Human AP endonuclease 1 (HAP1) protein expression in breast cancer correlates with lymph node status and angiogenesis

Abstract

Summary Human AP endonuclease (HAP1) plays a major role in the repair of apurinic/apyrimidinic (AP) sites in cellular DNA. We used immunohistochemistry to examine the expression of HAP1 in normal breast and in 102 primary breast carcinomas. In normal breast epithelium, HAP1 had a uniformly nuclear localization. However, in lactating glandular epithelium, the expression of HAP1 was predominantly cytoplasmic. In carcinomas, both nuclear and cytoplasmic (44%), cytoplasmic (28%) or nuclear staining (24%) were observed. In four cases (4%), no HAP1 expression was detected. All patterns of expression for HAP1 were demonstrated for ductal carcinomas in situ (DCIS), although comedo-type DCIS were usually accompanied by mostly cytoplasmic staining. Similarly, the HAP1 expression in regions of invasive tumour necrosis was cytoplasmic. Pure nuclear HAP1 expression was significantly correlated with low angiogenesis (P = 0.007) and negative lymph node status (P = 0.001). In contrast, cases with cytoplasmic as well as nuclear staining were associated with poor prognostic factors, such as high angiogenesis (P = 0.03) and node positivity (P = 0.03). The pure nuclear staining may be related to better differentiation, as in normal breast, and hence better prognostic features, and cytoplasmic staining to a more metabolically active phenotype with high protein synthesis, as in lactating breast.Keywords: HAP1; breast cancer; immunohistochemistry; DNA repairThe DNA of all organisms, although inherently stable, is under constant threat from both endogenous and exogenous factors. The DNA repair process is of fundamental importance for the survival of all species, and recent studies have established the association of defective DNA repair machinery and cancer (Fishel et al, 1993;Leach et al, 1993).One of the most common lesions that arise in cellular DNA is the apurinic/apyrimidinic (AP) site, which results from the hydrolysis of the N-glycosyl bond linking the base to the deoxyribose moiety. AP sites are considered to be both cytotoxic and mutagenic, and they have been estimated to occur spontaneously at a rate of approximately 104 cell-' day-' from the mammalian cell genome (Loeb et al, 1986). Reactive oxygen species generated either during normal cellular metabolism or by exogenous agents, such as ionizing radiation, can increase this high error rate still further (Hutchinson, 1985;Teoule, 1987).There are specific DNA repair enzymes that recognize AP sites. The major human AP endonuclease (HAPI), also known as APE, APEX or Ref-1, is a 37-kDa protein that shows strong primary sequence similarity to Escherichia coli exonuclease III protein (Demple et al, 1991;Seki et al, 1991; Correspondence to: AL Harris residue is subsequently removed by a phosphodiesterase, followed by filling in of the nucleotide gap by DNA polymerase and DNA ligase, which seals the nick and permits the accurate progress of a DNA replication fork.Apart from its identification as a DNA repair protein, HAPI has been shown to regulate the reductive activation of oxidiz...

Human apurinic/apyrimidinic endonuclease (APE1) is a prognostic factor in ovarian, gastro-oesophageal and pancreatico-biliary cancers

“…APE1 localisation is predominantly nuclear, whereas in breast carcinomas, nuclear, cytoplasmic, and nuclear/cytoplasmic stainings were observed (Kakolyris et al, 1998;Puglisi et al, 2002). Furthermore, while nuclear localisation was associated with good prognostic features (being related to better differentiation, low angiogenesis, and negative lymph node status), cytoplasmic and combined nuclear/cytoplasmic localisation were associated with poor prognostic factors, such as angiogenesis together with node and p53 positivity (Kakolyris et al, 1998;Puglisi et al, 2002).…”

“…Furthermore, while nuclear localisation was associated with good prognostic features (being related to better differentiation, low angiogenesis, and negative lymph node status), cytoplasmic and combined nuclear/cytoplasmic localisation were associated with poor prognostic factors, such as angiogenesis together with node and p53 positivity (Kakolyris et al, 1998;Puglisi et al, 2002). A dysregulation in nuclear vs cytoplasmic ratio towards increased cytoplasmic staining was also observed in thyroid carcinomas (Tell et al, 2000) and prostate cancer (Kelley et al, 2001).…”

Prognostic role of Ape/Ref-1 subcellular expression in stage I-III breast carcinomas

“…In this latter tumor, APE/Ref-I can be detected both in the nucleus and in the cytoplasm and nuclear expression was inversely associated with lymph node status and angiogenesis, although survival did not carrel ate with APE/~ef-J statu~ (20).…”

“…Since APE/Ref-1 is a main aclor in the maintenance of DNA integrity and in the control of cell proliferation, its expression has been studied in a variety of tumors, including lung (18), colon (19) and breast cancer (20). In this latter tumor, APE/Ref-I can be detected both in the nucleus and in the cytoplasm and nuclear expression was inversely associated with lymph node status and angiogenesis, although survival did not carrel ate with APE/~ef-J statu~ (20).…”

Expression of Leukemia-Associated Fusion Proteins Increases Sensitivity to Histone Deacetylase Inhibitor–Induced DNA Damage and Apoptosis

“…This suggests that Ape1 downregulation may be integral to the enhanced DNA damage observed in LAFP-expressing cells treated with vorinostat. Generally, Ape1 overexpression has been correlated with aggressive proliferation and poor prognosis (43,46,47). Decreasing Ape1 levels via knockdown or chemical inhibition has been shown to reduce cancer cell growth and sensitize cells to DNA-damaging agents (48,49).…”