Robert M. Hoffman

The extensive homology between mRNA sequences of normal and SV40-transformed human fibroblasts

The poly(A)-containing messenger RNA of normal diploid fibroblast and SV40-transformed progeny cells are compared by cross-hybridizing cDNA. We find a high degree of homology between the mRNA from normal and transformed cells. Despite imperfections in the procedure, the technique permits the conclusion that, at most, 3% of the mRNA in the transformed cell has sequences not present in the normal parental cell. Furthermore, much of the difference appears to occur in low and intermediate complexity classes of mRNA molecules. Extension homology in the mRNA sequences of disparate cell lines may be a general phenomenon, and even HeLa cell mRNA is nearly identical to that of diploid human fibroblasts.

Reversion to methionine independence by malignant rat and SV40-transformed human fibroblasts.

Abstract Although many lines of malignant and transformed cells are unable to grow in folate- and cobalamin-supplemented medium in which methionine is replaced by homocysteine its immediate metabolic precursor, rare cells from these lines regained the normal ability to grow under these conditions. Six revertant lines, one from Walker-256 rat breast carcinoma cells and five from SV40-transformed human fibroblasts, have been characterized with regard to growth and three measures of methionine biosynthetic capacity: methionine synthetase and methylenetetrahydrofolate reductase activities in cell extracts, and uptake of label from [5- 14 C]methyltetrahydrofolate by intact cells. When all three measures of methionine biosynthetic capacity were considered, two revertants isolated from SV40-transformed cells had regained the ability to grow like normal cells in homocysteine medium without substantial changes in these measures. Increased methionine biosynthesis thus is not a prerequisite to reversion of the methionine auxotrophy present in the transformed parental lines.

Genetic Restriction of Energy Conservation in Schizophyllum

A genetically determined malfunction of energy conservation reduces assimilation of substrate to half or less its normal level while leaving oxidative processes apparently unchanged. This metabolic defect, which differs in many ways from any previously described, is related to the function of the B incompatibility factor and occurs both in the common A heterokaryon (A = B ≠)—in which two compatible, wild B factors interact—and in mutant-B homokaryons.

Genetic Impairment of Energy Conservation in Development of Schizophyllum: Efficient Mitochondria in Energy-starved Cells

SUMMARY A mutant-Bβ strain of Schizophyllum commune, in which the B-sequence of sexual morphogenesis is constitutive, utilizes glucose in the production of cellular material with an efficiency of about 9% of that of wild-type mycelium. The production of ATP by mitochondria isolated from the mutant is equal to that of mitochondria of normal mycelium, however, and mitochondrial ATPase activity appears the same from mycelia of the two types. Other comparative studies show the mutant to achieve approximately the same yield on ethanol and glucose, whereas wild type grows considerably less on ethanol. The mutant is much more sensitive than wild type to temperature and to inhibition by Krebs-cycle intermediaries. Both mutant and wild type are sensitive to the phosphorylation-inhibiting agent, DCCD. The over-all effect is a partial uncoupling of energy-conserving from energy-yielding processes. It was not possible to determine if the agents responsible for uncoupling were solely mitochondrial or cytoplasmic.

Laparoscopic Fluorescence Imaging for Identification and Resection of Pancreatic and Hepatobiliary Cancer

In surgery for pancreatic and hepatobiliary cancers, the ability to properly delineate tumor margins for complete resection is of utmost importance in achieving cure and giving the patient the best ch

Fluorescent humanized anti-CEA antibody specifically labels metastatic pancreatic cancer in a patient-derived orthotopic xenograft (PDOX) mouse model

Specific tumor targeting can result in selective labeling of cancer in vivo for surgical navigation. In the present study, we show that the use of an anti-CEA antibody conjugated to the near-infrared (NIR) fluorescent dye, IRDye800CW, can selectively target and label pancreatic cancer and its metastases in a clinically relevant patient derived xenograft mouse model.

Fluorescent Metastatic Mouse Models of Pancreatic Cancer for Drug Discovery

Here we describe our cumulative experience with the development and preclinical application of imageable, clinically-relevant, metastatic orthotopic mouse models of pancreatic cancer. These models utilize the human pancreatic cancer cell lines which have been genetically engineered to selectively express high levels of green fluorescent protein (GFP) or red fluorescent protein (RFP). Fluorescent tumors are established subcutaneously in nude mice, and tumor fragments are then surgically transplanted onto the pancreas. Locoregional tumor growth and distant metastasis of these orthotopic implants occurs spontaneously and rapidly throughout the abdomen in a manner consistent with clinical human disease. Highly specific, high-resolution, real-time quantitative imaging of tumor growth and metastasis may be achieved in vivo without the need for contrast agents, invasive techniques, or expensive imaging equipment. We have shown a high correlation between florescent optical imaging and magnetic resonance imaging in these models. Transplantation of RFP-expressing tumor fragments onto the pancreas of GFP-expressing transgenic mice may be used to facilitate visualization of tumor–host interaction between the pancreatic cancer cells and host-derived stroma and vasculature. Such in vivo models have enabled us to serially visualize and acquire images of the progression of pancreatic cancer in the live animal, and to demonstrate the real-time antitumor and antimetastatic effects of novel therapeutic strategies on pancreatic malignancy. These fluorescent models are therefore powerful and reliable tools with which to investigate metastatic human pancreatic cancer and novel therapeutic strategies directed against it.