Effect of the kaurenoic acid on genotoxicity and cell cycle progression in cervical cancer cells lines

Highlights

• Toxicity of kaurenoic acid (KA) was evaluated in three cervical cancer cell lines: HeLa, CaSki and C33A.

• KA showed a strong positive correlation with DNA damage and micronuclei frequency.

• At high concentrations, the KA inhibited the expression of E6 and E7 HPV genes.

• The assays pointed to the possibility of using KA as feedstock for therapeutic agents against cervical cancer with HPV.

Introduction

Cervical cancer represents >500,000 new cases of cancer and >250,000 deaths per year worldwide (Ferlay et al., 2015). Epidemiological studies of cervical lesions have suggested the participation of venereal carcinogens (semen, Epstein-Barr virus, cytomegalovirus, herpes simplex virus type-2). Human papillomavirus (HPV) appeared as the main suspect when found in about 90% of cervical cancers and because it has oncogenes (E6 and E7) with potential for transformation (Arends et al., 1998; Brenna and Syrjanen, 2003; Rivoire et al., 2006). HPVs have also been detected in a wide range of asymptomatic controls, indicating that further events are required for the development of neoplasms, such as viral persistence and/or altered expression of viral genes, often after integration of the viral genome (Rivoire et al., 2006).

Although most HPV infections resolve spontaneously within a few months, others persist and express viral oncogenes that inactivate the p53 and Rb proteins, leading to increased genomic instability, accumulation of somatic mutations and, in some cases, integration of HPV into the genome of the host (Moody and Laimins, 2010). The association with cancer risk and histologic subtypes varies substantially among types of carcinogenic HPVs, but the reasons for these differences are poorly understood.

The disease begins in a curable pre-invasive lesion in up to 100% of cases, which usually progresses slowly for 10 to 20 years until reaching the invasive stage, where healing becomes more difficult, if not impossible (Muller et al., 2008; INCA, 2016). Effective preventive vaccines against more oncogenic forms of HPV have been available for several years, with vaccination having the long-term potential to reduce the number of cervical cancer cases. However, vaccines will act as a means of preventing cervical cancer only for individuals who previously had access to them before the onset of sexual life. Out of this context, the fight against cervical cancer must still be made through the detection of precursor lesions and their due treatment and clinical follow-up (Nakagawa et al., 2010).

The use of medicinal plants is a tradition maintained until the present. Reports on folk medicine in the Brazilian Amazon region have been documented in the literature, especially regarding the oil-resin extracted from the copaíba trunk (different species of the Copaifera genus) (Tappin et al., 2004; Comelli Jr. et al., 2010), with numerous applications of relevant medical importance, including anti-inflammatory, antiulcerogenic, antitumor, antinociceptive, antimelanoma, antitilipoperoxidation, antioxidant and antimicrobial properties (Ohsaki et al., 1994; Paiva et al., 2002; Gomes et al., 2007; Lima Silva et al., 2009; dos Santos et al., 2011; Toubouti et al., 2017). This natural product has great social and economic representation in the Amazon region, since it represents about 95% of all oil-resin production in Brazil (Medeiros and Vieira, 2008). Particularly, the diterpenes (kaurenoic and polyaltic acids) present in pure oil appear to have healing and anti-inflammatory properties (Tappin et al., 2004; Comelli Júnior et al., 2010).

The objective of the present study was to evaluate the in vitro genotoxic activity of kaurenoic acid extracted from Copaifera langsdorffii and the effect of this compound on the transcription of genes involved in cell cycle control in three cervical cancer cell lines.