Cytoprotective Effect of Vitamin D on Doxorubicin-Induced Cardiac Toxicity in Triple Negative Breast Cancer.

BACKGROUND: Doxorubicin (Dox) is a first-line treatment for triple negative breast cancer (TNBC), but its use may be limited by its cardiotoxicity mediated by the production of reactive oxygen species. We evaluated whether vitamin D may prevent Dox-induced cardiotoxicity in a mouse TNBC model. METHODS: Female Balb/c mice received rodent chow with vitamin D3 (1500 IU/kg; vehicle) or chow supplemented with additional vitamin D3 (total, 11,500 IU/kg). the mice were inoculated with TNBC tumors and treated with intraperitoneal Dox (6 or 10 mg/kg). Cardiac function was evaluated with transthoracic echocardiography. The cardiac tissue was evaluated with immunohistochemistry and immunoblot for levels of 4-hydroxynonenal, NAD(P)H quinone oxidoreductase (NQO1), C-MYC, and dynamin-related protein 1 (DRP1) phosphorylation. RESULTS: At 15 to 18 days, the mean ejection fraction, stroke volume, and fractional shortening were similar between the mice treated with vitamin D + Dox (10 mg/kg) vs. vehicle but significantly greater in mice treated with vitamin D + Dox (10 mg/kg) vs. Dox (10 mg/kg). Dox (10 mg/kg) increased the cardiac tissue levels of 4-hydroxynonenal, NQO1, C-MYC, and DRP1 phosphorylation at serine 616, but these increases were not observed with vitamin D + Dox (10 mg/kg). A decreased tumor volume was observed with Dox (10 mg/kg) and vitamin D + Dox (10 mg/kg). CONCLUSIONS: Vitamin D supplementation decreased Dox-induced cardiotoxicity by decreasing the reactive oxygen species and mitochondrial damage, and did not decrease the anticancer efficacy of Dox against TNBC.

Pre-Clinical Investigation of Liquid Paclitaxel for Local Drug Delivery: A Pilot Study.

The purpose of this pilot study was to investigate the feasibility of a perfusion catheter to deliver liquid paclitaxel into arterial segments. A clinically relevant rabbit ilio-femoral injury model was utilized to determine the impact of liquid paclitaxel delivered locally into the vessel wall using a perfusion catheter at 1 h to 14 days. Treatment by two clinically available forms of liquid paclitaxel, a solvent-based (sb) versus an albumin-bound (nab), along with a control (uncoated balloons), were investigated. Pharmacokinetic results demonstrated an increase in the retention of the sb-paclitaxel versus the nab-paclitaxel at 1 h; however, no other differences were observed at days one, three, and seven. Histological findings at 14 days showed significantly less neointimal area in the sb-paclitaxel treated arteries as compared with the nab-paclitaxel and the uncoated balloon-treated arteries. Additionally, percent area stenosis was significantly less in the sb-paclitaxel group. These results support the concept of local liquid delivery of paclitaxel into the arterial segments.

EGFR signaling promotes resistance to CHK1 inhibitor prexasertib in triple negative breast cancer.

Aim: Innate resistance to the CHK1 inhibitor prexasertib has been described, but resistance mechanisms are not understood. We aimed to determine the role epidermal growth factor receptor (EGFR) plays in innate resistance to prexasertib in triple negative breast cancer (TNBC). Methods: Using a panel of pre-clinical TNBC cell lines, we measured the sensitivity to prexasertib. We examined the effect activation of EGFR had on prexasertib sensitivity. We measured the synergy of dual blockade of EGFR with erlotinib and CHK1 with prexasertib in TNBC cell lines and xenografts. Results: EGFR overexpression and activation increased resistance to CHK1 inhibition by prexasertib. EGFR promoted the phosphorylation of BCL2-associated agonist of cell death (BAD), inactivating its pro-apoptotic functions. Inhibition of EGFR reversed BAD phosphorylation, increasing sensitivity to prexasertib. Conclusion: The use of prexasertib as a monotherapy in TNBC has been limited due to modest clinical responses. We demonstrated that EGFR activation contributes to innate resistance to prexasertib in TNBC and potentially other cancers. EGFR expression status should be considered in clinical trials examining prexasertib's use as a monotherapy or combination therapy.

PATHOPHYSIOLOGIC EVALUATION OF THE TRANSGENIC CFTR "GUT-CORRECTED" PORCINE MODEL OF CYSTIC FIBROSIS.

This study evaluated the pulmonary pathophysiology of the transgenic CFTR "gut-corrected" cystic fibrosis (CF) pigs. Four sows produced 18 piglets of which 11 were stillborn with only 2 animals surviving beyond 2 weeks. Failure to survive beyond the neonatal period by 5 piglets was judged to result from metabolic dysfunction related to genetic manipulation for CFTR gut expression or due to cloning artifact. Plasma analysis showed very low plasma proteins, highly elevated liver enzymes, and severe acidosis. All surviving offspring received furosemide for systemic edema. Physiologic evaluation was performed with lung tissues from the two surviving pigs. Both acetylcholine and forskolin induced mucous liquid secretion that was significantly lower in CF bronchi than non-CF bronchi. The percent non-volatile solids in mucus secreted from CF bronchi was elevated following acetylcholine or forskolin. Mucociliary transport in excised tracheas was reduced in the CF tracheas relative to nonCF tracheas. The diameter of CF tracheas was less than that of non-CF pigs in spite of their greater body weight. Despite exhibiting severe metabolic dysfunction during the neonatal period, this CF animal model appears to express important characteristics of human CF pulmonary disease.

Mitochondrial DNA Repair through OGG1 Activity Attenuates Breast Cancer Progression and Metastasis.

Production of mitochondrial reactive oxygen species and integrity of mitochondrial DNA (mtDNA) are crucial in breast cancer progression and metastasis. Therefore, we evaluated the role of mtDNA damage in breast cancer by genetically modulating the DNA repair enzyme 8-oxoguanine DNA glycosylase (OGG1) in the PyMT transgenic mouse model of mammary tumorigenesis. We generated mice lacking OGG1 (KO), mice overexpressing human OGG1 subunit 1α in mitochondria (Tg), and mice simultaneously lacking OGG1 and overexpressing human OGG1 subunit 1α in mitochondria (KO/Tg). We found that Tg and KO/Tg mice developed significantly smaller tumors than KO and wild-type (WT) mice after 16 weeks. Histologic analysis revealed a roughly 2-fold decrease in the incidence of lung metastases in Tg mice (33.3%) compared to WT mice (62.5%). Furthermore, lungs from Tg mice exhibited nearly a 15-fold decrease in the average number of metastatic foci compared with WT mice (P ≤ 0.05). Primary tumors isolated from Tg mice also demonstrated reduced total and mitochondrial oxidative stress, diminished mtDNA damage, and increased mitochondrial function. Targeting hOGG1 to the mitochondria protected cells from mtDNA damage, resulting in downregulation of HIF1α and attenuated phosphorylation of Akt. Collectively, we demonstrate proof of concept that mtDNA damage results in breast cancer progression and metastasis in vivo. Moreover, our findings offer new therapeutic strategies for modulating the levels of mtDNA repair enzymes to delay or stall metastatic progression.