No abstract

Pancreatic cancer remains a major unsolved health problem, with conventional cancer treatments having little impact on disease course. Almost all patients who have pancreatic cancer develop metastases and die. The main risk factors are smoking, age, and some genetic disorders, although the primary causes are poorly understood. Advances in molecular biology have, however, greatly improved understanding of the pathogenesis of pancreatic cancer. Many patients have mutations of the K-ras oncogene, and various tumour-suppressor genes are also inactivated. Growth factors also play an important part. However, disease prognosis is extremely poor. Around 15-20% of patients have resectable disease, but only around 20% of these survive to 5 years. For locally advanced, unresectable, and metastatic disease, treatment is palliative, although fluorouracil chemoradiation for locally advanced and gemcitabine chemotherapy for metastatic disease can provide palliative benefits. Despite pancreatic cancer's resistance to currently available treatments, new methods are being investigated. Preoperative chemoradiation is being advocated, with seemingly sound reasoning, and a wider role for gemcitabine is being explored. However, new therapeutic strategies based on the molecular biology of pancreatic cancer seem to hold the greatest promise.

Purpose: Pancreatic cancer is almost always lethal, and the only U.S. Food and Drug Administration^approved therapies for it, gemcitabine and erlotinib, produce objective responses in <10% of patients.We evaluated the clinical biological effects of curcumin (diferuloylmethane), a plant-derived dietary ingredient with potent nuclear factor-nB (NF-nB) and tumor inhibitory properties, against advanced pancreatic cancer. Experimental Design: Patients received 8 g curcumin by mouth daily until disease progression, with restaging every 2 months. Serum cytokine levels for interleukin (IL)-6, IL-8, IL-10, and IL-1 receptor antagonists and peripheral blood mononuclear cell expression of NF-nB and cyclooxygenase-2 were monitored. Results:Twenty-five patients were enrolled, with 21evaluable for response. Circulating curcumin was detectable as drug in glucuronide and sulfate conjugate forms, albeit at low steady-state levels, suggesting poor oral bioavailability. Two patients showed clinical biological activity. One had ongoing stable disease for >18 months; interestingly, one additional patient had a brief, but marked, tumor regression (73%) accompanied by significant increases (4-to 35-fold) in serum cytokine levels (IL-6, IL-8, IL-10, and IL-1 receptor antagonists). No toxicities were observed. Curcumin down-regulated expression of NF-nB, cyclooxygenase-2, and phosphorylated signal transducer and activator of transcription 3 in peripheral blood mononuclear cells from patients (most of whom had baseline levels considerably higher than those found in healthy volunteers). Whereas there was considerable interpatient variation in plasma curcumin levels, drug levels peaked at 22 to 41ng/mL and remained relatively constant over the first 4 weeks. Conclusions: Oral curcumin is well tolerated and, despite its limited absorption, has biological activity in some patients with pancreatic cancer.

A better understanding of drug resistance mechanisms is required to improve outcomes in patients with pancreatic cancer. Here we characterized patterns of sensitivity and resistance to three conventional chemotherapeutic agents with divergent mechanisms of action (gemcitabine, 5-fluorouracil, and cisplatin) in pancreatic cancer cells. Four (L3.6pl, BxPC-3, CFPAC-1, SU86.86) were sensitive and five (PANC-1, Hs766T, AsPC-1, MIAPaCa-2, Mpanc96) were resistant to all 3 agents based on GI50 (50% growth inhibition). Gene expression profiling and unsupervised hierarchical clustering revealed that the sensitive and resistant cells formed two distinct groups and differed in expression of specific genes including several features of “epithelial-mesenchymal transition” (EMT). Interestingly, an inverse correlation between E-cadherin and its transcriptional suppressor, Zeb-1 was observed in the gene expression data and was confirmed by real time PCR. Independent validation experiment using 5 new pancreatic cancer cell lines confirmed that an inverse correlation between E-cadherin and Zeb-1 correlated closely with resistance to gemcitabine, 5-fluorouracil, and cisplatin. Silencing Zeb-1 in the mesenchymal lines not only increased the expression of E-cadherin but also other epithelial markers such as EVA1 and MAL2 and restored drug sensitivity. Importantly, immunohistochemical analysis of E-cadherin and Zeb-1 in primary tumors confirmed that expression of the two proteins was mutually exclusive (p=0.012). Therefore, our results suggest that Zeb-1 and other regulators of EMT may maintain drug resistance in human pancreatic cancer cells, and therapeutic strategies to inhibit Zeb-1 and reverse EMT should be evaluated.

The algorithms that the authors developed achieved a cross-validated accuracy of 64% and an accuracy of 64% on an 1851-patient independent test set, compared with 9% accuracy when a random classifier was used.

Sorafenib has significant disease-stabilizing activity in metastatic renal cell carcinoma and is tolerable with chronic daily therapy.

With recent advances in pancreatic imaging and surgical techniques, a distinct subset of pancreatic tumors is emerging that blurs the distinction between resectable and locally advanced disease: tumors of "borderline resectability." In our practice, patients with borderline-resectable pancreatic cancer include those whose tumors exhibit encasement of a short segment of the hepatic artery, without evidence of tumor extension to the celiac axis, that is amenable to resection and reconstruction; tumor abutment of the superior mesenteric artery involving <180 degrees of the circumference of the artery; or short-segment occlusion of the superior mesenteric vein, portal vein, or their confluence with a suitable option available for vascular reconstruction because the veins are normal above and below the area of tumor involvement. With currently available surgical techniques, patients with borderline-resectable pancreatic head cancer are at high risk for a margin-positive resection. Therefore, our approach to these patients is to use preoperative systemic therapy and local-regional chemoradiation to maximize the potential for an R0 resection and to avoid R2 resections. In our experience, patients with favorable responses to preoperative therapy (radiographical evidence of tumor regression and improvement in serum tumor marker levels) are the subset of patients who have the best chance for an R0 resection and a favorable long-term outcome.

Aberrant epidermal growth factor receptor (EGFR) signaling is a major cause of tumor progression and metastasis; the underlying mechanisms, however, are not well understood. In particular, it remains elusive whether deregulated EGFR pathway is involved in epithelial-mesenchymal transition (EMT), an early event that occurs during metastasis of cancers of an epithelial origin. Here, we show that EGF induces EGFRexpressing cancer cells to undergo a transition from the epithelial to the spindle-like mesenchymal morphology. EGF reduced E-cadherin expression and increased that of mesenchymal proteins. In search of a downstream mediator that may account for EGF-induced EMT, we focused on transcription repressors of E-cadherin, TWIST, SLUG, and Snail and found that cancer cells express high levels of TWIST and that EGF enhances its expression. EGF significantly increases TWIST transcripts and protein in EGFR-expressing lines. Forced expression of EGFR reactivates TWIST expression in EGFR-null cells. TWIST expression is suppressed by EGFR and Janusactivated kinase (JAK)/signal transducer and activator of transcription 3 (STAT3) inhibitors, but not significantly by those targeting phosphoinositide-3 kinase and MEK/ERK. Furthermore, constitutively active STAT3 significantly activates the TWIST promoter, whereas the JAK/STAT3 inhibitor and dominant-negative STAT3 suppressed TWIST promoter. Deletion/mutation studies further show that a 26-bp promoter region contains putative STAT3 elements required for the EGFresponsiveness of the TWIST promoter. Chromatin immunoprecipitation assays further show that EGF induces binding of nuclear STAT3 to the TWIST promoter. Immunohistochemical analysis of 130 primary breast carcinomas indicates positive correlations between non-nuclear EGFR and TWIST and between phosphorylated STAT3 and TWIST. Together, we report here that EGF/EGFR signaling pathways induce cancer cell EMT via STAT3-mediated TWIST gene expression. [Cancer Res 2007;67(19):9066-76]