1. BRCA1-DEFICIENT CANCER CELLS TAKE
ADVANTAGE OF DNA.
SILIBININ KILLS SKIN CELLS MUTATED BY
UVA RADIATION.
REPAIR MECHANISM.
Tatiana Gil Franco
Medicine Student
3° semestre
U.P.B

4. Introduction
 The BRCA1 protein helps
to mend double-strand
DNA breaks by promoting
homologous
recombination.
 Silibinin, kills skin cells
mutated by UVA radiation
and protects against
damage by UVB
radiation.

5. BRCA1-deficient
cancer cells take
advantage of DNA
repair
mechanism.
The Journal of Cell
Biology.
(Jan 22, 2013)

6. BRCA1-DEFICIENT CANCER CELLS TAKE
ADVANTAGE OF DNA REPAIR MECHANISM
BRCA1
 It’s a human caretaker gene
that produces a protein
called breast cancer type 1
susceptibility protein,
responsible for repairing
DNA.
 The BRCA1 protein helps to
mend double-strand DNA
breaks by promoting
homologous recombination.

7. BRCA1-DEFICIENT CANCER CELLS TAKE
ADVANTAGE OF DNA REPAIR MECHANISM
53BPA1 Cathepsin L
 It’s a protein that helps  It’s a protease that
orchestrate a different destroys 53BP1 by
DNA repair entering the nucleus.
mechanism,
nonhomologous end  vitamin D is a
joining (NHEJ) cathepsin L inhibitor
 Cells lacking BRCA1
compensate by cutting
back on 53BP1.

8. BRCA1-DEFICIENT CANCER CELLS TAKE
ADVANTAGE OF DNA REPAIR MECHANISM
 When they cultured breast cancer cells that were missing
BRCA1, the cells stopped growing. After two weeks of
lethargy, however, BOGA cells (BRCA1-deficient cells that
overcome growth arrest), began to divide again.
 These cells showed increased levels of cathepsin L and
reduced amounts of 53BP1.
 Eliminating cathepsin L from BOGA cells or dosing them with
vitamin D, a cathepsin L inhibitor, prevented the decline in
53BP1 abundance.

9. PERSONAL OPINION
This article explains how cancer
cells by cathepsin, 53BP1
attack, inhibiting DNA repair
mechanism. I think this is very
important because the authors are
proposing a treatment for breast
cancer.

10. Silibinin kills skin
cells mutated by
UVA radiation and
protects against
cancer.
Photochemistry and
photobiology.
(Jan. 31, 2013 )

11. SILIBININ KILLS SKIN CELLS MUTATED BY UVA
RADIATION AND PROTECTS AGAINST CÁNCER
 Silibinin, also known
as silybin, is the major
active constituent
of silymarin, a
standardized extract of
the milk thistle seeds
containing mixture
of flavonolignans.  Silibinin has also
demonstrated in vitro
anti-cancer effects,
estrogen dependent
and independent
human breast
carcinoma cells.

12. SILIBININ KILLS SKIN CELLS MUTATED BY UVA
RADIATION AND PROTECTS AGAINST CÁNCER
 The first study, published
in the
journal Photochemistry
and Photobiology worked
with human skin cells
subjected to UVA
radiation.
 The Agarwal Lab treated
these UVA-affected cells
with silibinin. With
silibinin, the rate at which
these damaged cells died
increased dramatically.

13. SILIBININ KILLS SKIN CELLS MUTATED BY UVA
RADIATION AND PROTECTS AGAINST CÁNCER
 The second study shows
that instead of
beneficially killing cells
damaged by UVA
radiation, treatment with
silibinin protects human
skill cells from damage
by UVB radiation.
 The UVB radiation makes
up about 5 percent of the
sun's radiation reaching
Earth.

14. PERSONAL OPINION
I think that it’s a very important new
because this tell us about the great
damage that UV light causes us
and show us how with the help of
the silibinin and a DNA repair
mechanism can prevent this
damage.

16. MEDICAL UTILITY
 Knowing about the mechanisms of DNA repair is
very important in the field of medicine as these
mechanisms are closely linked to health problems
such as cancer.

17. MEDICAL UTILITY
In the first news tell us
about breast cancer and
the BRCA1 protein
function in this pathology.

18. MEDICAL UTILITY
The second new describe
us the operation of
silibinin killing cells
damaged by UV rays.

19. REFERENCES
 News medical “Silibinin kills skin cells mutated by UVA radiation and protects
against cáncer”
Jan 31, 2013. Photochemistry and photobiology.
< http://www.news-medical.net/news/20130131/Silibinin-kills-skin-cells-mutated-by-
UVA-radiation-and-protects-against-cancer.aspx>
 News medical “BRCA1-deficient cancer cells take advantage of DNA repair
mechanism”
Jan 22, 2013. The Journal of Cell Biology.
<http://www.news-medical.net/news/20130122/BRCA1-deficient-cancer-cells-take-
advantage-of-DNA-repair-mechanism.aspx>
 MARTINEZ SÁNCHEZ, Lina María. Biología molecular. 2. ed. Medellín: UPB.
Fac. de Medicina, 2006. 208 p.