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The aim of the study was to evaluate the serum lipid profile among untreated oral squamous cell carcinoma (OSCC) and oral submucous fibrosis (OSMF) patients.
This study was done in three groups of patients - OSMF, OSCC, and control. There are twenty participants in each group. Calorimetric method using semi-autoanalyzer was used for analyzing the lipid levels (cholesterol, triglycerides [TGL], and high-density lipids [HDL]) after collecting 2 ml of fasting blood from these patients. Low-density lipid [LDL] values were obtained by calculator method.
There was a significant decrease in serum lipid levels of patients with OSMF and OSCC.
The decrease in lipid levels in OSMF and OSCC patients is due to its utilization by the cells during the cancer process.
“Early detection is otherwise called secondary prevention”
Early detection is the key for oral cancer control. Premalignant lesions and conditions usually precede oral cancer. Oral submucous fibrosis (OSMF), an insidious chronic disease, reported mainly in Indians associated with the use of areca nut is a precancerous condition and has a significant tendency to develop oral and esophageal cancer.
The relation of high lipid profile and coronary heart disease is well established. Several carcinomas such as colon, breast, ovarian, and prostrate have hypercholesterolemia as a predisposing factor. By contrast, the relation of serum lipid profile and oral cancer is inversely proportional. Rose et al. were the first person to report the inverse association.
The search for molecular markers in body fluids for detecting cancer has not ceased. Serum lipids can be one such reliable marker. To add to the curiosity of the unanswered question whether hypolipidemia is a cause or effect of cancer, this study was aimed at analyzing the serum lipid profile in OSMF and OSCC patients [Figures [Figures11 and and22].
The study subjects were selected from those who visited the Outpatients Department of Oral Medicine and Radiology Vinayaka Mission's Sankarachariyar Dental College, Salem. Informed consent was obtained from all the participants. The control group included 20 patients who visited the hospital for some other minor dental procedures such as prophylaxis and restorative treatment who were otherwise healthy. There were two study groups. Group 1 consisted of twenty clinically and histopathologically diagnosed new cases of OSMF and Group 2 consisted of twenty clinically and histopathologically diagnosed new cases of OSCC. Participants were excluded if they were suffering from any other major illness in the recent past or systemic disorder, especially uncontrolled diabetes, hypertension, thyroid disorders, and liver dysfunction. Subjects who were obese were also excluded from the study.
This study was initiated after obtaining the Ethical Committee clearance. After taking thorough case history and clinical examination of the lesion, informed written consent was obtained and biopsy was done under aseptic conditions. The tissue was fixed in 10% formalin solution and sent for histopathological examination. Complete blood count was done for all patients before biopsy. A volume of 2 ml of fasting (10–12 h) blood was collected following proper asepsis using 3 ml syringe and stored in a plain sterile glass bulb [Figure 3] and was allowed to clot for 20 min at 37°C in the incubator. The samples were centrifuged [Figure 3] at 3000 rpm. The serum was separated and stored at 4°C until analyzed.
Plasma cholesterol values were estimated using Enzymatic colorimetric method using cholesterol kit obtained from Merck diagnostics. The cholesterol kit [Figure 4] reagent contains phenol sodium cholate, 4-aminoantipyrine, cholesterol esterase, cholesterol oxidase, and peroxidase. To 500 μl of reagent, 5 μl of sample was added and mixed well and was incubated for 5 min at room temperature. A semi-automated analyzer was used and the values were read at a wavelength of 505 nm at 37°C.
Plasma triglyceride values are estimated by Enzymatic colorimetric method using in vitro diagnostic reagents (triglyceride kit) obtained from Merck diagnostics. The triglyceride kit [Figure 4] contains magnesium ion, p-chlorophenol, ATP, potassium ferrocyanide, lipoprotein lipase, glycerol kinase, glycerol-3-phosphate oxidase, and peroxidase. To 1000 μl of reagent, 10 μl of sample was added and mixed well and was incubated for 10 min at 37°C. A semi-automated analyzer [Figure 1] was used and the values were read at a wavelength of 505 nm at 37°C.
Plasma HDL values are estimated by Direct Enzymatic–Liquid method using in vitro diagnostic reagents (HDL kit) obtained from Lab kit diagnostics [Figure 4]. The HDL kit contains two reagents (R1 and R2): R1 contains N1N-BIS (2-hydroxyethyl)-2-aminoethane sulfonic acid, cholesterol esterase, cholesterol oxidase, catalase, and ascorbic oxidase HDAOS. R2 contains N1N-BIS (2-hydroxyethyl)-2-aminoethane sulfonic acid and peroxidase 4-Amino-antipyrine (4-AP). To 300 μl of reagent, 3 μl of sample was added and mixed well and was incubated for 5 min at 37°C. After which 100 μl of R2 is added and incubated for 5 min at 37°C, the readings are read immediately at 600 nm.
Calculator method - TGL ÷ 5-CHOLESTROL + HDL
Collected data were analyzed using SPSS 16. Percentages, mean, standard deviation, and one-way ANOVA with Bonferroni correction and Scheffe post hoc at 95% confidence interval was used to analyze and present the data.
There is a significant difference between the means of normal, OSMF, and oral cancer patients in total cholesterol, high-density cholesterol, and low-density cholesterol. There is no significant difference between means in triglycerides [Table 1 and Figure 5].
The question whether hypolipidemia is a predisposing factor or result of cancer, still remains unanswered. In some malignant diseases, blood cholesterol undergoes early and significant changes. Low levels of cholesterol in the proliferating tissues and in blood compartments could be due to the process of carcinogenesis. The previous literatures evidence that hypolipidemia may result due to the direct lipid lowering effect of tumor cells or secondary to malfunction of the lipid metabolism.
There are three main competing hypotheses to explain the relation between low cholesterol and oral cancer. (a) Low cholesterol may be an indicator of cancer process even before cancer manifests clinically. (b) Low cholesterol serves as a marker for some other causal sets of variables, and its association with oral cancer may be secondary even though if it precedes cancer. (c) Low cholesterol levels may precede the development of cancer and may be causally associated with some forms of cancer. Taking cue from these statements, the present study was undertaken to compare the serum lipid profile of patients with premalignant condition (OSMF) and OSCC with that of control subjects.
OSMF has always been a challenging disease with high prevalence in India. In this study, most of the OSMF cases were in the 2nd and 3rd decades of life and there was a prominent male predilection which positively supports other authors such as Mehrotra et al. and Lohe et al. Attempts were made to select patients in a wide range of age 20–70 in all the groups to avoid bias in the values of lipid as age plays a role in serum lipid concentrations; however, it is unavoidable to get OSMF patients in the 2nd decades and oral cancer patients in the 5th and 6th decades.
In this study, all the patients with OSMF had the habit of tobacco chewing and almost 75% of patients with oral cancer were tobacco chewers. All the patients were categorized under three types of chewing habits: tobacco, betel nut, and betel leaf with slaked lime. Almost all the patients with OSMF were tobacco chewers alone or in combination with betel leaf and nut. Lohe et al. categorized patients under 14 types of chewing. According to her tobacco chewing in the form of readily available pouch or tobacco with lime and bidi/cigarette were common among patients with oral precancerous conditions.
Increased lipid peroxidation leads to increased breakage of cellular structural blocks such as lipids automatically leading to decreased lipid levels. The carcinogens present in tobacco cause increased lipid peroxidation by releasing reactive oxygen species and lipid peroxides. Patel et al. in his study have observed a significant decrease in lipid levels in tobacco chewers when compared to nonchewers. Neufeld et al. have reported passive smoking as a significant risk factor for decreased HDLC. This study can also serve as an example as most of our patients are smokers and had a decreased lipid profile.
Histopathologically, patients with squamous cell carcinoma were graded as well differentiated, moderately differentiated, and poorly differentiated. Lohe et al. in her study correlated the serum lipid profile in these three groups and found no significance.
Chawda et al. found while comparing all the lipid levels between three different groups of oral cancer patients, there was no significant difference found. Most of the cases included in this study belong to well-differentiated squamous cell carcinoma.
In this study, there was a significant decrease in plasma total cholesterol, HDL cholesterol, and LDL cholesterol among the patients with OSMF and OSCC when compared to that of normal subjects. Plasma triglycerides showed no significant difference between the groups. Alexopoulos et al. have found nonsignificant difference in serum triglycerides between controls and patients. While others have observed elevated triglycerides levels in cancer patients such as Halton et al.
Hypertriglyceridemia may also predispose to malignancy. Elevated triglyceride levels have been demonstrated in patients with several different types of cancer. However, they found a nonsignificant difference in serum triglycerides between controls and cancer patients. The exact mechanism by which hypertriglyceridemia and decreased HDL-cholesterol concentration occurs in patients with cancer is not known. It has, however, been suggested that lipoprotein lipase (LPL) may regulate the clearance of TG from blood to tissue and its activity in white adipose tissue is decreased in patients with cancer, thus contributing to hypertriglyceridemia. Since precursor particles of HDL-cholesterol are thought to derive from lipolysis of TG, and the LPL activity is decreased in cancer, increased plasma TG may be one of the factors that results in lower HDL cholesterol concentration. However, in contradiction to this, there was a significant decrease in HDL in our study, but there was no significant decrease in triglyceride levels.
Gupta observed a significant decrease in plasma total cholesterol, HDLC, and triglycerides in the patients with the precancerous lesions and conditions as compared to the controls which is in accordance with this study except for triglyceride levels. This may be due to the fact that the sample size is comparatively higher. However, Gupta showed a higher levels of cholesterol and lower levels of HDLC and triglycerides as compared to the OSCC group. This is contradictory to our study as there was a decreased HDL, TC, and LDL in OSCC patients compared to OSMF patients. The decrease in plasma cholesterol in squamous cell carcinoma cases may be due to enhanced lipid peroxidation due to decline in antioxidants.
Subapriya et al. have reported enhanced lipid peroxidation with decline in antioxidants in venous blood of patients with OSCC at different intraoral sites.
Manoharan et al. reported that overproduction of lipid peroxidation byproducts and disturbances in antioxidant defense system have been implicated in the pathogenesis of several diseases including oral cancer. Lipid peroxidation is an essential biochemical process that involves the oxidation of polyunsaturated fatty acids, the important components of cell membranes. Tobacco carcinogens generate reactive oxygen species and lipid peroxides, leading to tissue injury due to elevated lipid peroxidation, further damaging the cellular structural blocks such as lipids, proteins, and DNA.
The levels of Vitamin E and reduced glutathione were significantly decreased in oral cancer patients as compared to healthy participants and were gradually decreased from Stage II to Stage IV of oral cancer patients.
All these results strengthen the results obtained from our study.
Schatzkin et al. and Chyou et al. have observed an inverse trend between lower serum cholesterol in head and neck as well as esophageal cancers. This study strengths the results obtained by showing decreased plasma cholesterol, HDL, and LDL in OSCC patients and OSMF patients.
Kark et al. in his study in Evans country stated the central finding of the study is that incident cancer cases had significantly lower mean serum cholesterol levels at intake than the noncancer population. The association tended to be stronger overall for males than females and was quite consistent for the various cancer sites and cell types. It was present for the incidence of cancer as well as for mortality from cancer and it persisted when new cases or deaths occurring within the first 4 years of follow-up were excluded from the analysis.
Naheed Quaid Memon et al. estimated that lowering the serum cholesterol of the whole population by 10% should lengthen median life by 1 year, but the percentage of deaths from cancer should rise from 26.8% to 29.6%. Thus, he explains that there is a 3% more incidence of cancer in persons having decreased cholesterol. According to him, hypocholestremia is a cause of cancer. However, this statement is very unlikely as it has not been still proved whether hypocholestremia is a cause or effect of cancer.
This inverse correlation between TC levels and incidence of tumor is more markedly associated with the advance disease status. Periodical follow-up of the levels of lipid profile was not done in this study which would have added fuel to the above statement. Decrease in cholesterol levels with increasing severity of the disease explains hypocholestremia as an effect of cancer. Many other authors have also proved the relationship of lipid levels with early and advanced stages of cancer.
Chyou et al., 1992, stated that there was a significant inverse trend for cases of oral/pharyngeal/esophageal cancer combined. The association was present for cases diagnosed within 10 years of examination but not for cases diagnosed after 10 years. This suggests that the inverse association is due to the metabolic effects of undiagnosed oral/pharyngeal/esophageal cancer upon serum cholesterol levels which strengthen the results from our study. Chyou also showed that serum LDL-cholesterol levels were inversely associated with all-cause cancer incidence, which is in accordance with our study.
Alsheikh-Ali and Richard Karas (Tufts University School of Medicine, Boston, MA) showed there was a “significant and linear relationship” between LDL levels achieved and risk of new cancer cases. The “reverse-causality” hypothesis suggests that depressed LDL-cholesterol levels are the result of subclinical cancer, whereas the “forward causality” hypothesis states that depressed LDL cholesterol is a precursor to disease. The depressed LDL levels in our study may be due to the disease process.
In the BUPA study, done by Wald proved that a low serum cholesterol is not a cause of cancer. Rose et al. reported 66% higher mortality rate due to cancer in the group of cancer patients with lowest plasma cholesterol than in the highest plasma cholesterol.
Hence, the reduced serum cholesterol, HDL cholesterol, and LDL cholesterol in patients with precancerous condition and OSCC which was highly significant in our study may be due to the effect of cancer process.
There are no conflicts of interest.
The authors would like to thank Dr. R. V. Suresh Balaji, M. D. S and Dr. Abdul Samad M. D. S.