OmoMYC blunts promoter invasion by oncogenic MYC to inhibit gene expression characteristic of MYC-dependent tumors

MYC genes have both essential roles during normal development and exert oncogenic functions during tumorigenesis. Expression of a dominant-negative allele of MYC, termed OmoMYC, can induce rapid tumor regression in mouse models with little toxicity for normal tissues. How OmoMYC discriminates between physiological and oncogenic functions of MYC is unclear. We have solved the crystal structure of OmoMYC and show that it forms a stable homodimer and as such recognizes DNA in the same manner as the MYC/MAX heterodimer. OmoMYC attenuates both MYC-dependent activation and repression by competing with MYC/MAX for binding to chromatin, effectively lowering MYC/MAX occupancy at its cognate binding sites. OmoMYC causes the largest decreases in promoter occupancy and changes in expression on genes that are invaded by oncogenic MYC levels. A signature of OmoMYC-regulated genes defines subgroups with high MYC levels in multiple tumor entities and identifies novel targets for the eradication of MYC-driven tumors.

Consensus on precision medicine for metastatic cancers: a report from the MAP conference

Recent advances in biotechnologies have led to the development of multiplex genomic and proteomic analyses for clinical use. Nevertheless, guidelines are currently lacking to determine which molecular assays should be implemented in metastatic cancers. The first MAP conference was dedicated to exploring the use of genomics to better select therapies in the treatment of metastatic cancers. Sixteen consensus items were covered. There was a consensus that new technologies like next-generation sequencing of tumors and ddPCR on circulating free DNA have convincing analytical validity. Further work needs to be undertaken to establish the clinical utility of liquid biopsies and the added clinical value of expanding from individual gene tests into large gene panels. Experts agreed that standardized bioinformatics methods for biological interpretation of genomic data are needed and that precision medicine trials should be stratified based on the level of evidence available for the genomic alterations identified.

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.