How HPV causes cancer Essay Example | Topics and Well Written Essays - 1750 words

How HPV causes cancer - Essay Example Most of cancer cases that exist in the world happen because of viruses. Both DNA and RNA viruses are able to cause cancer in humans. One of the DNA viruses is Human papilloma virus (HPV)(Liao, 2006), which belongs to the family of papoviruses, non-enveloped, double stranded DNA viruses (Levinson and Jawetz, 2000) figure 1. Human papillomavirus were discovered after cottontail rabbit papillomavirus (CRVP). The first investigation of HPV in human cancer was conducted in 1970s, particularly in patients with epidermodysplasia verruciformis. (Howley, 2006). HPV usually causes benign papillomas or warts in humans (Liao, 2006). These viruses can also affect humans worldwide, especially women as they are susceptible to acquiring cervical cancer (Schiffman et al., 2007). Most studies consider these viruses as a major cause of cervical cancer. Also, these studies have identified the mechanism of cervical cancer development (Schneider, 1993; Boulet et al., 2007; Schiffman et al., 2007). This ca n explain the progression of disease. Most, if not all cases of cervical cancer occur due to the persistent infection of HPV, particularly the HPV-16 (Liao, 2006). Furthermore, HPV can be divided into several types and species such as HPV16, 18, 31, 33, 35, and 39 (Zur Hausen, 1999). Specific types of HPV linked with cervical cancer are HPV16, 18, 31 and 45 (Chumworathayi et al., 2010). The genome of the virus can encode several proteins such as (E1, E2, E4, E5, E6, E7 and E8) and two capsid proteins (L1, L2). This classification depends on the types of HPV (Su et al., 2010). Cervical cancer requires particular genes to be developed, such as E6 and E7 as Boulet and his colleagues have found (Boulet et al., 2007) and that have been encoded by HPV (Howley, 2006). Once HPV enters epithelia cells and integrates in the host DNA, the malignant transformation increases by the E6 and E7 production (Liao, 2006). These genes have effects on cell cycle progression in cervical cancer. However, HPV can also play a role in aggravating other forms of cancer in humans such as head and neck tumor and skin cancers in immunocompromised individuals (Liao, 2006). Apart from cervical cancer, HPV can also cause cancer according to HPV diversity both in humans and animals. Examples are the cottontail rabbit papillomavirus (CRVP) infection in domestic rabbits, epidermodysplasia verruciformis patient HPV5, 8, 14, Bovin paoillomavirus type 4 (BPV4), alimentary tract cancer in cattle, and Bovin papillomavirus type 1 in horses (Howley, 2006). As several studies observe the association between HPV and cervical cancer, this essay aims at discussing cancer development caused by HPV. Transmission and infection of HPV: Human papillomavirus can be transmitted in different ways both sexually and non-sexually. However, the most common transmission happens through sexual intercourse. This causes anogenital warts of type (6 and 11 HPV) which are considered low in risk with respect to many HPV types. Other types of cervical cancer such a s HPV16, 18 are responsible for about 70 % of cervical cancer and 50 % of cervical intraepithelial neoplasia (CIN) grade 3 (CIN3) (Schiffman et al., 2007; Smith et al., 2007). The HPV16 and 18 are considered as high risk types of HPV. Additionally, infection of HPV is usually transmitted by direct contact such as skin to skin and mucosa to mucosa, nevertheless, the likelihood of infection for each sexual intercourse is still unknown. Furthermore, several types of HPV can be transmitted collectively according to high proportion of infected women. On the other hand, men also may be infected by different types of HPV, therefore, any sexual act can quickly result in the transmission HPV types (Schiffman et al., 2007). In case of non sexual transmission, a child can acquire the infection of HPV from the mother (Castellsague et al., 2009) especially by placenta as Rombaldi and his colleagues have observed. For example, transmission from mother to the child may occur via amniotic fluid and fetal