Identification and treatment of chemoresistant inoperable or metastatic GIST: experience with the selective tyrosine kinase inhibitor imatinib mesylate (STI571)

Structure-based screening of FDA-approved drugs identifies potential histone deacetylase 3 repurposed inhibitor: molecular docking and molecular dynamic simulation approaches

Histone deacetylase 3 (HDAC3) is a member of the histone deacetylase family that has emerged as a crucial target in the quest for novel therapeutic interventions against various complex diseases, including cancer. The repositioning of FDA-approved drugs presents a promising avenue for the rapid discovery of potential HDAC3 inhibitors. In this study, we performed a structure-based virtual screening of FDA-approved drugs obtained from DrugBank. Candidate hits were selected based on their binding affinities and interactions with HDAC3. These promising hits were then subjected to a comprehensive assessment of their biological properties and drug profiles. Our investigation identified two FDA-approved drugs, Imatinib and Carpipramine, characterized by their exceptional affinity and specificity for the binding pocket of HDAC3. These molecules demonstrated a strong preference for HDAC3 binding site and formed interactions with functionally significant residues within the active site pocket. To gain deeper insights into the binding dynamics, structural stability, and interaction mechanisms, we performed molecular dynamics (MD) simulations spanning 300 nanoseconds (ns). The results of MD simulations indicated that Imatinib and Carpipramine stabilized the structure of HDAC3 and induced fewer conformational changes. Taken together, the findings from this study suggest that Imatinib and Carpipramine may offer significant therapeutic potential for treating complex diseases, especially cancer.

Phase II Trial of Imatinib Plus Binimetinib in Patients With Treatment-Naive Advanced Gastrointestinal Stromal Tumor

PURPOSE

Dual targeting of the gastrointestinal stromal tumor (GIST) lineage-specific master regulators, ETV1 and KIT, by MEK and KIT inhibitors were synergistic preclinically and may enhance clinical efficacy. This trial was designed to test the efficacy and safety of imatinib plus binimetinib in first-line treatment of GIST.

METHODS

In this trial (NCT01991379), treatment-naive adult patients with confirmed advanced GISTs received imatinib (400 mg once daily) plus binimetinib (30 mg twice daily), 28-day cycles. The primary end point was RECIST1.1 best objective response rate (ORR; complete response plus partial response [PR]). The study was designed to detect a 20% improvement in the ORR over imatinib alone (unacceptable rate of 45%; acceptable rate of 65%), using an exact binomial test, one-sided type I error of 0.08 and type II error of 0.1, and a planned sample size of 44 patients. Confirmed PR or complete response in > 24 patients are considered positive. Secondary end points included Choi and European Organisation for Research and Treatment of Cancer Response Rate, progression-free survival (PFS), overall survival (OS), pathologic responses, and toxicity.

RESULTS

Between September 15, 2014, and November 15, 2020, 29 of 42 evaluable patients with advanced GIST had confirmed RECIST1.1 PR. The best ORR was 69.0% (two-sided 95% CI, 52.9 to 82.4). Thirty-nine of 41 (95.1%) had Choi PR approximately 8 weeks. Median PFS was 29.9 months (95% CI, 24.2 to not estimable); median OS was not reached (95% CI, 50.4 to not estimable). Five of eight patients with locally advanced disease underwent surgery after treatment and achieved significant pathologic response (≥ 90% treatment effect). There were no unexpected toxicities. Grade 3 and 4 toxicity included asymptomatic creatinine phosphokinase elevation (79.1%), hypophosphatemia (14.0%), neutrophil decrease (9.3%), maculopapular rash (7.0%), and anemia (7.0%).

CONCLUSION

The study met the primary end point. The combination of imatinib and binimetinib is effective with manageable toxicity and warrants further evaluation in direct comparison with imatinib in frontline treatment of GIST.

Molecular Pathogenesis of Gastrointestinal Stromal Tumor: A Paradigm for Personalized Medicine

Over the past three to four decades, the molecular pathogenesis of gastrointestinal stromal tumors (GISTs) has been elucidated in great detail. In this review, we discuss the biological genesis of GISTs, identification of the various primary activating driver mutations (focusing on KIT and PDGFRA), oncogene addiction and targeted therapies with imatinib and other tyrosine kinase inhibitors, and the subsequent characterization of the various mechanisms of drug resistance. We illustrate how GIST has become a quintessential paradigm for personalized medicine. Expected final online publication date for the Annual Review of Pathology: Mechanisms of Disease, Volume 17 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

A Phase I Study of Binimetinib (MEK162) Combined with Pexidartinib (PLX3397) in Patients with Advanced Gastrointestinal Stromal Tumor

Lessons Learned.

The combination of pexidartinib and binimetinib was safe and tolerable and demonstrated encouraging signs of efficacy in two patients with advanced gastrointestinal stromal tumor (GIST) refractory to tyrosine kinase inhibitors (TKIs).

Molecular profiling of GISTs at diagnosis and upon progression may provide insight into the mechanisms of response or resistance to targeted therapies.

Additional trials are needed to further explore combined KIT and MEK inhibition in treatment‐naïve and TKI‐refractory patients with advanced GIST.

Background.

Nearly all patients with advanced gastrointestinal stromal tumor (GIST) develop resistance to imatinib, and subsequent treatments have limited efficacy. Dual inhibition of KIT and MAPK pathways has synergistic antitumor activity in preclinical GIST models.

Methods.

This was an investigator‐initiated, phase I, dose escalation study of the MEK inhibitor binimetinib combined with pexidartinib, a potent inhibitor of CSF1R, KIT, and FLT3, in patients with advanced or metastatic GIST who progressed on imatinib. The primary endpoint was phase II dose determination; secondary endpoints included safety, tolerability, and efficacy. An expansion cohort to further evaluate safety and efficacy was planned.

Results.

Two patients were treated at dose level one (binimetinib 30 mg b.i.d. and pexidartinib 400 mg every morning and 200 mg every evening), after which the study was terminated by the manufacturer. No dose‐limiting toxicities (DLTs) were reported, and treatment was well tolerated. The only grade ≥3 treatment‐emergent adverse event (TEAE) was asymptomatic elevated creatine phosphokinase (CPK). Both patients had a best response of stable disease (SD) by RECIST. Progression‐free survival (PFS) and overall survival (OS) were 6.1 and 14.6 months, respectively, in one patient with five prior lines of therapy. The second patient with NF1‐mutant GIST had a 27% decrease in tumor burden by RECIST and remains on study after 19 months of treatment.

Conclusion.

Pexidartinib combined with binimetinib was tolerable, and meaningful clinical activity was observed in two imatinib‐refractory patients.

Imatinib Mesylate

Imatinib mesylate (Gleevec, Glivec [Novartis, Basel, Switzerland], formerly referred to as STI571 or CGP57148B) represents the paradigm of a new class of anticancer agents, so-called small molecules. They have a high selectivity against a specific molecular target known to be the cause for the establishment and maintenance of the malignant phenotype. Imatinib is a rationally designed oral signal transduction inhibitor that specifically targets several protein tyrosine kinases, Abl, Arg (Abl-related gene), the stem cell factor receptor (c-KIT), platelet-derived growth factor receptor (PDGF-R), and their oncogenic forms, most notably BCR-ABL. Imatinib has been shown to have remarkable clinical activity in patients with chronic myeloid leukemia (CML) and malignant gastrointestinal stroma tumors (GIST) leading to its approval for treatment of these diseases. Treatment with imatinib is generally well tolerated with a low incidence of severe side effects. The most common adverse events include mild to moderate edema, muscle cramps, diarrhea, nausea, skin rashes, and myelosuppression. Several mechanisms of resistance have been identified. Clonal evolution, amplification, or overexpression of BCR-ABL as well as mutations in the catalytic domain, P-loop, and other mutations have been demonstrated to play a role in primary and secondary resistance to imatinib, respectively. Understanding of the underlying mechanisms of resistance has led to the development of new second- and third-generation tyrosine kinase inhibitors (see chapters on dasatinib, nilotinib, bosutinib, and ponatinib).

Direct molecular dissection of tumor parenchyma from tumor stroma in tumor xenograft using mass spectrometry-based glycoproteomics

The most widely used cancer animal model is the human-murine tumor xenograft. Unbiased molecular dissection of tumor parenchyma versus stroma in human-murine xenografts is critical for elucidating dysregulated protein networks/pathways and developing therapeutics that may target these two functionally codependent compartments. Although antibody-reliant technologies (e.g., immunohistochemistry, imaging mass cytometry) are capable of distinguishing tumor-proper versus stromal proteins, the breadth or extent of targets is limited. Here, we report an antibody-free targeted cross-species glycoproteomic (TCSG) approach that enables direct dissection of human tumor parenchyma from murine tumor stroma at the molecular/protein level in tumor xenografts at a selectivity rate presently unattainable by other means. This approach was used to segment/dissect and obtain the protein complement phenotype of the tumor stroma and parenchyma of the metastatic human lung adenocarcinoma A549 xenograft, with no need for tissue microdissection prior to mass-spectrometry analysis. An extensive molecular map of the tumor proper and the associated microenvironment was generated along with the top functional N-glycosylated protein networks enriched in each compartment. Importantly, immunohistochemistry-based cross-validation of selected parenchymal and stromal targets applied on human tissue samples of lung adenocarcinoma and normal adjacent tissue is indicative of a noteworthy translational capacity for this unique approach that may facilitate identifications of novel targets for next generation antibody therapies and development of real time preclinical tumor models.

A Clinical case of Duodenal Gastrointestinal Stromal Tumor with a Peculiarity in the Surgical Approach

We describe a case of duodenal, third portion, segmental resection for gastrointestinal stromal tumor. A 76-year-old man was referred for gastrointestinal bleeding, dyspnea and asthenia. Esophagogastroduodenoscopy showed a duodenal bleeding fistula. Computerized tomography demonstrated a retroperitoneal mass that compressed and displaced forward the third duodenal tract. Segmental resection of the third portion of the duodenum with a subtotal gastrectomy was performed. The patient was reconstructed with a termino-terminal duodenal anastomosis of the second and the fourth tract and with a Roux-en-Y gastrojejunum anastomosis. There were no postoperative complications. This duodenectomy procedure could be useful as a less extensive resection for duodenal gastrointestinal stromal tumor located in the third portion of the duodenum when the tumor is well capsulated, when the surrounding structures are not infiltrated and when there are no vascular difficulties. The technique reduces the morbidity and mortality correlated with duodenocefalopancreasectomy and improves postsurgical quality of life without worsening the risk of recurrence.

Case report of diffusely metastatic rectal GIST

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Rectal gastrointestinal tumors (GISTs) are rare mesenchymal tumors.

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Rectal GISTs are extremely rare and account for approximately 2% of all GIST tumors.

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Majority of GISTs have a benign course.

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Treatment with imatinib mesylate should be arranged as soon as possible.

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The most common cause of death after resection of a rectal GIST is distant metastasis.

This is a case report of an aggressive, diffusely disseminated Stage IV rectal gastrointestinal stromal tumor (GIST) in a 57-year-old male that presented for symptoms of malaise, constipation, and twenty pound weight loss in 2 months. Upon rectal examination, a hard 4 centimeter submucosal mass was found at the 9–12 o’clock position. Liver and lung metastases were visualized on computerized tomography (CT) of the chest, abdomen, and pelvis on metastatic work-up. He was deemed a poor surgical candidate due to diffuse metastatic disease and referred for palliative chemotherapy. The patient had suffered a perforation of his rectal wall two weeks after his initial presentation and passed away shortly thereafter. He never received palliative chemotherapy. We present a case report as a unique case of an extremely aggressive and quickly fatal GIST tumor.

Orai1 mediates tumor-promoting store-operated Ca2+ entry in human gastrointestinal stromal tumors via c-KIT and the extracellular signal-regulated kinase pathway

Gastrointestinal stromal tumors originate from interstitial cells of Cajal, the pacemaker cells of the gut. Ca²⁺ regulates the pacemaker activity of interstitial cells of Cajal. Store-operated Ca²⁺ entry mediates the majority of Ca²⁺ entry in most cancer cells and may be a factor in regulating intracellular Ca²⁺ in interstitial cells of Cajal and gastrointestinal stromal tumors. Therefore, a blockade of this mechanism may affect the progression of gastrointestinal stromal tumors. Orai1 is the pore subunit of store-operated Ca²⁺ channels. Here, we reported that Orai1 was overexpressed in gastrointestinal stromal tumor tissues and was positively correlated with a high-risk grade in gastrointestinal stromal tumor patients. Furthermore, upon Orai1 silencing, the functional store-operated Ca²⁺ entry in gastrointestinal stromal tumor cells was decreased, indicating that the function of store-operated Ca²⁺ entry was mediated by Orai1. Inhibition of Orai1-mediated store-operated Ca²⁺ entry by Orai1 silencing or store-operated Ca²⁺ entry blockers (SKF-96365 and 2-aminoethyl diphenylborate) induced obvious cell proliferation suppression, cell-cycle distribution, and apoptosis stimulation in GIST-T1 cells. Conversely, Orai1 overexpression increased store-operated Ca²⁺ entry and cell proliferation in GIST882 cells. In addition, we found that activation of c-KIT and the extracellular signal-regulated kinase pathway participated in the oncogenic functions of Orai1-mediated store-operated Ca²⁺ entry in gastrointestinal stromal tumor cells. These results revealed that Orai1-mediated store-operated Ca²⁺ entry is critical for gastrointestinal stromal tumor cell proliferation via c-KIT and ERK signaling pathway activation. Orai1-mediated store-operated Ca²⁺ entry plays an oncogenic role and may be a novel prognostic factor and therapeutic target for patients with gastrointestinal stromal tumors.

GEIS guidelines for gastrointestinal sarcomas (GIST)

Gastrointestinal stromal sarcomas (GISTs) are the most common mesenchymal tumours originating in the digestive tract. They have a characteristic morphology, are generally positive for CD117 (c-kit) and are primarily caused by activating mutations in the KIT or PDGFRA genes(1). On rare occasions, they occur in extravisceral locations such as the omentum, mesentery, pelvis and retroperitoneum. GISTs have become a model of multidisciplinary work in oncology: the participation of several specialties (oncologists, pathologists, surgeons, molecular biologists, radiologists…) has forested advances in the understanding of this tumour and the consolidation of a targeted therapy, imatinib, as the first effective molecular treatment in solid tumours. Following its introduction, median survival of patients with advanced or metastatic GIST increased from 18 to more than 60months. Sunitinib and Regorafenib are two targeted agents with worldwide approval for second- and third-line treatment, respectively, in metastatic GIST.

Molecular chess? Hallmarks of anti-cancer drug resistance

Background

The development of resistance is a problem shared by both classical chemotherapy and targeted therapy. Patients may respond well at first, but relapse is inevitable for many cancer patients, despite many improvements in drugs and their use over the last 40 years.

Review

Resistance to anti-cancer drugs can be acquired by several mechanisms within neoplastic cells, defined as (1) alteration of drug targets, (2) expression of drug pumps, (3) expression of detoxification mechanisms, (4) reduced susceptibility to apoptosis, (5) increased ability to repair DNA damage, and (6) altered proliferation. It is clear, however, that changes in stroma and tumour microenvironment, and local immunity can also contribute to the development of resistance. Cancer cells can and do use several of these mechanisms at one time, and there is considerable heterogeneity between tumours, necessitating an individualised approach to cancer treatment. As tumours are heterogeneous, positive selection of a drug-resistant population could help drive resistance, although acquired resistance cannot simply be viewed as overgrowth of a resistant cancer cell population. The development of such resistance mechanisms can be predicted from pre-existing genomic and proteomic profiles, and there are increasingly sophisticated methods to measure and then tackle these mechanisms in patients.

Conclusion

The oncologist is now required to be at least one step ahead of the cancer, a process that can be likened to ‘molecular chess’. Thus, as well as an increasing role for predictive biomarkers to clinically stratify patients, it is becoming clear that personalised strategies are required to obtain best results.

Unprecedently Large-Scale Kinase Inhibitor Set Enabling the Accurate Prediction of Compound-Kinase Activities: A Way toward Selective Promiscuity by Design?

Drug discovery programs frequently target members of the human kinome and try to identify small molecule protein kinase inhibitors, primarily for cancer treatment, additional indications being increasingly investigated. One of the challenges is controlling the inhibitors degree of selectivity, assessed by in vitro profiling against panels of protein kinases. We manually extracted, compiled, and standardized such profiles published in the literature: we collected 356 908 data points corresponding to 482 protein kinases, 2106 inhibitors, and 661 patents. We then analyzed this data set in terms of kinome coverage, results reproducibility, popularity, and degree of selectivity of both kinases and inhibitors. We used the data set to create robust proteochemometric models capable of predicting kinase activity (the ligand-target space was modeled with an externally validated RMSE of 0.41 ± 0.02 log units and R02 0.74 ± 0.03), in order to account for missing or unreliable measurements. The influence on the prediction quality of parameters such as number of measurements, Murcko scaffold frequency or inhibitor type was assessed. Interpretation of the models enabled to highlight inhibitors and kinases properties correlated with higher affinities, and an analysis in the context of kinases crystal structures was performed. Overall, the models quality allows the accurate prediction of kinase-inhibitor activities and their structural interpretation, thus paving the way for the rational design of compounds with a targeted selectivity profile.

Survival for oesophageal, stomach and small intestine cancers in Europe 1999-2007: Results from EUROCARE-5

BACKGROUND

European regional variation in cancer survival was reported in the EUROCARE-4 study for patients diagnosed in 1995-1999. Relative survival (RS) estimates are here updated for patients diagnosed with cancer of the oesophagus, stomach and small intestine from 2000 to 2007. Trends in RS from 1999-2001 to 2005-2007 are presented to monitor and discuss improvements in patient survival in Europe.

MATERIALS AND METHODS

EUROCARE-5 data from 29 countries (87 cancer registries) were used to investigate 1- and 5-year RS. Using registry-specific life-tables stratified by age, gender and calendar year, age-standardised 'complete analysis' RS estimates by country and region were calculated for Northern, Southern, Eastern and Central Europe, and for Ireland and United Kingdom (UK). Survival trends of patients in periods 1999-2001, 2002-2004 and 2005-2007 were investigated using the 'period' RS approach. We computed the 5-year RS conditional on surviving the first year (5-year conditional survival), as the ratio of age-standardised 5-year RS to 1-year RS.

RESULTS

Oesophageal cancer 1- and 5-year RS (40% and 12%, respectively) remained poor in Europe. Patient survival was worst in Eastern (8%), Northern (11%) and Southern Europe (10%). Europe-wide, there was a 3% improvement in oesophageal cancer 5-year survival by 2005-2007, with Ireland and the UK (3%), and Central Europe (4%) showing large improvements. Europe-wide, stomach cancer 5-year RS was 25%. Ireland and UK (17%) and Eastern Europe (19%) had the poorest 5-year patient survival. Southern Europe had the best 5-year survival (30%), though only showing an improvement of 2% by 2005-2007. Small intestine cancer 5-year RS for Europe was 48%, with Central Europe having the best (54%), and Ireland and UK the poorest (37%). Five-year patient survival improvement for Europe was 8% by 2005-2007, with Central, Southern and Eastern Europe showing the greatest increases (⩾9%).

CONCLUSIONS

Survival for these cancer sites, particularly oesophageal cancer, remains poor in Europe with wide variation. Further investigation into the wide variation, including analysis by histology and anatomical sub-site, will yield insights to better monitor and explain the improvements in survival observed over time.

Combined inhibition of MAP kinase and KIT signaling synergistically destabilizes ETV1 and suppresses GIST tumor growth

Gastrointestinal stromal tumor (GIST), originating from the interstitial cells of Cajal (ICC), is characterized by frequent activating mutations of the KIT receptor tyrosine kinase. Despite the clinical success of imatinib, which targets KIT, most patients with advanced GIST develop resistance and eventually die of the disease. The ETS family transcription factor ETV1 is a master regulator of the ICC lineage. Using mouse models of Kit activation and Etv1 ablation, we demonstrate that ETV1 is required for GIST initiation and proliferation in vivo, validating it as a therapeutic target. We further uncover a positive feedback circuit where MAP kinase activation downstream of KIT stabilizes the ETV1 protein, and ETV1 positively regulates KIT expression. Combined targeting of ETV1 stability by imatinib and MEK162 resulted in increased growth suppression in vitro and complete tumor regression in vivo. The combination strategy to target ETV1 may provide an effective therapeutic strategy in GIST clinical management.

SIGNIFICANCE

ETV1 is a lineage-specific oncogenic transcription factor required for the growth and survival of GIST. We describe a novel strategy of targeting ETV1 protein stability by the combination of MEK and KIT inhibitors that synergistically suppress tumor growth. This strategy has the potential to change first-line therapy in GIST clinical management.

GEIS 2013 guidelines for gastrointestinal sarcomas (GIST)

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal soft tissue sarcoma of the gastrointestinal tract. Correct diagnosis with thorough use of pathologic and molecular tools of GIST mutations has been of the foremost importance. GIST are usually (95 %) KIT positive and harbor frequent KIT or platelet-derived growth factor receptor α-activating mutations. This deep molecular understanding has allowed the correct classification into risk groups with implications regarding prognosis, essential use in the development of targeted therapies and even response prediction to this drugs. Treatment has been evolving and an update to include lessons learned from recent trials in advanced disease as well as controversies in the adjuvant setting that are changing daily practice, is reviewed here. An effort from the Spanish Group for Sarcoma Research with investigators from the group has been undertaken to launch this third version of the GIST guidelines and provide a practical means for the different disciplines that treat this complex disease.

Gastrointestinal stromal tumors (GIST) related emergencies

BACKGROUND

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract, accounting for 1-3% of all gastrointestinal malignancies. Throughout the whole length of the gastrointestinal tract, GIST arises most commonly from the stomach followed by small bowel. The clinical presentations of GIST are highly variable according to their site and size. The most frequent symptoms are anemia, weight loss, gastrointestinal bleeding, abdominal pain and massrelated symptoms. Patients may present with acute abdomen, obstruction, perforation or rupture and peritonitis. Surgical resection is the "gold standard" for therapy of GIST. Recently, targeted therapy with inhibitors of tyrosine kinase receptors (imatinib) has been introduced for the management of advanced and metastatic tumors.

PURPOSE

The aim of this work is to present the experience of the Gastrointestinal Surgery Unit, Alexandria Faculty of Medicine in the management of patients with GIST related emergencies.

PATIENTS AND METHODS

This study was carried out on all patients with gastrointestinal stromal tumors who presented to the Gastrointestinal Surgery Unit, Main Alexandria University Hospital in an emergency situation during the period from January 2005 till December 2012. All patients' data, clinical presentations, radiological and endoscopic data, surgical procedures, complications, and survival data were collected, reviewed and analyzed. After approval of local ethics committee, all patients included in the study were informed well about the procedure and an informed written consent was obtained from every patient before carrying the procedure.

RESULTS

Between January 2005 and December 2012; 92 patients (54 males and 38 females) were admitted with different emergency presentations of clinically and radiologically suspected GISTs. The tumors were located in the stomach in 49 patients, in the duodenum in 6 patients, in the small intestine in 27 patients, in the small intestinal mesentery in 4 patients, in the colon in 3 patients and in the rectum in 3 patients. The most frequent presenting symptom was gastrointestinal bleeding in 45 patients. Twenty-six patients presented with intestinal obstruction, 14 patients with intraperitoneal hemorrhage and 7 patients with rupture and peritonitis. Ninety patients were operated upon. Two patients presented with extensive GIST, and were not candidate for surgical treatment. All operated patients underwent surgical resection. Complete macroscopic resection was achieved in 86 patients (95.6%), while 4 patients (4.4%) had incomplete resection. All over 11 patients developed metastases, or recurrence. The 3 and 5-years overall survival rates for all patients, using the Kaplan-Meier actuarial curve, were 92.1% and 81.4% respectively. The 3 and 5-years disease-free survival rates for all patients were 73.2% and 64.5% respectively.

CONCLUSION

Although GISTs are uncommon, their incidence is probably increasing especially their emergency presentations. The emergency surgeon must be acquainted with the disease, its emergency presentation and principles of surgery in the presence of GIST tumors. Early diagnosis and treatment would save life of many patients who presented with GIST related emergencies. Surgery is still the gold standard treatment in localized GIST, although the percentage of relapse is not low even after radical surgery. The prognosis is strictly related to size and completeness of surgical resection. We strongly advocate that all patients with a GIST be carefully and regularly followed-up for an indefinite period. The large number of patients in this series is an alarming signal for further studies to elucidate the pathogenesis of this disease.

Imatinib mesylate

Imatinib mesylate (Gleevec, Glivec [Novartis, Basel, Switzerland], formerly referred to as STI571 or CGP57148B) represents the paradigm of a new class of anticancer agents, so-called small molecules. They have a high selectivity against a specific molecular target known to be the cause for the establishment and maintenance of the malignant phenotype. Imatinib is a rationally designed oral signal transduction inhibitor that specifically targets several protein tyrosine kinases, Abl, Arg (Abl-related gene), the stem cell factor receptor (c-KIT), platelet-derived growth factor receptor (PDGF-R), and their oncogenic forms, most notably BCR-ABL. Imatinib has been shown to have remarkable clinical activity in patients with chronic myeloid leukemia (CML) and malignant gastrointestinal stroma tumors (GIST) leading to its approval for treatment of these diseases. Treatment with imatinib is generally well tolerated with a low incidence of severe side effects. The most common adverse events include mild to moderate edema, muscle cramps, diarrhea, nausea, skin rashes, and myelosuppression. Several mechanisms of resistance have been identified. Clonal evolution, amplification, or overexpression of BCR-ABL as well as mutations in the catalytic domain, P-loop, and other mutations have been demonstrated to play a role in primary and secondary resistance to imatinib, respectively. Understanding of the underlying mechanisms of resistance has led to the development of new second- and third-generation tyrosine kinase inhibitors (see chapters on dasatinib, nilotinib, bosutinib, and ponatinib).

In vivo imaging-based mathematical modeling techniques that enhance the understanding of oncogene addiction in relation to tumor growth

The dependence on the overexpression of a single oncogene constitutes an exploitable weakness for molecular targeted therapy. These drugs can produce dramatic tumor regression by targeting the driving oncogene, but relapse often follows. Understanding the complex interactions of the tumor's multifaceted response to oncogene inactivation is key to tumor regression. It has become clear that a collection of cellular responses lead to regression and that immune-mediated steps are vital to preventing relapse. Our integrative mathematical model includes a variety of cellular response mechanisms of tumors to oncogene inactivation. It allows for correct predictions of the time course of events following oncogene inactivation and their impact on tumor burden. A number of aspects of our mathematical model have proven to be necessary for recapitulating our experimental results. These include a number of heterogeneous tumor cell states since cells following different cellular programs have vastly different fates. Stochastic transitions between these states are necessary to capture the effect of escape from oncogene addiction (i.e., resistance). Finally, delay differential equations were used to accurately model the tumor growth kinetics that we have observed. We use this to model oncogene addiction in MYC-induced lymphoma, osteosarcoma, and hepatocellular carcinoma.

Modern treatment of gastric gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GIST) are rare mesenchymal smooth muscle sarcomas that can arise anywhere within the gastrointestinal tract. Sporadic mutations within the tyrosine kinase receptors of the interstitial cells of Cajal have been identified as the key molecular step in GIST carcinogenesis. Although many patients are asymptomatic, the most common associated symptoms include: abdominal pain, dyspepsia, gastric outlet obstruction, and anorexia. Rarely, GIST can perforate causing life-threatening hemoperitoneum. Most are ultimately diagnosed on cross-sectional imaging studies (i.e., computed tomography and/or magnetic resonance imaging in combination with upper endoscopy. Endoscopic ultrasonographic localization of these tumors within the smooth muscle layer and acquisition of neoplastic spindle cells harboring mutations in the c-KIT gene is pathognomonic. Curative treatment requires a complete gross resection of the tumor. Both open and minimally invasive operations have been shown to reduce recurrence rates and improve long-term survival. While there is considerable debate over whether GIST can be benign neoplasms, we believe that all GIST have malignant potential, but vary in their propensity to recur after resection and metastasize to distant organ sites. Prognostic factors include location, size (i.e., > 5 cm), grade (> 5-10 mitoses per 50 high power fields and specific mutational events that are still being defined. Adjuvant therapy with tyrosine kinase inhibitors, such as imatinib mesylate, has been shown to reduce the risk of recurrence after one year of therapy. Treatment of locally-advanced or borderline resectable gastric GIST with neoadjuvant imatinib has been shown to induce regression in a minority of patients and stabilization in the majority of cases. This treatment strategy potentially reduces the need for more extensive surgical resections and increases the number of patients eligible for curative therapy. The modern surgical treatment of gastric GIST combines the novel use of targeted therapy and aggressive minimally invasive surgical procedures to provide effective treatment for this lethal, but rare gastrointestinal malignancy.

Efficacy of PET-CT for predicting the malignant potential of gastrointestinal stromal tumors

PURPOSES

Gastrointestinal stromal tumor (GIST) is the most common sarcoma of the intestinal tract. The risk category is usually determined by tumor size and mitotic count, but accurate preoperative diagnosis of GIST is very difficult. The purpose of this study is to evaluate the efficacy of positron emission tomography (PET)-CT for predicting the malignant potential of gastrointestinal stromal tumors.

METHODS

Ten patients with GIST who underwent a preoperative PET-CT examination were divided into two groups by risk category, and various factors were compared between the two groups. The relationships between the maximum standardized uptake value (SUVmax) and GIST parameters were examined.

RESULTS

Patients were classified into two groups by their risk category: (low/intermediate-risk or high-risk). The SUVmax was significantly higher in the high-risk group (11.0 ± 3.04) than in the low/intermediate-risk group (2.1 ± 1.5). The Ki67 labeling index was also significantly higher in the high-risk group (8.63 ± 6.2) than in the low/intermediate-risk group (1.75 ± 0.52). There was a significant correlation between the Ki67 labeling index and the SUVmax (p = 0.028) and between the mitotic index and the SUVmax (p = 0.029).

CONCLUSIONS

PET-CT can predict malignant potential. Cases with a SUVmax of over 5 may have malignant potential.

Synthesis of Potent Anticancer Thieno[2,3-d]Pyrimidine Derivatives

As part of our program to identify novel cytotoxic agents, various series of hexahydrocycloocta[4,5]thieno[2,3- d] pyrimidines and pyrimidin-4-ones substituted by aryl at the C-2 position together with phenylethylamino, substituted amino, hydrazinyl or arylidenhydrazinyl substituents at the C-4 position were synthesised. These compounds were prepared as bioisosteres of gefitinib, an antitumour drug used for the treatment of gastrointestinal stromal tumours. All compounds exhibited antitumour activity against (HCT 116) cell line in vitro. Eight compounds (IC50: 3.89, 4.65, 6.63, 6.94, 7.89, 9.53, 12.00 and 12.30 μg mL−1 respectively) exhibited 4.3 to 1.3 fold more potent antitumour activity than imatinib (IC50: 16.93 μg mL−1). Also, a docking study of the newly synthesised compounds with the active site of CDK2 was described.

Synthesis of Thieno[2,3-d]Pyrimidines, Thieno[2,3-d]Triazinones and Thieno[2,3-e]Diazepinones of Anticipated Anti-Cancer Activity

A novel series of 4-aminohexahydrocycloocta[4,5]thieno[2,3- d]pyrimidines, hexahydrocycloocta[4,5]thieno[2,3- d]-1,2,3-triazin-4-one and its N-3 substituted derivatives in addition to 3-aryl hexahydrocycloocta[4,5] thieno[2,3- e]-1,4-diazepin-5-ones were synthesised. Also, 2-(N-ethylcarbamothioylamino) hexahydrocycloocta[b] thiophene-3-carbonitrile and 19-imino tetradecahydrocycloocta[4’,5'] thieno[2’,3’:4,5]pyrimido[1,6- a] cycloocta[4,5]thieno [3,2- e]pyrimidine-9-thione were prepared. Almost all the synthesised compounds exhibited anti-tumour activity against human colon carcinoma (HCT 116) cell line in vitro. Five compounds (IC50: 15.92, 22.59, 25.85, 27.40 and 29.70 μM, respectively) exhibited 2.16 to 1.15 fold more potent antitumour activity than imatinib (IC50: 34.40 μM).

Secondary resistance of extra-gastrointestinal stromal tumors to imatinib mesylate: report of a case

Extra-gastrointestinal stromal tumors (EGISTs) that do not originate in the digestive tract are rare. We report a case of multiple EGISTs, which was monitored closely by KIT gene mutation analysis and other investigations. The patient was a 52-year-old man in whom multiple tumors in the abdominal cavity were diagnosed as EGISTs. Immunohistochemical analysis revealed positive staining for c-kit; however, no mutations were found in the KIT gene. The tumors decreased in size remarkably following treatment with imatinib mesylate, but after 2 years of this treatment, multiple liver metastases and some regrowth of the abdominal masses were found simultaneously. The liver metastasis and the abdominal masses were excised, and further analysis of the KIT gene revealed the same mutation in exon 11 in the KIT gene in the metastatic tumors. We speculate that the treatment might have triggered development of the imatinib mesylate-resistant clone, which may have existed in the primary lesion as a KIT gene mutant. This report provides valuable insight into the mechanisms of recurrent GISTs after treatment with imatinib mesylate.

F-FDG PET Imaging in the Evaluation of Treatment Response to New Chemotherapies beyond Imatinib for Patients with Gastrointestinal Stromal Tumors

Aim. (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) is a powerful tool for staging and defining "good responders" to chemotherapy in tumor setting. Gastrointestinal stromal tumors (GISTs) are sarcoma involving gastrointestinal tract and may require a chemotherapy including imatinib, a tyrosine kinase inhibitor agent. Some GIST patients become refractory to imatinib; therefore, other tyrosine kinase inhibitors or concomitant chemotherapy may be considered for treatment. The aim of this paper is to assess if (18)F-FDG PET imaging is a useful tool to evaluate treatment response to new chemotherapies beyond imatinib for GIST patients. Methods. We performed a review of the literature about the role of (18)F-FDG PET in the evaluation of treatment response to new chemotherapies beyond imatinib for GIST patients. Results and Conclusions. (18)F-FDG PET seems to be able to assess therapy response earlier than computed tomography (CT) imaging in imatinib refractory GIST patients treated with other agents. However, a dual modality PET-CT imaging is recommendable to achieve a better detection of all lesions.

Circulating levels of cell adhesion molecule L1 as a prognostic marker in gastrointestinal stromal tumor patients

BACKGROUND

L1 cell adhesion molecule (CD171) is expressed in many malignant tumors and its expression correlates with unfavourable outcome. It thus represents a target for tumor diagnosis and therapy. An earlier study conducted by our group identified L1 expression levels in primary gastrointestinal stromal tumors (GIST) as a prognostic marker. The aim of the current study was to compare L1 serum levels of GIST patients with those of healthy controls and to determine whether levels of soluble L1 in sera could serve as a prognostic marker.

METHODS

Using a sensitive enzyme-linked immunosorbent assay (ELISA), soluble L1 was measured in sera of 93 GIST patients und 151 healthy controls. Soluble L1 levels were then correlated with clinicopathological data.

RESULTS

Median levels of soluble L1 were significantly higher (p < 0.001; Mann-Whitney U test) in sera of GIST patients compared to healthy individuals. Median soluble L1 levels were particularly elevated in patients with recurrence and relapse (p < 0.05; Mann Whitney U test).

CONCLUSION

These results suggest that high soluble L1 levels predict poor prognosis and may thus be a promising tumor marker that can contribute to individualise therapy.

Gastrointestinal stromal tumours treated before and after the advent of c-kit immunostaining

BACKGROUND

Recently developed immunohistochemical markers have revolutionised the classification of gastrointestinal stromal tumours (GISTs) whilst tyrosine kinase inhibitors (imatinib) have had a significant impact on the treatment of advanced tumours. We review the clinicopathological features of previously resected mesenchymal tumours of the gastrointestinal tract in our institution to 1) reclassify the histological diagnosis of those stained prior to c-kit availability; 2) perform survival analysis to identify prognostic factors, and 3) to consider the implications for patients.

METHODS

Clinicopathological records of patients with a diagnosis of mesenchymal tumours treated between May 1992 and April 2007 were reviewed.

RESULTS

82 patients were reviewed. 26 (32%) were reclassified as GISTs following c-kit immunostaining and a further 14 patients were treated for GIST up to April 2007 (Total: 40 patients; 21 males and 19 females, mean age 67, range 30-92 years). 36 (90%) underwent complete resection. 5-year survival of patients with GIST alone was 80%. Females had a better median survival (M: F 43 months: 73 months).

CONCLUSIONS

The availability of c-kit staining allowed 32% of previously diagnosed mesenchymal tumours to be reclassified as GISTs. This may have implications for the follow-up of patients diagnosed prior to the availability of this method.

Treatment implications of the emerging molecular classification system for melanoma

Melanoma is an aggressive disease with few standard treatment options. The conventional classification system for this disease is based on histological growth patterns, with division into four subtypes: superficial spreading, lentigo maligna, nodular, and acral lentiginous. Major limitations of this classification system are absence of prognostic importance and little correlation with treatment outcomes. Recent preclinical and clinical findings support the notion that melanoma is not one malignant disorder but rather a family of distinct molecular diseases. Incorporation of genetic signatures into the conventional histopathological classification of melanoma has great implications for development of new and effective treatments. Genes of the mitogen-associated protein kinase (MAPK) pathway harbour alterations sometimes identified in people with melanoma. The mutation Val600Glu in the BRAF oncogene (designated BRAF(V600E)) has been associated with sensitivity in vitro and in vivo to agents that inhibit BRAF(V600E) or MEK (a kinase in the MAPK pathway). Melanomas arising from mucosal, acral, chronically sun-damaged surfaces sometimes have oncogenic mutations in KIT, against which several inhibitors have shown clinical efficacy. Some uveal melanomas have activating mutations in GNAQ and GNA11, rendering them potentially susceptible to MEK inhibition. These findings suggest that prospective genotyping of patients with melanoma should be used increasingly as we work to develop new and effective treatments for this disease.

Epidemiology, survival, and costs of localized gastrointestinal stromal tumors

Purpose:

The aim of this study is to examine the epidemiologic and economic burden in surgically resected localized gastrointestinal stromal tumor (GIST) patients versus age- and gender-matched controls.

Method:

Two data sources were used to conduct a series of complementary analyses. First, the Surveillance, Epidemiology, and End Results (SEER) cancer registry was used to identify diagnosed GIST patients from 1993 to 2002 and determine incidence, prevalence, and 3-year survival. Second, using the SEER–Medicare linked database, a matched case-control analysis was conducted to determine resource utilization, GIST recurrence, and costs. Because GIST recurrence is not explicitly defined in the database, patterns in resource use were used to identify probable recurrence. Kaplan–Meier Sample Average (KMSA) Estimator technique was used to estimate costs of GIST and recurrence.

Results:

SEER registry results show over the 10-year time horizon average annual GIST incidence was 0.32 per 100,000 persons in the United States, 15-year limited-duration prevalence was 1.62 per 100,000 persons, and 3-year survival was 73%. A total of 292 GIST patients were included in the SEER–Medicare analyses; 35 were identified with probable recurrence. GIST patients had increased risk of mortality (hazard ratio: 1.23; 95% confidence intervals: 0.94–1.61) compared to controls. Median recurrence-free and postrecurrence survival was 45 and 46 months, respectively. GIST patients incurred significantly higher medical care costs in the first year after initial resection, with $23,221 attributable to GIST. GIST recurrence costs totaled $101,700 over 5 years after initial resection.

Conclusions:

GIST is associated with substantial medical care costs, estimated recurrence costs more than $100,000; treatments that delay or reduce recurrence could substantially reduce the burden of GIST.

Mutations in the c-Kit gene disrupt mitogen-activated protein kinase signaling during tumor development in adenoid cystic carcinoma of the salivary glands

The Ras/mitogen-activated protein kinase (MAPK) pathway is considered to be a positive regulator of tumor initiation, progression, and maintenance. This study reports an opposite finding: we have found strong evidence that the MAPK pathway is inhibited in a subset of adenoid cystic carcinomas (ACCs) of the salivary glands. ACC tumors consistently overexpress the receptor tyrosine kinase (RTK) c-Kit, which has been considered a therapeutic target. We performed mutational analysis of the c-Kit gene (KIT in 17 cases of ACC and found that 2 cases of ACC had distinct missense mutations in KIT at both the genomic DNA and messenger RNA levels. These mutations caused G664R and R796G amino acid substitutions in the kinase domains. Surprisingly, the mutations were functionally inactive in cultured cells. We observed a significant reduction of MAPK (ERK1/2) activity in tumor cells, as assessed by immunohistochemistry. We performed further mutational analysis of the downstream effectors in the c-Kit pathway in the genes HRAS, KRAS, NRAS, BRAF, PIK3CA, and PTEN. This analysis revealed that two ACC tumors without KIT mutations had missense mutations in either KRAS or BRAF, causing S17N K-Ras and V590I B-Raf mutants, respectively. Our functional analysis showed that proteins with these mutations were also inactive in cultured cells. This is the first time that MAPK activity from the RTK signaling has been shown to be inhibited by gene mutations during tumor development. Because ACC seems to proliferate despite inactivation of the c-Kit signaling pathway, we suggest that selective inhibition of c-Kit is probably not a suitable treatment strategy for ACC.

Time-specific blockade of PDGFR with Imatinib (Glivec®) causes cataract and disruption of lens fiber cells in neonatal mice

This study aimed at investigating the response of lens epithelial cells in postnatal mice to Imatinib (Glivec®, a potent inhibitor of platelet-derived growth factor receptor (PDGFR)) treatment. Mouse eyes were sampled 10 days after administration of Imatinib (0.5 mg·g(-1)·day(-1)) for 3 days, at either 7, 14, or 21 days postpartum. Structural changes of lens were revealed by routine H.E. staining. Levels of proliferation and apoptosis were revealed by BrdU incorporation and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, respectively, and immunofluorescent staining with anti-PDGFRα antibody was carried out on the sections of eyeball. PDGFRα and p-PDGFRαprotein levels were evaluated by Western blot. Our results indicated that administration of Imatinib led to blockade of PDGFR signaling. Formation of cataracts was found only in those mice where treatment started from 7 days postpartum (P7), but was not observed in those samples from P14 nor P21. Fiber cells were disorganized in cataract lens core as observed histologically, and migration of epithelial cells was also inhibited. No apoptosis was detected with the TUNEL method. Our results indicated blockade of PDGFR at the neonatal stage (P7) would lead to cataracts and lens fiber cells disorganization, suggesting that PDGFR signaling plays a time-specific and crucial role in the postnatal development of lens in the mouse, and also may provide a new approach to produce a congenital cataract animal model.

Dasatinib: a potent SRC inhibitor in clinical development for the treatment of solid tumors

SRC is a tyrosine kinase that plays a role in oncogenic, invasive and bone-metastatic processes. It has therefore been prioritized as a candidate therapeutic target in patients with solid tumors. Several SRC inhibitors are now in development, of which dasatinib has been most explored. Preclinical studies in a wide variety of solid tumor cell lines, including prostate, breast and glioma, have shown that that dasatinib acts as a cytostatic agent, inhibiting the processes of cell proliferation, invasion and metastasis. Dasatinib also inhibits the activity of osteoclasts, which have a major role in the development of metastatic bone lesions. Dasatinib has additive or synergistic activity in combination with a number of other agents, including cytotoxic agents and targeted therapies, providing a rationale for combination treatment in a clinical setting. Emerging clinical data with dasatinib support experimental observations, with preliminary phase 1 and 2 data demonstrating activity, both as a single agent and as combination therapy, in a range of solid tumors. Future clinical trials will further assess the clinical value of SRC inhibition with dasatinib.

Gastrointestinal stromal tumours: Our experience

BACKGROUND

Gastrointestinal stromal tumours (GIST) are histologically heterogenous group of mesenchymal tumours arising in gastrointestinal tract (GIT), though they represent only 0.2% of all GI tumours. The advent of effective chemotherapy for GIST has altered but not diminished the role of surgery which remains the standard therapy for all resectable non-metastatic tumours.

PURPOSE

To present our experience of management of GIST which are most common sarcomas of the GIT, commonly seen in stomach and small bowel.

METHODS

All cases of GIST managed at our centre from April 2006 to June 2008 were included in the study.

RESULTS

Thirteen cases of GIST were operated in the study period. Commonest presenting symptoms were, lump abdomen and dull abdominal pain. After initial USG, CECT was done in all cases. Tumour was seen to arise from small bowel (7/13), stomach (4/13) and one each from oesophagus and omentum. Resection and anastomosis was done in (12/13) cases, one case was inoperable at surgery. Histopathological examination confirmed GIST in all. Immunohistochemistry studies were done in 4/13 cases. 2/13 patients required postoperative chemotherapy.

CONCLUSION

GIST has varied presentation as shown by our study. All patients require accurate delineation by CECT scan and individualised management. Immunohistochemistry should be done in all, and those who are in high risk group, metastatic or unresectable require imatinib mesylate. Patients who are CD117 positive show good response to imatinib mesylate. Six monthly follow up is recommended with USG/CECT.

Postnatal development of interstitial cells of Cajal in mouse colon in response to Kit signal blockade with Imatinib (Glivec)

This study investigated the response of interstitial cells of Cajal (ICC) in postnatal mouse colon to treatment with Imatinib (Glivec), a potent inhibitor of Kit receptor). ICC were revealed by immunofluorescent staining on frozen cross-sections and whole-mount preparations by anti-Kit and DOG1 antibodies. Kit and p-Kit protein were also evaluated by Western blot. After administration of Imatinib for 4 days beginning at 8 days post-partum (P8), the mean density of Kit+ ICC, which were localized around the myenteric nerve plexus (ICC-MY), within smooth muscle layers (ICC-IM) and in the connective tissue beneath the serosa (ICC-SS), was dramatically decreased to about 50% when compared with controls, but those Kit+ cells located at the submucosal border of circular smooth muscle layer (ICC-SM) seemed to be unchanged in both cell number and morphology. A small number of DOG1+/Kit(-) cells appeared during Imatinib administration. However, these Kit+ ICC were not changed in mice even after 12 days of Imatinib treatment from P24. When Imatinib was discontinued, the number of ICC recovered to normal within 4 days. Our results indicate that the postnatal development of ICC in the mouse colon is Kit dependent, but ICC-SM are unlikely, and the Kit dependence of ICC development is also age-dependent.

Imatinib mesylate

IMATINIB MESYLATE (Gleevec, Glivec [Novartis, Basel, Switzerland], formerly referred to as STI571 or CGP57148B) represents the paradigm of a new class of anticancer agents, the so-called small molecules. They have a high selectivity against a specific molecular target known to be the cause for the establishment and maintenance of the malignant phenotype. Imatinib is a rationally designed oral signal transduction inhibitor that specifically targets several protein tyrosine kinases, Abl, Arg (Abl-related gene), the stem-cell factor receptor (c-KIT), platelet-derived growth factor receptor (PDGF-R), and their oncogenic forms, most notably Bcr-Abl. Imatinib has been shown to have remarkable clinical activity in patients with chronic myeloid leukemia (CML) and malignant gastrointestinal stroma tumors (GIST) leading to its approval for treatment of these diseases.Treatment with imatinib is generally well tolerated with a low incidence of severe side effects. The most common adverse events (AE) include mild to moderate edema, muscle cramps, diarrhea, nausea, skin rashes, and myelosuppression.Several mechanisms of resistance have been identified. Clonal evolution, amplification, or overexpression of Bcr-Abl as well as mutations in the catalytic domain, P-loop, and other mutations have been demonstrated to play a role in primary and secondary resistance to imatinib, respectively. Improved understanding of the underlying mechanisms of resistance has led to the development of new second-generation tyrosine kinase inhibitors (see Chaps. 7-9).

Ki67 and p53 in gastrointestinal stromal tumors--GIST

CONTEXT

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor. Cellular proliferation and apoptosis is gaining importance for predicting prognosis in several cancers.

OBJECTIVE

To investigate the Ki67 and p53 immunostaining in GISTs.

METHODS

Specimens from 40 patients with GIST were assessed for immunohistochemical expression of Ki67 and p53. The tumors were divided according the risk of recurrence in two groups: I with high or intermediate risk and; II with low or very low risk.

RESULTS

Among the 40 patients, 21 were men, the mean age was 56 years, 16 occurred in the small intestine and 13 in the stomach, 5 in the retroperitonium, 4 in the colon or rectum and 2 in the mesenterium. Thirty two tumors were from group I and 8 from group II. Half of the patients developed recurrence, being 90% of the group I (P = 0.114). The tumor Ki67 labelling index ranged from 0.02 to 0.35 (mean level 0.12). This index was marginally higher in the group I patients with recurrence (P = 0.09) compared to the patients of the same group without recurrence. p53 staining was expressed in 65% of the GISTs. A higher frequency of p53 and Ki67 had been found in the group I tumors when compared to the other group (P = 0.022; OR = 8.00 - IC 95%: 1.32-48.65).

CONCLUSION

The most common site was the small intestine and 80% had a malignant potential justifying the high recurrence observed. No significant correlation was found between p53 and overall outcome of the patients. In group I patients, the evaluation Ki67LI may be a marker of prognosis. The positivity of both markers is higher among the patients with worst prognosis than in the others.

Activity of FB2, a novel dual Abl/Src tyrosine kinase inhibitor, against imatinib-resistant chronic myeloid leukemia in vivo and in vitro

FB2 is a novel Abl/Src dual tyrosine kinase inhibitor which is designed to overcome imatinib resistance. Besides imatinib-sensitive cell lines (K562), FB2 significantly inhibited the growth of imatinib-resistant cell lines of different resistance mechanisms (K562/G5.0 and K562/G01), and decreased the expression of autophosphorylation of Bcr/Abl, c-Src and Lyn kinases on them. It also inhibited the proliferation of Src over activated cells DU145 and MDA-MB-231. Furthermore, FB2 potently prolonged the survival time of non-obese diabetic/severe combined immunodeficient mice harboured K562/G5.0 cells. These results indicated that FB2, an Abl/Src dual tyrosine kinase inhibitor, is a promising candidate for imatinib-resistant CML and Src over activated cancer.

Using germline genotype in cancer pharmacogenetic studies

Pharmacogenetics provides great opportunity for improving both the chance of therapeutic benefit and the ability to avoid adverse drug events. To date, the majority of pharmacogenetic studies have been performed using germline DNA. DNA collection in most clinical trials provides a wealth of samples from which pharmacogenetic studies can be launched. However, there is concern that the data from germline DNA pharmacogenetics might be of limited value for diseases, such as cancer, where germline variants may not adequately represent the genetic data obtained from the somatic DNA. In this perspective, we evaluate the literature that compares pharmacogenetic variants between germline DNA and matched somatic DNA. The analysis of these studies indicates that there is almost complete concordance between germline and somatic DNA in variants of pharmacogenetic genes. Although somatic variants are clinically significant and independently provide genetic information that cannot be gained from the germline, the use of germline DNA for pharmacogenetic studies is achievable and valuable. This use of germline DNA offers great opportunities for the implementation of individualized therapy.

Gain-of-function PDGFRA mutations, earlier reported in gastrointestinal stromal tumors, are common in small intestinal inflammatory fibroid polyps. A study of 60 cases

The inflammatory fibroid polyp is a rare benign lesion occurring throughout the digestive tract. It usually forms a solitary mass, characterized by a proliferation of fibrovascular tissue infiltrated by a variable number of inflammatory cells. The etiology of this lesion is unknown and conflicting histogenetic theories have been proposed. Recently, mutations in platelet-derived growth factor receptor (PDGFRA) and PDGFRA expression were reported in gastric inflammatory fibroid polyps. In this study, PDGFRA exons 12, 14, and 18 were screened for activating mutations in 60 small intestinal inflammatory fibroid polyps. In addition, the PDGFRA expression was evaluated immunohistochemically. Mutations in PDGFRA were identified in 33 of 60 (55%) cases, whereas 95% expressed PDGFRA. There were 26 deletions, three deletion-insertions, duplication, and single nucleotide substitution in exon 12, and a single nucleotide substitution and deletion in exon 18. The majority (n=23) of exon 12 deletions were 1837_1851del leading to S566_E571delinsR. However, 1835_1852delinsCGC leading to the same S566_E571delinsR, were found in two tumors. Three inflammatory fibroid polyps had 1836_1850del leading to S566_E571delinsK. A complex deletion-insertion affecting a similar region (1837_1856delinsGATTGATGATC) and leading to S566_I573delinsRIDDL was identified once. In addition, duplication and single nucleotide substitution were found 5' to the common inflammatory fibroid polyp mutational 'hot spot'. These mutations consist of 1808_1828dup leading to I557_E563dup, and 1821T>A resulting in 561V>D substitution. A 2664A>T and 2663_2674del leading to 842D>V and D842_H845del, respectively, were identified in exon 18. Similar gain-of-function PDGFRA mutations reported in gastrointestinal stromal tumors have been considered to be a driving pathogenetic force. This study showed consistent expression and common mutational activation of PDGFRA in small intestinal inflammatory fibroid polyps as in their gastric counterparts, and these lesions should be considered PDGFRA-driven benign neoplasms. We also suggest that these polyps may develop from earlier described PDGFRA-positive mesenchymal cells distributed along the villus membrane after oncogenic PDGFRA activation.

Class effects of tyrosine kinase inhibitors in the treatment of chronic myeloid leukemia

Tyrosine kinase inhibitors have revolutionized the treatment of chronic myeloid leukemia (CML), offering patients several targeted therapeutic options that provide the possibility of sustained remissions and prolonged survival. With the availability of imatinib, nilotinib and dasatinib, physicians must weigh the efficacy and safety profile of each agent when choosing the best therapeutic option for individual patients. Each agent targets tyrosine kinases within the cell uniquely to cause the desired antiproliferative effect. In addition to inhibiting the BCR-ABL kinase, imatinib and nilotinib target the same array of other tyrosine kinases, including c-KIT and platelet-derived growth factor receptor (PDGFR), albeit with differing potencies. While targeting BCR-ABL with the highest potency among approved agents in CML, dasatinib also targets a broad array of off-target kinases, including SRC family members, PDGFR and EPHB4. The differences in kinase inhibition profiles among these agents in vitro probably account for the differing clinical safety profiles of these agents. This paper reviews the various kinases inhibited by imatinib, nilotinib and dasatinib, and describes the potential impact of kinase inhibition on the efficacy and safety of each agent.

Somatic pharmacogenomics in cancer

Many of the initial examples of the clinical utility of pharmacogenetics were elucidated in the field of oncology. Those examples were largely based on the existence of germline genetic variation that influences the metabolism of cytotoxic drugs. However, with the development of kinase inhibitors, drugs designed to preferentially target altered proteins driving oncogenesis, pharmacogenetics in cancer has shifted to understanding the somatic differences that determine response to these targeted agents. It is becoming increasingly clear that understanding the molecular genetics of cancer will lead to the further development of targeted therapeutics. Therefore, it is imperative that pharmacogenomics researchers understand the motivations and challenges of developing targeted therapies to treat cancer as a paradigm for personalized medicine. However, much of the discussion in the pharmacogenomics community in cancer is still largely focused on the germline variants as predictors of drug toxicity. In light of that fact, this review presents a detailed discussion of the development of commonly used targeted therapies for the treatment of hematological and solid tumors, the somatic mutations that determine response to those therapies, and the mechanisms of drug resistance.

Prognostic stratification of high-risk gastrointestinal stromal tumors in the era of targeted therapy

BACKGROUND

Recently, a trial of adjuvant imatinib for primary R0-resected intermediate and high-risk gastrointestinal stromal tumors (GISTs) significantly improved recurrence-free survival. But identifying patients having higher chances of recurrence will reduce economic losses and prevent adverse side effects caused by adjuvant treatment.

METHODS

Tissue samples from 93 patients with high-risk GISTs were studied for p16, CD34, and CD44 protein expression and mutations of KIT and PDGFRA gene. Clinicopathologic, immunohistochemical, and mutation results were compared with clinical outcome by univariate and multivariate analyses.

RESULTS

KIT mutations were observed in 75 cases (81%) including 46 exon 11 deletion mutations and 31 deletions affecting codons 557-558. A novel 12 bp deletion mutation (KHNG484-488) on KIT exon 9 was detected in a small intestinal GIST. For recurrence-free survival, R0 resection, organ-confined disease stage, and female sex are better prognostic factors in univariate analysis and disease stage was the only factor predicting recurrence (P = 0.02) in multivariate analysis. In overall survival, mutation types, presence of mutation, location of GISTs, and mitosis were significant by univariate analysis. After multivariate analysis, mitotic counts and presence of KIT mutation corresponded to independent prognostic factors. Moreover, mitosis, KIT exon 11 deletion mutation, and deletions affecting exon 557-558 predict recurrence in R0-resected high-risk GISTs (P < 0.05).

CONCLUSION

Prognostic stratification in high-risk GISTs will help identify patients with high-risk GIST who may benefit from adjuvant therapy.