Abstract P1-09-12: TP53 expression in relation to clinical and etiologic factors in breast cancer subtypes

TP53 is a well-known tumor suppressor gene and mutations in TP53 are the most frequent genomic event in most cancers including breast cancer. Recent studies have shown that the frequency, spectrum, timing, and clinical implications of TP53 mutations varied in different molecular subtypes of breast cancer. For example, the frequency of TP53 mutations is the highest in basal-like subtype and lowest in luminal A tumors. However, the evaluation of TP53 protein expression, as a surrogate for TP53 mutations, in large studies in the context of tumor subtypes is limited. In addition, the etiologic relevance of TP53 expression is yet to be investigated. The goal of this study is to evaluate the association of clinical and breast cancer risk factors with TP53 expression, measured using immunohistochemistry (IHC), in breast cancer molecular subtypes. The analysis included 7,226 women with invasive breast cancer who were diagnosed and treated in a tertiary hospital in Beijing, China. Subtypes were defined as Luminal A: ER+ and PR+, HER2–, and low grade (grades 1 or 2); luminal B/HER2–: ER+ and/or PR+, HER2–, and high grade (grade 3); luminal B/HER2+: ER+ and/or PR+, HER2+ (regardless of grade); HER2-enriched: ER–, PR–, and HER2+; Triple-negative (TN): ER–, PR–, and HER2–. As expected, positive TP53 staining showed the lowest frequency in the luminal A (46%) and highest in the TN (61%) and HER2-enriched (63%) subtypes (P-value <0.001). Overall and particularly in luminal A patients, positive TP53 staining was associated with higher frequencies of aggressive tumor features such as higher grade, larger tumor size, higher proliferative index, and EGFR expression. Compared with TP53– patients, TP53+ patients were more likely to have younger ages at onset and increased parity, but these associations were largely driven by the luminal A subtype [OR (95% CI) vs nulliparity = 2.67 (1.59, 4.51); 2.63 (1.52, 4.55); 3.68 (2.01, 6.72) for 1, 2, and ≥3 children, respectively (P-trend = 0.006)]. Luminal A/TP53+ patients were also more likely to have breastfed [OR (95% CI) ever vs never = 1.38 (1.03, 1.85)] than luminal A/TP53– patients. These findings suggest that TP53 IHC staining might be used to further refine the classification of luminal A breast cancer into subgroups with distinct clinical and etiologic relevance.

Citation Format: Yang XR, Abubakar M, Guo C, Koka H, Sung H, Guida J, Deng J, Zhou B, Hu N, Lu N. TP53 expression in relation to clinical and etiologic factors in breast cancer subtypes [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-09-12.

An ordered low-temperature phase of barium nitroprusside trihydrate studied by neutron diffraction

Crystals of barium pentacyanonitrosylferrate trihydrate (barium nitroprusside trihydrate), Ba[Fe(CN)(5)(NO)].3H(2)O, have been studied by neutron diffraction in order to examine the structural behaviour of the compound in the 20-120 K temperature range and to determine the structure at 105 K. The results show the existence of a new crystal phase of the compound at 80 K (with a duplicated a parameter), which still exists at 20 K. The crystal structure at 105 K shows a rearrangement of the water molecules, which results in an ordered structure with P1 symmetry. Two of the four independent nitroprusside cations are rotated by 4.5 degrees around the [100] direction.

Induction of central tolerance by intrathymic inoculation of adenoviral antigens into the host thymus permits long-term gene therapy in Gunn rats

Recombinant adenoviruses are highly efficient at transferring foreign genes in vivo. However, duration of gene expression is limited by the host antiviral immune response which precludes expression upon viral readministration. We tested the feasibility of prolonging gene expression by induction of central tolerance to adenoviral antigens in bilirubin-UDP-glucuronosyltransferase-1 (BUGT1)-deficient Gunn rats. Tolerance was induced by intraperitoneal injection of antilymphocyte serum, followed by intrathymic inoculation of one of the following: a recombinant adenovirus (Ad), adenovirus human UDP-glucuronosyltransferase (Ad-hBUGT1) carrying the hBUGT1 gene; a protein extract of the same virus; or viral infected hepatocytes. Controls received intrathymic injections of normal saline. After 12 d all groups were injected intravenously with 5 x 10(9) pfu of either Ad-hBUGT1 or adenovirus beta-galactosidase (Ad-LacZ) (expressing the Escherichia coli beta-galactosidase [LacZ] gene). In all three groups of tolerized rats, hBUGT1 was expressed in the liver after administration of Ad-hBUGT1, with glucuronidation of biliary bilirubin of above 95%. Serum bilirubin levels decreased from 7.2 to 1.8 mg/dl within 1 wk and remained low for 7 wk. Similar findings were observed following repeat injections given on days 45 and 112. In control rats serum bilirubin levels were reduced for only 4 wk, and viral readministration was ineffective. In all tolerized groups, but not in controls, there was a marked inhibition of appearance of neutralizing antibodies and cytotoxic lymphocytes against the recombinant adenovirus. Injection of wild type adenovirus-5 (Ad5) into the tolerized rats elicited a wild type-specific cytotoxic lymphocyte response. This is the first demonstration of Ad-directed long-term correction of an inherited metabolic disease following central tolerization with thymic antigen.

Long term correction of bilirubin-UDP-glucuronosyltransferase deficiency in Gunn rats by administration of a recombinant adenovirus during the neonatal period

Injection of a recombinant adenovirus expressing human bilirubin-UGT1 (Ad-hBUGT1) (3 x 10(9) plaque-forming units (pfu) intravenously) in adult bilirubin-UDP-glucuronosyltransferase-1 (BUGT1)-deficient Gunn rats resulted in biliary excretion of bilirubin glucuronides and a 70% reduction of serum bilirubin levels. However, the effect was transient, and host humoral and cellular immune response prevented transgene expression after subsequent injections. To determine whether injection during the neonatal period would tolerize the host to the recombinant virus, we injected 1 x 10(8) pfu of Ad-hBUGT1 or Ad-LacZ (a recombinant adenovirus expressing Escherichia coli beta-galactosidase) into 1-3-day-old Gunn rats. Two subsequent injections (3 x 10(9) pfu) were given 56 and 112 days after the initial injection. Injection of Ad-BUGT1, but not Ad-LacZ, reduced serum bilirubin by 70-76% of the levels in untreated pups (9 +/- 1.3 mg/dl), followed by a gradual increase to 3.25 +/- 0.3 mg/dl in 56 days; similar or greater reductions occurred after the second and third injection. Serum neutralizing antibody titer and cytotoxic lymphocyte activity against adenovirus-infected hepatocytes were low or undetectable. Thus, tolerization by injection of the virus during the neonatal period permits long term gene therapy by repeated injection of the virus.