Abstract
Cervical cancers are almost exclusively caused by an infection with the human papillomavirus (HPV). When patients suffering from cervical cancer have contraindications for chemoradiotherapy, radiotherapy combined with hyperthermia is a good treatment option. Radiation-induced DNA breaks can be repaired by nonhomologous end-joining (NHEJ) or homologous recombination (HR). Hyperthermia can temporarily inactivate homologous recombination. Therefore, combining radiotherapy with hyperthermia can result in the persistence of more fatal radiation-induced DNA breaks. However, there is no consensus on the optimal sequence of radiotherapy and hyperthermia and the optimal time interval between these modalities. Moreover, the temperature of hyperthermia and HPV-type may also be important in radiosensitization by hyperthermia. In this study we thoroughly investigated the impact of different temperatures (37–42 °C), and the sequence of and time interval (0 up to 4 h) between ionizing radiation and hyperthermia on HPV16+: SiHa, Caski; HPV18+: HeLa, C4I; and HPV−: C33A, HT3 cervical cancer cell lines. Our results demonstrate that a short time interval between treatments caused more unrepaired DNA damages and more cell kill, especially at higher temperatures. Although hyperthermia before ionizing radiation may result in slightly more DNA damage, the sequence between hyperthermia and ionizing radiation yielded similar effects on cell survival.
Highlights
Most cases of cervical cancer are caused by infection with human papillomavirus (HPV)
To evaluate the effects of the sequence and the time interval between ionizing radiation and hyperthermia on cell survival, clonogenic assays were performed after hyperthermia or ionizing radiation only or hyperthermia followed by ionizing radiation and after the reversed order
Different time intervals between ionizing radiation and hyperthermia (0, 2, and 4 h) were tested and the effect of different temperatures was investigated for HPV16+, HPV18+, and HPV-negative cervical carcinoma cell lines
Summary
Most cases of cervical cancer are caused by infection with human papillomavirus (HPV). 16 and 18 are responsible for >70% of all cases of cervical cancer in the world [1]. HPV infections are the major risk factor of this disease, which, worldwide, is the second most common form of cancer in women. The combination of radiotherapy and cisplatin-based chemotherapy is presently a standard treatment for patients suffering from cervical cancer. If patients have contraindications for cisplatin-based chemotherapy, radiotherapy can be combined with hyperthermia.
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