Sabato 27 ottobre 2012 - Pacini Editore

COmuNiCaziONi ORali
or identification of patients who would benefit from particular
therapies).
The mechanisms of DNA repair seem involved both in development
and in chemoresistance of ovarian cancer (Bast et al., 2009;
Alvero et al., 2009). In this article we focus our attention on the
immunohistochemical expression of two proteins involved in
DNA repair mechanisms: APE1/Ref-1 (APE1) and nucleolar/
nucleoplasmic protein Nucleophosmin 1 (NPM1).
APE1 is the main apurinic/apyrimidinic endonuclease in mammalian
cells and catalyzes a rate limiting step in BER. Upregulation
of this ubiquitous and vital protein is at the basis of chemoresistance
in several tumors, such as hepatic, prostate and ovarian
cancers; for this reasons the protein is emerging as a promising
target for combination cancer therapy (Kelley et al., 2011; Wilson
and Simeonov, 2010).
Nucleophosmin 1 (NPM1) is an abundant protein, which specifically
resides within the granular region of the nucleolus,
implicated in a variety of cellular processes including centrosome
duplication, maintenance of the genome integrity and ribosome
biogenesis (Frehlick et al., 2007).
We have found that NPM1 plays a significant stimulatory effect
on APE1 DNA-repair activity in BER and that the loss of this
interaction impacts on proliferation of tumor cell lines, thus providing
a new means through which APE1 may affect cell growth
and gene expression in cancer cells.
These evidences suggest that an aberrant APE1/NPM1 functional
interaction can be associated with the genomic instability of
cancers and support the concept that interfering with the APE1/
NPM1 association may be a good approach for improving sensitization
of patients to chemotherapy.
Objective. To correlate the expression profile of APE1/Ref-1
(APE1) with that of nucleolar/nucleoplasmic protein Nucleophosmin
1 (NPM1) in association with the tumor aggressiveness
and its progression.
Material and Methods. Retrospective study considering a tissue
microarray of 82 women who had a pathological diagnosis
of ovarian serous carcinoma between January 2003 and July
2008. We included only primary interventions with a diagnosis
of ovarian serous carcinoma and we excluded all patients who
performed chemotherapy before surgery. All these cases were
staged according to the International Federation of Gynecology
and Obstetrics (FIGO) staging system (Stages I, II, III, IV) and to
the TNM classification of malignant tumors for ovarian cancer;
the histopathological grading of these cases was also evaluated
using both Silverberg (grade 1, 2, 3) and Malpica System (low
and high grade). Information such as clinical history and management
for each patient were gathered using clinical files. Data
included age at intervention, date and radicality of intervention,
contingent assumption of any hormonal or non-hormonal therapy,
parity, gravidity, last menses before intervention, and clinical
follow up until January 2011. The Tissue Microarray technique
was used to simultaneously analyze multiple tissues. Protein
expression was assessed by immunohistochemistry on primitive
tumor masses and synchronous peritoneal metastases if present.
Semiquantitative analysis of the immunohistochemical staining
was performed independently by two pathologists and the
staining was semiquantitatively evaluated as H-score (product of
percentage of positivity and intensity).
Results. The mean age at surgery was 63.35 years (±12.12),
76% were postmenopausal and the median overall survival was
40 months (22-56) after the first operation. In 60% of cases, the
stage was greater than or equal to FIGO III with a grade 3 of Silverberg
in 69% of cases. Moreover, all the women were treated
similarly with repeated surgery and chemotherapy if feasible.
APE1 and NPM1 semiquantitative immunohistochemical scores
were significantly correlated in ovarian serous cancer. Both
primitive ovarian mass and peritoneal metastasis were expressing
in a comparable manner these two proteins. Then, a significant
321
Fig. 1. Kaplan-meier curves of overall survival, fiGO staging, Silverberg
grading, and nucleolar/nucleoplasmic protein Nucleophosmin 1
(NPM1) expression (p-values refer to log-rank test). (a): Stage iii-iV and
Npm1 expression, among the stage iii-iV (dot-dash line) considering
NPM1 expression we identified two subgroups. one subgroup of
women with a nuclear Npm1 H-score above the 50th percentile of
the distribution (H-score > 10, dashed line) showed a significant lower
survival than the subgroup with H-score under the 50th percentile
of the distribution (solid line) (log-rank test p < 0.05). (b): Npm1 Hscore
in stage i-ii and iii-iV (p-value refers to Wilcoxon test). (c): G3
Silverberg grade and Npm1 expression; among the grade 3 (dot-dash
line), considering Npm1 expression we identified two subgroups. One
subgroup of women with a nuclear Npm1 H-score above the 50th
percentile of the distribution (H-score > 10, dashed line) showed a
significant lower survival than the subgroup with H-score under the
50th percentile of the distribution (solid line) (log-rank test p < 0.05).
over-expression of nuclear NPM1 protein in ovarian cancer was
present among women who had a worse prognosis. Considering
the NPM1 expression in stage III-IV cancers (5 years overall
survival 32% CI.95 21-49%) we had identified two subgroups
one with low protein expression and 5 years overall survival of
48% (31%-76%) and one subgroup with high protein expression
and 5 year overall survival of 17% (7%-43%) (p < 0.05) (see
Figure). We found also the same pattern of differences in high
grade tumors. The same were found in Cox proportional hazards
multivariate regression model where NPM1 nuclear staining was
a significant independent factor for overall survival after correction
for stage, grade, women age, cytoreduction completeness,
and platinum resistance.
Conclusions. Our study demonstrated an over-expression of
nuclear NPM1 proteins in ovarian cancer among women who
had a worse prognosis. Interestingly, we found a significant
positive correlation between APE1 and NPM1 H-scores possibly
associated with the emerging role that these two proteins play
in the onset of chemoresistance that may be associated to their
function in DNA repair. The relative contribution of NPM1 overexpression
to cancer progression may be ascribable to its roles
in the generation of a permissive condition for further oncogenic
transformation, associated to its indirect stimulatory effect on
APE1 (Fantini et al., 2010; Vascotto et al., 2009). The presence
of high NPM1 levels may limit DNA damage and the DNA damage
response (due to increased BER), associated with oncogenic
stressor signals activation in a normal cell, and therefore may
support, in association with an increased APE1 expression level,
cell survival during cancer development. Our evidence suggests
that overexpression of APE1/NPM1 proteins can be associated
with cancer aggresiveness, which supports the concept that interfering
with APE1/NPM1 interaction may be a good candidate
for improving sensitization of cancer cells to chemotherapy and
radiotherapy. This data could influence the clinical management
(prognosis determination) and the planning of future therapies
suggesting new paths for drug development and testing on ovar-