Androgen Receptor Signaling in Castration-Resistant Prostate Cancer Alters Hyperpolarized Pyruvate to Lactate Conversion and Lactate Levels In Vivo

PURPOSE

Androgen receptor (AR) signaling affects prostate cancer (PCa) growth, metabolism, and progression. Often, PCa progresses from androgen-sensitive to castration-resistant prostate cancer (CRPC) following androgen-deprivation therapy. Clinicopathologic and genomic characterizations of CRPC tumors lead to subdividing CRPC into two subtypes: (1) AR-dependent CRPC containing dysregulation of AR signaling alterations in AR such as amplification, point mutations, and/or generation of splice variants in the AR gene; and (2) an aggressive variant PCa (AVPC) subtype that is phenotypically similar to small cell prostate cancer and is defined by chemotherapy sensitivity, gain of neuroendocrine or pro-neural marker expression, loss of AR expression, and combined alterations of PTEN, TP53, and RB1 tumor suppressors. Previously, we reported patient-derived xenograft (PDX) animal models that contain characteristics of these CRPC subtypes. In this study, we have employed the PDX models to test metabolic alterations in the CRPC subtypes.

PROCEDURES

Mass spectrometry and nuclear magnetic resonance analysis along with in vivo hyperpolarized 1-[¹³C]pyruvate spectroscopy experiments were performed on prostate PDX animal models.

RESULTS

Using hyperpolarized 1-[¹³C]pyruvate conversion to 1-[¹³C]lactate in vivo as well as lactate measurements ex vivo, we have found increased lactate production in AR-dependent CRPC PDX models even under low-hormone levels (castrated mouse) compared to AR-negative AVPC PDX models.

CONCLUSIONS

Our analysis underscores the potential of hyperpolarized metabolic imaging in determining the underlying biology and in vivo phenotyping of CRPC.

Abstract 5404: C6-ceramide containing anionic nanoliposomes are effective chemotherapy delivery vehicles for pancreatic cancer

Pancreatic ductal adenocarcinomas (PDACs) are highly fibrotic and poorly vascularized tumors, making systemic delivery of standard chemotherapies ineffective. To overcome the obstacles to delivering therapeutics to PDAC tumors, we have devised an innovative, biocompatible nanocarrier formulation that can deliver chemotherapeutic drugs to pancreatic cancer cells: pegylated anionic nanoliposomes (anionic NLs). By dynamic light scattering, anionic NLs are 85-90 nm in diameter and have a zeta potential of -20 mV. Compared to the more commonly used neutral NLs, the empty (unloaded) anionic NL formulation did not alter proliferation of either normal pancreatic epithelial cells (HPDEs) or PDAC cells. A variety of chemotherapeutic agents were then tested for their ability to be effectively encapsulated into anionic NLs via a temperature-dependent trapping mechanism. The chemotherapeutic drugs vincristine, vinblastine and 5-fluorouracil (5FU) were all effectively encapsulated into the anionic NL formulation, and anionic NLs encapsulated 5FU at reproducible concentrations of 3-4 mM. At 48 hours after a single dose of anionic NL-encapsulated 5FU, in vitro proliferation of pancreatic cancer cells was significantly reduced compared to unloaded NLs or to vehicle controls (p<0.01). When used in a dose-response assay, anionic NLs that delivered a dose of 1-2 μM 5FU were equally effective at inhibiting cancer cell proliferation as 250 μM free, unencapsulated 5FU. To further enhance the effectiveness of these NLs, we then incorporated the pro-apoptotic bioactive lipid C6-ceramide, which had previously been shown to block PDAC tumor growth (Jiang et al., 2011), into a second-generation anionic NL formulation. Incorporation of C-6 ceramide (3mM) into anionic NLs had no effect on the efficiency of chemotherapeutic drug encapsulation. While NLs containing either bioactive C6-ceramide or a single chemotherapeutic agent were effective at blocking pancreatic cancer cell growth, dual-loaded NLs containing C6-ceramide plus vincristine, vinblastine or 5FU showed increased efficacy, completely inhibiting PDAC cell growth at 48 hours after a single-dose treatment. Overall, this study demonstrates that our novel approach of encapsulating standard-of-care chemotherapeutic drugs and C6-ceramide into anionic NLs provides more efficacious drug delivery with a decreased likelihood of toxic side-effects and could be further developed as a safe and effective way to treat PDAC. Supported by NIH grants CA170121 to GLM and CA167535 to MK and GLM. The Penn State Research foundation has licensed ceramide-based nanoliposome technology to Keystone Nano Inc, PA and MK is the co-founder and CMO of Keystone Nano Inc.

Citation Format: Christopher McGovern, Sriram Shanmugavelandy, Sara Shimko, Samuel Linton, Jenny Dai, Mark Kester, Jill P. Smith, Gail L. Matters. C6-ceramide containing anionic nanoliposomes are effective chemotherapy delivery vehicles for pancreatic cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5404. doi:10.1158/1538-7445.AM2014-5404

Targeting glucosylceramide synthase synergizes with C6-ceramide nanoliposomes to induce apoptosis in natural killer cell leukemia

Abstract Natural killer (NK) cell leukemia is characterized by clonal expansion of CD3 - NK cells and comprises both chronic and aggressive forms. Currently no effective treatment exists, thus providing a need for identification of novel therapeutics. Lipidomic studies revealed a dysregulated sphingolipid metabolism as evidenced by decreased levels of overall ceramide species and increased levels of cerebrosides in leukemic NK cells, concomitant with increased glucosylceramide synthase (GCS) expression. GCS, a key enzyme of this pathway, neutralizes pro-apoptotic ceramide by transfer of a uridine diphosphate (UDP)-glucose. Thus, we treated both rat and human leukemic NK cells in combination with: (1) exogenous C6-ceramide nanoliposomes in order to target mitochondria and increase physiological pro-apoptotic levels of long chain ceramide, and (2) 1-phenyl-2-palmitoylamino-3-morpholino-1-propanol (PPMP), an inhibitor of GCS. Co-administration of C6-ceramide nanoliposomes and PPMP elicited an increase in endogenous long-chain ceramide species, which led to cellular apoptosis in a synergistic manner via the mitochondrial intrinsic cell death pathway in leukemic NK cells.