Comparative histopathological findings in the pancreas of cigarette smokers and non-smokers

The pathobiological impact of cigarette smoke on pancreatic cancer development (review)

Despite extensive efforts, pancreatic cancer remains incurable. Most risk factors, such as genetic disposition, metabolic diseases or chronic pancreatitis cannot be influenced. By contrast, cigarette smoking, an important risk factor for pancreatic cancer, can be controlled. Despite the epidemiological evidence of the detrimental effects of cigarette smoking with regard to pancreatic cancer development and its unique property of being influenceable, our understanding of cigarette smoke-induced pancreatic carcinogenesis is limited. Current data on cigarette smoke-induced pancreatic carcinogenesis indicate multifactorial events that are triggered by nicotine, which is the major pharmacologically active constituent of tobacco smoke. In addition to nicotine, a vast number of carcinogens have the potential to reach the pancreatic gland, where they are metabolized, in some instances to even more toxic compounds. These metabolic events are not restricted to pancreatic ductal cells. Several studies show that acinar cells are also greatly affected. Furthermore, pancreatic cancer progenitor cells do not only derive from the ductal epithelial lineage, but also from acinar cells. This sheds new light on cigarette smoke-induced acinar cell damage. On this background, our objective is to outline a multifactorial model of tobacco smoke-induced pancreatic carcinogenesis.

The role of tobacco-derived carcinogens in pancreas cancer

The extremely poor outcome from pancreas cancer is well known. However, its aetiology less well appreciated, and the molecular mechanisms underlying this are poorly understood. Tobacco usage is one of the strongest risk factors for this disease, and this is a completely avoidable hazard. In addition, there are well described hereditary diseases which predispose, and familial pancreas cancer. We have sought here to summarise the role of tobacco-derived carcinogens and the mode of their tumorigenic action on the pancreas. There is compelling evidence from animal and human studies (laboratory including cell line studies and epidemiologic) that tobacco derived carcinogens cause pancreas cancer. However, the manner in which they do so is not entirely apparent. There is also compelling evidence that synergism with genetic and other life-style factors-like diet obesity-results in a multifactorial causation of the disease. Ascertaining the role of tobacco carcinogens in the development of this cancer and their interaction with other risk factors will enable novel therapeutic and preventative strategies to improve outcome from this appalling malignancy.

A "catastrophic hypothesis" for pancreas cancer progression

Exocrine pancreas cancer has a dismal prognosis. The precise reasons accounting for its biological and clinical behavior are not known. A "catastrophe" takes place in the course of pancreas cancer development/progression so that, once it occurs, the evolution of the tumor is very rapid, leading to local invasion and metastasis. Up to now, such behavior cannot be conclusively ascribed to a single molecular event. If correct, this hypothesis has important implications regarding pancreas cancer research. Further work is warranted to examine this hypothesis and to identify the putative "catastrophic" elements participating in this tumor.

Neoplasms of the ampulla of vater with concurrent pancreatic intraductal neoplasia: a histological and molecular study

Adenoma and adenocarcinoma of the ampulla of Vater are uncommon neoplasms of the gastrointestinal tract. Only one report has analyzed the relationship between ampullary adenocarcinoma and pancreatic intraductal neoplasia (PanIN), the precursor lesion of pancreatic adenocarcinoma. An association between PanIN and ampullary adenoma has not been reported previously. Case reports have documented the progression of PanIN to invasive pancreatic adenocarcinoma. We reviewed five resected ampullary adenoma and 17 ampullary adenocarcinoma cases and evaluated the pancreas for PanIN. Pancreatic sections from 35 autopsies were reviewed as a control group. Immunohistochemistry for overexpression of p53 and COX-2 proteins was performed in selected cases, as was PCR analysis for K-ras mutations. Follow-up clinical data were obtained. All 22 ampullary neoplasms were associated with PanIN, which was high grade in two (40%) adenoma cases and seven (41%) adenocarcinoma cases. In 16 (73%) evaluable cases, PanIN extended to the pancreatic resection margin; two of which had high grade PanIN. Among the autopsy controls eight (23%) had low-grade PanIN. Seven of the 22 ampullary cases but none of the autopsy controls had coexistent pancreatitis. A smoking history was present in two of four autopsy cases in which this history was available. Overexpression of the p53 and COX-2 proteins was present in only one case of high-grade PanIN. K-ras mutations were present in four of four of the PanIN lesions evaluated, including one autopsy case. Clinical follow-up revealed no progression of PanIN to invasive carcinoma in the remnant pancreas, although the follow-up period was too short to adequately assess that risk (an average of 3.8 y for adenoma cases and 2.5 y for adenocarcinoma cases). We conclude that adenomas and carcinomas of the ampulla are associated with PanIN, and often high-grade PanIN. Although its malignant potential has not been fully established, PanIN is underreported and often unrecognized. PanIN may be analogous to colorectal adenoma in that both are prevalent in the older adult population, but few progress to carcinoma.

One thousand faces of Langerhans islets

Studies with different strains of Syrian hamsters and Syrian golden hamsters have revealed the remarkable potential of islet cells to undergo orthotopic and heterotopic metaplasia. The most common spontaneous change included the development of hepatocytes in aged and malnourished hamsters. Of the many other alterations that occurred during carcinogenesis, most of the metaplastic changes originated within the islet periphery and progressed inside and outside the islets. The development of ductular structures within islets and their progression either to structures identical to human serous cystadenoma or to highly invasive adenocarcinomas were the most common alterations. The remarkably greater invasive potential of cancer cells arising within the islets contrasted sharply with the slow growth of the tumors developing within ducts (intraductal tumors). Studies in human tissue also showed development of malignant cells within islets, and, in some cases, transition of islet cells to malignant cells was suggested. The overall results, along with recent findings in other studies in cultured human and hamster islets, indicate the enormous potential of islet cells to differentiate and undergo malignant transformation. Whether the metaplastic and malignant cells derive from stem cells embedded within islets or from transdifferentiated islet cells remains to be seen.

Pancreas cancer, tobacco smoking and consumption of alcoholic beverages: a case-control study

A population-based case-control study investigated pancreas cancer in relation to consumption of alcoholic beverages, tobacco smoking and pancreatitis, utilizing historical proxy data for 662 decedent Finnish pancreas cancer cases and 1770 cancer controls. Tobacco smoking increased the risk, with an attributable case fraction of 0.27. The data are consistent with a joint effect of early and late stage carcinogens in tobacco smoke. Consumption of distilled beverages did not increase risk, but heavy drinking of wine or beer did. History of pancreatitis was a strong risk factor.