Caloric restriction in humans reveals immunometabolic regulators of health span

The extension of life span driven by 40% caloric restriction (CR) in rodents causes trade-offs in growth, reproduction, and immune defense that make it difficult to identify therapeutically relevant CR-mimetic targets. We report that about 14% CR for 2 years in healthy humans improved thymopoiesis and was correlated with mobilization of intrathymic ectopic lipid. CR-induced transcriptional reprogramming in adipose tissue implicated pathways regulating mitochondrial bioenergetics, anti-inflammatory responses, and longevity. Expression of the gene Pla2g7 encoding platelet activating factor acetyl hydrolase (PLA2G7) is inhibited in humans undergoing CR. Deletion of Pla2g7 in mice showed decreased thymic lipoatrophy, protection against age-related inflammation, lowered NLRP3 inflammasome activation, and improved metabolic health. Therefore, the reduction of PLA2G7 may mediate the immunometabolic effects of CR and could potentially be harnessed to lower inflammation and extend the health span.

Abstract 3855: Oncogenic Kras-mediated regulation of the tumor microenvironment in lung cancer

Lung cancer remains the leading cause of cancer-related deaths worldwide, with an estimated 1.6 million deaths each year. Non-small cell lung cancer (NSCLC) is with 85% by far the most common subtype of lung cancer, comprising adenocarcinomas and lung squamous cell carcinoma. Mutations in Kirsten rat sarcoma viral oncogene homolog (KRAS), epidermal growth factor receptor (EGFR) and anaplastic lymphoma receptor tyrosine kinase (ALK) genes are common with the worst overall survival for KRAS mutant adenocarcinoma patients. We have established a murine model of lung cancer, wherein expression of oncogenic Kras can be controlled genetically, allowing activation of oncogenic KrasG12D (Kras*) to initiate tumor growth, tumor eradication upon Kras* depletion and re-activation as a means to model relapse. Oncogenic Kras depletion (deactivation) has previously been reported to result in tumor cell apoptosis even in the presence of tumor suppressor loss. However, the mechanisms of apoptosis, the role of the immune system on these changes, and the mechanisms allowing some tumor cells to escape apoptosis, which typically results in tumor relapse, are unknown. Here, we interrogated the immune response in mediating tumor regression and relapse using this genetically engineered models. Multiplex immunohistochemistry as well as CyTOF provided insight into the changes in immune contexture upon Kras* depletion in mice haploinsufficient for tumor suppressor p53 or mutant for p53 (R172H). Interestingly, total number of T cells including cytotoxic T cells (CTLs) was elevated in lung tumors from p53 mutant mice supporting findings of heightened immune activation and overall response to immune therapy with an increased mutational burden. Kras* inactivation and thus inhibition of MAPK signaling resulted in an overall decrease in abundance of CTLs and antigen presenting cells (APC) as well as engagement of CTL with tumor cells and APCs indicating a decrease in immune presence likely due to proceeding tumor cell kill and immune recruitment. However, intracellular distance of CTL with tumor cells indicated active tumor cell kill of the CTLs to eradicate remaining tumor cells. In summary, these findings support recent observation of increased immune activation in tumors with higher mutational load as well as changes mediated by inhibition of MAPK signaling which both maybe harnessed for enhancing future immunotherapies.

Citation Format: Nina Steele, Kristena Y. Abdelmalak, Sarah F. Ferris, Jennifer M. Lee, Carlos Espinoza, Yaqing Zhang, Sundaresh Ram, Craig Galban, Nithya Ramnath, Timothy L. Frankel, Marina Pasca di Magliano, Stefanie Galbán. Oncogenic Kras-mediated regulation of the tumor microenvironment in lung cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3855.

Abstract 4066: Early assessment of the XL184 treatment by Diffusion-Weighted MRI in metastatic prostate cancer to the bone murine model

Ninety percent of patients with advanced prostate cancer develop metastases to the bone1. At present, there is no definitive means for assessing response to therapy, with RECIST identifying tumors in the bone as “unmeasureable”. Cabozantinib (XL184) is an oral small molecular pan-tyrosine kinase inhibitor of primarily MET and vascular endothelial growth factor receptor 2 (VEGFR2). MET is known to play key roles in cellular proliferation, migration and invasion, which contribute to the survival and metastasis of cancer cells. XL184 is already in Phase 2 trials to evaluate the therapeutic benefit on castration-resistant prostate cancer metastatic to the bone. Diffusion-weighted MRI (DW-MRI) is highly sensitive to microscopic changes in tumor tissue. Our goal was to evaluate DW-MRI for detection and quantification of changes in tumor tissue following one-week XL184 treatment. MR experiments were performed on a 9.4T MRI. Human prostate cancer (PC3) cells were implanted by direct intra-tibial injection into male SCID mice, which serves as a model for prostate bone metastases2. Upon measuring tumor volume of ∼10mm3 on anatomical scans, mice were distributed into 2 groups: XL184 at 30 mg/kg (N=7) and vehicle (N=5). Treatments were delivered by oral gavage once a day for 7 days. DW-MRI was performed at days 0 (pre-treatment), 1, 4, 7, 11, 14 and twice a week after. Apparent diffusion coefficient (ADC) maps were calculated analytically from DW-MR images acquired at b-value 120 and 1200 s/mm2. End point of the study was when tumor volume reached 5x the initial measure. Unpaired Student t-test was performed to compare MRI metrics. XL184 treated mice had smaller tumor volume growth rate than control mice. Significant differences in tumor volume were not observed until 14 days post-treatment initiation (p<0.05). In contrast, significantly higher ADC values (p<0.0.5) for the treated group compared to control were observed at day 7. These results demonstrate the use of DW-MRI as a early biomarker of tumor response to XL184 in a metastatic prostate cancer tumor model. DW-MRI may serve as a surrogate endpoint for assessing patient response to treatment in clinical trials. References: 1. Carlin BI et al. Cancer. 2000;88(12):2989-2994. 2. Lee KC et al. Cancer Res. 2007;67(8):3524-3528.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4066. doi:1538-7445.AM2012-4066

Abstract 5090: Targeted inhibition of MEK and AKT pathways in combination with radiation as a novel treatment paradigm in pancreatic cancer

There is an urgent need for the development of novel therapies to treat pancreatic cancer, which is among the most lethal of all cancers. KRAS activating mutations, which are found in >90% of pancreatic adenocarcinomas, drive tumor dependency on the RAS/MAPK and AKT signaling pathways. Radiation is currently being explored in both the post-operative and inoperable settings as a component of the standard treatment regimen for pancreatic cancer. The purpose of this study was to test the hypothesis that MEK inhibitors will offer clear therapeutic benefit when integrated into radiotherapy treatment regimens for treatment of this disease. We explored the activation of the MAPK and AKT pathways in response to radiation in multiple pancreatic tumor cell lines. Small molecule inhibitors of MEK (PD0325901) and AKT (API-2) were subsequently evaluated for their radiosensitizing potential alone and in combination. In vivo efficacy was tested in subcutaneous MiaPaCa2 xenografts and diffusion MRI (dMRI) was explored as a surrogate biomarker of response. Phosphorylated levels of ERK and AKT were found to increase in response to radiation treatment in our pancreatic tumor cell line panel. MEK inhibitor-induced radiosensitization was observed in vitro as well as in vivo, where changes in dMRI strongly correlated with changes in tumor burden. The further addition of an AKT inhibitor to the MEK inhibitor/radiation regimen resulted in enhanced therapeutic gain as measured by radiosensitization and tumor cell death. In conclusion, MEK inhibition results in growth arrest, apoptosis, and radiosensitization of multiple preclinical pancreatic tumor models and the effects can be enhanced by combination with an AKT inhibitor. These results provide rationale for further testing of a treatment regimen in pancreatic cancer that combines MEK inhibition with radiation, optimally in conjunction with AKT inhibition.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5090. doi:10.1158/1538-7445.AM2011-5090

Abstract 5281: Gemcitabine is evaluated as an alternative treatment to temozolomide for high grade gliomas

Glioblastoma multiforme (GBM) remains a challenging malignancy due to intrinsic resistance to therapy. Pre-clinical mouse models which recapitulate the human disease provide an opportunity to identify and test novel agents that could be used alone or in combination with other systemic agents and/or radiation therapy. Here we describe the use of a genetically engineered murine GBM model [Ink4a-Arf-/- PtenloxP/loxp/ Ntv-a RCAS/PDGF(+)/Cre(+)] and functional magnetic resonance imaging (MRI) to evaluate systemic agents alone or in combination with radiation. The current standard therapy for patients bearing GBMs is Temozolomide (TMZ) combined with radiation yet recent analysis of O-6-methylguanine-DNA methyltransferase (MGMT) status in GBMs has linked unmethylated MGMT promoter with poor outcome. Thus we evaluated Gemcitabine (GEM) as a novel therapy for GBM concurrent with radiation and compared it to standard therapy. GEM, a deoxycytidine analog, is a potent radiosensitizer that demonstrates cytotoxic, anti-clonogenic, and radiosensitizing effects in GBM cell lines.

Therapeutic efficacy was quantified by contrast-enhanced MRI and diffusion-weighted MRI (DW-MRI) for growth rate and tumor cellularity, respectively. Mice treated with GEM, TMZ or radiation alone showed a significant reduction in tumor volume compared to control mice as early as three days post treatment start. Both combined treatment (GEM+IR and TMZ+IR) resulted in improved effectiveness over single therapies. A significant reduction in tumor volume compared to GEM, TMZ or IR groups was observed. Furthermore, both combination therapies significantly prolonged survival compared to the other groups as early as day 7 after start of treatment. There was no significant difference between both combined treatments either in tumor growth or in survival. ADC values were found to increase immediately upon administration of GEM in both alone and combination therapies. In contrast, a gradual increase in ADC values was observed in tumors treated with IR and TMZ, both alone and in combination.GEM concurrent with radiation resulted in significant reduction in tumor volume and prolonged survival in this clinically-relevant GBM mouse model. GEM combined with radiation had the same effect GBM as compared to TMZ combined with radiation. We also demonstrated the successful implementation of an imaging biomarker surrogate (ADC) which correlated with efficacy. Ink4a-Arf-/- PtenloxP/loxP/ Ntv-a RCAS/PDGF(+)/Cre(+) mice serve as a valuable pre-clinical GBM model with the potential to identify novel therapeutics for early phase I/II testing for GBM patients. Based on these results, GEM combined with IR appears to be a suitable alternative to treat tumors that have a poor response to traditional therapies (eg. unmethylated MGMT).

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5281. doi:10.1158/1538-7445.AM2011-5281

A rabbit model for assessing the ocular barriers to the transscleral delivery of triamcinolone acetonide

Transscleral delivery of triamcinolone acetonide into the vitreous using sub-Tenon's injections may be a safer alternative to reduce the sight-threatening complications of direct intravitreal injections. However, sub-Tenon's injections have demonstrated low and poorly sustained vitreous drug levels in animal studies. To improve our understanding of the clearance mechanisms of corticosteroids, we evaluated vitreous drug levels following sub-Tenon's injection of triamcinolone acetonide in rabbits with selective elimination of conjunctival lymphatic/blood vessels and the choroid. Pigmented rabbits were given a sub-Tenon's injection of a preservative-free triamcinolone acetonide formulation of either a 10- or 20-mg dose in the superotemporal quadrant. The effect eliminating both conjunctival and choroidal clearance was evaluated by injecting the drug, followed by immediate euthanasia, effectively terminating both lymph and blood flow in the conjunctiva and choroid. To inhibit only the clearance from conjunctival lymphatics/blood vessels of a sub-Tenon's injection of triamcinolone acetonide, a group of rabbits had a 'conjunctival window' created by incising an 7 mmx7 mmx7 mm square through the conjunctiva to bare sclera in the superotemporal quadrant. To eliminate only the clearance of drug from the choroidal circulation, cryotherapy was performed in another group of rabbits creating a chorioretinal scar in the superotemporal quadrant. Following the sub-Tenon's drug injection, the eyes were enucleated in all groups after 3 hr and vitreous drug levels were measured with HPLC. In normal animals, a 10-mg sub-Tenon's injection showed no detectable vitreous drug levels; however, a 20-mg injection showed positive vitreous drug levels. This suggested that collectively, the transscleral clearance mechanisms inhibiting delivery into the vitreous may be saturated with a drug depot that has a higher release rate. A 10-mg sub-Tenon's drug depot was able to deliver drug into the vitreous when both the conjunctival and choroidal drug clearance was eliminated by euthanizing the animal immediately following the drug injection. In rabbits that had only a 'conjunctival window', selectively eliminating conjunctival drug clearance, vitreous drug levels were detected. However, in rabbits that had only cryotherapy, selectively eliminating choroidal drug clearance, vitreous drug levels were not detected suggesting that the conjunctival lymphatics/blood vessels may be an important barrier to the transscleral delivery of triamcinolone acetonide. Variability in the vitreous drug levels between rabbits in each group precluded statistical testing. In summary, the rabbit appeared to demonstrate saturable ocular barriers to transscleral delivery of triamcinolone acetonide into the vitreous following a sub-Tenon's injection. The results suggested that the conjunctival lymphatics/blood vessels may be an important barrier to the delivery of triamcinolone acetonide to the vitreous in this rabbit model. The barrier location and clearance abilities of the ocular tissues are important to consider when developing a successful transscleral drug delivery system. Animal models, retaining the dynamics of blood and lymph flow, may improve the basic understanding of the ocular barriers involved with transscleral drug transport and warrants further investigation.

Intensive care during prolonged anhepatic state after total hepatectomy and porto-caval shunt (two-stage procedure) in surgical complications of liver transplantation

BACKGROUND/AIMS

Recently, total hepatectomy and temporary porto-caval shunt has been indicated in surgical complications of liver transplantation. Four cases of liver transplantation which presented liver hemorrhage at the time of implant, and a 5th case with surgical trauma of hepatic hilum are presented.

METHODOLOGY

The graft was removed and a porto-caval shunt was performed in all patients. Retransplantation was possible in all recipients, after an anhepatic period of 16-24 hours.

RESULTS

Early persistent ionic hypocalcemia and late olyguric renal failure were the most constant and prominent complications during the anhepatic period. Two patients died of renal failure and respiratory distress syndrome at 6 and 28 days, respectively, after liver transplantation. The other 3 patients are alive and without complications at 48, 33 and 11 months of follow-up.

CONCLUSIONS

Total hepatectomy with a temporary porto-caval shunt and later retransplantation must be considered as a useful procedure for surgical complications of liver transplantation which may not be treated using other techniques. Special attention should be paid to preserve renal function in the anhepatic state in order to improve survival in similar cases of two-stage liver transplantation.