared to normal colon cells, ANRIL expression levels in Caco2 and SW620 colon cancer cell lines were much higher (FHC).
Previous research had found that ANRIL was substantially expressed in cancer tissues and cell lines from colon cancer patients [28, 29]. Although Gan et al. found considerable ANRIL overexpression in colon cancer tissues; they found no link between ANRIL lncRNA expression and colon cancer prognosis [28]. The new functions of ANRIL, which can enhance cell proliferation and transformation via stem-like cancer cell induction, have been established. ANRIL can also reprogram glucose metabolism to satisfy urgent energy needs by boosting glucose uptake for glycolysis to produce more ATP, which is regulated by the mTOR signal pathway [30]. ANRIL was shown to be substantially expressed in colon cancer cell lines, particularly the SW480 cell line, according to a recent study [31].
A previous study used a bioinformatics tool to determine target miRNAs for ANRIL, demonstrating the targeting of miR-186 with seven complementary binding sites. The luciferase reporter test verified their prediction. MiR-186 could reverse the action of ANRIL in cervical cancer cells in rescue tests, showing a physiological antagonism between ANRIL and miR-186 [15]. There was a negative connection between ANRIL and miR-186-5p expression in this investigation. A subsequent research in multiple myeloma [32] confirmed these findings.
In this investigation, miR 186-5p RNA expression was considerably higher in tumour tissues of colon cancer patients with or without DM than in the distal normal intestinal mucosa. In addition, when compared to normal colon cells (FHC), the expression of miR-186-5p was significantly reduced in Caco2 and SW620 colon cancer cell lines. This is similar to Li et al., who found that colorectal cancer cell lines (HT116, H29, SW620, and LoVo) have lower miR-186-5p expression than normal colonic epithelial cell line NCM460. Overexpression of MiR-186-5p in colorectal cancer cell line LoVo suppresses proliferation, metastasis, and epithelial-to-mesenchymal transition (EMT) [33]. MiR-186 was also found to be down-regulated in colon cancer tissues and highly metastatic SW620 and LoVo cells, according to Chen et al.
Concerning in vitro study of the current research, miR-186-5p expression was inhibited through the overexpressed ANRIL gene in a high glucose induced colon cancer cell lines.
The impact of the HG environment on ANRIL expression has been investigated in many cell types. ANRIL was upregulated in human retinal endothelial cells HRECs and diabetic mouse retinal tissues in response to high glucose and diabetes [11]. In HG-induced podocytes, LncRNA ANRIL was also substantially expressed [12]. When HG-treated mouse mesangial cells (SV40-MES13 cells) were compared to regular glucose-treated SV40-MES13 cells and osmotic control-treated SV40-MES13 cells, ANRIL expression was considerably higher. In HG-treated SV40-MES13 cells, knocking down Lnc-ANRIL decreased cell growth and accelerated cell death [13]. In HG-induced cardiomyocytes, however, Liu et al found low expression of miR-186-5p [35]. In AC16 cardiomyocytes, Jiang et al confirmed that downregulation of miRNA-186-5p causes HG-induced cytotoxicity and death [36].
Multiple targets controlled by a single miR can function in concert to regulate the same biological process. Bioinformatics prediction identified HIF-1 as the potential target gene of miR-186 (http://www.microrna.org/microrna/home.do). Through miR-186 introduction and ablation, the negative regulatory effect of miR-186 on HIF-1 was confirmed. The direct binding of miR-186 to HIF-1 was validated using a luciferase reporter experiment [21]. That was validated by other investigations. HIF-1 was a miR-186-5p downstream target [37, 38].
Downregulation of HIF-1 mediated by miR-186 is accompanied by a decrease in intracellular glucose and lactate levels in osteosarcoma cells, showing that miR-186 may restrict glycolysis via HIF-1 suppression [38]. In gastric cancer cell lines MKN45 and SGC7901, MiR-186 inhibits cell growth mediated by HIF-1 [39]. We discovered that downregulation of miR-186-5p facilitated increase of HIF-1 expression in the current study. HIF-1 promotes the synthesis of glucose transporters (Glut) and glycolytic enzymes, which improves glycolysis in cancer cells [22].
Hexokinase, an HIF-1 target gene, is one of the glycolytic pathway's rate-limiting enzymes [40]. There are four subtypes of hexokinase in mammals; type II is insulin-sensitive and overexpressed in poorly differentiated tumour tissues [41]. PFK-1 (phosphofructokinase 1), a possible transcriptional target of HIF-1, is another rate-limiting enzyme in the glycolytic process. PFK-1 is a tetrameric enzyme that comes in three different isoforms: platelet (PFKP), muscle (PFKM), and liver (PFKL), with PFKP being the most common in tumours [42].
We demonstrated that high glucose circumstances can promote glucose uptake, lactate accumulation and cell proliferation in two colon cancer cell lines through a series of in vitro investigations.
The capacity of cancer cells to alter glucose metabolism is one of their most dangerous characteristics. Normal metabolism produces enough energy to keep things running smoothly. The Warburg effect occurs when cancer cells shift to an inefficient glycolytic mode due to high energy demands, driving a large flux of resources into glycolysis rather than oxidative phosphorylation (OXPHOS). Cancer cells boost the synthesis of glycolytic intermediates by upregulating glycolysis. [43]. Cancer cells ingest more glucose than normal cells for this reason, giving them a selective advantage in nutrient-limited environments. These constraints do not exist in hyperglycemia since glucose is readily available. As a result, hyperglycemia stimulates glycolysis in a variety of cancer cells [44]. It improves metabolic reprogramming by increasing the expression of glycolytic enzymes such hexokinase-II (HK-2) and pyruvate kinase M. Lactate produced as a consequence of this rewiring is also used by tumour cells as a shuttle and energy source in areas where blood and oxygen cannot reach due to poor angiogenesis [45].
Under hyperglycemic conditions, normal cells develop slowly. In cancer, however, this process is reversed. Hyperglycemia provides the extra energy needed for cell proliferation. In vitro and under vivo, cancer cells multiply faster in high glucose environments with little apoptosis [46]. Studies in cancer cells show that hyperglycemia promotes cancer cell proliferation by oncogene or metabolic and molecular changes [25]. A recent study found that colon cancer cells cultivated with high glucose had better proliferation ability than colon cancer cells cultured with low glucose [47].
In the formation of malignant tumour cells, the anti-apoptotic impact is extremely important. This study looked at the levels of expression of apoptosis regulating genes including Bcl-2 and Bax in cancer colon cell lines. The results showed that as the glucose concentration in cancer cell lines increased, Bcl-2 expression increased and Bax expression dropped. The elevated production of HIF- is responsible for hyperglycemia's anti-apoptotic action [21, 48].
To our knowledge, the current findings are the first to show that a high-glucose environment can improve ANRIL's tumor-promoting function. ANRIL can promote colon cancer cell proliferation and change glucose metabolism by downregulating miR 186-5p, which leads to increased production of glycolysis enzymes and apoptosis inhibition. T2DM colon cancer patients exhibited a worse prognosis than those without diabetes, which could be because of their increased ANRIL expression.