Cervical cancerExposure to sunlight

Several ecological studies reported a reduced risk of cervical cancer incidence and/or mortality rate with respect to indices for solar ultraviolet-B (UVB) doses as a proxy for vitamin D production. These include one study in the United States that also used indices for smoking1, and two studies in China using latitude2 or annual solar UVB doses3.

A study looking at incidence of various cancers with respect to diagnosis of nonmelanoma skin cancer found a reduced risk of cervical cancer after correcting for smoking in each study4

A study of cancer incidence in an area (state) of Germany known for winegrowing found a trend of lower significantly reduced standardized incidence ratio (SIR) of cervical cancer as the fraction of land devoted to winegrowing increased while the SIR for skin cancer and melanoma increased slightly with increased fraction of land in winegrowing5. It was pointed out that this study found a beneficial effect of UVB in reducing the risk of cervical cancer in a study looking for the effects of pesticide use6

However, there is also evidence that risk of cervical cancer increases in summer. A study in the Netherlands investigated the seasonality of “cervical smears positive for HPV based on histopathologic epithelial changes pathognomonic of HPV” and found a peak in August78. By comparing the diagnosis rate with an index of sexual activity and conception, it was determined that the peak in August was not due to a higher rate of sexual activity that month. The study also found that during a 16-year period, “maximum HPV detection rate and maximum UV fluency are positively correlated (r=0.59, P<0.01); the sunnier the year, the greater the rate of HPV.” The authors proposed that a “UV-mediated suppression of immune surveillance” was the cause of this peak.

A related explanation is that increased “release of nitric oxide from intracutaneous photolabile nitric oxide derivates9 by ultraviolet-A (UVA) (320–400 nm) changes the reaction to HPV. A laboratory study found: 

“Exposure of cells maintaining episomal high-risk HPV genomes to NO increased HPV early transcript levels 2- to 4-fold but did not increase viral DNA replication. Accompanying increased E6 and E7 mRNA levels were significant decreases in p53 and pRb protein levels, lower apoptotic indices, increased DNA double-strand breaks, and higher mutation frequencies when compared with HPV-negative cells10”.

The role of nitric oxide from UVA irradiance was proposed earlier as a factor for poorer prognosis for squamous cell carcinoma of the skin11.

Page last edited: 22 August 2011

References

  1. Grant, W. B. Garland, C. F. The association of solar ultraviolet B (UVB) with reducing risk of cancer: multifactorial ecologic analysis of geographic variation in age-adjusted cancer mortality rates. Anticancer Res. 2006 Jul-Aug; 26 (4A): 2687-99.
  2. Grant, W. B. Does solar ultraviolet irradiation affect cancer mortality rates in China?. Asian Pac J Cancer Prev. 2007 Apr-Jun; 8 (2): 236-42.
  3. Chen, P. Hu, P. Xie, D. Qin, Y. Wang, F. Wang, H. Meta-analysis of vitamin D, calcium and the prevention of breast cancer. Breast Cancer Res Treat. 2010 Jun; 121 (2): 469-77.
  4. Grant, W. B. A meta-analysis of second cancers after a diagnosis of nonmelanoma skin cancer: additional evidence that solar ultraviolet-B irradiance reduces the risk of internal cancers. J Steroid Biochem Mol Biol. 2007 Mar; 103 (3-5): 668-74.
  5. Seidler, A. Hammer, G. P. Husmann, G. Konig, J. Krtschil, A. Schmidtmann, I. Blettner, M. Cancer risk among residents of Rhineland-Palatinate winegrowing communities: a cancer-registry based ecological study. J Occup Med Toxicol. 2008; 312.
  6. Grant, W. B. Cancer risk ecological study in Rhineland-Palatinate, Germany, provides strong support for the ultraviolet B-vitamin D-cancer hypothesis. J Occup Med Toxicol. 2010 19 July 2010; 19 July 2010
  7. Hrushesky, W. J. Sothern, R. B. Rietveld, W. J. Du Quiton, J. Boon, M. E. Season, sun, sex, and cervical cancer. Cancer Epidemiol Biomarkers Prev. 2005 Aug; 14 (8): 1940-7.
  8. Hrushesky, W. J. Sothern, R. B. Rietveld, W. J. Du-Quiton, J. Boon, M. E. Sun exposure, sexual behavior and uterine cervical human papilloma virus. Int J Biometeorol. 2006 Jan; 50 (3): 167-73.
  9. Oplander, C. Volkmar, C. M. Paunel-Gorgulu, A. van Faassen, E. E. Heiss, C. Kelm, M. Halmer, D. Murtz, M. Pallua, N. Suschek, C. V. Whole body UVA irradiation lowers systemic blood pressure by release of nitric oxide from intracutaneous photolabile nitric oxide derivates. Circ Res. 2009 Nov 6; 105 (10): 1031-40.
  10. Wei, L. Gravitt, P. E. Song, H. Maldonado, A. M. Ozbun, M. A. Nitric oxide induces early viral transcription coincident with increased DNA damage and mutation rates in human papillomavirus-infected cells. Cancer Res. 2009 Jun 1; 69 (11): 4878-84.
  11. Villiotou, V. Deliconstantinos, G. Nitric oxide, peroxynitrite and nitroso-compounds formation by ultraviolet A (UVA) irradiated human squamous cell carcinoma: potential role of nitric oxide in cancer prognosis. Anticancer Res. 1995 May-Jun; 15 (3): 931-42.