Role of c-kit/SCF in cause and treatment of gastrointestinal stromal tumors (GIST)

An integrative proteomics approach identifies tyrosine kinase KIT as a therapeutic target for SPINK1-positive prostate cancer

Elevated serine peptidase inhibitor, Kazal type 1 (SPINK1) levels in ∼10%-25% of prostate cancer (PCa) patients associate with aggressive phenotype, for which there are limited treatment choices and dismal clinical outcomes. Using an integrative proteomics approach involving label-free phosphoproteome and proteome profiling, we delineated the downstream signaling pathways involved in SPINK1-mediated tumorigenesis and identified tyrosine kinase KIT as highly enriched. Furthermore, high to moderate levels of KIT expression were detected in ∼85% of SPINK1-positive PCa specimens. We show KIT signaling orchestrates SPINK1-mediated oncogenesis, and treatment with KIT inhibitor reduces tumor growth and metastases in preclinical mice models. Mechanistically, KIT signaling modulates WNT/β-catenin pathway and confers stemness-related features in PCa. Notably, inhibiting KIT signaling led to restoration of AR/REST levels, forming a feedback loop enabling SPINK1 repression. Overall, we uncover the role of KIT signaling downstream of SPINK1 in maintaining lineage plasticity and provide distinct treatment modalities for advanced-stage SPINK1-positive patients.

c-Kit signaling potentiates CAR T cell efficacy in solid tumors by CD28- and IL-2-independent co-stimulation

The limited efficacy of chimeric antigen receptor (CAR) T cell therapy for solid tumors necessitates engineering strategies that promote functional persistence in an immunosuppressive environment. Herein, we use c-Kit signaling, a physiological pathway associated with stemness in hematopoietic progenitor cells (T cells lose expression of c-Kit during differentiation). CAR T cells with intracellular expression, but no cell-surface receptor expression, of the c-Kit D816V mutation (KITv) have upregulated STAT phosphorylation, antigen activation-dependent proliferation and CD28- and interleukin-2-independent and interferon-γ-mediated co-stimulation, augmenting the cytotoxicity of first-generation CAR T cells. This translates to enhanced survival, including in transforming growth factor-β-rich and low-antigen-expressing solid tumor models. KITv CAR T cells have equivalent or better in vivo efficacy than second-generation CAR T cells and are susceptible to tyrosine kinase inhibitors (safety switch). When combined with CD28 co-stimulation, KITv co-stimulation functions as a third signal, enhancing efficacy and providing a potent approach to treat solid tumors.

Identification of Thiazolo[5,4-b]pyridine Derivatives as c-KIT Inhibitors for Overcoming Imatinib Resistance

c-KIT is a promising therapeutic target against gastrointestinal stromal tumor (GIST). In order to identify novel c-KIT inhibitors capable of overcoming imatinib resistance, we synthesized 31 novel thiazolo[5,4-b]pyridine derivatives and performed SAR studies. We observed that, among these substances, 6r is capable of inhibiting significantly c-KIT and suppressing substantially proliferation of GIST-T1 cancer cells. It is of note that 6r is potent against a c-KIT V560G/D816V double mutant resistant to imatinib. Compared with sunitinib, 6r possesses higher differential cytotoxicity on c-KIT D816V Ba/F3 cells relative to parental Ba/F3 cells. In addition, kinase panel profiling reveals that 6r has reasonable kinase selectivity. It was found that 6r remarkably attenuates proliferation of cancer cells via blockade of c-KIT downstream signaling, and induction of apoptosis and cell cycle arrest. Furthermore, 6r notably suppresses migration and invasion, as well as anchorage-independent growth of GIST-T1 cells. This study provides useful SAR information for the design of novel c-KIT inhibitors overcoming imatinib-resistance.

Pathological analysis of hesperetin-derived small cell lung cancer by artificial intelligence technology under fiberoptic bronchoscopy

Lung cancer is one of the most common tumors. There are 1.8 million new cases worldwide each year, accounting for about 13% of all new tumors. Lung cancer is the most important cause of cancer-related deaths. 1.4 million people die of lung cancer each year. This article uses artificial intelligence technology to analyze the pathology of hesperetin-derived small cell lung cancer under fiberoptic bronchoscopy. This article takes 48 lung slice samples as the research object. Among them, 36 cases of lung small cell carcinoma have history slices from Lhasa City Institute of Biology, the patient has complete cases, and the other 12 normal lung slices come from Xinjiang Biotechnology Laboratory. In this paper, the above-mentioned 36 lung cancer slices became the study group, and 12 normal slices became the reference group. This article presents a method for hesperetin-fiber bronchoscope to study the pathological mechanism of lung small cell carcinoma (H-FBS), which is used to study slices. The above-mentioned 48 samples were taken for slice observation. First, the 48 slices were technically tested by artificial intelligence fiber bronchoscope combined with hesperetin derivatives, and then the slice observation results were verified by CTC technology. In addition, in each step, the C5orf34 in the tissue is detected separately, which is beneficial to adjust the content of C5orf34 so that the treatment of lung cancer can control the development of lung cancer under fiberoptic bronchoscopy. Experimental results show that the diagnostic accuracy rate of this method is 97.9%, which is higher than that of lung biopsy (89%); compared with multiple CTC detection, the cost is low and the time is shor.

Tivozanib mediated inhibition of c-Kit/SCF signaling on Tregs and MDSCs and reversal of tumor induced immune suppression correlates with survival of HCC patients

The immune modulatory effect of tivozanib, a tyrosine kinase inhibitor, and the underlying immune mechanisms impacting survival of HCC patients have not been investigated. Pre-clinical studies have shown that tivozanib reduces Tregs and MDSCs accumulation through inhibition of c-Kit/SCF axis. We rationalized that c-Kit/SCF axis antagonism by tivozanib may reverse tumor-induced immune suppression in HCC patients. The frequency of circulating Tregs, MDSCs, CTLA-4⁺Tregs, PD-1⁺T cells, c-Kit⁺pERK-2⁺Tregs, and c-Kit⁺pERK-2⁺MDSCs were quantified in HCC patients at baseline and two time points during tivozanib treatment. We report for the first time that reduction in Tregs after tivozanib treatment and increased levels of baseline CD4⁺PD-1⁺T cells correlated with significant improvement in overall survival (OS) of the patients and these signatures may be potential biomarkers of prognostic significance. This immune modulation resulted from tivozanib-mediated blockade of c-Kit/SCF signaling, impacting ERK2 phosphorylation on Tregs and MDSCs. Low pre-treatment CD4⁺T cells: Treg ratio and reduction in the frequencies of Foxp3⁺c-Kit⁺pERK⁺Tregs after tivozanib treatment correlated significantly with progression free survival. In a comparative analysis of tivozanib vs sorafenib treatment in HCC patients, we demonstrate that decrease in the baseline numbers or frequencies of Foxp3⁺Tregs, MDSCs and exhausted T cells was significantly greater following tivozanib treatment. Additionally, greater increase in CD4⁺T cell: Treg ratio after tivozanib treatment was associated with significant improvement in OS compared to sorafenib treatment, highlighting the greater efficacy of tivozanib. These insights may help identify patients who likely would benefit from c-Kit/SCF antagonism and inform efforts to improve the efficacy of tivozanib in combination with immunotherapy.

Patient-derived scaffolds uncover breast cancer promoting properties of the microenvironment

Tumor cells interact with the microenvironment that specifically supports and promotes tumor development. Key components in the tumor environment have been linked to various aggressive cancer features and can further influence the presence of subpopulations of cancer cells with specific functions, including cancer stem cells and migratory cells. To model and further understand the influence of specific microenvironments we have developed an experimental platform using cell-free patient-derived scaffolds (PDSs) from primary breast cancers infiltrated with standardized breast cancer cell lines. This PDS culture system induced a series of orchestrated changes in differentiation, epithelial-mesenchymal transition, stemness and proliferation of the cancer cell population, where an increased cancer stem cell pool was confirmed using functional assays. Furthermore, global gene expression profiling showed that PDS cultures were similar to xenograft cultures. Mass spectrometry analyses of cell-free PDSs identified subgroups based on their protein composition that were linked to clinical properties, including tumor grade. Finally, we observed that an induction of epithelial-mesenchymal transition-related genes in cancer cells growing on the PDSs were significantly associated with clinical disease recurrences in breast cancer patients. Patient-derived scaffolds thus mimics in vivo-like growth conditions and uncovers unique information about the malignancy-inducing properties of tumor microenvironment.

Silencing of COPB2 inhibits the proliferation of gastric cancer cells and induces apoptosis via suppression of the RTK signaling pathway

Emerging studies have reported that coatomer protein complex subunit β2 (COPB2) is overexpressed in several types of malignant tumor; however, to the best of our knowledge, no studies regarding COPB2 in gastric cancer have been published thus far. Therefore, the present study aimed to determine the significance and function of COPB2 in gastric cancer. COPB2 expression in gastric cancer cell lines was measured using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis. In addition, lentivirus-short hairpin RNA (shRNA) COPB2 (Lv-shCOPB2) was generated and used to infect BGC-823 cells to analyze the effects of COPB2 on the cancerous phenotype. The effects of shRNA-mediated COPB2 knockdown on cell proliferation were detected using MTT, 5-bromo-2-deoxyuridine and colony formation assays. In addition, the effects of COPB2 knockdown on apoptosis were analyzed by flow cytometry. Nude mice and fluorescence imaging were used to characterize the regulation of tumor growth in vivo, and qPCR and immunohistochemistry were subsequently conducted to analyze COPB2 expression in xenograft tumor tissues. Furthermore, a receptor tyrosine kinase (RTK) signaling pathway antibody array was used to explore the relevant molecular mechanisms underlying the effects of COPB2 knockdown. The results revealed that COPB2 mRNA was abundantly overexpressed in gastric cancer cell lines, whereas knockdown of COPB2 significantly inhibited cell growth and colony formation ability, and led to increased cell apoptosis in vitro. The tumorigenicity assay revealed that knockdown of COPB2 reduced tumor growth in nude mice, and fluorescence imaging indicated that the total radiant efficiency of mice in the Lv-shCOPB2-infected group was markedly reduced compared with the mice in the Lv-shRNA control-infected group in vivo. The antibody array assay revealed that the levels of phosphorylation in 23 target RTKs were significantly reduced: In conclusion, COPB2 was highly expressed in gastric cancer cell lines, and knockdown suppressed colony formation and promoted cell apoptosis via inhibiting the RTK signaling and its downstream signaling cascade molecules. Therefore, COPB2 may present a valuable target for gene silencing strategy in gastric cancer.

Inhibition of N822K T>A mutation-induced constitutive c-KIT activation in AML cells triggers apoptotic and autophagic pathways leading to death

Background: The D816V mutation of c-KIT can constitutively activate tyrosine kinase, thereby promote core binding factor acute myeloid leukemia (CBF-AML) cell proliferation and inhibit apoptosis. Previous studies have indicated similar proliferation and apoptosis between N822K and D816V mutations.The current study aims to determine the occurrence and potential functions of N822K mutation-induced c-KIT activation in AML cells, and explore possible mechanisms of poor prognosis of CBF-AML. Methods: c-KIT N822K mutation status in AML cells was determined by exon 17 sequencing. The level of c-KIT expression was detected by flow cytometry (FCM) and colony formation was assessed after hu-SCF stimulation. After exposure to sunitinib (a kind of tyrosine kinase inhibitor, TKI), cell proliferation inhibition was tested by MTT, cell cycle and apoptosis were measured by FCM, autophagy was assessed by fluorescence microscopy and immunoblotting. Results: Kasumi-1 cell line was detected to bear c-KIT N822K (T>A) mutation. After hu-SCF stimulation, CD117 expression was decreased and the colony formation efficiency was not altered in Kasumi-1 cells. After sunitinib inhibited the c-KIT activity, the colony formation efficiency was reduced, and the half-maximal inhibitory concentration (IC₅₀) of sunitinib was low (0.44±0.17μM) at 48 hours. Moreover, cells were arrested in G0/G1 phase, corresponding to an increase of apoptosis ratio. Acidic vesicular organelles (AVO) were observed along with an altered expression of autophagy-related proteins in Kasumi-1 cells. Conclusions: Our data indicated that inhibition of N822K T>A mutation-induced constitutive c-KIT activation in AML cells triggered apoptotic and autophagic pathways leading to death, and c-KIT N822K mutation may have clinical application as a CBF-AML treatment target.

Stem cell factor and NSC87877 combine to enhance c-Kit mediated proliferation of human megakaryoblastic cells

Enhancement of hematopoietic stem cells (HSCs) proliferation is a central aim in bone marrow transplantation (BMT). A stem cell factor (SCF) and c-Kit mediated extracellular signaling trigger proliferation of HSCs. This signaling is negatively regulated by protein tyrosine phosphatases (PTPs), SHP-1 and SHP-2. Although NSC87877 (N) is known to inhibit SHP-1/SHP-2, c-Kit-mediated HSCs proliferation by inhibiting SHP-1/SHP-2 has not been reported. This study investigated the combined effect of SCF (S) and N in c-Kit mediated proliferation and underlying mechanisms. The growth of human megakaryoblastic cell line, MO7e and HSCs, upon treatment with S and N alone, and in combination was assessed by PrestoBlue staining. The expression of c-Kit, phosphorylated c-Kit, SHP-1/SHP-2 and HePTP inhibition using S and N treatment were evaluated in the MO7e cells. Megakaryoblast cell proliferation was determined by quantification of Ki-67+, S-phase, BrdU+ and CFDA-SE+ cells using flow cytometry. The combination of S and N leads to enhanced cell growth compared with either S or N alone. Collectively, the results reveal a novel mechanism by which S in combination with N significantly enhances proliferation of human megakaryoblast cells. The pretreatment of N before S enhances proliferation of cells than S alone. This promising combination would likely play an essential role in enhancing the proliferation of cells.

Expression of AMHR2 and C-KIT in cervical lesions in Uyghur Women of Xinjiang, China

BACKGROUND

Cervical cancer is one of the most common malignant tumors in women. Anti-Müllerian hormone receptor 2 (AMHR2) and C-Kit were two members of protein kinase which were reported increased in some cancers like ovarian carcinoma and breast cancer. The present study aimed to assess the expression of AMHR2 and c-Kit in cervical cancer of different differentiated degrees as well as in cervicitis sections.

METHODS

All the lesions were collected randomly during clinical observations in hospitals located in Xinjiang, China. Polymerase chain reaction (PCR) and immunohistochemical staining were used to detect AMHR2 and c-Kit expression in cervical samples from women who had been infected with human papilloma virus (HPV)16. The expression rate was compared between cervical cancer of well, moderately and poorly differentiated and cervicitis.

RESULTS

The average age of the patients was 45 years; ranged from 23 to 80. For AMHR2, all 17 cervicitis samples ranged from (++) to (++++), while cervical cancer showed 11 (+), 9 (++), 15 (+++),9 (++++), and 8 (-), which showed AMHR2 expression was lessen with the poorer of differentiation degree of cervical cancer (P < .05). For c-Kit, 18 cervicitis samples mainly expressed as (-) with none showed (+++) or (++++), while cervical cancer samples showed 7 (-), 6 (+), 1 (++), 2 (+++), and 8 (++++), which indicated c-Kit's expression increased with the reduction of cervical cancer's differentiation degree (P < .05).

CONCLUSION

AMHR2 might have some correlation with self defense of our body, while c-Kit might link with the potential invasive capacity of cervical cancer.

Association of Gastrointestinal Stromal Tumor and Acute Myeloid Leukemia Preceded by Myelodysplastic Syndrome with Refractory Anemia

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. GISTs are believed to be related to mutational activation of receptor tyrosine kinases, KIT, or platelet-derived growth factor receptor-alpha. The coexistence of GISTs with other neoplams has been extensively addressed in the literature. The most common second neoplasms are colorectal cancer, prostate cancer, and neoplasms derived from lymphoid tissue. In this case report, we describe a patient affected by GIST and acute myeloid leukemia preceded by myelodysplastic syndrome with refractory anemia. The clinicopathological characteristics of the patient are discussed and the literature is reviewed.

The clinical significance of c-Kit mutations in metastatic oral mucosal melanoma in China

c-Kit mutations are frequently detected in mucosal melanomas, but their clinical significance in metastatic oral mucosal melanomas (OMM) remains unclear. The main purpose of this study was to investigate the clinical and pathological features of metastatic OMMs with c-Kit mutations and the efficiency of the tyrosine kinase inhibitor imatinib in treating metastatic OMMs. We found thatresidual primary lesion and neck lymph nodes could act as independent prognostic factors in metastatic OMM patients. c-Kit mutations were detected in 22 out of 139 (15.8%) metastatic OMM patients. Under chemotherapy, the overall survival (OS) of c-Kit mutant patients was significantly shorter than that of wild-type patients. The Ki67 expression was significantly higher in c-Kit mutant patients than in wild-type patients. In distant metastatic OMM patients with c-Kit mutations, the treatment with c-Kit inhibitor resulted in a better OS. In conclusion, residual primary lesion, cervical lymph nodes and c-Kit mutations act as adverse prognostic factors of metastatic OMMs. The Kit inhibitor imatinib could benefit metastatic OMM patients with c-Kit mutations.

The stem cell factor (SCF)/c-KIT signalling in testis and prostate cancer

The stem cell factor (SCF) is a cytokine that specifically binds the tyrosine kinase receptor c-KIT. The SCF/c-KIT interaction leads to receptor dimerization, activation of kinase activity and initiation of several signal transduction pathways that control cell proliferation, apoptosis, differentiation and migration in several tissues. The activity of SCF/c-KIT system is linked with the phosphatidylinositol 3-kinase (PI3-K), the Src, the Janus kinase/signal transducers and activators of transcription (JAK/STAT), the phospholipase-C (PLC-γ) and the mitogen-activated protein kinase (MAPK) pathways. Moreover, it has been reported that cancer cases display an overactivation of c-KIT due to the presence of gain-of-function mutations or receptor overexpression, which renders c-KIT a tempting target for cancer treatment. In the case of male cancers the most documented activated pathways are the PI3-K and Src, both enhancing abnormal cell proliferation. It is also known that the Src activity in prostate cancer cases depends on the presence of tr-KIT, the cytoplasmic truncated variant of c-KIT that is specifically expressed in tumour tissues and, thus, a very interesting target for drug development. The present review provides an overview of the signalling pathways activated by SCF/c-KIT and discusses the potential application of c-KIT inhibitors for treatment of testicular and prostatic cancers.

Radotinib induces high cytotoxicity in c-KIT positive acute myeloid leukemia cells

Previously, we reported that radotinib, a BCR-ABL1 tyrosine kinase inhibitor, induced cytotoxicity in acute myeloid leukemia (AML) cells. However, the effects of radotinib in the subpopulation of c-KIT-positive AML cells were unclear. We observed that low-concentration radotinib had more potent cytotoxicity in c-KIT-positive cells than c-KIT-negative cells from AML patients. To address this issue, cell lines with high c-KIT expression, HEL92.1.7, and moderate c-KIT expression, H209, were selected. HEL92.1.7 cells were grouped into intermediate and high c-KIT expression populations. The cytotoxicity of radotinib against the HEL92.1.7 cell population with intermediate c-KIT expression was not different from that of the population with high c-KIT expression. When H209 cells were grouped into c-KIT expression-negative and c-KIT expression-positive populations, radotinib induced cytotoxicity in the c-KIT-positive population, but not the c-KIT-negative population. Thus, radotinib induces cytotoxicity in c-KIT-positive cells, regardless of the c-KIT expression intensity. Therefore, radotinib induces significant cytotoxicity in c-KIT-positive AML cells, suggesting that radotinib is a potential target agent for the treatment of c-KIT-positive malignancies including AML.

Role of stem cell growth factor/c-Kit in the pathogenesis of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a functional bowel disease with a complicated etiopathogenesis, often characterized by gastrointestinal motility disorder and high visceral sensitivity. IBS is a comprehensive multi-systemic disorder, with the interaction of multiple factors, such as mental stress, intestinal function and flora, heredity, resulting in the disease. The existence of a common mechanism underlying the aforementioned factors is currently unknown. The lack of therapies that comprehensively address the disease symptoms, including abdominal pain and diarrhea, is a limitation of current IBS management. The current review has explored the role of the SCF/c-Kit receptor/ligand system in IBS. The SCF/c-Kit system constitutes a classical ligand/receptor tyrosine kinase signaling system that mediates inflammation and smooth muscle contraction. Additionally, it provides trophic support to neural crest-derived cell types, including the enteric nervous system and mast cells. The regulation of SCF/c-Kit on the interstitial cells of Cajal (ICC) suggest that it may play a key role in the aberrant intestinal dynamics and high visceral sensitivity observed in IBS. The role of the SCF/c-Kit system in intestinal motility, inflammation and nerve growth has been reported. From the available biomedical evidence on the pathogenesis of IBS, it has been concluded that the SCF-c-Kit system is a potential therapeutic target for rational drug design in the treatment of IBS.

Repigmentation patterns induced by NB-UVB and their relationship with melanocytic migration and proliferation in vitiligo

BACKGROUND/PURPOSE

Vitiligo is the most commonly acquired depigmentation disorder of the skin and is characterized by the destruction of melanocytes. Ultraviolet phototherapy with narrow band (UVB-NB) induces proliferation, differentiation, maturation, and migration of melanocytes. The clinical repigmentation is featured by follicular, marginal, and diffuse patterns. The aim of this study was to observe the process involved in the melanocyte migration and proliferation among these patterns and the unresponsive lesions following UVB-NB phototherapy. The focal adhesion kinase (FAK) and c-KIT were used as markers of melanocyte migration and differentiation, respectively.

METHODS

A total of 17 vitiligo patients under UVB-NB therapy were selected. The patients expressed the three repigmentation patterns as well as unresponsive lesions at the conclusion of a 30-session cycle. Skin biopsies were evaluated by immunohistochemistry and qRT-PCR.

RESULTS

We found an increased expression of c-KIT in the follicular pattern compared to the diffuse pattern that was expressed predominantly of FAK. Marginal pattern expressed both proteins. The unresponsive achromic lesions showed poor expressions of both markers.

CONCLUSION

Proliferation was prominent in the follicular pattern, but migration was prominent in the diffuse pattern. For the marginal pattern, both dynamics were present. The absence of these markers in vitiligo lesions suggests a lack of response to UVB-NB.

Primary malignant mucosal melanoma of the upper lip: a case report and review of the literature

Background

Malignant melanoma of oral cavity is a rare condition, accounting for 0.5 % of all oral malignancies and about 1–2 % of all melanomas. Oral melanomas have extremely poor prognosis with 5 years survival rate of 12.3 %. The poor prognosis compared to cutaneous melanoma may be attributed to delay in reporting by patient and diagnosis, and apt to become ulcerated due to repeated trauma. The ‘chameleonic’ presentation of a mainly asymptomatic condition, the rarity of these lesions, the poor prognosis and the necessity of a highly specialized treatment are factors that should be seriously considered by the involved health provider.

Case presentation

We present a case of 32 years old male of Han ethnicity with mucosal melanoma of upper lip, comparing his clinical presentation and histological findings at his first visit and following the recurrence. The patient complained of black discoloration on the left side of upper lip since 4 years which gradually increased in size and later involved the skin of the lip. Excision with 5 mm safety margin was performed but the patient presented with the similar lesion after three and half years of the treatment. So, again wide excision with 2 cm safety margin was performed followed by reconstruction of the lip.

Conclusion

This case provides an example of aggressive behavior of mucosal melanoma and emphasizes on the fact that any pigmented lesion detected in the oral cavity may exhibit potential growth and should be submitted to biopsy to exclude malignancy. It also exemplifies of how the time of diagnosis and the evolution of a disease could be seriously influenced by patient’s behavior.

Hyperplasia of interstitial cells of cajal in sprouty homolog 4 deficient mice

Gastrointestinal stromal tumors, which are thought to derive from interstitial cells of Cajal or their precursors, often harbor an oncogenic mutation of the KIT receptor tyrosine kinase. Sprouty homolog 4, a known negative regulator of ERK pathway, has been identified in the interstitial cells of Cajal in the Kit^K641E murine model of gastrointestinal stromal tumors. Sprouty homolog 4 was upregulated both at the mRNA and protein level in these cells, suggesting that Sprouty homolog 4 is downstream of oncogenic KIT activation and potentially engaged in the negative feedback loop of ERK activation in this model. Here, we used Kit^K641E heterozygous and Sprouty homolog 4 knock out animals to quantify interstitial cells of Cajal in situ, using quantitative immunofluorescence for the receptor tyrosine kinase Kit and for phosphodiesterase 3a (PDE3A). In the antrum of Sprouty homolog 4 knock out mice, hyperplasia of interstitial cells of Cajal was reminiscent of the Kit^K641E heterozygous mice antrum. Additionally, the density of interstitial cells of Cajal was higher in the colon of adult Sprouty homolog 4 knock out mice than in WT littermates, although hyperplasia seemed more severe in Kit^K641E heterozygous mice. Functional transit studies also show similarities between Sprouty homolog 4 knock out and Kit^K641E heterozygous mice, as the total transit time in 9 month old animals was significantly increased in both genotypes compared to WT littermates. We concluded that the lack of Sprouty homolog 4 expression leads to hyperplasia of the interstitial cells of Cajal and is functionally associated with a delayed transit time.

High expression of c-kit mRNA predicts unfavorable outcome in adult patients with t(8;21) acute myeloid leukemia

The reason that a certain subgroup of acute myeloid leukemia (AML) patients with t(8;21) translocation (generating the AML1/ETO fusion gene) displays a poor survival remains elusive. The proto-oncogene c-kit is expressed in approximately 80% of AML cases. The kinase domain mutation of the c-kit gene, one of the most common gain-of-function mutations associated with t(8;21) AML, predicts higher relapse risk and poor prognosis. However, the role of c-kit high expression in t(8;21) AML remains poorly understood. Here we evaluated the prognostic significance of c-kit expression levels in AML patients. The mRNA expression of c-kit was determined by real-time quantitative reverse transcription PCR in 132 adult AML patients. Patients were grouped into quartiles according to c-kit expression levels (Q1–Q4, each quartile containing 25% of patients) and divided into c-kit high (Q4; n = 33) and c-kit low (Q1–Q3; n = 99). High c-kit expression was associated with AML1/ETO-positive and with c-kit mutation. Of note, 35.8% of the AML1/ETO-positive AML patients carrying wild-type c-kit expressed high levels of c-kit, suggesting that other factors are involved in c-kit overexpression. High c-kit expression was associated with inferior overall and event-free survival in AML1/ETO-positive patients and was independently predictive for overall and event-free survival in multivariate analyses in a c-kit mutation-independent manner. Thus, high c-kit expression serves as a reliable molecular marker for poor prognosis, supporting a pathogenetic role of c-kit signaling in AML1/ETO-positive AML. AML1/ETO-positive patients with high c-kit expression might benefit from early treatment modifications and molecular target therapies.

Ten things you should know about protein kinases: IUPHAR Review 14

Many human malignancies are associated with aberrant regulation of protein or lipid kinases due to mutations, chromosomal rearrangements and/or gene amplification. Protein and lipid kinases represent an important target class for treating human disorders. This review focus on 'the 10 things you should know about protein kinases and their inhibitors', including a short introduction on the history of protein kinases and their inhibitors and ending with a perspective on kinase drug discovery. Although the '10 things' have been, to a certain extent, chosen arbitrarily, they cover in a comprehensive way the past and present efforts in kinase drug discovery and summarize the status quo of the current kinase inhibitors as well as knowledge about kinase structure and binding modes. Besides describing the potentials of protein kinase inhibitors as drugs, this review also focus on their limitations, particularly on how to circumvent emerging resistance against kinase inhibitors in oncological indications.

The SCF/c-KIT system in the male: Survival strategies in fertility and cancer

Maintaining the delicate balance between cell survival and death is of the utmost importance for the proper development of germ cells and subsequent fertility. On the other hand, the fine regulation of tissue homeostasis by mechanisms that control cell fate is a factor that can prevent carcinogenesis. c-KIT is a type III receptor tyrosine kinase activated by its ligand, stem cell factor (SCF). c-KIT signaling plays a crucial role in cell fate decisions, specifically controlling cell proliferation, differentiation, survival, and apoptosis. Indeed, deregulating the SCF/c-KIT system by attenuation or overactivation of its signaling strength is linked to male infertility and cancer, and rebalancing its activity via c-KIT inhibitors has proven beneficial in treating human tumors that contain gain-of-function mutations or overexpress c-KIT. This review addresses the roles of SCF and c-KIT in the male reproductive tract, and discusses the potential application of c-KIT target therapies in disorders of the reproductive system.

Dendritic cell c-kit signaling and adaptive immunity: implications for the upper airways

PURPOSE OF REVIEW

Binding of the receptor tyrosine kinase, c-kit, to its ligand, stem cell factor (SCF), mediates numerous biological functions. Important roles for c-kit in hematopoiesis, melanogenesis, erythropoiesis, spermatogenesis, and carcinogenesis are well documented. Similarly, activation of mast cells and eosinophils by c-kit ligation has long been known to result in degranulation with concomitant release of pro-inflammatory mediators including cytokines. This review will highlight a recently discovered function of c-kit in regulating the adaptive immune responses with relevance to allergic diseases.

RECENT FINDINGS

Recent studies in a number of laboratories including our own highlight the previously unappreciated functions for c-kit in immunological processes. Increased expression of c-kit and its ligand, SCF, on dendritic cells by Th2/Th17-inducing stimuli leads to c-kit activation and immune skewing toward these subsets and away from Th1 responses. Treatment of dendritic cells with inhibitors of c-kit activation such as imatinib mesylate (Gleevec) induces breach of T-cell tolerance, skewing of responses toward Th1, and activation of natural killer cells.

SUMMARY

Taken together, these observations suggest that the c-kit/SCF axis may be a useful target for redirecting deleterious immune responses in various disease settings, including allergic diseases that are often associated with Th2 and Th17 responses.

MicroRNA-137 down-regulates KIT and inhibits small cell lung cancer cell proliferation

MiR-137 expression was examined in parental and drug-resistant cell lines, H446 and H446/CDDP, of small lung cancer (SCLC), and the results showed there was fewer miR-137 expressed in H446/CDDP cells followed by KIT expression emergence. In order to confirm physiological function of these abnormal expressions, H446 and H446/CDDP cells were transfected with miR-137 inhibitor and miR-137 mimics, respectively, after that, miR-137 and KIT expression in two cell lines and drug sensitivity of these cells were evaluated. Results indicated that sensitivity of H446 cells to cisplatin significantly decreased after transfected with miR-137 inhibitor, while miR-137 mimics transfection increased drug sensitivity of H446/CDDP cells and deregulated KIT expression. Our data provided combined evidence that miR-137 was closely related to MDR of SCLC, and interfering of miR-137 expression may attenuate drug resistant of H446/CDDP cells to cisplatin partially through KIT expression regulation. Besides, it has also been proved that KIT might be only one of the downstream molecules of miR-137 that related to SCLC MDR.

Low expression of cyclinH and cyclin-dependent kinase 7 can decrease the proliferation of human esophageal squamous cell carcinoma

BACKGROUND

Increased expression of cyclinH (CCNH) and cyclin-dependent kinase 7 (CDK7) has a relationship with poor prognosis in most human cancers.

AIM

Investigate the expression of CCNH and CDK7 in human esophageal squamous cell carcinoma (ESCC) and the effect of chemotherapy on their expression.

METHODS

Western blotting and immunohistochemistry were used to measure the expression of CCNH and CDK7 proteins in ESCC and adjacent normal tissue in 98 patients. We use Cell Counting Kit-8 and cell flow to analyze the effects of cisplatin and interference of CCNH and CDK7 in cell cycle process.

RESULTS

Immunohistochemical analysis showed that CCNH and CDK7 expression were significantly associated with unfavorable clinicopathologic variables. CCNH and CDK7 protein levels were elevated in ESCC tissues in comparison with adjacent normal tissues. Survival analysis revealed that CCNH and CDK7 overexpression were significantly associated with overall survival (P < 0.001). Cisplatin or interference of CCNH or CDK7 led cells to grow slowly. Overexpression of CCNH and CDK7 in TE1 cells can lead to resistance to cisplatin.

CONCLUSIONS

We can conclude that CCNH and CDK7 may play an important role in the tumorigenesis and development of ESCC. CCNH and CDK7 expression affected the chemotherapy of tumor.

Antitumor T-cell responses contribute to the effects of dasatinib on c-KIT mutant murine mastocytoma and are potentiated by anti-OX40

Targeted and immune-based therapies are thought to eradicate cancer cells by different mechanisms, and these approaches could possibly complement each other when used in combination. In this study, we report that the in vivo antitumor effects of the c-KIT inhibitor, dasatinib, on the c-KIT mutant P815 mastocytoma tumor were substantially dependent on T cell-mediated immunity. We found that dasatinib treatment significantly decreased levels of Tregs while specifically enhancing tumor antigen-specific T-cell responses. We sought to further enhance this therapy with the addition of anti-OX40 antibody, which is known to provide a potent costimulatory signal to T cells. The combination of dasatinib and anti-OX40 antibody resulted in substantially better therapeutic efficacy compared with either drug alone, and this was associated with enhanced accumulation of tumor antigen-specific T cells in the tumor microenvironment. Furthermore, the combination regimen inhibited the function of Tregs and also resulted in significantly up-regulated expression of the IFN-γ-induced chemokines CXCL9, 10, and 11 in the tumor microenvironment, which provides a feasible mechanism for the enhanced intratumoral CTL infiltration. These studies delineate a strategy by which targeted therapy and immunotherapy may be combined to achieve superior antitumor responses in cancer patients.

KIT gene mutations and patterns of protein expression in mucosal and acral melanoma

BACKGROUND

Recently characterized KIT (CD117) gene mutations have revealed new pathways involved in melanoma pathogenesis. In particular, certain subtypes harbor mutations similar to those observed in gastrointestinal stromal tumors, which are sensitive to treatment with tyrosine kinase inhibitors.

OBJECTIVE

The purpose of this study was to characterize KIT gene mutations and patterns of protein expression in mucosal and acral melanoma.

METHODS

Formalin-fixed, paraffin-embedded tissues were retrieved from our archives. Histologic assessment included routine hematoxylin-eosin stains and immunohistochemical staining for KIT. Genomic DNA was used for polymerase chain reaction-based amplification of exons 11 and 13.

RESULTS

We identified 59 acral and mucosal melanoma cases, of which 78% showed variable levels of KIT expression. Sequencing of exons 11 and 13 was completed on all cases, and 4 (6.8%) mutant cases were isolated.

CONCLUSION

We successfully optimized conditions for the detection of KIT mutations and showed that 8.6% of mucosal and 4.2% of acral melanoma cases at our institution harbor KIT mutations; all mutant cases showed strong, diffuse KIT protein expression. Our case series represents the first Canadian study to characterize KIT gene mutations and patterns of protein expression in acral and mucosal melanoma.

Targeting cancer with small-molecular-weight kinase inhibitors

Protein and lipid kinases fulfill essential roles in many signaling pathways that regulate normal cell functions. Deregulation of these kinase activities lead to a variety of pathologies ranging from cancer to inflammatory diseases, diabetes, infectious diseases, cardiovascular disorders, cell growth and survival. 518 protein kinases and about 20 lipid-modifying kinases are encoded by the human genome, and a much larger proportion of additional kinases are present in parasite, bacterial, fungal, and viral genomes that are susceptible to exploitation as drug targets. Since many human diseases result from overactivation of protein and lipid kinases due to mutations and/or overexpression, this enzyme class represents an important target for the pharmaceutical industry. Approximately one third of all protein targets under investigation in the pharmaceutical industry are protein or lipid kinases.The kinase inhibitors that have been launched, thus far, are mainly in oncology indications and are directed against a handful of protein and lipid kinases. With one exception, all of these registered kinase inhibitors are directed toward the ATP-site and display different selectivities, potencies, and pharmacokinetic properties. At present, about 150 kinase-targeted drugs are in clinical development and many more in various stages of preclinical development. Kinase inhibitor drugs that are in clinical trials target all stages of signal transduction from the receptor protein tyrosine kinases that initiate intracellular signaling, through second-messenger-dependent lipid and protein kinases, and protein kinases that regulate the cell cycle.This review provides an insight into protein and lipid kinase drug discovery with respect to achievements, binding modes of inhibitors, and novel avenues for the generation of second-generation kinase inhibitors to treat cancers.

Preliminary evidence of an association between the functional c-kit rs6554199 polymorphism and achalasia in a Turkish population

BACKGROUND

C-kit-positive interstitial cells of Cajal (ICC) of the lower esophageal sphincter are reduced in achalasia. Two functional gene polymorphisms (rs2237025 and rs6554199) within the c-kit gene may affect its transcriptional activity. In this pilot study, we hypothesized that these polymorphisms would be associated with achalasia.

METHODS

Genomic DNA was extracted and real-time PCR reactions were used to determine the rs2237025 and rs6554199 c-kit polymorphisms in 88 Turkish patients with achalasia and 101 healthy controls.

KEY RESULTS

The frequency of the T allele of rs6554199 was significantly higher in patients with achalasia [odds ratio (OR): 1.55; 95% confidence interval (CI), 1.03-2.34; P = 0.038] compared with the G allele. Under a dominant model of inheritance, the carriage of at least one T allele was significantly more frequent in patients with achalasia (80.7%) than in controls (65.3%; OR: 2.21; 95% CI, 1.13-4.33; P = 0.022). No association of the c-kit rs2237025 polymorphism with achalasia was detected.

CONCLUSIONS & INFERENCES

Despite the small sample size and the possibility of a false positive finding, our preliminary data support the hypothesis that the T allele of the c-kit rs6554199 polymorphism may be associated with achalasia in the Turkish population. These findings need to be replicated in other racial-ethnically diverse populations.

Imatinib mesylate: past successes and future challenges in the treatment of gastrointestinal stromal tumors

Just over a decade ago, gastrointestinal tumours were a poorly understood mesenchymal neoplasm unsuccessfully treated with chemotherapy. Cytotoxic therapy for advanced disease yielded response rates of 10% and median survival of just 18 months. However, the discovery of KIT and platelet derived growth factor receptor alpha (PDGFRA) mutations as oncogenic drivers of most gastrointestinal tumours, paved the way for targeted therapy. Imatinib mesylate, a tyrosine kinase inhibitor, produces a clinical benefit rate (complete response, partial response, and stable disease) of more than 80% in metastatic setting and a median survival of 57 months. Imatinib is now also approved in adult patients following resection of KIT-positive GIST. Major insights into the mechanism of action of imatinib, unique pharmacokinetics, drug resistance, and management of low grade but chronic adverse effects continue to be made.

MicroRNAs and vascular (dys)function

MicroRNAs (miRNAs) are small non-coding RNAs, that control diverse cellular functions by either promoting degradation or inhibition of target messenger RNA translation. An aberrant expression profile of miRNAs has been linked to human diseases, including cardiovascular dysfunction. This review summarizes the latest insights in the identification of vascular-specific miRNAs and their targets, as well as their roles and mechanisms in the vasculature. Furthermore, we discuss how manipulation of these miRNAs could represent a novel therapeutic approach in the treatment of vascular dysfunction.

Effects of stem cell factor on hypoxia-inducible factor 1 alpha accumulation in human acute myeloid leukaemia and LAD2 mast cells

Stem cell factor (SCF) is a hematopoietic growth factor that exerts its activity by signalling through the tyrosine kinase receptor known as Kit or CD117. SCF-Kit signalling is crucial for the survival, proliferation and differentiation of hematopoietic cells of myeloid lineage. Furthermore, since myeloid leukaemia cells express the Kit receptor, SCF may play an important role in myeloid leukaemia progression too. However, the mechanisms of this pathophysiological effect remain unclear. Recent evidence shows that SCF triggers accumulation of the inducible alpha subunit of hypoxia-inducible factor 1 (HIF-1) in hematopoietic cells—a transcription complex that plays a pivotal role in cellular adaptation to low oxygen availability. However, it is unknown how SCF impacts on HIF-1α accumulation in human myeloid leukaemia and mast cells. Here we show that SCF induces HIF-1α accumulation in THP-1 human myeloid leukaemia cells but not in LAD2 mast cells. We demonstrated that LAD2 cells have a more robust glutathione (GSH)-dependent antioxidative system compared to THP-1 cells and are therefore protected against the actions of ROS generated in an SCF-dependent manner. BSO-induced GSH depletion led to a significant decrease in HIF-1α prolyl hydroxylase (PHD) activity in THP-1 cells and to near attenuation of it in LAD2 cells. In THP-1 cells, SCF-induced HIF-1α accumulation is controlled via ERK, PI3 kinase/PKC-δ/mTOR-dependent and to a certain extent by redox-dependent mechanisms. These results demonstrate for the first time an important cross-talk of signalling pathways associated with HIF-1 activation—an important stage of the myeloid leukaemia cell life cycle.

Apoptotic effect of imatinib on human colon adenocarcinoma cells: influence on actin cytoskeleton organization and cell migration

Imatinib mesylate (STI571) is the first member of a new class of agents that act by inhibiting specific tyrosine kinases, rather than killing all rapidly dividing cells. This drug is usually used in the treatment of chronic myelogenous leukemia and gastrointestinal stromal tumors. It was recognized to inhibit activity of kinases such as Bcr/Abl, platelet-derived growth factor receptor, and c-kit. These proteins play important roles in cell growth, motility, and survival. Therefore, studies on the biological effects of imatinib on different cellular models are very important. Human colon adenocarcinoma LS180 cell line was used in the studies presented. Cells were exposed to 0.1-100 μM imatinib for 24 and 48 h. Dose-dependent decreases in cell viability and morphological changes were observed. Moreover, the apoptotic effect of imatinib (10 μM, 50 μM) after 24 h of exposure was demonstrated as evaluated by translocation of phosphatidylserine to external membrane leaflet and by increased activity of caspase-3. Special attention was focused on imatinib influence on actin cytoskeleton organization and migration ability of LS180 cells. Distinct alterations in actin cytoskeleton architecture occurred in response to drug treatment, accompanied by appearance of filamentous actin aggregates and decrease in actin polymerization state. These changes were correlated with remarkable decrease in cell migration capacity. In summary, our data clearly demonstrate that imatinib induces apoptosis and inhibits human colon adenocarcinoma cell migration. Therefore, this drug may have potential in colon cancer therapy in the future.

Insulin regulates the expression of stem cell factor in rat colonic smooth muscle cells

AIM: To investigate the effect of insulin on the expression of stem cell factor (SCF) in rat colonic smooth muscle cells.

METHODS: Rat colonic smooth muscle cells (SMCs) were separated by mechanical and enzymatic methods and identified by immunofluorescence staining of α-actin. Identified colonic SMCs were randomly divided into two groups: cells treated with different concentrations of insulin (0, 2.5, 5, 20, 40, 80 mg/L) and those treated with insulin for different durations (0, 8, 16, 24 h). The expression of SCF was detected by Western blot and RT-PCR. MTT assay was used to measure the proliferation of colonic SMCs.

RESULTS: At a concentration of 5 mg/L, insulin remarkably promoted the proliferation of colonic SMCs (0.052 ± 0.006 vs 0.018 ± 0.006, P < 0.05). Insulin at a concentration of 2.5, 5 or 20 mg/L promoted SCF expression in colonic SMCs (protein: 0.735 ± 0.035, 0.754 ± 0.057, 0.741 ± 0.051 vs 0.658 ± 0.024; mRNA: 0.688 ± 0.077, 0.690 ± 0.080, 0.698 ± 0.074 vs 0.528 ± 0.053; all P < 0.05), but there were no marked differences in the expression levels of SCF protein and mRNA among these three groups of cells. When the dosage of insulin was elevated to 40 mg/L, SCF expression reached its peak (protein: 0.899 ± 0.048 vs 0.658 ± 0.024; mRNA: 0.938 ± 0.117 vs 0.528 ± 0.053; both P < 0.05). The expression of SCF reached the peak at 16 hours after insulin treatment (protein: 0.899 ± 0.011 vs 0.628 ± 0.015; mRNA: 1.038 ± 0.053 vs 0.709 ± 0.042; both P < 0.05).

CONCLUSION: Insulin promotes cell proliferation and up-regulates SCF expression in rat colonic SMCs.

Global analysis of the eukaryotic pathways and networks regulated by Salmonella typhimurium in mouse intestinal infection in vivo

BACKGROUND

Acute enteritis caused by Salmonella is a public health concern. Salmonella infection is also known to increase the risk of inflammatory bowel diseases and cancer. Therefore, it is important to understand how Salmonella works in targeting eukaryotic pathways in intestinal infection. However, the global physiological function of Salmonella typhimurium in intestinal mucosa in vivo is unclear. In this study, a whole genome approach combined with bioinformatics assays was used to investigate the in vivo genetic responses of the mouse colon to Salmonella. We focused on the intestinal responses in the early stage (8 hours) and late stage (4 days) after Salmonella infection.

RESULTS

Of the 28,000 genes represented on the array, our analysis of mRNA expression in mouse colon mucosa showed that a total of 856 genes were expressed differentially at 8 hours post-infection. At 4 days post-infection, a total of 7558 genes were expressed differentially. 23 differentially expressed genes from the microarray data was further examined by real-time PCR. Ingenuity Pathways Analysis identified that the most significant pathway associated with the differentially expressed genes in 8 hours post-infection is oxidative phosphorylation, which targets the mitochondria. At the late stage of infection, a series of pathways associated with immune and inflammatory response, proliferation, and apoptosis were identified, whereas the oxidative phosphorylation was shut off. Histology analysis confirmed the biological role of Salmonella, which induced a physiological state of inflammation and proliferation in the colon mucosa through the regulation of multiple signaling pathways. Most of the metabolism-related pathways were targeted by down-regulated genes, and a general repression process of metabolic pathways was observed. Network analysis supported IFN-γ and TNF-α function as mediators of the immune/inflammatory response for host defense against pathogen.

CONCLUSION

Our study provides novel genome-wide transcriptional profiling data on the mouse colon mucosa's response to the Salmonella typhimurium infection. Building the pathways and networks of interactions between these genes help us to understand the complex interplay in the mice colon during Salmonella infection, and further provide new insights into the molecular cascade, which is mobilized to combat Salmonella-associated colon infection in vivo.

Cyclin H expression is increased in GIST with very-high risk of malignancy

BACKGROUND

Risk estimation of gastrointestinal stromal tumours (GIST) is based on tumour size and mitotic rate according to the National Institutes of Health consensus classification. The indication for adjuvant treatment of patients with high risk GIST after R0 resection with small molecule inhibitors is still a controversial issue, since these patients represent a highly heterogeneous population. Therefore, additional prognostic indicators are needed. Here, we evaluated the prognostic value of cyclin H expression in GIST.

METHODS

In order to identify prognostic factors of GIST we evaluated a single centre cohort of ninety-five GIST patients. First, GISTs were classified with regard to tumour size, mitotic rate and localisation according to the NIH consensus and to three additional suggested risk classifications. Second, Cyclin H expression was analysed.

RESULTS

Of ninety-five patients with GIST (53 female/42 male; median age: 66.78a; range 17-94a) risk classification revealed: 42% high risk, 20% intermediate risk, 23% low risk and 15% very low risk GIST. In patients with high risk GIST, the expression of cyclin H was highly predictive for reduced disease-specific survival (p = 0.038). A combination of cyclin H expression level and high risk classification yielded the strongest prognostic indicator for disease-specific and disease-free survival (p < or = 0.001). Moreover, in patients with tumour recurrence and/or metastases, cyclin H positivity was significantly associated with reduced disease-specific survival (p = 0.016) regardless of risk-classification.

CONCLUSION

Our data suggest that, in addition to high risk classification, cyclin H expression might be an indicator for "very-high risk" GIST.

Mucosal melanomas: a case-based review of the literature

Mucosal melanoma is a rare cancer that is clearly distinct from its cutaneous counterpart in biology, clinical course, and prognosis. Recent studies have shown important differences in the frequencies of various genetic alterations in different subtypes of melanoma. Activating mutations in the c-KIT gene are detected in a significant number of patients with mucosal melanoma. This observation has resulted in the initiation of several clinical trials aimed at exploring the role of receptor tyrosine kinases that inhibit c-KIT in this patient population. We herein present a comprehensive literature review of mucosal melanoma along with case vignettes of a number of pertinent cases. We further discuss melanomas of the head and neck, the female genital tract, and the anorectum, which are the three most common sites of mucosal melanoma, with a particular focus on the diagnostic, prognostic, and therapeutic data available in the literature.

Signaling of c-kit in dendritic cells influences adaptive immunity

The binding of the receptor tyrosine kinase, c-kit, to its ligand, stem cell factor (SCF), mediates numerous biological functions. Important roles for c-kit in hematopoiesis, melanogenesis, erythropoiesis, spermatogenesis, and carcinogenesis are well documented. Similarly, activation of granulocytes, mast cells, and of eosinophils in particular, by c-kit ligation has long been known to result in degranulation with concomitant release of pro-inflammatory mediators, including cytokines. However, recent work from a number of laboratories, including our own, highlights previously unappreciated functions for c-kit in immunologic processes. These novel findings strongly suggest that signaling through the c-kit-SCF axis could have a significant impact on the pathogenesis of diseases associated with an immunologic component. In our own studies, c-kit upregulation on dendritic cells via T helper (Th)2- and Th17-inducing stimuli led to c-kit activation and immune skewing toward these T helper subsets and away from Th1 responses. Others have shown that dendritic cell treatment with inhibitors of c-kit activation, such as imatinib mesylate (Gleevec), favored breaking of T-cell tolerance, skewing of responses toward production of Th1 cytokines, and activation of natural killer cells. These data all indicate that deeper understanding of, and ability to control, the c-kit-SCF axis could lead to improved treatment modalities aimed at redirecting unwanted and/or deleterious immune responses in a wide variety of conditions.

Molecular mechanisms of secondary imatinib resistance in patients with gastrointestinal stromal tumors

AIMS AND BACKGROUND

Most gastrointestinal stromal tumor (GIST) patients respond to KIT inhibition therapy of imatinib, but eventually become resistant with a median time to progression of 2 years. The mechanism of acquired resistance to imatinib and oncogenic KIT signal transduction in GISTs has not been well defined. We sought to investigate the spectrum of molecular and genomic changes in imatinib-resistant GIST patients.

METHODS

KIT and PDGFRA mutations were evaluated in 48 samples obtained from 32 GIST patients who underwent surgery after imatinib treatment. KIT downstream signaling profiles were also investigated in eight specimens of five patients who were clinically responsive or resistant to imatinib therapy. Biochemical inhibition of KIT, mitogen-activated protein kinase (MAPK), mammalian target of rapamycin (MTOR), AKT, proliferating cell nuclear antigen (PCNA) and BCL-2 were determined by western blotting for protein activation.

RESULTS

In all 32 GIST patients, activating mutations in the KIT gene were seen in 26 (81.3%) patients, PDGFRA gene mutations were seen in 2 (6.2%) patients and no primary mutations were found in 4 (12.5%) patients. Secondary KIT mutations were identified in 11/14 (78.6%) imatinib-acquired-resistance patients, with nine patients in KIT gene exon17, and the other two in exon 13. The expressions of p-KIT, p-AKT, PCNA and BCL-2 were higher in the samples of imatinib-resistant GISTs than those of imatinib-responsive ones. P-KIT, p-AKT expressions were higher in imatinib acquired-resistance GISTs with secondary KIT mutations than imatinib-responsive ones with primary mutation. Total KIT, MAPK, p-MAPK, p-MTOR expressions were comparable in all varied GISTs.

CONCLUSIONS

Novel additional mutations of KIT gene exon 13 or exon 17 indicate the likely mechanism of secondary resistance to imatinib. The PI3-K/AKT pathway might be more relevant than MEK/MAPK for therapeutic targeting in imatinib-resistant GIST patients with secondary mutation.

Low frequency of MAP kinase pathway alterations in KIT and PDGFRA wild-type GISTs

AIMS

Gastrointestinal stromal tumours (GISTs) are commonly driven by oncogenic mutations in KIT and PDGFRA. However, 10-40% of these patients are wild-type for these genes. The prognostic significance of wild-type GISTs is controversial, and they rarely respond to imatinib. The aim of this study was to elucidate the molecular lesions underlying wild-type GISTs tumorigenesis.

METHODS AND RESULTS

Twenty-nine KIT and PDGFRA wild-type GISTs were re-assessed for the presence of 'cryptic'KIT exon 11 duplications. Using a specific polymerase chain reaction assay, three previously undetected mutations were identified. In the remaining 26 wild-type GISTs, KIT, stem cell factor (SCF), phospho-KIT and phospho-ERK expression was evaluated by immunohistochemistry. Samples were screened for gain-of-function mutations in the mitogen-activated protein kinase (MAPK) cascade. KIT and SCF co-expression associated with KIT activation was observed in approximately 30% of cases. Furthermore, phospho-ERK expression showed that MAPK is activated in approximately 30% of cases. None of RAS family (H-, K- and N-RAS) oncogenes exhibited activating mutations, whereas BRAF mutations were found in approximately 4% of cases.

CONCLUSIONS

In the absence of RAS mutations, MAPK could be activated through SCF/KIT autocrine/paracrine mechanisms and/or mutated BRAF in a subset of KIT/PDGFRA wild-type GISTs.

Phase I dose-escalation and pharmacokinetic study of dasatinib in patients with advanced solid tumors

PURPOSE

To determine the maximum tolerated dose, dose-limiting toxicity (DLT), and recommended phase II dose of dasatinib in metastatic solid tumors refractory to standard therapies or for which no effective standard therapy exists.

EXPERIMENTAL DESIGN

In this phase I, open-label, dose-escalation study, patients received 35 to 160 mg of dasatinib twice daily in 28-day cycles either every 12 hours for 5 consecutive days followed by 2 nontreatment days every week (5D2) or as continuous, twice-daily (CDD) dosing.

RESULTS

Sixty-seven patients were treated (5D2, n = 33; CDD, n = 34). The maximum tolerated doses were 120 mg twice daily 5D2 and 70 mg twice daily CDD. DLTs with 160 mg 5D2 were recurrent grade 2 rash, grade 3 lethargy, and one patient with both grade 3 prolonged bleeding time and grade 3 hypocalcemia; DLTs with 120 mg twice daily CDD were grade 3 nausea, grade 3 fatigue, and one patient with both grade 3 rash and grade 2 proteinuria. The most frequent treatment-related toxicities across all doses were nausea, fatigue, lethargy, anorexia, proteinuria, and diarrhea, with infrequent hematologic toxicities. Pharmacokinetic data indicated rapid absorption, dose proportionality, and lack of drug accumulation. Although no objective tumor responses were seen, durable stable disease was observed in 16% of patients.

CONCLUSION

Dasatinib was well tolerated in this population, with a safety profile similar to that observed previously in leukemia patients, although with much less hematologic toxicity. Limited, although encouraging, preliminary evidence of clinical activity was observed. Doses of 120 mg twice daily (5D2) or 70 mg twice daily (CDD) are recommended for further studies in patients with solid tumors.