Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancers worldwide. Despite significant progresses in the last decades, the origin of this cancer remains unclear and no efficient therapy exists. PDAC does not arise de novo: three remarkable different types of pancreatic lesions can evolve towards pancreatic cancer. These precursor lesions include: Pancreatic intraepithelial neoplasia (PanIN) that are microscopic lesions of the pancreas, Intraductal Papillary Mucinous Neoplasms (IPMN) and Mucinous Cystic Neoplasms (MCN) that are both macroscopic lesions. However, the cellular origin of these lesions is still a matter of debate. Classically, neoplasm initiation or progression is driven by several genetic and epigenetic alterations. The aim of this review is to assemble the current information on genetic mutations and epigenetic disorders that affect genes during pancreatic carcinogenesis. We will further discuss the interest of the genetic and epigenetic alterations for the diagnosis and prognosis of PDAC. Large genetic alterations (chromosomal deletion/amplification) and single point mutations are well described for carcinogenesis inducers. Mutations classically occur within key regions of the genome. Consequences are various and include activation of mitogenic pathways or silencing of apoptotic processes. Alterations of K-RAS, P16 and DPC4 genes are frequently observed in PDAC samples and have been described to arise gradually during carcinogenesis. DNA methylation is an epigenetic process involved in imprinting and X chromosome inactivation. Alteration of DNA methylation patterns leads to deregulation of gene expression, in the absence of mutation. Both genetic and epigenetic events influence genes and non-coding RNA expression, with dramatic effects on proliferation, survival and invasion. Besides improvement in our fundamental understanding of PDAC development, highlighting the molecular alterations that occur in pancreatic carcinogenesis could provide new clinical tools for early diagnosis of PDAC and the molecular basis for the development of new effective therapies.
Which is the molecular mechanism underlying K-ras alterations in carcinomas?

Protein kinases (PKs) and lipid kinases (LKs) are good choices for targets of signal transduction therapy as these enzymes are involved in signaling pathways, and are often related to the pathogenesis of lymphoid malignancies. The attractiveness of PKs and LKs as drug able targets is enhanced by the fact that they are enzymes whose biological activity can be turned off by drugs that block their catalytic site. In the last few years small molecular kinase inhibitors (KIs) have been synthesized and become available for preclinical studies and clinical trials. The first KI, introduced into clinical practice in 1998, was imatinib mesylate, which became the first choice drug in chronic myeloid leukemia. More recently, several KIs have been developed to target the proximal B-cell receptor (BCR) signaling pathway including spleen tyrosine kinase inhibitor (Fostamatinib) and Bruton's tyrosine kinase inhibitors (Ibrutinib, AVL-263). These agents are currently evaluated in early clinical trials in chronic lymphocytic leukemia (CLL) and other diseases. Cyclin-dependent kinase (Cdk) inhibitors, flavopiridol (alvocidib), BMS-387032 (SNS-032), sunitinib and sorafenib are currently under evaluation in clinical trials for relapsed/refractory CLL. Multi-tyrosine kinase inhibitors including vandetanib (ZD6474) bosutinib (SKI-606), TKI258 (CHIR-258), pazopanib (GW786034) and axitinib (AG013736) have been also developed for the treatment of lymphoid malignancies. Phosphatidylinositol 3-kinases (PI3K ) are a family of lipid kinases that mediate signals from cell surface receptors. CAL-101 (GS-1101) is an oral PI3K-specific inhibitor which has shown preclinical and clinical activity against CLL. This article summarizes recent achievements in the mechanism of action, pharmacological properties and clinical activity and toxicity of PK and LK inhibitors in CLL.
What is the name of Bruton's tyrosine kinase inhibitor that can be used for treatment of chronic lymphocytic leukemia?

Marek was a farmer who lived in a village far away. One day he became very ill, and everyone thought he would die. They sent for a doctor, who arrived two days later and examined the sick man. The doctor asked for a pen and some paper to write down the name of the medicine. But there was no pen or paper in the village, because no one could read or write. The doctor picked up a piece of burnt wood from the fire. Using the wood, he wrote the name of the medicine on the door of the house. "Get this medicine for him," he said,"and he will soon get better." Marek's family and friends did not know what to do. They could not read the strange writing. Then the village baker had an idea. He took off the door of the house, put it on his cart and drove to the nearest town. He bought the medicine, and Marek was soon well again. He would not let anyone wash the magic words away from the door.

On what did the doctor write the name of the medicine?

