Abstract 984: Race- and ancestry-related metabolites and SNPs associated with response to secondary hormonal therapy in metastatic castration-resistant prostate cancer

The number of new cases and deaths from prostate cancer (PCa) is highest for Black men compared with other racial and ethnic groups, and Black PCa patients have a shorter average survival as well as a greater risk of tumor recurrence than men of other racial and ethnic groups. However, recent studies have shown that Black PCa patients have a better response to certain therapeutic regimens than White PCa patients. This study focuses on addressing the critical need to determine novel relationships between ancestry-related genetic variation and PCa aggressiveness and response to secondary hormonal therapy in metastatic castration-resistant PCa (mCRPC). We conducted correlative science in a DoD Prostate Cancer Clinical Trials Consortium (PCCTC) prospective multicenter study of secondary hormonal therapy in mCRPC stratified by race, Abi Race. This study enrolled 50 self-reported Black and 50 self-reported White mCRPC patients, and such patients received abiraterone and prednisone until disease progression or adverse event. We performed metabolic profiling using serum samples from fasting patients at baseline and after treatment. In addition, we performed genome-wide genotyping using genomic DNA from whole blood specimens from patients at baseline. We then identified race- and ancestry-related metabolite and SNP variations that associated with outcome using a penalized Cox model approach. In addition, we used Ingenuity Pathway Analysis (IPA) and Lasso Analysis to further study race-related metabolites and SNPs. From these analyses, we identified sphingolipids such as ceramide as race-related metabolites associated with outcome as well as SNPs in Sphingosine Kinase Type 1-Interacting Protein (SKIP) associated with outcome. In addition, our analyses suggest that sphingolipids such as ceramides and SKIP may regulate cancer-related biofunctions differently in Black and White mCRPC patients undergoing abiraterone treatment. Both sphingolipids and SKIP are components of the Sphingosine Rheostat, the regulatory component of sphingolipid cellular metabolism often exploited by various cancers, in which ceramides displays a pro-apoptotic role whereas sphingosine-1-phosphate (S1P) is associated with an anti-apoptotic role and is indirectly regulated by SKIP via regulating the activity of Sphingosine Kinase (SPK1). Evaluation of the function of these sphingolipids and SKIP in PCa cell drug response and aggressiveness are currently underway. These findings are furthering understanding of race- and ancestry-related biological factors that influence response to secondary hormonal therapy in mCRPC and have the potential to impact selection of patients for secondary hormonal therapy and to mitigate PCa disparity.

Citation Format: Sean Alan Piwarski, Tyler Allen, Bonnie LaCroix, Lauren Howard, Morgan Paul, Nick Bachelder, Alex Sibley, Steve Patierno, Terry Hyslop, Kouros Owzar, Daniel George, Jennifer Freedman. Race- and ancestry-related metabolites and SNPs associated with response to secondary hormonal therapy in metastatic castration-resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 984.

Breast cancer treatment delay in African American women in Washington, DC

Abstract #4164

Background: Delays in follow-up after a positive breast cancer screen are thought to contribute to racial/ethnic disparities in breast cancer outcomes. The goal of this study was to determine the relative impact of self-identified race and other relevant socio-demographic and logistic variables on time to diagnosis after an abnormal mammogram, and time to first treatment after a cancer diagnosis within the context of data collection for a large research study of the effectiveness of patient navigation.
 Methods: Our sample includes 168 African-American and non-Hispanic white women with a documented invasive breast cancer diagnosis at an urban academic medical center during 2006 and 2007. The outcome variables were the number of days from abnormal mammogram to cancer diagnosis and from diagnosis to first treatment.
 Results: The median number of days to breast cancer diagnosis following an abnormal mammogram was 20.5 days for African-Americans compared to 15 days for non-Hispanic white women. Median days to first treatment after diagnosis was 21 days for African-American women compared to 16 days for non-Hispanic white women. Neither difference was statistically significant. In addition, 76% of African-American women had private insurance versus 81% of non-Hispanic white women.
 Conclusions: The identification of specific risk factors associated with a delay in diagnosis noted elsewhere in the literature and suggested in these preliminary findings could provide useful information regarding characteristics of women who are most likely to benefit from enhanced patient navigation efforts. Thus far, no statistically significant differences have been identified but the variety of factors that could contribute to the longer delay in disease management in African-American women compared to non-Hispanic white women, such as insurance status, provider location, household income, cultural issues, and other barriers to health care access, should be evaluated with a larger patient population.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 4164.

The opioid system in the gastrointestinal tract

Mu-, delta- and kappa-opioid receptors (ORs) mediate the effects of endogenous opioids and opiate drugs. Here we report (1) the distribution of muOR in the guinea-pig and human gastrointestinal tract in relation to endogenous ligands, to functionally distinct structures in the gut and to deltaOR and kappaOR; and (2) the ligand-induced muOR endocytosis in enteric neurones using in vitro and in vivo models. In the guinea pig, muOR immunoreactivity is confined mainly to the myenteric plexus. MuOR myenteric neurones are most numerous in the small intestine, followed by the stomach and the proximal colon. MuOR immunoreactive fibres are dense in the muscle layer and the deep muscular plexus, where they are in close association with interstitial cells of Cajal. This distribution closely matches the pattern of enkephalin. MuOR enteric neurones comprise functionally distinct populations of neurones of the ascending and descending pathways of the peristaltic reflex. In human gut, muOR immunoreactivity is localized to myenteric and submucosal neurones and to immune cells of the lamina propria. DeltaOR immunoreactivity is located in both plexuses where it is predominantly in varicose fibres in the plexuses, muscle and mucosa, whereas kappaOR immunoreactivity appears to be confined to the myenteric plexus and to bundles of fibres in the muscle. MuOR undergoes endocytosis in a concentration-dependent manner, in vitro and in vivo. Pronounced muOR endocytosis is observed in neurones from animals that underwent abdominal surgery that has been shown to induce delay in gastrointestinal transit. We can conclude that all three ORs are localized to the enteric nervous system with differences among species, and that muOR endocytosis can be utilized as a means to visualize enteric neurones activated by opioids and sites of opioid release.

Abdominal surgery induces μ opioid receptor endocytosis in enteric neurons of the guinea-pig ileum

Immunohistochemistry and confocal microscopy were used to investigate mu opioid receptor (muOR) internalization in enteric neurons of the guinea-pig ileum following abdominal surgery. The following surgical procedures were performed under halothane or isofluorane anesthesia: a) midline abdominal skin incision, b) laparotomy or c) laparotomy with intestinal manipulation. Gastrointestinal transit was evaluated by using a non-absorbable marker and measuring fecal pellet output. In neurons from normal and control (anesthesia alone) animals, muOR was predominantly at the cell surface. muOR endocytosis following skin incision was not significantly different from controls (21.2+/-3.5% vs. 13.7+/-2.1%, mean+/-S.E.M.), whereas it was significantly increased by laparotomy (46.5+/-6.1%; P<0.01 vs. controls) or laparotomy plus intestinal manipulation (40.5+/-6.1%; P<0.01 vs. controls) 30 min following surgery compared with controls. muOR endocytosis remained elevated at 4 h (38.6+/-1.2%; P<0.01 vs. controls), whereas it was similar to controls at 6 and 12 h (17.5+/-5.8% and 11.2+/-3.0%). muOR endocytosis occurred in cholinergic and nitrergic neurons. Gastrointestinal transit was significantly delayed by laparotomy or laparotomy plus intestinal manipulation (12.8+/-1.2 and 13.8+/-0.6 h vs. 7.0+/-0.5 in controls; P<0.01), but was not significantly changed by skin incision (8.2+/-0.6 h). The findings of the present study support the concept that the noxious stimulation caused by abdominal surgery induces release of endogenous opioids thus resulting in muOR endocytosis in neurochemically distinct enteric neurons. muOR internalization can serve as indirect evidence of opioid release and as a means to visualize neuronal pathways activated by opioids.

Ligand-induced mu opioid receptor endocytosis and recycling in enteric neurons

Immunohistochemistry and confocal microscopy were used to investigate endocytosis and recycling of the native mu opioid receptor (muOR) in enteric neurons. Isolated segments of the guinea-pig ileum were exposed to increasing concentrations of muOR agonists at 4 degrees C to allow ligand binding and warming to 37 degrees C for 0 min (baseline) to 6 h in ligand-free medium to allow receptor internalization and recycling. The endogenous ligand, [Met]enkephalin, and [D-Ala(2),MePhe(4),Gly-ol(5)] enkephalin (DAMGO), an opioid analog, and the alkaloids, etorphine and fentanyl, induced rapid internalization of muOR immunoreactivity in enteric neurons, whereas morphine did not. muOR internalization was prevented by muOR antagonists. Basal levels of muOR immunoreactivity in the cytoplasm were 10.52+/-2.05%. DAMGO (1 nM-100 microM) induced a concentration-dependent increase of muOR immunofluorescence density in the cytoplasm to a maximum of 84.37+/-2.26%. Translocation of muOR immunoreactivity in the cytoplasm was detected at 2 min, reached the maximum at 15-30 min, remained at similar levels for 2 h, began decreasing at 4 h, and was at baseline values at 6 h. A second exposure to DAMGO (100 nM) following recovery of internalized muOR immunoreactivity at the cell surface induced a translocation of muOR immunoreactivity in the cytoplasm comparable to the one observed following the first exposure (46.89+/-3.11% versus 43.31+/-3.80%). muOR internalization was prevented by hyperosmolar sucrose, phenylarsine oxide or potassium depletion, which inhibit clathrin-mediated endocytosis. muOR recycling was prevented by pre-treatment with bafilomycin A1, an acidotropic agent that inhibits endosomal acidification, but not by the protein synthesis inhibitor, cycloheximide. This study shows that native muOR in enteric neurons undergoes ligand-selective endocytosis, which is primarily clathrin-mediated, and recycles following endosomal acidification. Following recycling, muOR is activated and internalized by DAMGO indicating that recycled receptors are functional.

Dynamin and Rab5a-dependent trafficking and signaling of the neurokinin 1 receptor

Understanding the molecular mechanisms of agonist-induced trafficking of G-protein-coupled receptors is important because of the essential role of trafficking in signal transduction. We examined the role of the GTPases dynamin 1 and Rab5a in substance P (SP)-induced trafficking and signaling of the neurokinin 1 receptor (NK1R), an important mediator of pain, depression, and inflammation, by studying transfected cells and enteric neurons that naturally express the NK1R. In unstimulated cells, the NK1R colocalized with dynamin at the plasma membrane, and Rab5a was detected in endosomes. SP induced translocation of the receptor into endosomes containing Rab5a immediately beneath the plasma membrane and then in a perinuclear location. Expression of the dominant negative mutants dynamin 1 K44E and Rab5aS34N inhibited endocytosis of SP by 45 and 32%, respectively. Dynamin K44E caused membrane retention of the NK1R, whereas Rab5aS34N also impeded the translocation of the receptor from superficially located to perinuclear endosomes. Both dynamin K44E and Rab5aS34N strongly inhibited resensitization of SP-induced Ca(2+) mobilization by 60 and 85%, respectively, but had no effect on NK1R desensitization. Dynamin K44E but not Rab5aS34N markedly reduced SP-induced phosphorylation of extracellular signal regulated kinases 1 and 2. Thus, dynamin mediates the formation of endosomes containing the NK1R, and Rab5a mediates both endosomal formation and their translocation from a superficial to a perinuclear location. Dynamin and Rab5a-dependent trafficking is essential for NK1R resensitization but is not necessary for desensitization of signaling. Dynamin-dependent but not Rab5a-dependent trafficking is required for coupling of the NK1R to the mitogen-activated protein kinase cascade. These processes may regulate the nociceptive, depressive, and proinflammatory effects of SP.

Interlaboratory validation of a new assay for DNA-protein crosslinks

In 1992, a simple and sensitive assay for detecting DNA-protein crosslinks was developed [1]. In an effort to facilitate the greater use of the assay, a number of studies were conducted to evaluate its reliability and reproducibility. During this work, the assay was used to assess whether various metals and other compounds could induce crosslinks in cultured human lymphocytes (Epstein-Barr virus-transformed Burkitt's Lymphoma cell line). Potassium permanganate, mercury chloride, lead nitrate, magnesium perchlorate, aluminum chloride, and cadmium chloride did not induce DNA-protein crosslinks at either cytotoxic or non-cytotoxic levels. Copper sulfate, arsenic trioxide, and potassium chromate induced DNA-protein crosslinks only at cytotoxic concentrations. Acute lethality of the cells was assessed immediately after exposure to metals by trypan blue exclusion while long-term lethality was assessed by cell proliferation and trypan blue exclusion following an incubation period of 5 days after exposure to the metal compound. All metals exhibited more toxicity in the long-term lethality assay compared to the short-term assay. The cultured human lymphocytes treated with various doses of lead acetate, cadmium chloride, arsenic trioxide and copper sulfate, as well as cis-platinum and chromate, were sent to four different laboratories to compare the reliability and reproducibility of the DNA-protein crosslink assay. Depending on the chemical studied, there were quantitative differences in the results observed among the various laboratories using the assay. However, all laboratories generally showed that cis-platinum, chromate, arsenic trioxide and copper sulfate induced DNA-protein crosslinks at levels that produced acute cytotoxicity, whereas cadmium chloride and lead acetate did not.

BW2258U89: a GRP receptor antagonist which inhibits small cell lung cancer growth

The ability of reduced peptide bond analogues of gastrin releasing peptide (GRP) to antagonize small cell lung cancer (SCLC) GRP receptors was investigated. BW462U89, BW1023U90, BW2123U89 and BW2258U89 inhibited binding of (125I-Tyr4) BN to NCI-H345 cells with IC50 values of 5, 6, 140 and 10 nM respectively. The GRP analogues had no effect on basal cytosolic Ca2+ but inhibited the increase caused by 10 nM BN. BW462U89 reversibly blocked the increase in cytosolic Ca2+ caused by BN. The GRP analogues (1 microM) inhibited NCI-H345 colony formation in the absence or presence of 10 nM BN. Also, BW2258U89 (0.4 mg/kg, s.c. daily) inhibited xenograft growth in nude mice. These data indicate that BW2258U89 inhibits SCLC growth in vitro and in vivo.