Biology subjects

Graor, H. J.

Publications and source records attributed to Graor, H. J..

5 recordsLinked to original sources

bioRxiv2023

Targeting wild-type IDH1 enhances chemosensitivity in pancreatic cancer

Pancreatic cancer (PC) is one of the most aggressive types of cancer, with a five-year overall survival rate of 11% among all-comers. Current systemic therapeutic options are limited to cytotoxic chemotherapies which have limited clinical efficacy and are often associated with development of drug resistance. Analysis of The Cancer Genome Atlas showed that wild-type isocitrate dehydrogenase (wtIDH1) is overexpressed in pancreatic tumors. In this study, we focus on the potential roles of wtIDH1 in pancreatic cancer chemoresistance. We found that treatment of pancreatic cancer cells with chemotherapy induced expression of wtIDH1, and this serves as a key resistance factor. The enzyme is protective to cancer cells under chemotherapy-induced oxidative stress by producing NADPH and alpha-ketoglutarate to maintain redox balance and mitochondrial function. An FDA-approved mutant IDH1 inhibitor, ivosidenib (AG-120), is actually a potent wtDH1 inhibitor under a nutrient-deprived microenvironment, reflective of the pancreatic cancer microenvironment. Suppression of wtIDH1 impairs redox balance, results in increased ROS levels, and enhances chemotherapy induced apoptosis in pancreatic cancer vis ROS damage in vitro. In vivo experiments further revealed that inhibiting wtIDH1 enhances chemotherapy anti-tumor effects in patient-derived xenografts and murine models of pancreatic cancer. Pharmacologic wtIDH1 inhibition with ivosidenib represents an attractive option for combination therapies with cytotoxic chemotherapy for patients with pancreatic cancer. Based on these data, we have initiated phase Ib trial combining ivosidenib and multi-agent chemotherapy in patients with pancreatic cancer (NCT05209074).

cancer biology↗

bioRxiv2022

Surgical techniques and tips for a reliable murine model of primary and metastatic pancreatic cancer

For patients with pancreatic cancer, survival rates lag behind other common cancers. This is in part due to the relative resistance to conventional chemotherapeutics and novel immune- or targeted-therapies. Ongoing research efforts are needed to identify and validate effective therapies. It is the unfortunate reality that a significant proportion of pre-clinical success does not translate into improved patient outcomes, likely due to a multitude of factors. In the current research landscape, flank xenograft models are commonly utilized to study pancreatic cancer, as this technique is fast, fairly non-invasive, and reliable. However, this model is not anatomically or physiologically accurate, does not impact other intra-abdominal organs, and experiments are often ended based on tumor size rather than systemic illness. Orthotopic injections of cancer cells directly into the pancreas for study of localized disease or into the spleen for study of hepatic metastases can be performed via a quick, reliable, minimally invasive surgical procedure with minimal morbidity and mortality. Existing methodologic reports are often sparse. Thus, there are significant knowledge and technical gaps for researchers attempting these techniques for the first time. In the current report, details of orthotopic pancreatic injections and splenic injections for metastatic disease are provided. Details of commonly encountered operative issues and mistakes are presented with suggestions to improve performance are described. A summary of expected outcomes is also provided herein.

cancer biology↗

bioRxiv2022

Wild-type IDH1 inhibition enhances chemotherapy response in melanoma

Malignant melanoma is one of the most common types of cancer in the United States. Despite recent and well-described progress in melanoma treatment, advanced disease still carries a poor prognosis for many patients and chemotherapy has been appropriately abandoned as a front-line option. Wild-type isocitrate dehydrogenase 1 (wtIDH1) has recently been implicated as a metabolic dependency in cancer. The enzyme is protective to cancer cells under metabolic stress, including oxidative damage by conventional chemotherapy and nutrient limitation characteristic of the tumor microenvironment. Specifically, the cytosolic enzyme generates NADPH to maintain redox homeostasis. IDH1 also supports mitochondrial function through anaplerosis of its reaction product, -ketoglutarate. We show that melanoma patients express higher levels of the wtIDH1 enzyme compared to normal skin tissue, and elevated wtIDH1 expression portends poor patient survival. Knockdown of IDH1 by RNA interference inhibited cell proliferation and migration under low nutrient levels. Suppression of IDH1 expression in melanoma also decreased NADPH and glutathione levels, resulting in increased reactive oxygen species. An FDA-approved inhibitor of mutant IDH1, ivosidenib (AG-120), exhibited potent anti-wtIDH1 properties under low magnesium and nutrient levels, reflective of the tumor microenvironment in natura. Similarly, findings were replicated in murine models of melanoma. Further, wtIDH1 inhibition was synergistic to conventional anti-melanoma chemotherapy in pre-clinical models. This work points to a novel and readily available combination treatment strategy for patients with advanced and refractory melanoma.

cancer biology↗

bioRxiv2022

Increased glucose availability sensitizes pancreatic cancer to chemotherapy

Pancreatic cancer (Pancreatic Ductal Adenocarcinoma; PDAC) is highly resistant to chemotherapy. Effective alternative therapies have yet to emerge, leaving chemotherapy as the best available systematic treatment. The discovery of safe and available adjuncts that improve chemotherapeutic efficacy would potentially improve survival outcomes. We show that a hyperglycemic state enhances the efficacy of conventional single- and multi-agent chemotherapies against PDAC. Molecular analyses of tumors exposed to relatively high glucose levels revealed that a key metabolic pathway, glutathione biosynthesis, is diminished and underlies chemo-sensitization by enhancing oxidative injury to cancer cells. Inhibition of this pathway under normal conditions phenocopied a hyperglycemic state by enhancing chemotherapeutic efficacy in mouse PDAC, while rescuing the pathway under high glucose abrogated the anti-tumor effects observed with chemotherapy.

cancer biology↗

bioRxiv2020

Cancer cells are sensitive to wild-type IDH1 inhibition under nutrient limitation

Pancreatic cancer cells alter their metabolism to survive cancer-associated stress (1-4). For example, cancer cells must adapt to steep nutrient gradients that characterize the natural tumor microenvironment (TME) (5-7). In the absence of adaptive strategies, harsh metabolic conditions promote the generation of free radicals (8) and impair energy production in tumor cells. Towards this end, wild-type isocitrate dehydrogenase 1 (IDH1) activity is a metabolic requirement for cancer cells living in a harsh metabolic milieu. The cytosolic enzyme interconverts isocitrate and alpha-ketoglutarate, and uses NADP(H) as a cofactor. We show that under low nutrient conditions, the enzymatic reaction favors oxidative decarboxylation to yield NADPH and alpha-ketoglutarate. Metabolic studies showed that the IDH1 products directly support antioxidant defense and mitochondrial function in stressed cancer cells. Genetic IDH1 suppression reduced growth of pancreatic cancer cells in vitro under low nutrient conditions and in mouse models of pancreatic cancer. Surprisingly, allosteric inhibitors of mutant IDH1 proved to be potent wild-type IDH1 inhibitors under conditions specific to the TME, highlighting a natural therapeutic window. The presence of low magnesium enhanced allosteric inhibition by the drug, and ambient low glucose levels enhanced cancer cells dependence on wild-type IDH1. Thus, intrinsic TME conditions sensitized wild-type IDH1 to FDA-approved AG-120 (ivosidenib), and revealed the drug to be a potent single-agent therapeutic in cell culture and diverse in vivo cancer models. This work identified a potentially new repertoire of safe cancer therapies, including a clinically available compound, for the treatment of multiple wild-type IDH1 cancers (e.g., pancreatic).

cancer biology↗