Abstract 5863: RGX-202, a first-in-class small-molecule inhibitor of the creatine transporter SLC6a8, is a robust suppressor of cancer growth and metastatic progression

Background: Colorectal cancer (CRC) is one of the leading causes of cancer deaths worldwide with more than 140,000 patients diagnosed and nearly 50,000 deaths annually in the U.S. alone. Roughly 60% of patients present with locally advanced or distant metastatic disease, with the liver being a primary site of metastatic colonization. Creatine metabolism has been implicated in colon cancer progression and metastatic colonization of the liver. Metastatic colon cancer cells upregulate and release creatine kinase-B (CKB) into the extracellular space, where it phosphorylates creatine to generate the high-energy metabolite phosphocreatine. Phosphocreatine is imported via the creatine transporter SLC6a8. Intracellular phosphocreatine can be converted to ATP to fuel the survival of metastatic cancer cells within the hypoxic hepatic microenvironment. Consistent with this finding, genetic depletion of SLC6a8 in colon and pancreatic cancer cell lines significantly reduced liver colonization in mouse xenograft models.

Results: We herein demonstrate that the novel small molecule RGX-202 is a robust inhibitor of creatine uptake in cancer cells, both in vitro and in vivo. Oral administration of RGX-202 induced apoptosis of colon cancer cells in vivo, and significantly suppressed colon cancer liver metastatic colonization and primary tumor growth, both in KRAS wild-type and KRAS mutant colon cancer cell lines as well as in human PDX mouse models. Using genetic studies, these effects were found to be dependent on tumoral expression of SLC6a8. In addition, combination treatment of the CT26 syngeneic colon cancer mouse model with 5-FU resulted in synergistic antitumor activity, with complete tumor regressions observed in more than 40% of treated mice. Similarly, combination treatment of the KPC syngeneic mouse model with gemcitabine significantly reduced the growth of primary pancreatic tumors. Definitive 28-day GLP toxicology and pharmacokinetics studies of RGX-202 are currently ongoing. Preliminary observations suggest good tolerability in several animal species with a favorable pharmacokinetic profile, including bioavailability.

Conclusion: These results strongly support clinical development of RGX-202 in patients with gastrointestinal cancers, including colorectal and pancreatic cancer, both as monotherapy and in combination with standard-of-care treatment.

Citation Format: Isabel Kurth, Celia Andreu, Shugaku Takeda, Helen Tian, Foster Gonsalves, Katya Leites, Subhasree Sridhar, Jia Min Loo, Rob Busby, Sohail Tavazoie, Masoud Tavazoie. RGX-202, a first-in-class small-molecule inhibitor of the creatine transporter SLC6a8, is a robust suppressor of cancer growth and metastatic progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5863.

Abstract P4-03-01: Inhibition of Fatty Acid Synthase (FASN) Sensitizes Breast Cancer Cells to Chemotherapy and Disrupts the Lipid Rafts

MN

Background: Breast cancer is the second leading cause of cancer death of women worldwide. One of the major challenges for a better prognosis of breast cancer patients is the ineffectiveness of chemotherapy and drug resistance. To investigate the mechanisms of drug resistance, resistant cancer cell lines have been established with various anticancer agents. We found that FASN, an important metabolic enzyme overexpressed in aggressive carcinomas, is t responsible in part for the drug resistance phenotype of breast cancer cells. Our findings show that blockage of FASN augments the cytotoxicity of the anti-mitotic drug Taxol in breast cancer cells. Moreover, C75 and Taxol have a synergistic effect both drugs are combined. The in vivo effect of C75 and Taxol and the mechanism by which blockage of FASN sensitizes the cells to chemotherapy are unknown. Material and Methods: In this study first we show the effect of C75 plus Taxol in breast tumor growth. BT474 cells were injected into the mammary fat pad of nude mice to generate the tumors. When the tumors were measurable we treated the mice with C75, Taxol or with a combination of both drugs. Second we studied the lipid rafts disruption after treatments by sucrose gradient and immunofluorescence. Results: We found that C75 plus Taxol extensively inhibited the tumor growth 9 fold and reduced the tumor size in 4 fold comparedn to the control mice (no treatement). In comparison C75 alone reduced the tumor growth in 1.5 fold only; and Taxol 2.5 fold compared to the control mice. These results show for first time that blockage of FASN (with C75) sensitizes breast cancer tumors to Taxol treatment in vivo. In addition, we studied the possible mechanism involved in the sensitization of breast cancer cells to Taxol by FASN blockage. Previous studies reported that blockage of FASN or Taxol treatment decrease the sphingolipids synthesis. Sphingolipids and cholesterol are the most abundant fatty acid in the lipid rafts in the plasma membrane. Disruption of lipid rafts has been shown to induce apoptosis in different carcinoma cell lines. Based in these findings, we studied lipid rafts in BT474 cells treated with C75, Taxol or combination of both with sucrose gradient and immunofluorescence microscopy. Discussion: Our results show that C75 and Taxol disrupt the lipid rafts. Thesefindings show that FASN is a new mechanism of drug resistance and may be an ideal target for chemosensitization in breast cancer chemotherapy.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-03-01.

Impaired p53 function leads to centrosome amplification, acquired ERalpha phenotypic heterogeneity and distant metastases in breast cancer MCF-7 xenografts

In this study, we establish an MCF-7 xenograft model that mimics the progression of human breast carcinomas typified by loss of p53 integrity, development of centrosome amplification, acquired estrogen receptor (ERalpha) heterogeneity, overexpression of Mdm2 and metastatic spread from the primary tumor to distant organs. MCF-7 cells with abrogated p53 function (vMCF-7(Dnp53)) maintained nuclear ERalpha expression and normal centrosome characteristics in vitro. However, following mitogen stimulation, they developed centrosome amplification and a higher frequency of aberrant mitotic spindles. Centrosome amplification was dependent on cdk2/cyclin activity since treatment with the small molecule inhibitor SU9516 suppressed centriole reduplication. In contrast to the parental MCF-7 cells, when introduced into nude mice as xenografts, tumors derived from the vMCF-7(DNp53) cell line developed a strikingly altered phenotype characterized by increased tumor growth, higher tumor histopathology grade, centrosome amplification, loss of nuclear ERalpha expression, increased expression of Mdm-2 oncoprotein and resistance to the antiestrogen tamoxifen. Importantly, while MCF-7 xenografts did not develop distant metastases, primary tumors derived from vMCF-7(DNp53) cells gave rise to lung metastases. Taken together, these observations indicate that abrogation of p53 function and consequent deregulation of the G1/S cell cycle transition leads to centrosome amplification responsible for breast cancer progression.

MMPI-2 negative treatment indicators scale and irregular discharge

A sample of 18 psychiatric inpatients who had completed the MMPI-2 and subsequently received an irregular discharge from inpatient treatment were compared on the MMPI-2 Negative Treatment Indicators scale (TRT) with a random sample of 18 inpatients who received a regular discharge from inpatient care. Analysis showed no significant difference between the two groups on the Negative Treatment Indicators scale. The two groups did differ in K scale elevation. The possible need to interpret the Negative Treatment Indicators scale in the context of K scale elevation is discussed.

Prediction of twenty-four-hour energy expenditure in a respiration chamber in smokers and non-smokers

Fourteen subjects (seven smokers, seven non-smokers) underwent at least one measurement of 24-h energy expenditure (EE) in a respiration chamber, smoking or not smoking as normal. Activity levels (AL) were calculated as multiples of basal metabolic rate (BMR) from records of time spent in specified activity categories and their average published energy costs. Predicted 24-h EE was estimated by multiplying AL by BMR measured on exit from the chamber. Smokers smoked an average of 18.6 cigarettes during the 24-h EE measurement (range 9-29). Measured 24-h EE was higher than predicted in the smokers (7.1%, P < 0.001) but not significantly different from predicted in the non-smokers (2.6% lower). We conclude that smoking increases 24-h EE and that factorial prediction of EE using average published energy costs of activities under-estimates 24-h EE in smokers but not in non-smokers.

Influence of mild cold on 24 h energy expenditure in 'normally' clothed adults

Ten subjects aged 19-35 years (four men and six women) underwent two measurements of 24 h energy expenditure (EE) in a whole-body respiration calorimeter, one at a temperature of 28 degrees and one at 20 degrees. Choice of clothing was allowed. Dietary intake was standardized and subjects were asked to follow the same pattern of activity during both measurements. Mean 24 h EE was significantly greater at the cooler temperature by 5.0 (SD 5.5)%, with individual differences ranging from 4.6% lower to 12.6% higher. The difference in EE at the two temperatures was similar during the day and the night and occurred even though subjects wore more clothes and used more bedding at 20 degrees. No relationship was observed between response to 20 degrees and body-weight status. In conclusion, the assumption that mild cold is unlikely to affect EE in subjects wearing normal clothing may be incorrect.

Profiles of children with severe oral language disorders

The major purpose of this study is to determine whether children assigned to classes for severe oral language handicaps in California by a multidisciplinary diagnostic team exhibit a characteristic ITPA performance profile or a number of distinct profiles. A factor analysis and a cluster analysis was made on the scores of 237 children. It was found that on the factor analysis the results showed a clear auditory-vocal factor and a visual-motor factor. All five tests in the visual-motor channel were superior to the five tests in the auditory-vocal channel. Within the auditory-vocal channel the lowest scores were in auditory association and grammatic closure. Ninety-seven percent of the oral language handicapped children had the lowest scores on these two subtests. It appears from these results that the major deficit of children assigned to severe oral language classes is a deficit in the central organization process, formerly referred to as "central aphasia, or inner language".