HPV-Driven Pathways and Genetic Determinants of Cervical Cancer Susceptibility: A Comprehensive Analysis

Cervical cancer is currently the fourth most common among women and causes more than 300,000 deaths annually worldwide. And every year, over half a million were diagnosed with the disease. An important cause of cervical cancer occurrence is the infection by high-risk subtypes of Human papillomavirus (HPV)[1]. Most cases of cervical cancer can be prevented. Roughly 90% of cervical cancer incidents occur in low and middle-income countries where organized screening and HPV vaccination programs are often deficient. Recognizing risk factors is important for prevention.[2]. This can be exposure to the human papillomavirus. Smoking and dysfunction of the immune system. Long-term morbidity from such treatments is common, but it is important to note that most women are diagnosed with early-stage disease. If a female has a history of sexually transmitted infections, HPV, smoking, immune suppression, two or more sexual partners in their lifetime, and low socioeconomic status, they are more likely to develop cellular abnormalities.[3]. The main cause of CC development is a persistent HPV (high-risk human papillomavirus) infection. Development of hrHPV-associated CC is asymptomatic in the early stages. If the hrHPV is not examined at once, hrHPV may not be detectable, and it is an oncogenic alteration and that may lead to CC[4].  HPVs are categorized into high-risk (HR) or low-risk (LR) according to their causative relationship to cervical cancer and associated precursor lesions. These are low risk according to their causative relationship to cervical cancer and associated precursor lesions. These low-risk types of HPV are: 6, 11, 42, 43 and 44. These are rarely associated with high-risk types of HPV: 16,18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66, 68, 70. These are commonly found in cervical cancer. A few of the high-risk types that occur less frequently in cancers but quite frequently in squamous intraepithelial lesions(SILs) are sometimes referred to as intermediate-risk HPV types. Occasionally, low-risk types are found in cervical carcinomas also [5]. Approximately 80% of cervical cancers are squamous cells, and 15% are adenocarcinomas [6]. A combination of environmental and genetic factors, such as infections with the human papillomavirus, may cause cervical cancer. While cervical cancer growth requires HPV infections, they are not sufficient to cause the disease by themselves [7].

A significant proportion of HPV infections,  according to research, spontaneously regress with time. For example, a study found that HPV-16 had the lowest cumulative regression rate (62.8%), while HPV-11 had the highest rate (100%) (de Sanjose et al.).

On the flip side, a small number of individuals may have a genetic predisposition that allows certain infections to escalate into invasive cancer or precancerous conditions [8]. To truly grasp cervical carcinogenesis, we need to identify the genetic risk factors involved. Two disorders that have a genetic connection to cervical cancer are WHIM syndrome and Lynch syndrome [9]. For instance, Lynch syndrome is an inherited condition that raises the likelihood of developing endometrial and colorectal cancers, among others. While HPV infections are crucial in the onset of cervical cancer, they aren’t the sole factor. Genetic elements, like those found in WHIM syndrome and /lynch syndrome, significantly contribute to the development of cervical cancer linked to HPV infection  [10].

This review article delves into the origins, structural organization, biological functions, and therapeutic implications of all HPV E and L proteins in the context of cervical cancer development and progression. It also explores the signalling pathways of HPV infection related to cervical cancer through early and late proteins, as well as the influence of various genetic factors and genotypes on the progression of cervical cancer.

Origin of human papilloma virus (HPV)

The carcinogenic potential of Human Papillomavirus (HPV) was found less than 50 years ago. Still, significant research efforts culminated in a Nobel prize and the invention of HPV screening tests and vaccinations to prevent HPV-induced cancer[11]. HPV, a member of the papillomaviridae family, is a small (50-550nm) non-enveloped double-stranded DNA virus[12]. Based on the L1 ORF region nucleotide sequence, five subtypes of HPV are: alpha, beta, gamma, mu, and nu. Alpha types were the carcinogenic ones. In CC patients, the most common genotype is HPV16, followed by HPV18, as per the International Agency for Research on Cancer(IARC)[13]. The HPV16 genome is 7.9kb in length. The icosahedral capsid containing the HPV genome is separated into three domains i.e., the early ( E ) domain, which contains many precursor proteins such as E1, E2, E4, E5, E6 and E7, all of which are relevant to mechanisms such as virus DNA replication, cell cycle regulation, and oncogenic functions and hence play a key role in the initial stages of infection[14]. Proteins coded in the late(L) domain, which are involved in the major and minor viral capsid components,  consist of two segments, L1 and L2. Viral transcription and replication are regulated by Long Control Region (LCR), a non-coding region[15]. E6 and E7 are the primary regulators among the six E proteins relevant to virus pathogenesis. Viral oncoprotein expression E^ and E& interfere with mechanisms related to cellular repair, especially retinoblastoma and tumor suppressor protein p53 function[16].

Association of HPV with cellular pathways

HPV oncoproteins affect various biological pathways that contribute to oncoproteins:

1. HPV  with p53 pathway

Human papillomavirus (HPV) causes cancer, mostly through its interaction with the p53 pathway. HPV oncoproteins particularly E6, target p53, a tumor suppressor protein that is essential for maintaining genomic integrity and limiting uncontrolled cell proliferation. E6 forms a compound with E6- associated protein (E6AP), an E3 ubiquitin ligase , which ubiquitinates p53 and then degrades it in the proteasome[17]. This degradation of p53 interferes with its normal activities, which include cell cycle arrest, DNA repair and apoptosis induction in response to cellular stress or DNA damage. As a result, HPV- infected cells acquire genetic mutations and chromosomal abnormalities, which promote cellular transformation and cancer progression[18]. The lack of p53 activity also permits infected cells to avoid apoptosis and continue to proliferate, even in the presence of DNA damage, which contributes to the oncogenic process. This process is especially significant in the development of cervical cancer, where chronic infection with high-risk HPV strains is the predominant cause[19].

2. HPV with MAPK/ERK Pathway

HPV proteins can activate the MAPK pathway, which promotes cellular proliferation and tumor growth. MAPKs are Ser/Thr that are activated by various signalling pathways. These pathways control key biological functions including proliferation, differentiation, angiogenesis, and cell survival[20]. This pathway is an important signaling cascade implicated in cervical cancer growth. While the cited publications do not specifically discuss CC, the MAPK pathway is identified as a downstream effector of the c-MET signaling in head and neck squamous cell carcinoma (HNSCC)[21]. This supports a similar involvement in CC, given that both are HPV- related diseases[22]. To summarize, while the direct link between HPV and the MAPK/ERK pathway in cervical cancer is not explicitly stated in the given context, the involvement of HPV oncoproteins in various signalling pathways, including PI3K/AKT, Wnt and Notch, implies that the MAPK/ERK pathway may also be affected. Additional research is required to determine the particular connections between HPV and MAPK?ERK pathway in cervical cancer progression[23].

3. HPV with pRb/E2F Pathway

One of the key events in HPV- mediated carcinogenesis in the disruption of the pRb/E2F pathway, which regulates the cell cycle. The retinoblastoma protein(pRb) typically functions as a tumor suppressor by binding to E2F transcription factors and preventing the transcription of genes necessary for cell cycle progression[24]. The E7oncoprotein, which is produced by high-risk HPV strains like HPV-16 and HPV-18, directly binds to and deactivates pRb, causing the release of E2F and unchecked cell proliferation[25]. E7 mediated pRb inactivation involves binding to the pocket domain of pRb, which inhibits its regulatory function and promotes the transcription of genes that propel the cell cycle[26]. This disparity causes genomic instability, elevated DNA replication stress and early S-phase entrance, all of which aid in oncogenesis[27]. Additionally, a compensatory upregulation of p16, a biomarker commonly used to identify HPV- related malignancies, results from the loss of pRb function[28]. Since it offers potential targets for treatments meant to restore pRb function or prevent downstream carcinogenic effects, an understanding of the molecular relationships between HPV E7 and the pRb/E2F pathway has significant therapeutic significance[29].

4. HPV and the PI3K/Akt Pathway

The PI3K/Akt signaling system regulates several cellular activities, including survival, growth, metabolism and apoptosis. Dysregulation of this system is common in many malignancies, including HPV- associated cervical cancer. These viral oncoproteins play an important role triggering the malignant transformation of infected cells[16]. The E6 oncoprotein directly targets the tumor suppressor p53, causing its degradation and inhibiting apoptosis[21]. This improves cellular survival, even in the presence of DNA damage. Furthermore, by affecting other signaling molecules, including mTOR, E6 can indirectly activate the PI3K/Akt pathway, which in turn supports cell growth and survival[30]. The E7 oncoprotein permits unchecked cell cycle progression by interfering with the activity of pRb protein. Cyclin-dependent kinases (CDKs) are upregulated as a result of this disturbance, and this can further activate the PI3K/Akt signaling activation in CC is frequently linked to metastases, treatment resistance and poor prognosis. Additionally, the pathway enhances the invasiveness of cancer cells by promoting the epithelial to mesenchymal transition(EMT)[31]. The PI3K/Akt pathway is now a desirable therapeutic target due to its crucial involvement in tumor growth[32]. Clinical trials are being conducted to evaluate inhibitors that target different parts of the cascade, such as PI3K, Akt or mTOR which have shown promise in preclinical research[33]. These medicines seek to diminish tumor cell survival, improve the efficacy of conventional therapies such as chemotherapy and radiation and overcome resistance mechanisms mediated by HPV oncoproteins[34]. Thus, knowing the complex link between HPV and the PI3K/Akt pathway is critical for developing more effective therapies for HPV-related malignancies, particularly CC and improving patient outcomes[35].

5. HPV and Wnt/β-catenin pathway

The development of cancer, especially cervical cancer, is intimately associated with the Wnt/β- catenin signaling system and the human papillomavirus (HPV). Cell fate, proliferation and proliferation and differentiation are all regulated by this pathway. Typically a destruction complex breaks down β-catenin[36]. This complex is inhibited by Wnt ligands, which permit β-catenin to buildup and trigger the transcription of target genes[37]. This process is disrupted by HPV oncoproteins. E6 promotes oncogenesis, increases the transcription of Wnt target genes and stabilizes β-catenin by inhibiting its degradation[38]. E7 further stabilizes β-catenin by interacting with the destruction complex. Increased cell survival, proliferation, resistance to apoptosis and possible metastasis are the results of this imbalance. Malignancy develops from normal cells due to the synergistic interaction between HPV oncoproteins and the Wnt/β-catenin pathway[39].

6. HPV and JAK/STAT pathway

Cytoplasmic transcription factors known as signal transducers and activators of transcription (STATs) and Janus kinases (JAKs) make up the JAK-STAT pathway. These transcription factors become active in response to receptor-mediated activation. STATs go to the nucleus after activation to alter gene expression. Apoptosis, migration, differentiation and proliferation are among the processes that are influenced by the STAT family, which consists of STAT-1, -2, -3, -4, -5 and -6[40]. When ligands attach to certain receptors, the receptor subunit is altered, which triggers intracellular signaling, and the JAK-STAT cascade is activated[41]. The members of the JAK family in mammals include Tyk2, JAK1, JAK2 and JAK3. To initiate subsequent signaling processes, these kinases phosphorylate STATs and other substrates. To avoid immune detection, HPV a DNA virus linked to several malignancies, manipulates the JAK/STAT pathway[42]. By interfering with Tyk2 and preventing its phosphorylation as well as that of STAT-1/2, the HPV E6 oncoprotein blocks the JAK-STAT signaling pathway. Tyk2’s ability to connect with IFN-alpha receptor ! is similarly inhibited by this interaction, which lowers the host’s antiviral response[43]. To sustain episomes and proliferate its genome, HPV must suppress STAT-1 since its proteins target immune signaling pathways to guarantee a chronic infection. In particular, STAT-5 is linked to the amplication of the HPV genome in differentiated cell through the activation of the ATM DNA damage pathway, however, its function in undifferentiated cells is still unclear[44].

7. HPV and YY1 pathway

In viral gene regulation and carcinogenesis, the Yin Yang 1 (YY1) transcription factor and the HPV are intimately related. A versatile transcription factor, YY1 plays a role in cellular functions such as development, proliferation and differentiation. Depending on the cellular environment and its interacting partners, it can both activate and inhibit the expression of genes. YY1 is essential for controlling the viral life cycle and oncogene production in high-risk HPV strains such as HPV16 and HPV18[45]. To aid in its proliferation and avoid immune detection, the virus integrates into the host genome and modifies cellular processes. By attaching itself to the HPV genomes long control region (LCR), YY1 suppresses the production of the viral oncogenes E6 and E7[46]. Although HPV has developed defenses against YY1’s activity, this suppression can restrict viral proliferation and oncogenesis.E6 oncoproteins can block interferon-inducible genes via modulating YY1 activity, which impairs the hosts immune system and permits prolonged infection[47]. The long-term viability and development of the virus into cancer are facilitated by this immune evasion. Furthermore, YY1 has two functions in HPV infection. Viral oncogene production can be suppressed: however, the virus uses YY1’s actions to inhibit immune responses and interfere with regular cell cycle control. Comprehending this interplay is essential for creating focused treatments for malignancies linked to HPV[47].

8. HPV and AP-1 Pathway

A dimeric transcription factor made up of proteins from the Jun, Fos, ATF and MAF families, activator protein-1 (AP-1) is essential for controlling genes related to cell division, proliferation and death. The long control region(LCR), a crucial regulatory element that controls the production of early viral genes E6 and E7 that are critical for the viral life cycle and oncogenesis, is where AP-1 interacts inside the HPV genome[48]. These genes disrupt tumor suppressor pathways; E6 encourages p53 degradation, which allows the virus to avoid apoptosis, while E7 deactivates pRb, which causes uncontrolled cell cycle entrance into the S-phase and increases genetic instability[49]. In addition to its function in controlling viral genes, AP-1 is frequently overexpressed or aberrantly activated in cancers linked to HPV, where it promotes the transcription of cellular  genes that aid in the development of the disease[22]. This includes the overexpression of cyclins and cyclin dependent kinases (CDKs), which support unchecked cancer cell proliferation and enable continuous cell cycle progression. Furthermore, AP-1 enhances tumor development by influencing genes related to angiogenesis and cell survival. Another important aspect of HPV pathophysiology is its persistence and capacity to evade immune detection[50]. Cytokines and chemokines are important mediators of inflammation and immunological responses and AP-1 controls their expression. For HPV to establish persistent infections, which is a prerequisite for the development of HPV-induced cancer, this immune regulation may provide an immunosuppressive microenvironment[51].

9. HPV & NF-kB Pathway   

Genes implicated in immunological and inflammatory responses as transactionally triggered by infections usually activate the NF-kB pathway[52]. To inhibit the immune response and aid in the development of persistent infections, HPV proteins like E6 & E7 alter this pathway. By interacting with IkB kinase (IKK), for example, E7 suppresses NF-kB activation by blocking NF-kB release and nuclear translocation because of this suppression, HPV can avoid immune monitoring, which is essential to its persistence and eventual development of cancer. One characteristic of HPV- related malignancies is chronic inflammation, which is caused by dysregulated NF-kB signaling[53]. Continuous production of growth factors and pro-inflammatory cytokines that foster a tumor promoting environment is the outcome of persistent NF-kB activation[54]. Despite promoting tumor formation, this inflammatory milieu also fuels genetic instability, which accelerates the carcinogenic process[55]. HPV also promotes cell survival and proliferation through its manipulation of NF-kB by breaking down the tumor suppressor p53, the viral oncoprotein E6 prevents apoptosis and increases cell survival. Furthermore, HPV-infected cells’ NF-kB activation triggers the transcription of anti-apoptotic genes, ensuring the survival of these potentially malignant cells[56]. A key component of HPV’s carcinogenic potential is its capacity to take over the NF-kB pathway to inhibit apoptosis and promote cell division[57]. One intriguing treatment option for HPV-associated malignancies is to target the NF-kB pathway. The ability of certain NF-kB inhibitors, such as IKK inhibitors and other compounds that stop NF-kB activation, to lower inflammation and stop tumor growth in HPV-positive individuals is being studied[58]. To effectively develop targeted therapeutics to mitigate these carcinogenic processes, it is imperative to clarify the specific mechanisms by which HPV modifies NF-kB activity[59].

10. HPV & CXCL12/CXCR4 pathway

A chemokine-receptor combination essential for cell migration, homing and angiogenesis is CXCL12, sometimes referred to as stromal cell-derived factor (SDF-1) and its receptors CXCR4[60]. By encouraging cancer cell motility and invasion, which are essential for metastasis, the interaction between HPV and the CXCL12/CXCR4 pathway adds to the oncogenic process. Because of its increased propensity for metastasis, CXCR4 expression is often overexpressed in HPV related malignancies, particularly cervical cancer, and is linked with a poor prognosis[61]. Cell survival, proliferation and migration are enhanced by downstream signaling pathways such as PI3K/AKT and MAPK/ERK, which are triggered when CXCL12 binds to CXCR4. Tumor cell migration to tissues rich in CXCL12 is facilitated by the CXCL12/CXCR4 axis, which is essential in the tumor microenvironment and causes metastasis, CXCR4expression is often overexpressed in HPV related malignancies, particularly cervical cancer and is linked with a poor prognosis[62]. Cell survival, proliferation and migration are enhanced by downstream signaling pathways such as PI3K/AKT and MAPK/ERK, which are triggered when CXCL12 binds to CXCR4. Tumor cell migration to tissues rich in CXCL12 is facilitated by the CXCL12/CXCR4 axis, which is essential in the tumor microenvironment and causes metastasis[63]. CXCR4 expression enhances cell’s ability to respond to CXCL12 gradients, promoting migration and invasion in HPV associated cancers. Cancer cells cannot spread from the primary supports angiogenesis, which is essential for tumor development and metastasis[64]. By encouraging the recruitment of endothelial progenitor cells and the development of new blood vessels, CXCL12 supplies oxygen and nutrients to the tumor. To promote angiogenesis and aid in tumor growth and metastasis. By encouraging the recruitment of endothelial progenitor cells and the development of new blood vessels, CXCL12 supplies oxygen and nutrients to the tumor. HPV infected cells may take advantage of this route. One possible method for preventing tumor development and metastasis in HPV-associated malignancies is to target the CXCL12/CXCR4 axis[25]. To decrease tumor cell migration and invasion, the CXCL12-CXCR4 interaction is blocked with CXCR4 antagonists and inhibitors, such as AMD3100 (plerixafor). The potential of these inhibitors to reduce metastasis and enhance patient outcomes in HPV-positive malignancies is being investigated in preclinical and clinical trials[54]. With an 8-kilobase genome, HPV is a non-enveloped DNA virus that comes in low-risk and high-risk varieties. HPV16, HPV18, HPV30, HPV33, and HPV45 are high-risk strains[65]. The virus generates late proteins (L1 and L2) that construct the viral capsid and early proteins (E1, E2, E4, E5, E6, and E7) involved in replication and cellular transformation. By inhibiting P53 via ubiquitination, the E6 protein promotes oncogenesis and inhibits DNA damage repair and apoptosis[66]. Comprising three domains, the E7 protein disrupts cell cycle control by inducing S-phase advancement, binding to the retinoblastoma protein (pRb), and interacting with other proteins, including P27CDK inhibitors. HPV can increase the chance of developing cancer by promoting unchecked cell proliferation through these oncogenic processes[67].

Genetic Predictors of Cervical Cancer Susceptibility:

ANRIL and MALAT1's association with long non-coding RNAs (lncRNAs). Cervical cancer polymorphism: According to a genome-wide association (GWAS) study, host genetic variables may have a significant role in the development of cervical cancer[68]. Long non-coding RNAs (lncRNAs) in host genes have been the subject of several investigations. These lncRNAs can either function as carcinogenic or tumor suppressors. Numerous cancers are linked to chromosome 9p21, which contains the lncRNA antisense non-coding RNA at the INK4 gene (ANRIL)[69].

Recent research has investigated the part single-nucleotide polymorphisms (SNPs) play in the development of cervical cancer (CC) in non-coding RNA genes. Potential contributors to CC susceptibility in a Han Chinese population were found to be rs3200401 in MALAT1 and rs4977574 in ANRIL[70]. These results demonstrate how important genetic changes in non-coding RNA regions are for the development of cancer. A small sample size and the absence of functional confirmation of these SNPs in vitro and in vivo were two of the study's drawbacks[71]. Future investigations should concentrate on extensive association studies in a variety of groups and functional trials to clarify the specific functions of these SNPs in the development of CC in order to build on these preliminary findings. The relationship between the genetic variation rs217727 and the risk of cervical cancer (CC) has been the subject of inconsistent findings in several previous investigations[72]. Although some studies did not find a significant correlation, others proposed that rs217727 could increase CC susceptibility by changing the expression of the MRPL23-AS12,3 gene linked to cancer and the way the H19 gene interacts with associated microRNAs[73]. With a statistical power of 0.891, the A allele of rs217727 was linked to an increased risk of CC in research on the Chinese Han population, supporting the results. In contrast, rs2366152-C was shown to be significantly associated with CC patients who had low HOTAIR levels in another study conducted in India[74]. However, no such link was found in the larger population that was studied. Nevertheless, the interaction between genetic variables and other risk factors could not be thoroughly examined because of insufficient clinical data. The precise molecular pathways through which rs217727 may cause CC are yet unknown, underscoring the need for more research to examine these correlations and confirm results in a variety of populations and clinical conditions[75].

Table 1: Biological functions and therapeutic significance of all HPV E and L proteins in the initiation and progression of cervical cancer.

Table 2 Oncoproteins of HPV and their role in stimulating cell transformation in cervical cancer

Table 3: Long non-coding RNAs (lncRNAs) and their polymorphisms play key roles in the development of different cancers2.