Abstract LB-395: Hepatocyte growth factor: a potential therapeutic target in pancreatic cancer

Pancreatic stellate cells (PSCs, which produce the desmoplastic reaction of pancreatic cancer) interact with pancreatic cancer (PC) cells to potentiate PC progression. A candidate factor that may mediate this interaction is the hepatocyte growth factor (HGF). High serum HGF levels in PC patients correlate with poor outcome. However, there is limited knowledge about the role of HGF in PC. Aims: To i) determine whether human PSCs and PC cell lines express HGF; and

ii) assess the effects of HGF inhibition on PC progression in an orthotopic mouse model.

Methods:

i) HGF expression in PSCs and PC cells assessed by RT-PCR, immunoblotting/immunocytochemistry.

ii) Orthotopic model: AsPC-1 (a human PC cell line) ± human PSCs implanted into the pancreas mice. One week later, mice divided into groups (n=8 mice/group) and treated with: HGF antibody AMG102 [(Amgen Inc.), 300 or 600μg IP biweekly] or isotype IgG (600 μg IP biweekly). Seven weeks later, tumour size and metastasis assessed.

Results:

i) PSCs express HGF at both mRNA and protein levels. In contrast, PC cells (MiaPaCa2, Panc-1, AsPC-1) express negligible HGF mRNA.

ii) Orthotopic model: a) IgG treated AsPC-1+PSC mice showed larger tumours than mice injected with AsPC-1 alone (Table); b) 300 and 600μg AMG102 inhibited tumour growth in AsPC-1+PSC mice compared to the IgG treated group. However, AMG102 did not reduce tumour size in mice injected with AsPC-1 alone (Table). c) 600μg AMG102 inhibited metastasis (liver, diaphragm, mediastinum) in AsPC-1+PSC mice (p<0.05) compared to IgG treated mice.

Conclusions: We have shown for the first time that i)human PSCs synthesise HGF; ii)HGF inhibition reduces tumour growth and metastasis of tumours representative of human PC i.e., exhibiting both tumour elements and a stromal reaction, but not in the clinically non-representative cancers formed by PC cells alone.

Implication: Targeting the stromal reaction with relevant specific inhibitors may represent a novel therapeutic approach in PC.

Influence of the culture medium on the synthesis of alpha-D-glucans by Streptococcus cricetus AHT

Three different alpha-D-glucosyltransferases (GTFs) were separated from culture filtrates of Streptococcus cricetus strain AHT grown in a complex, standard medium in batch culture or under defined conditions of growth in the chemostat. Two of the enzymes (GTF-S1 and GTF-S2) converted sucrose into branched, soluble dextrans, and the third (GTF-I) produced a relatively linear, water-insoluble, predominantly (1----3)-linked alpha-D-glucan. When the organism was grown in complex medium modified by the removal of the fraction of high molecular weight, only GTF-S1 and GTF-S2 were released, and no GTF-I was detected. The water-insoluble glucan fraction obtained by incubating the cell-free filtrate with sucrose contained from 17 to 25% of (1----3)-glucosidic linkages, and accounted for up to 78 and 4% of the total glucans derived from growth in standard and modified medium, respectively. The soluble glucans produced in the same reaction were fractionated with ethanol to give, from both media, two distinct dextrans comprising (1) a highly branched dextran similar to the S1-dextran product of GTF-S1 and (2) a dextran containing fewer branch linkages and up to 86% of (1----6)-alpha-D-glucosidic linkages. A GTF responsible for the synthesis of the latter dextran was not separated. The structures of the glucan fractions and the products of the separated GTF were examined by enzymic degradation and methylation analysis.

Purification and characterisation of proteins with cardiac stimulatory and haemolytic activity from the anemone Actinia tenebrosa

Three new proteins with cardiac stimulatory and haemolytic activity, designated tenebrosins-A, -B and -C, have been purified from the Australian sea anemone Actinia tenebrosa. These proteins are basic (pI greater than or equal to 9.4), have mol. wt of about 20,000, and have very similar amino acid compositions and N-terminal amino acid sequences. None of the proteins contains cysteine or cystine residues. On isolated, spontaneously beating guinea pig atria they exhibit at 1-2 nM strong positive inotropic and slight to moderate chronotropic effects. In some cases a transient negative inotropic effect occurs prior to onset of the positive inotropic response. The proteins are also haemolytic, producing 50% haemolysis of guinea pig erythrocytes at concentrations similar to those showing positive inotropic effects.