Complementary activity of tyrosine kinase inhibitors against secondary kit mutations in imatinib-resistant gastrointestinal stromal tumours.

BACKGROUND: Most patients with KIT-mutant gastrointestinal stromal tumours (GISTs) benefit from imatinib, but treatment resistance results from outgrowth of heterogeneous subclones with KIT secondary mutations. Once resistance emerges, targeting KIT with tyrosine kinase inhibitors (TKIs) sunitinib and regorafenib provides clinical benefit, albeit of limited duration. METHODS: We systematically explored GIST resistance mechanisms to KIT-inhibitor TKIs that are either approved or under investigation in clinical trials: the studies draw upon GIST models and clinical trial correlative science. We subsequently modelled in vitro a rapid TKI alternation approach against subclonal heterogeneity. RESULTS: Each of the KIT-inhibitor TKIs targets effectively only a subset of KIT secondary mutations in GIST. Regorafenib and sunitinib have complementary activity in that regorafenib primarily inhibits imatinib-resistance mutations in the activation loop, whereas sunitinib inhibits imatinib-resistance mutations in the ATP-binding pocket. We find that rapid alternation of sunitinib and regorafenib suppresses growth of polyclonal imatinib-resistant GIST more effectively than either agent as monotherapy. CONCLUSIONS: Our data highlight that heterogeneity of KIT secondary mutations is the main mechanism of tumour progression to KIT inhibitors in imatinib-resistant GIST patients. Therapeutic combinations of TKIs with complementary activity against resistant mutations may be useful to suppress growth of polyclonal imatinib-resistance in GIST.

Regorafenib as a single-agent in the treatment of patients with gastrointestinal tumors: an overview for pharmacists.

Regorafenib (BAY 73-4506, Stivarga® Bayer HealthCare Pharmaceutical Inc) is an oral multikinase inhibitor with a distinct and wide-ranging profile of tyrosine kinase inhibition, resulting in antiangiogenic and antiproliferative properties in tumors. Single-agent regorafenib administered as a 160-mg daily dose for the first 21 days of a 28-day cycle is approved for use in patients with pretreated metastatic colorectal cancer (mCRC) and gastrointestinal stromal tumor (GIST) progressing on imatinib and sunitinib, following publication of data from the phase III CORRECT and GRID studies respectively. Regorafenib is currently under phase III investigation in patients with hepatocellular carcinoma and is in several phase II studies in patients with gastrointestinal (GI) tumors. This review describes the clinical development of regorafenib in patients with GI cancers, and highlights the key issues important for the modern day clinical pharmacist who forms part of the multidisciplinary team ensuring safe and effective delivery of the drug to the patient. This information is considered of particular importance to the clinical pharmacist for the future development of regorafenib in this treatment setting.

Effects of aqueous soybean, mistletoe and red clover extracts on activities of adenosine deaminase and xanthine oxidase enzyme.

Soybean (Glycine max), mistletoe (Viscum album) and red clover (Trifolium pratence) have been argued to have anti-cancer effects. In the present study it was aimed to investigate possible effects of these plant extracts on the activities of DNA turn-over enzymes, namely adenosine deaminase (ADA) and xanthine oxidase (XO) in cancerous and non-cancerous gastric and colon tissues. For this aim, 6 cancerous and 6 non-cancerous adjacent human gastric tissues, and 7 cancerous and 7 non-cancerous adjacent colon tissues were obtained by surgical operations. Our results suggest that aqueous soybean, mistletoe and red clover extracts may exhibit anti-tumoral activity by depleting hypoxanthine concentration in the cancer cells through XO activation, which may lead to lowered salvage pathway activity necessary for the cancer cells to proliferate in the cancerous colon tissue. Some foods like soybean, mistletoe and red clover may provide nutritional support to medical cancer therapy through inhibiting and/or activating key enzymes in cancer metabolism (Tab. 4, Ref. 33).

Thyroid hormone inactivation in gastrointestinal stromal tumors.

Gastrointestinal stromal tumors (GISTs) are resistant to traditional chemotherapy but are responsive to the tyrosine kinase inhibitors imatinib and sunitinib. The use of these agents has improved the outcome for patients but is associated with adverse effects, including hypothyroidism. Multiple mechanisms of this effect have been proposed, including decreased iodine organification and glandular capillary regression. Here we report the finding of consumptive hypothyroidism caused by marked overexpression of the thyroid hormone-inactivating enzyme type 3 iodothyronine deiodinase (D3) within the tumor. Affected patients warrant increased monitoring and may require supernormal thyroid hormone supplementation.

Optimizing tyrosine kinase inhibitor therapy in gastrointestinal stromal tumors: exploring the benefits of continuous kinase suppression.

The oral tyrosine kinase inhibitor (TKI) imatinib has revolutionized the treatment of gastrointestinal stromal tumors (GISTs), most of which harbor oncogenic mutation in genes that encode the receptor tyrosine kinases KIT or PDGFA. Imatinib is the standard of care for patients with advanced GIST and for patients with primary GIST at significant risk of recurrence after surgery. Design. This review discusses data supporting continuous kinase suppression with imatinib and key issues, including response to imatinib reintroduction, effect of treatment interruption on secondary resistance to imatinib, and prognostic factors associated with sustained response to imatinib. Results. Long-term follow-up results of the B2222 study and updated results of the BFR14 trial demonstrate that continuous imatinib treatment in patients with advanced GIST is associated with reduced risk of progression. For patients progressing on or intolerant of imatinib, continuing therapy with TKIs sunitinib followed by regorafenib is recommended. In the adjuvant setting, final results of the trial by the Scandinavian Sarcoma Group and the Sarcoma Group of the Arbeitsgemeinschaft Internistische Onkologie demonstrate that 3 years of adjuvant imatinib, compared with 1 year, significantly reduces the risk of recurrence and improves overall survival of patients with KIT-positive GIST at high risk of recurrence. Conclusions. Maintenance of therapy with TKIs is the key to successful treatment of GIST. Results from recent studies provide a strong rationale for continuous imatinib treatment for 3 years following surgical resection and long-term continuous administration in advanced or metastatic GIST.

Methionine aminopeptidases as potential targets for treatment of gastrointestinal cancers and other tumours.

Methionine aminopeptidases (MetAP) are intracellular metalloproteins responsible for the removal of the initiator NH(2)-terminal methionine from newly synthesized proteins, thereby facilitating their intracellular translocation from the ribosome. Two types of MetAP enzymes, MetAP-1 (type-I) and MetAP-2 (type-II), which have a similar three-dimensional structure despite a low homology in their sequences, have been described. Since the discovery that fumagillin, an irreversible MetAP-2 inhibitor, prevents angiogenesis, different studies have been carried out to analyze the role of MetAP proteins as potential targets in cancer treatment. Data obtained indicate that anticancer effect of MetAP-2 inhibitors may be a result of the combined effect of MetAP-2 inhibition in endothelial cells (anti-angiogenesis) and in tumour cells directly. Moreover, it has been recently described that MetAP-1 has a potential role on cell division, and MetAP-1-specific inhibition is able to induce apoptosis in both HeLa and HT-1080 cell lines. A new subtype of MetAP-1, called MetAP-1D, has been found overexpressed in samples from colon cancer patients, its inhibition resulting in a decreased cell growth. Although molecular mechanisms of action of these proteins are largely unknown, a significant progress has been made to understand their structure-function relationships and their physiological roles. Their potential as promising targets in cancer treatment and in the development of new antitumour agents is analyzed focusing on MetAP irreversible inhibitors. The present review summarizes recent research data on different molecules able to induce MetAP inhibition in gastrointestinal cancers and other tumours.

Tumor M2 pyruvate kinase: a tumor marker and its clinical application in gastrointestinal malignancy.

Proliferating cells, in particular tumor cells, express a dimeric isoenzyme of pyruvate kinase, termed Tumor M2 pyruvate kinase. In the last few years, much attention has been paid to this novel tumor marker that can be determined in EDTA-plasma and in the feces. It has been used in diagnosis and surveillance of a variety of malignant diseases. As compared with the established tumor markers, Tumor M2-PK in EDTA-plasma proves to have at least equal sensitivity in pancreatic, gastric, esophageal, colorectal and cholangiocellular cancer. In combination with established tumor markers, EDTA-plasma M2-PK is a useful tool in diagnosis and surveillance of gastrointestinal tumors. In colorectal cancer, M2-PK in EDTA-plasma even proves superiority as compared with CEA. Fecal Tumor M2-PK testing resembles a good noninvasive screening parameter for colorectal cancer with a reported sensitivity of 68.8-91.0% and a specificity of 71.9-100%. It is superior to fecal occult blood testing in colorectal cancer screening. Since it is effective, easy to handle and bears rather low costs, fecal Tumor M2-PK testing is recommended for large-scale CRC screening.

[The effect of pre-operative chemotherapy on calpain in cells of gastrointestinal malignant tumors].

OBJECTIVE: Primary to search the rule of pre-operative chemotherapy and suitable duration for it by investigating the changes of calpain content and activity after 5'-deoxy-5-fluorouridine (5'-DFUR) per oral administered pre-operatively in different time. Further to investigate the mechanism of chemotherapy. METHODS: Seventy-three patients with gastrointestinal malignant tumors were divided into 4 groups by the time of 5'-DFUR (600 approximately 1200 mg/d) by oral administration before operation, group A, 3 days, 27 cases; group B, 1 week, 22 cases; group C, 2 weeks, 15 cases; group D, 2 months, 9 cases. And group E, control group, had 24 patients with gastrointestinal malignant tumors at the same term. The patients above all had not received the other chemotherapy and radiotherapy. Western blot and immunoelectron microscopy were employed to detect the expressing levels and activities of calpain in tumor tissues of different groups. RESULTS: Electronic microscopic examination showed gold granula mainly on the membranes of mitochondria of tumor cells to groups after chemotherapy. And the tumor cells of group A were mildly damaged. Besides that, serious injury for tumor cells of group B could be seen, and the phenomena were common in group C. But the damages to tumor cells of group D were mainly about mildness. The results of immunoelectron microscopy revealed that the contents of calpain increased following the time of chemotherapy prolonging, and peaked in group C. Still more, there was no significant difference for the results between group C and group D. The changes of calpain activities observed by western blot had the same tendency as the results from immunoelectron microscopy (r = 0.86, P < 0.0001). CONCLUSIONS: 5'-DFUR via oral administered pre-operation could have anti-cancer effect through calpain. And the effect might be strongest in 2 weeks also after chemotherapy.

Thymidylate synthase expression and prognosis of patients with gastrointestinal cancers receiving adjuvant chemotherapy: a review.

BACKGROUND AND AIMS: Many studies have been published that report an association between thymidylate synthase (TS) and response to fluoropyrimidine-based chemotherapy and the overall outcome of patients with gastrointestinal cancer. The results have given rise to the possibility that, by determination of TS levels, the physician may decide if the patient has a potential benefit from fluoropyrimidine-based treatment, similar to measurements of oestrogen receptors in breast cancer. The purpose of this review is to summarize critically the reports on TS measurement in gastrointestinal cancer, focusing on the adjuvant fluoropyrimidine treatment situation. METHODS: We reviewed more than 20 studies that reported the association of TS with the clinical outcome in patients with gastrointestinal cancer who had undergone complete resection of the primary tumour only or were receiving additional adjuvant chemotherapy. RESULTS: Patients with metastasized disease who expressed high TS levels display a low probability of responding to fluoropyrimidine-based treatment and have a poorer survival rate. Patients with high TS levels who undergo complete surgical resection of the primary tumour also have a poorer prognosis than those with tumours with low TS expression. In contrast to advanced disease and to surgery alone, patients with high TS levels appear to benefit, especially, from adjuvant fluoropyrimidine-based chemotherapy after complete primary tumour resection, while patients with low TS levels do not. CONCLUSION: Patients with gastrointestinal cancers that express high TS levels have a poor prognosis with regard to fluoropyrimidine-based palliative chemotherapy or complete primary tumour resection. In contrast, patients with high TS levels might benefit from adjuvant fluoropyrimidine-based treatment after primary tumour resection. However, additional prospective studies are mandatory to define the precise role of TS in adjuvant therapy.

Methylenetetrahydrofolate reductase polymorphism is associated with folate pool in gastrointestinal cancer tissue.

The folate pool in cancer tissue is a critical factor for the effect of 5-FU-based chemotherapy. Methylenetetrahydrofolate reductase (MTHFR) plays a role in the metabolism of folate. The gene of MTHFR is polymorphic (C667T, alanine-to-valine), and this is related to the activity of the enzyme. We analyzed the association between MTHFR genotype and the folate pool in gastrointestinal cancer tissues. MTHFR genotypes were determined in 67 surgically-resected gastrointestinal cancer tissues by PCR-RFLP analysis. Forty-five patients received no treatment and 22 patients received oral administration of UFT, a combination of Uridine and Tegafur, before surgery. 5,10-Methylenetetrahydrofolate (CH2FH4) and tetrahydrofolate (FH4) were measured by fluoro-dUMP (FdUMP) binding assay as representative values of the folate pool. The number of FdUMP binding sites on Thymidylate synthase (TS) was quantified in the samples from UFT-administered patients. The incidences of MTHFR genotype were as follows: Ala/Ala, 27; Ala/Val, 30; Val/Val, 10. In the UFT(-) group, the amount of FH4 in Ala/Val-type cancer tissue was higher than that in Ala/Ala-type (1.50 +/- 1.13 versus 0.72 +/- 0.64, p < 0.05). This relationship was also observed on the sum of CH2FH4 and FH4 (2.88 +/- 1.85 versus 1.75 +/- 1.06, p < 0.05). Val/Val-type cancer tissue had higher amount of either CH2FH4 and FH4 than Ala/Ala-type, although this finding did not reach statistical significance. In the UFT(+) group, no relationship between MTHFR genotype and the free folate pool was observed, presumably due to the influence of the amounts of FdUMP and TS in the tissue. The calculation of total CH2FH4 from the value of free CH2FH4, free TS and total TS showed a weak genotype-dependent difference in total CH2FH4. The TS inhibition rate also showed a weak genotype-dependent difference. These results suggest a link between MTHFR genotype and the folate pool in gastrointestinal cancer, leading to the association of MTHFR genotype with TS inhibition rate upon 5-FU exposure. The MTHFR genotype might be considered in the design of 5-FU-based chemotherapy, especially in patient-specific strategies with leucovorin supplementation.

[Theoretical construction of chemotherapeutic tactics for advanced or recurrent gastrointestinal carcinoma].

The anti-cancer effect of 5-fluorouracil (5-FU) is significantly affected by the intratumoral environment. Elevated expression of thymidylate synthase (TS), the target enzyme of 5-FU, and a lack of reduced folate or FdUMP results in insufficient inhibition of TS. Further, elevated expression of DPD in the tumor tissue results in a lack of FdUMP. TS-1, which contains tegafur and dihydroxypyridine (CDHP), a potent DPD inhibitor, is a promising anticancer drug. Isovorin has been available in Japan since autumn 1999. In cancer patients, folate deficiency may be derived from increased consumption and/or absorption disturbance of folate. In such situations, sufficient TS inhibition cannot be obtained if 5-FU is administered without supplementation of reduced folate. We describe in detail the metabolism of those substances in relation to the anticancer effect of 5-FU. Further, we show the theoretical construction of first-line and second-line chemotherapy with consideration of TS and DPD expression.

Molecular cloning of a human transmembrane-type protein tyrosine phosphatase and its expression in gastrointestinal cancers.

To determine the expression of various protein-tyrosine phosphatases (PTPs) in human gastric cancers, cDNAs encoding conserved PTP domains were amplified by reverse transcriptase polymerase chain reaction from KATO-III cell mRNA and sequenced. Among 72 polymerase chain reaction clones, one of the cDNA sequences encoded a novel potential PTP (stomach cancer-associated PTP, SAP-1). The full length (3.9 kilobases) of the SAP-1 cDNA was further isolated from the KATO-III cell cDNA library and the WiDr cell cDNA library. The predicted amino acid sequence of the SAP-1 cDNA showed that mature SAP-1 consisted of 1093 amino acids and a transmembrane-type PTP, which possessed a single PTP-conserved domain in the cytoplasmic region. The extracellular region of SAP-1 consisted of eight fibronectin type III-like structure repeats and contained multiple N-glycosylation sites. These data suggest that SAP-1 is structurally similar to HPTP beta and that SAP-1 and HPTP beta represent a subfamily of transmembrane-type PTPs. SAP-1 was mainly expressed in brain and liver and at a lower level in heart and stomach as a 4.2-kilobase mRNA, but it was not detected in pancreas or colon. In contrast, among cancer cell lines tested, SAP-1 was highly expressed in pancreatic and colorectal cancer cells. The bacterially expressed SAP-1 fusion protein had tyrosine-specific phosphatase activity. Immunoblotting with anti-SAP-1 antibody showed that SAP-1 is a 200-kDa protein. In addition, transient transfection of SAP-1 cDNA to COS cells resulted in the predominant expression of a 200-kDa protein recognized by anti-SAP-1 antibody. SAP-1 is mapped to chromosome 19 region q13.4 and might be related to carcinoembryonic antigen mapped to 19q13.2.

Clinical effects of total-body hyperthermia combined with anticancer chemotherapy for far-advanced gastrointestinal cancer.

The authors treated 17 patients with far-advanced gastrointestinal cancer with extracorporeally induced total-body hyperthermia (TBHT) combined with anticancer chemotherapy. Although all patients' tumors were clinically resistant to prior chemotherapy with 1-(2-tetrahydrofurlyl)-5-fluorouracil or 5-fluorouracil and mitomycin C, three patients had an objective response to TBHT plus the same anticancer agents with or without cyclophosphamide. That is, a partial response was obtained in 2 of 12 patients with recurrent gastric cancer and in 1 of 5 patients with recurrent large bowel cancer. However, their survival time was not markedly prolonged. As a characteristic complication of TBHT, the authors noted reversible weakness of the muscles of the lower extremities. Two patients died due to hepatorenal syndrome; preoperatively these patients had manifested hepatic or renal dysfunction. Therefore, in patients with hepatic or renal dysfunction, the application of TBHT must be considered carefully.