Oral cancers are considered as the 6th most common predominant cancers in males. Some of the etiological components include
viruses, alcohol and tobacco. Most common viruses include Hepatitis C virus, Epstein-Barr virus, Herpes simplex virus (HSV) and
human papilloma virus (HPV). No doubt, the role of viruses is inevitable in progression and initiation of OSCC (Oral Squamous Cell
Carcinoma). Rapid detection of these viruses can result in prevention and early treatment so that disease will not be progressed
further.
OSCC (Oral Squamous Cell Carcinoma) is known to be the 6th
most common cancer throughout the whole world. The disease is
widespread between smokers in comparison with non-smokers
[1]. Research shows that there have been seven times more
smokers which have been suffered with oral cancer as compared to
non-smokers [2,3]. OSCC is a disease predominant in males but the
recent cancer ratio depicts that it is found in females as well. Oral
cancers occur at the age of 40 years and above [4-8]. Typically, the
disease occurs in floor of mouth and tongue [9-13].
Oral cancer is a multi-step procedure in pathogenesis which
leads to normal regulatory pathways disruption that regulate
normalized cellular roles including cell death, differentiation and
cell division [14,15]. Even though chemical carcinogens such as
alcohol and tobacco have been the main etiology. They tend to
participate in producing mutations in P53 suppresser genes which
lead to tumour progression and initiation. Numerous viruses cause
alteration in DNA coding and oral epithelial which result in oral
carcinomas [16].
HPV (Human papilloma virus) belongs to the family of
Papovaviridae, un-wrapped dual standard spherical DNA viruses
[17]. They cause infections and particularly target basal cell of
epithelium. Typically, HPV 6,11,16 and 18 are found in cancer
epithelial cells [18]. Research indicates that prenatal transmission
and oral sex cause infection [19].
The protein of HPV is comprised of a non-structural protein
(genes encode E1-E7) and structural protein (late genes encodes
L1-L2). Tumour transcription and replication transformation
is regulated by early protein and final stages of viral cycle is
carried out by late genes. HPV consisting of lower risk result in
warts whereas HPV having high risk can cause malignant lesions
[17,20,21,22,23]. P53 tumour suppressor gene (TP53) is degraded
by the early protein E6 [24]. Q1 transition to S phase is regulated by
TP53 in cell cycle [25]. Furthermore, this leads to damaging DNA,
proliferation, increased cell and inadequacies can cause malignant
transformation [26].
Herpes Simplex Virus (HSV)
HSV1 and HSV2 (Herpes simplex virus) cause infection to
genital, ocular and oral areas. They stimulate the cellular protein
expression and induce shock proteins [27]. These infections cause
cell RNA and cell protein formation. Mechanism of Shut off becomes
activated which is fundamentally an area of genome mtr1 of HSV1
and mtr2 of HSV2 respectively. Typically, there are two phases
found. Phase 1 is more linked with viral activity which is followed
right after infections [28]. Phase 2 requires expressions of viral
genes, causes cell transformation and removes synthesis of host
protein [29].
Hepatitis C virus (HCV)
Johnson exposed one of the possible contributions of Hepatitis
C virus in oral cavity besides liver which causes genetic factor
mutation of cells [30]. Hepatitis C virus is a packed and single strand
RNA virus which is infected by detoxification of humanoid factor
VIII (Cho et al.) [31]. Viral poly protein breakdown by translation
of RNA results in capsid formation, viral proteases (NS2, NS3) and
glycoproteins (E1, E2) which seem essential for malignancy and
replication of RNA [32].
Epstein-Bar Virus (EBV)
EBV virus is comprised of dual stuck DNA genome which
encodes 90 proteins with 172,000 base pairs. The latent proteins
of EBV are LMP2 and LMP1 [33]. LMP1 works in B cell destruction
and cell transformation. LMP1 with various groups of carboxyl is
attracted to act on TRAFs (Tumour Necrosis Factor Receptor) [33-
35]. P38, jun, NF-JB present higher activity in LMP1 due to this
interaction representing B cells and epithelial cells [36-38]. It helps
to activate apoptotic genetic factors such as fibroblast growth factor
(FGF) and metalloprotinease-9 (MMP-9). LMP2 mimics signals of B
cell receptor (P13K/AKT pathways) which results in abnormal cell
development [39].
Oral cancer increases the risk of infections and causes immune
suppression. Contact of viruses in people can be a causative
component for progression and initiation of disease. Additional
studies on viruses will work as a supporting tool for new therapies,
diagnosis and early examinations.
Filion M, Skup D, Suh M (1988) “Specific induction of cellular gene transcription in herpes simplex virus type-2-transformed cells.” Journal of General Virology 69(8): 2011-2019.