Table 2.

Review of published applications of hyperpolarized magnetic resonance (HP-MR) in preclinical pancreatic ductal adenocarcinoma (PDAC) models.

Purpose of study	Mouse model/cell line/site of injection	HP-MR probe and downstream reaction	Results	Implications for HP-MR	Reference
To investigate whether pancreatic preneoplasia can be detected prior to the development of invasive cancers in GEMa models of PDAC using HP-MR.	I. For early-onset PDAC: GEM (K-Ras and p53 mutations); cell line II. For late-onset PDAC: GEM (only K-Ras mutation); cell line III. Wild-type mice; pancreatitis induced using caerulein injection	[1-13C] pyruvate Pyruvate to lactate and pyruvate to alanine	I. The alanine-to-lactate signal ratio decreases progressively from the normal pancreas to pancreatitis to low-grade PanINb to high-grade PanIN to PDAC, using HP-MR II. Holds true for individual mice with time as well as upon comparing the three groups, considering their genetic proximity to PDAC (I>II>III) III. Caused by increasing LDHc activity and decreasing ALTd activity	Clinical potential for early detection of advanced pancreatic preneoplasia in high-risk patients using the alanine-to-lactate signal ratio as a biomarker. Diseased areas can be monitored over time. Kinetic rate constants (kPA and kPL) can be used as metabolic imaging biomarkers of pancreatic premalignant lesions	Düwel et al [22], Dutta et al [50]
I. To determine if HP-MR can inform the sensitivity of pancreatic tumors to the hypoxia-activated prodrug TH-302 II. To test whether an adjuvant injection of pyruvate would enhance TH-302 efficacy	I. In female SCID mice: (i) highly sensitive to TH-302: SCe injection of the PDXf Hs766t; (ii) moderately sensitive to TH-302: SC injection of the PDX MIAPaCa-2; (iii) resistant to TH-302: SC injection of the PDX SU.86.86 II. Treatment groups: (i) Control, (ii) TH-302, (iii) TH-302+pyruvate	[1-13C] Pyruvate Pyruvate to lactate	I. Higher lactate-to-pyruvate ratio observed in Hs766t and MIAPaCa groups; lower lactate-to-pyruvate ratio in SU.86.86 group II. Treatment with only TH-302: response of Hs766t (highly sensitive)> MIAPaCa-2> SU.86.86 (resistant). Treatment with TH-302+pyruvate: Hs766t and MIAPaCa-2 respond to a greater extent; SU.86.86 still resistant III. Exogenous pyruvate would be a successful adjuvant to enhance TH-302 efficacy because it stimulates oxygen consumption in glycolytic cells and decreases tumor pO2 transiently	HP-MR can be used to predict treatment response to hypoxia-activated prodrugs, and thus provide a prognostic biomarker	Stødkilde-Jørgensen et al [63]
I. To determine a genetic biomarker of the response to the LDH-A inhibitor FX11 II. To test the response of HP-MR output to FX11 in PDAC murine models	I. In male nu/nu athymic mice: SC injection of PDX of PDAC with (i) wild-type TP53 or (ii) mutant TP53 II. Treatment groups: (i) Control, (ii) FX11	[1-13C] Pyruvate Pyruvate to lactate	I. Mice injected with mutant TP53 PDAC responded to FX11; those injected with wild-type TP53 did not respond to FX11 by the end of 4 weeks II. The TP53 target gene TIGAR was responsible for the lack of response in wild-type TP53 PDAC. TIGAR lowers glycolytic flux and diverts glucose-6-phosphate into the PPPg, reducing the dependence on glucose. III. Prior to FX11 treatment, the lactate-to-pyruvate ratio was increased in wild-type TP53 PDAC; following FX11 treatment, the lactate-to-pyruvate ratio decreased in mutant TP53 PDAC	I. HP-MR can be used to confirm the desired effect of metabolic therapies in tumors in early stages of drug development II. The lactate-to-pyruvate ratio can serve as a biomarker for response to metabolic therapies early in the treatment regimen	Wojtkowiak et al [64]
To determine if treating a PDAC cell line with β-lapachone, a chemotherapeutic agent activated by the enzyme NQ01 (upregulated in PDAC), will lead to the breakdown of energetic metabolic pathways such as glycolysis and the tricarboxylic acid cycle (due to depletion of NAD+ and ATP).	I. In vitro model: MIAPaCa2 (NQO1+) pancreatic cancer cells (sensitive to β-lapachone) II. Treatment groups: (i) β-lapachone, (ii) no treatment	[1-13C] Pyruvate Pyruvate to lactate	HP [1-13C] pyruvate conversion to lactate was lower in cells treated with β-lapachone, suggesting that the activity of LDH is compromised from treatment	HP-MR can noninvasively detect the metabolic response of β-lapachone-treated cells. Thus, it can be used as a direct readout of treatment efficacy in PDAC patients with NQ01 upregulation	Rajeshkumar et al [65]
To determine whether measurement of the apparent diffusion coefficient (ADC) and conversion of injected copolarized 13C-labeled pyruvic acid and fumaric acid can detect changes in lactate export and necrosis, respectively	In vitro model: (i) human breast cancer cell line MCF-7 (do not upregulate MCT1 or MCT4 under hypoxic conditions); (ii) mouse PDAC cell line 8932	Mixture of [1-13C] pyruvic acid and [1,4-13C2] fumarate Pyruvate to lactate Fumarate to malate	I. The ADClac-to-ADCpyr ratio is significantly greater in PDAC cells compared to that in MCF-7 cells II. This is corroborated by greater extracellular concentrations from the PDAC line III. Fumarate to malate conversion is detectable only in necrotic cells lysed with Triton X-100; no lactate formation was observed due to dilution of LDH and NADHh.	I. Diffusion and conversion of HP pyruvate can provide information about the lactate efflux using the ADClac-to-ADCpyr ratio, which is linked to the relative distribution of lactate in the intra- and extracellular compartments II. Diffusion MR and conversion of HP fumarate can inform necrosis; the rationale is that intracellular ADC<extracellular ADC due to restricted diffusion inside the cell III. Together, the cell’s viability can be assessed. This may be used (1) to localize necrotic areas and (2) to assess the therapeutic response, especially for antiangiogenic agents such as bevacizumab	Silvers et al [54]
To determine whether mice injected with cancer cells (transfected with luciferase) in the peritoneum could be imaged using HP-MR and D2O radicals	BALB/cA nu/nu mice: (i) peritoneal metastasis; (ii) intraperitoneal injection of human pancreatic carcinoma (SUIT-2) cells	Free radical (Oxo 63, CmP, nitroxyl)-D2O probe	The image intensity correlated positively with the density of malignant ascites in the peritoneum	Radical-D2O and HP-MR can be used to selectively visualize H2O in the peritoneal cavity of mice and hence detect peritoneal metastasis early; this may then also be used to evaluate drug efficacy	Karlsson et al [66]

^aGEM: genetically engineered mouse.

^bPanIN: pancreatic intraepithelial neoplasia.

^cLDH: lactate dehydrogenase.

^dALT: alanine transaminase.

^eSC: subcutaneous.

^fPDX: pancreatic ductal adenocarcinoma xenograft.

^gPPP: pentose phosphate pathway.

^hNADH: nicotinamide adenine dinucleotide hydrogen.