Pancreatic cancer: from molecular pathogenesis to targeted therapy

Pancreatic cancer is a deadly malignancy with still high mortality and poor survival despite the significant advances in understanding, diagnosis, and access to conventional and novel treatments. Though cytotoxic chemotherapy based on the purine analogue gemcitabine remains the standard approach in adjuvant and palliative setting the need for novel agents aiming at the main pathophysiological abnormalities and molecular pathways involved remains soaring. So far, evidence of clinical benefit, though small, exists only from the addition of the targeted agent erlotinib on the standard gemcitabine chemotherapy. Apart from the popular monoclonal antibodies and small molecules tyrosine kinase inhibitors, other novel compounds being tested in preclinical and clinical studies target mTOR, NF-kappaB, proteasome and histone deacetylase. These new drugs along with gene therapy and immunotherapy, which are also under clinical evaluation, may alter the unfavorable natural course of this disease. In this review we present the main pathophysiological alterations met in pancreatic cancer and the results of the florid preclinical and clinical research with regards to the targeted therapy associated to these abnormalities.

Spectrum of activity and mechanism of action of VEGF/PDGF inhibitors

BACKGROUND

Angiogenesis plays an important role in tumor growth and metastasis.

METHODS

We review the function of the vascular endothelial growth factor (VEGF) in vessel formation that is complemented by platelet-derived growth factor (PDGF). We also review the agents designed to target VEGF, PDGF, and/or their receptors.

RESULTS

VEGF plays a central role in tumor angiogenesis. It is expressed at increased levels in colorectal, liver, lung, thyroid, breast, as well as in bladder, ovary, uterine cancers, and in angiosarcomas, germ cell tumors, intracranial tumors, and others. VEGF blockade has been shown to have a direct and rapid antivascular effect in both animal and human tumors, through deprivation of tumor vascular supply and inhibition of endothelial proliferation. Overexpression of PDGFs and their receptors has also been reported in many types of cancers such as prostate, ovarian, and non-small-cell lung cancer. Many VEGF and PDGF inhibitors are available. The use of some of these inhibitors has significantly improved the survival of cancer patients. Several agents are in development and currently are being tested in clinical trials.

CONCLUSIONS

Angiogenic agents inhibiting VEGF and PDGF have shown promising clinical results. Targeting more than one pathway by combining different agents may increase the antitumor activity of these drugs. The implementation of reliable radiologic and pathologic angiogenesis monitoring techniques is necessary to implement antiangiogenic therapies in cancer.