TAMI-25. UPREGULATION OF CREATINE METABOLISM BY MYELOID CELLS RESULTS IN GLIOBLASTOMA PROGRESSION

Malignant brain tumors are uniquely immunosuppressive, with a predominant infiltration of immunosuppressive tumor-associated myeloid cells (TAMCs) and a deficit in T-cells unrivaled to any other tumor. This unique tumor microenvironment (TME) promotes resistance to both conventional and immune therapies for this disease. The underlying mechanisms by which TAMCs promote glioblastoma (GBM) progression are not fully understood. We found that TAMCs specifically upregulate de-novo creatine metabolism within GBM using unbiased genetic and metabolic screening. This metabolic phenotype was confirmed in human GBM patients by comparing peripheral versus tumor-infiltrating myeloid cells. Examination of de-novo creatine generation using Carbon13 arginine flux revealed that TAMCs, but not tumor-infiltrating CD8+ T-cells, can produce creatine. Furthermore, we demonstrate that TAMCs actively secrete de-novo generated creatine into cell cultures. Examination of the single-cell microenvironment of GBM revealed that malignant cells preferentially express the creatine transporter, indicating that TAMC-derived creatine is taken up by GBM. Notably, SLC6A8 is directly upregulated in the context of hypoxia and suggests that creatine uptake is a mechanism to promote survival under hypoxic stress. Indeed, exogenous creatine supplementation promoted both the migration and survival of multiple glioblastoma cell lines in-vitro. Utilizing an established inhibitor of creatine metabolism, β-Guanidinopropionic acid (β -GPA), we found that β -GPA blocks both the migration and survival of glioma cells under hypoxic stress. Lastly, β -GPA also inhibited creatine secretion by TAMCs, showing that creatine blockade can also influence TAMC metabolic phenotype. In the future, we will examine the importance of creatine metabolism on both immune suppression and tumor progression in-vivo. This work provides novel insights into the role of creatine metabolism in GBM and identifies a unique therapeutic avenue for this devastating disease.

Therapeutic targeting of SLC6A8 creatine transporter inhibits KRAS mutant and wildtype colon cancer and modulates human creatine levels

ABSTRACTColorectal cancer (CRC) is a leading cause of cancer mortality. Creatine metabolism was previously shown to critically regulate colon cancer progression. We report that RGX-202, an oral small-molecule SLC6A8 creatine transporter inhibitor, robustly inhibits creatine import in vitro and in vivo, reduces intracellular phosphocreatine and ATP levels and induces tumor cell apoptosis in CRC. RGX-202 suppressed tumor growth across KRAS wild-type and KRAS mutant xenograft, syngeneic and patient-derived xenograft colorectal cancers. Anti-tumor efficacy correlated with tumoral expression of creatine kinase B. Combining RGX-202 with 5- fluorouracil or the DHODH inhibitor leflunomide caused regressions of multiple colorectal xenograft and PDX tumors of distinct mutational backgrounds. RGX-202 also perturbed creatine metabolism in metastatic CRC patients enrolled in a Phase-1 trial, mirroring pharmacodynamic effects on creatine metabolism observed in mice. This is, to our knowledge, the first demonstration of pre-clinical and human pharmacodynamic activity for creatine metabolism targeting in oncology, revealing a critical target for CRC.

Cyclocreatine suppresses prostate tumorigenesis through dual effects on SAM and creatine metabolism

ABSTRACTProstate cancer is highly prevalent, being the second most common cause of cancer mortality in men worldwide. Applying a novel genetically engineered mouse model (GEMM) of aggressive prostate cancer driven by deficiency of PTEN and SPRY2 (Sprouty 2) tumour suppressors, we identified enhanced creatine metabolism within the phosphagen system in progressive disease. Altered creatine metabolism was validated in in vitro and in vivo prostate cancer models and in clinical cases. Upregulated creatine levels were due to increased uptake through the SLC6A8 creatine transporter and de novo synthesis, resulting in enhanced cellular basal respiration. Treatment with cyclocreatine (a creatine analogue that potently and specifically blocks the phosphagen system) dramatically reduces creatine and phosphocreatine levels. Blockade of creatine biosynthesis by cyclocreatine leads to cellular accumulation of S-adenosyl methionine (SAM), an intermediary of creatine biosynthesis, and suppresses prostate cancer growth in vitro. Furthermore, cyclocreatine treatment impairs cancer progression in our GEMM and in a xenograft liver metastasis model. Hence, by targeting the phosphagen system, cyclocreatine results in anti-tumourigenic effects from both SAM accumulation and suppressed phosphagen system.

Diagnostic and Pharmacological Potency of Creatine in Post-Viral Fatigue Syndrome

Post-viral fatigue syndrome (PVFS) is a widespread chronic neurological disease with no definite etiological factor(s), no actual diagnostic test, and no approved pharmacological treatment, therapy, or cure. Among other features, PVFS could be accompanied by various irregularities in creatine metabolism, perturbing either tissue levels of creatine in the brain, the rates of phosphocreatine resynthesis in the skeletal muscle, or the concentrations of the enzyme creatine kinase in the blood. Furthermore, supplemental creatine and related guanidino compounds appear to impact both patient- and clinician-reported outcomes in syndromes and maladies with chronic fatigue. This paper critically overviews the most common disturbances in creatine metabolism in various PVFS populations, summarizes human trials on dietary creatine and creatine analogs in the syndrome, and discusses new frontiers and open questions for using creatine in a post-COVID-19 world.

Creatine Metabolism in Female Reproduction, Pregnancy and Newborn Health

Creatine metabolism is an important component of cellular energy homeostasis. Via the creatine kinase circuit, creatine derived from our diet or synthesized endogenously provides spatial and temporal maintenance of intracellular adenosine triphosphate (ATP) production; this is particularly important for cells with high or fluctuating energy demands. The use of this circuit by tissues within the female reproductive system, as well as the placenta and the developing fetus during pregnancy is apparent throughout the literature, with some studies linking perturbations in creatine metabolism to reduced fertility and poor pregnancy outcomes. Maternal dietary creatine supplementation during pregnancy as a safeguard against hypoxia-induced perinatal injury, particularly that of the brain, has also been widely studied in pre-clinical in vitro and small animal models. However, there is still no consensus on whether creatine is essential for successful reproduction. This review consolidates the available literature on creatine metabolism in female reproduction, pregnancy and the early neonatal period. Creatine metabolism is discussed in relation to cellular bioenergetics and de novo synthesis, as well as the potential to use dietary creatine in a reproductive setting. We highlight the apparent knowledge gaps and the research “road forward” to understand, and then utilize, creatine to improve reproductive health and perinatal outcomes.