Role Of Tyrosine Kinase Inhibitors Research Articles

Tyrosine Kinase Inhibitors in Pulmonary Arterial Hypertension: A Double-Edge Sword?

New treatments for pulmonary arterial hypertension (PAH) are a crucial need. The increased proliferation, migration, and survival of pulmonary vascular cells within the pulmonary artery wall in PAH have allowed successful transposition of pathophysiological elements from oncologic researches. Next steps will require translation of these biological advances in PAH therapeutic arsenal and guidelines. This review synthesizes recent data concerning the role of receptor tyrosine kinases and their inhibitors in PAH, with implications in animal models and humans. Results of clinical trials are now accumulating to establish beneficial role of tyrosine kinase inhibitors (TKIs) in PAH and further findings are expected in the near future. Beside this curative approach, evidences of a possible TKI-induced cardiotoxicity are emerging. These safety issues raise concern about a potential amplified harmful effect in PAH, a pathology characterized by an underlying cardiac dysfunction. In addition, analyses of PAH registries shed light on a selective pulmonary vascular toxicity triggered by TKIs, especially dasatinib. These possible dual effects of the TKIs in PAH need to be taken in account for future pharmacological development of this therapeutic class in PAH.

Role of tyrosine kinase inhibitors in the management of high-grade gliomas

Recent years have witnessed an explosion of promising therapies for cancer patients. New insights into the biology of malignancies have led to the development of targeted agents with the potential to improve survival and quality of life. One of the most important classes of these compounds are tyrosine kinase inhibitors. These agents are beginning to offer a clinically relevant benefit to patients with tumors that until recently have been refractory to medical therapies. High-grade gliomas represent one class of medically refractory solid tumors. This article summarizes the state of the art of tyrosine kinase inhibitors in the management of patients with high-grade gliomas.

Role of Tyrosine Kinase Inhibitors in the Management of Philadelphia Chromosome–Positive Acute Lymphoblastic Leukemia

The Philadelphia chromosome is the most common cytogenetic abnormality found in adult patients diagnosed with acute lymphoblastic leukemia. The result of this abnormality is the BCR-ABL protein, a constitutively active kinase involved in cell signaling and survival. When managed with multiagent chemotherapy regimens alone, patients have traditionally had an inferior outcome in terms of remission duration and overall survival when compared with patients who are Philadelphia chromosome-negative. Small-molecule tyrosine kinase inhibitors, such as imatinib and dasatinib, directly inhibit the BCR-ABL kinase, offering a targeted approach as a therapeutic option. As a result of several clinical trials with adequate follow-up, imatinib combined with chemotherapy represents the current standard of care for patients with newly diagnosed disease. Allogeneic stem cell transplantation has previously been the only modality to offer the potential for a cure, and it still should be considered for all patients deemed able to tolerate such an intervention. Second-generation tyrosine kinase inhibitors, such as dasatinib, may further improve the outcome in these patients. The role of molecular monitoring and the use of tyrosine kinase inhibitors after stem cell transplantation are areas of active investigation, and the results of ongoing trials will help to clarify the optimal management of these patients.

Imatinib mesylate as second-line treatment in a c-kit-positive esthesioneuroblastoma.

e12513 Background: Esthesioneuroblastoma is a rare malignant tumour of the upper nasal cavity and is thought to arise from the olfactory epithelium. Multimodal treatment including surgery and radiotherapy is commonly applied. Platin-based chemotherapy, etoposide and temozolomide are described as effective in a palliative setting. Recently, sunitinib mesylate was reported to induce remission in a patient with esthesioneuroblastoma, suggesting that other biological treatments might be effective as well. Methods: A 46 year-old man presented with a large frontobasal tumour, infiltrating the lamina cribriformis, the right maxillary sinus and the right orbit. After resection in March 2000 and further revisions the patients received 3 cycles of cisplatine and etoposide following a fractionated intensity modulated radiotherapy of 59,4 Gy and a second percutaneous radiotherapy of cervical lymphnodes metastasis in November 2001. Due to recurrent tumour three reoperations with partial resection of the maxilla and the zygomatic bone was necessary. In August 2004 tumour progression was again evident in MRI. Results: The paraffin sections of the tumour resection were immunohistochemically positive for c-kit, but EGFR was negative. Since second-line chemotherapy is not established for esthesioneuroblastoma we presumed, that imatinib mesylate might be a feasible therapeutic option with little toxicity. From August 2004 until April 2007 the patient received 400mg per day achieving a partial remission. The dosage was raised to 400mg twice daily, when detecting a local progress of the tumour. With the doubled dosage the remission prolonged for another 18 months. Conclusions: Imatinib mesylate may be an effective treatment options in heavily pretreated patients inducing long time remission and stabilization of disease. Esthesioneuroblastoma should be systematically investigated for c-kit expression and further clinical trials are needed to elucidate the role of tyrosine kinase inhibitors in esthesioneuroblastoma.

A Phase I Trial to Determine the Safety of Imatinib in Combination With Vatalanib in Patients With Advanced Malignancies

The role of tyrosine kinase inhibitors (TKIs) in the treatment of advanced malignancies is well established. Imatinib and vatalanib are oral TKIs with different mechanisms of action. This trial sought to establish the safety, tolerability, and maximum tolerated dose (MTD) of the two agents in combination. Secondary objectives included determination of potential pharmacologic interactions among vatalanib and imatinib and observation of antitumor activity. Patients with biopsy-proven advanced refractory solid tumors were enrolled in this single-center dose-escalation trial. Patients initially received imatinib and vatalanib once daily following a 14-day run-in period of daily oral vatalanib only, and were observed for a full 28-day treatment cycle prior to dose escalation. An amendment divided the vatalanib dose into two daily doses and gradually escalated the dose over a 2–3 week period. Patients continued combination therapy until disease progression or intolerable toxicity. Forty-five patients were enrolled between September 2004 and November 2007. As of September 2009, a total of 247 cycles of treatment had been administered (range: –44+, median = ). The MTD was determined to be vatalanib 1250 mg daily and imatinib 400 mg daily. Thirty-five patients (78%) were evaluable for response; 2 patients achieved PR, while 14 patients had SD ( had stable disease ≥ cycles). The combination of vatalanib and imatinib was well tolerated. Twice-daily vatalanib dosing improved tolerability and ease of full-dose administration. These results suggest that vatalanib-containing combinations may be active and tolerable, warranting further study.

Role of Tyrosine Kinase Inhibitors in Tumor Immunology

Various immune cells are involved in both innate and acquired immunity against tumors. NK cells and cytotoxic T lymphocytes play a role as effector cells to directly kill tumor cells. On the other hand, antigen-presenting cells, particularly dendritic cells, control tumor-specific immune responses. In addition, much focus has been paid on the immune regulatory cells in tumor sites, including CD4(+)CD25(+) regulatory T cells and myeloid-derived suppressor cells. The recent advances in molecular-targeted therapy for cancer have provided small-molecule kinase inhibitors, which are effective for several hematopoietic malignancies as well as solid tumors in the clinical setting. Most drugs generally have inhibitory effects on several kinases, including tyrosine kinases, which are critical molecules for the survival, proliferation, migration and invasion of tumor cells. Since the host immune surveillance against tumors affects tumor progression, it is of interest to understand how these molecular-targeted drugs affect immune function in the tumor-bearing host. Besides this, there are emerging findings that myeloid cells could be involved in tumor angiogenesis. In this article, we address the role of tyrosine kinase inhibitors in tumor immunology by summarizing their effects on myeloid cells, such as antigen-presenting cells and regulatory cells, and their role in tumor immunity and angiogenesis.

The role of tyrosine kinase inhibitors in tuberous sclerosis

The role of tyrosine kinase inhibitors in tuberous sclerosis

Chronic myeloid leukemia patient manifesting fatal hepatitis B virus reactivation during treatment with imatinib rescued by liver transplantation: case report and literature review

Imatinib mesylate (imatinib) is now a standard treatment for patients with chronic myeloid leukemia (CML). Although imatinib is known to have a potential impact on various infectious organisms by altering the T-cell mediated immune response, only two cases of hepatitis B virus (HBV) reactivation during imatinib treatment have actually been reported. The role of liver transplantation (LT) after fatal HBV reactivation in patients with potentially treatable or curable hematologic malignancy is also unknown. Therefore, this report presents a case of fatal HBV reactivation during imatinib treatment for CML, where the patient is rescued by LT. Following a successful living donor LT, the liver function improves rapidly and the patient remains in complete cytogenetic remission after retreatment with imatinib for 6 months. The present report also covers the role of tyrosine kinase inhibitor in triggering HBV reactivation and a literature review of fulminant hepatic failure in CML patients taking imatinib.

Role of Tyrosine Kinase Inhibitors in Lung Cancer

Protein tyrosine kinases are enzymes which catalyze the phosphorylation of tyrosine residues and activate a downstream cascade of cellular signalling pathways which regulate cell proliferation, differentiation and apoptosis and a wide variety of cellular functions. Clinical developments over the past decade have identified several novel therapeutic agents which inhibit tyrosine kinase activity, either by direct receptor inhibition or indirect inhibition of tyrosine kinase controlled pathways. Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR TKI), such as gefitinib and erlotinib have been studied extensively in patients with refractory non-small cell lung cancer (NSCLC). Early studies with gefitinib showed undoubted clinical activity but failed to show a survival benefit, whereas studies with erlotinib showed a small but statistically significant benefit in overall survival. Subsequent studies explored the possibility of synergistic activity between targeted agents (gefitinib or erlotinib) and conventional chemotherapy drugs reporting disappointing results. Clinical trial results with gefitinib and erlotinib, either as monotherapy or in combination with chemotherapy, have failed to match the encouraging results noted in the pre-clinical setting. It is now increasingly recognised that clinical exploration of molecular targeted agents may not conform well to traditional phase I/II/III drug trial designs. Therapeutic responses may be limited to a small subpopulation of patients, therefore diluting the overall therapeutic effect. Hypothesising a genetic basis for the heterogeneity in trial results, biomarkers (such as EGFR gene mutation analysis, EGFR protein expression, and increased EGFR gene copy number) have been studied with a view to identifying a target population most likely to benefit from these drugs. Future clinical trials with targeted agents need to be carefully designed to incorporate correlative translational research elements that will allow selection of appropriate treatment strategies for individual patients. For assessment of phase III trial results in advanced disease, progression free survival may serve as a more appropriate end-point than response rate in an adequately designed trial in the appropriately selected population, although there should be no substitute for the overall survival and quality of life end points. The role of EFGR TKI in NSCLC will be discussed in detail and data from these studies will be used to illustrate the challenges in designing clinical trials and interpreting outcomes.

EGFR protein overexpression and mutation in areca quid–associated oral cavity squamous cell carcinoma in Taiwan

Epidermal growth factor receptor (EGFR)-targeted therapy has been extensively assessed in human cancer treatment. We appraised the possible role of tyrosine kinase inhibitors (TKIs) in areca quid (AQ)-associated oral cavity squamous cell carcinomas (OSCCs) by examining EGFR protein overexpression and its tyrosine kinase domain mutations. EGFR overexpression was evaluated by immunohistochemical staining, and tyrosine kinase mutations was determined by direct sequencing of DNAs from 172 OSCC tumors. Overexpression of EGFR was found in 27.9% (48 of 172) of the OSCCs and was associated with lymph node metastasis (p = .013) and extracapsular spread (p = .022). Only 1 (0.58%) OSCC displayed somatic EGFR mutation but in a silent form (T725T, ACG-->ACA). EGFR-targeted therapy might have some potential in AQ-associated OSCCs for their EGFR frequently overexpressed, although EGFR mutations were rare. However, the feasibility of TKIs in AQ-associated OSCCs needs further clinical testing.

The Novel Role of Tyrosine Kinase Inhibitor in the Reversal of Immune Suppression and Modulation of Tumor Microenvironment for Immune-Based Cancer Therapies

In tumor-bearing hosts, myeloid-derived suppressor cells (MDSC) and T regulatory cells (Treg) play important roles in immune suppression, the reversal of which is vitally important for the success of immune therapy. We have shown that ckit ligand is required for MDSC accumulation and Treg development. We hypothesized that sunitinib malate, a receptor tyrosine kinase inhibitor, could reverse MDSC-mediated immune suppression and modulate the tumor microenvironment, thereby improving the efficacy of immune-based therapies. Treatment with sunitinib decreased the number of MDSC and Treg in advanced tumor-bearing animals. Furthermore, it not only reduced the suppressive function of MDSCs but also prevented tumor-specific T-cell anergy and Treg development. Interestingly, sunitinib treatment resulted in reduced expression of interleukin (IL)-10, transforming growth factor-beta, and Foxp3 but enhanced expression of Th1 cytokine IFN-gamma and increased CTL responses in isolated tumor-infiltrating leukocytes. A significantly higher percentage and infiltration of CD8 and CD4 cells was detected in tumors of sunitinib-treated mice when compared with control-treated mice. More importantly, the expression of negative costimulatory molecules CTLA4 and PD-1 in both CD4 and CD8 T cells, and PDL-1 expression on MDSC and plasmacytoid dendritic cells, was also significantly decreased by sunitinib treatment. Finally, sunitinib in combination with our immune therapy protocol (IL-12 and 4-1BB activation) significantly improves the long-term survival rate of large tumor-bearing mice. These data suggest that sunitinib can be used to reverse immune suppression and as a potentially useful adjunct for enhancing the efficacy of immune-based cancer therapy for advanced malignancies.

BCR-ABL Protein Detection by Flow Cytometry in Acute Lymphoblastic Leukemia Samples

The development of agents directed specifically against the BCR-ABL tyrosine kinase has opened therapeutic avenues that have profoundly modified the management of diseases which harbor the genetic abnormality that leads to the production of the BCRABL transcript. While the role of tyrosine kinase inhibitors of 1st and 2nd generation in chronic myeloid leukemia (CML) patients is well established, important clinical responses have been documented also in BCR-ABL+ acute lymphoblastic leukemia (ALL), the most relevant genetic ALL subgroup which accounts for about 25% of adult cases and is associated with a dismal prognosis. Following the administration of tyrosine kinase inhibitors alone as induction treatment, complete hematologic remissions have in fact been recorded in virtually all cases. Thus, the possibility of identifying the presence of the BCR-ABL transcript in the shortest possible time and with a simple and broadly utilizable technique would translate into the timely implementation of a targeted therapy. The availability of a method capable of highlighting the presence of the BCR-ABL protein has important implications because it can document the effective transduction of the molecular transcript; since tyrosine kinase inhibitors are effective on the protein, this would unequivocally support the use of such specific agents in these cases. For this purpose, we have utilized the BCR-ABL Protein Kit**Research Use Only, not for diagnostics or therapeutic procedures. (BD Biosciences, San José, CA) which consists of an immunoassay that identifies qualitatively the presence of the BCR-ABL protein in the lysates of leukemic cell populations. The BCR-ABL fusion protein is captured and detected on Cytometric Bead Array (CBA) and analyzed on a FACSCanto (BD Biosciences) flow cytometer. Lysates from normal mononuclear cells and from the K562 cell line were used as negative and positive controls, respectively. The presence of the BCR-ABL protein was investigated on fresh bone marrow or peripheral blood samples from 56 consecutive cases of acute leukemia aged between 11 and 81 years referred to our Institution. The BCR-ABL protein could be documented in 11 of the 56 cases analyzed. By conventional immunophenotypic analysis they proved to be a B-lineage ALL in 9 cases and a B lymphoid blast crisis of CML in 2. In all 11 cases, the presence of the BCR-ABL transcript was subsequently documented by molecular biology. In the other 45 cases the diagnosis was: B-lineage ALL in 26 (2 of which were ALL/AF4+), T-ALL in 2, acute myeloid leukemia in 22 (5 of which were PML-RARα+) and acute biphenotypic leukemia in 1. None of these latter 45 cases harbored the BCRABL transcript. The assay utilized was successfully completed within a maximum of 4 hours from the marrow or blood collection on 20 × 106 cells containing at least 20% of leukemic cells. The correlation between the presence/absence of the BCR-ABL protein evaluated using the BCR-ABL Protein Kit* and the positivity/negativity of the transcript assessed according to conventional genetic techniques has been absolute. In our laboratory, the assay has shown to be reliable, reproducible and of simple execution. It allows in a very short time to identify the presence of the BCR-ABL protein – both p190 and p210 – through a flow cytometric analysis and thus to reliably offer proteomic information to investigators researching targeted anti-tyrosine kinase treatment.

Transient Massive Lymphoid Bone Marrow Infiltrate Developing during Therapy with the Tyrosine Kinase Inhibitors Imatinib and Nilotinib: Report of 2 Patients.

Clinical use of tyrosine kinase inhibitors (TKIs) for chronic myeloid leukemia (CML) has highlighted uncommon side effects of this group of novel anti-cancer agents. One of these peculiar side effects observed with imatinib (IM) is the occurrence of a bone marrow (BM) polyclonal lymphoid (Ly) infiltrate, usually accounting for 15–30% of total BM cellularity, sometimes taking the form of mature lymphoid follicles. No such effect has so far been described with nilotinib (NIL). We report on 2 CP-CML pts, one on IM and the second one on NIL, who developed transient massive BM Ly infiltrate without any clinical modification and with stable disease. Case1 A 40 yr old male pt was started on IM 400 mg/day as first line therapy in July 2003. Complete Cytogenetic Response (CCyR) and complete molecular response (CMoR) were obtained at 3 and 12 mos respectively. Routine BM monitoring showed progressive increase of the Ly infiltrate coincident with CCyR, up to 30%. In March 2007, BM examination disclosed massive infiltration with mature lymphocytes accounting for 60% of total BM cellularity; cytogenetic and molecular monitoring for CML were negative and peripheral blood count (PBC) was normal. The BM examination repeated a month later showed a spontaneous regression of Ly infiltrate to 25%; the remaining lymphocytes were prevalently B, polyclonal by molecular biology; cariotype was normal; FISH showed non specific abnormality (18% of 45 nuclei positive for del 17p13). Subsequent follow up disclosed normal BM with stable lymphocyte infiltrate and persistent CCyR and CMoR. Case2 A 60 yr old female pt resistant to IM was switched to NIL on November 2005. CCyR were obtained at 12 mos. BM monitoring showed progressive increase of the Ly infiltrate coincident with CCyR, up to 25%. The pt was mildly leucopenic throughout treatment. In March 2007, BM examination disclosed a 50% infiltration of mature lymphocytes; cytogenetic, molecular analysis and PBC were invariate. BM examination was repeated and the Ly infiltrate had spontaneously regressed to 20%. Considering the paucity of residual lymphoid cells, no further analysis was performed. Subsequent follow up showed normal BM with stable Ly infiltrate and persistent CCyR. Discussion. Data from the literature support the correlation between clinical efficacy of IM and increased BM Ly infiltration. Such correlation has also been found in our pts receiving IM and NIL. What has not yet been described is the massive transient polyclonal Ly infiltrate observed in our pts with both IM and NIL. This finding are of uncertain clinical relevance: PBCs were unaffected and molecular studies did not disclose presence of other hematological disorders. However, the known possibility of chronic lymphoproliferative disorders developing during CML needs to be kept in mind. An environmental factor - e.g. a subclinical viral infection - can not be excluded considering that both pts developed the same BM changes concomitantly. The role of TKIs is still unclear, in this case, and the clinical relevance of this event is uncertain. However, the similar mechanism of action of IM and NIL may suggest that a similar mechanism underlies the development of the BM massive Ly infiltrate observed in our pts.

Role of Tyrosine Kinase Inhibitors in the Treatment of Advanced Colorectal Cancer

Colorectal cancer (CRC) is a common health problem in Western countries. In advanced disease, either FOLFOX (oxaliplatin/5-fluorouracil [5-FU]/leucovorin [LV]) or FOLFIRI (irinotecan/LV/5-FU) are accepted first-line chemotherapy regimens, but median survival appears to plateau with a chemotherapy-only approach. The use of epidermal growth factor receptor (EGFR)- and vascular endothelial growth factor (VEGF)-targeting monoclonal antibodies has increased the median survival of patients with advanced CRC beyond 20 months. However, the precise role of cetuximab, panitumumab and bevacizumab in combination with different chemotherapeutic regimens is still being determined in first- and second-line settings. The activity and tolerance of the EGFR tyrosine kinase inhibitors (TKIs), gefitinib erlotinib, and EKB-569, alone or in combination with chemotherapy, have been explored in patients with metastatic CRC. Regarding VEGF receptor TKIs, 2 phase III clinical trials determined the role of vatalanib in combination with FOLFOX. Efficacy of the oral multitargeted TKIs sorafenib and sunitinib is under investigation. This article aims to review the role of TKIs in advanced CRC.

Allogeneic haematopoietic stem cell transplant in Philadelphia-positive acute lymphoblastic leukaemia

ALL in which the Philadelphia (Ph) chromosome is detected is one of the few diseases in which there is almost unequivocal agreement that a matched sibling allogeneic haematopoietic stem cell transplant in first CR is the most appropriate therapy for patients within certain age limits. Extension of allogeneic stem cell transplant to patients without matched sibling donors or to older individuals is increasingly possible due to unrelated donors, umbilical cord blood and reduced-intensity conditioning regimens. Here, we carefully review evidence supporting current practice and examine recent evidence relating to the use of newer allogeneic transplant technologies in Ph-pos ALL. We explore the burgeoning literature on the role of tyrosine kinase inhibitors in this disease and summarize their impact on the transplant practice.

Over-expression of c-kit in a primary leiomyosarcoma of the thyroid gland

Primary leiomyosarcoma of the thyroid gland is rare. In this paper, we report a case of high-grade leiomyosarcoma of the thyroid gland in a 43-year-old man. Lung metastasis was also noted in this patient. Despite of aggressive surgical treatment, the patient died of uncontrolled local recurrent disease 6 months after the initial operation. Immunohistochemical studies showed the tumor cells were positive for c-kit proto-oncogene product. Imatinib mesylate was used as a post-operative adjuvant treatment but the response was poor. The role of tyrosine kinase inhibitors on the treatment of thyroid leiomyosarcomas is still unclear because this is the first report of c-kit over-expression in such tumors. Nevertheless, our results show that c-kit over-expression might not be an indicator of good response to imatinib mesylate treatment in thyroid leiomyosarcomas.

Immunohistochemical and mutational analysis of PDGF and PDGFR in desmoid tumours: is there a role for tyrosine kinase inhibitors in c‐kit‐negative desmoid tumours?

To determine the platelet-derived growth factor (PDGF) alpha and beta status of desmoid tumours. Desmoid tumours are rare monoclonal neoplasms that appear to have no metastatic potential. Surgical resection and radiotherapy in the event of a positive surgical margin is the first-line treatment. Recurrences are frequent. Treatment results using non-steroidal anti-inflammatory agents, anti-oestrogen compounds and other agents such as Imatinib mesylate have been published. Therapy with Imatinib has been proposed as a therapeutic option, although in most reports desmoid tumours are reported to be c-kit-. We performed immunohistochemical analysis on 124 archived samples (85 patients) of desmoid tumours using antibodies to PDGFalpha, PDGFbeta, PDGFRalpha and PDGFRbeta. All desmoid tumours showed immunoreactivity with antibodies to PDGFalpha and PDGFRalpha, whereas with antibodies to PDGFbeta and PDGFRbeta no specific reaction could be detected. Mutational analysis of PDGFRalpha (exons 11, 12, 17 and 18) and PDGFRbeta (exon 12) on frozen material from 14 patients was performed, but no mutations leading to amino acid changes in the mature protein were identified. The absence of an activating mutation in a protooncogene does not exclude the efficacy of tyrosine kinase inhibitors through other possible mechanisms, and these might be a therapeutic option for patients with desmoid tumours in whom established local and systemic approaches fail to control the disease.

Urokinase plasminogen activator receptor (uPAR) expression is reduced by tyrosine kinase inhibitors

Previously we reported that tyrosine kinase inhibitors (TKI) produced a reduction in uPA expression in prostatic cancer cells, and that TKI-treated cells were less invasive compared to untreated cells. Nevertheless, no change in cell migration was observed when TKI-treated cells were supplied with external uPA, thus indicating more complex mechanisms leading to decreased cell invasion. uPAR expression was measured with an enzyme-linked immunosorbent assay (ELISA) in PC-3 and DU-145 prostate carcinoma cells treated with the two TKI genistein and AG-1478. uPAR mRNA levels were measured with real-time reverse transcriptase-polymerase chain reaction (RT-PCR). uPAR immunocytochemistry was used to examine the receptor distribution in cells grown on a reconstituted basal lamina. Immunocytochemistry showed an intense uPAR immunostaining in invading cells, particularly in the leading edge membrane. Treatment with genistein and AG-1478 led to a decreased expression of uPAR in DU-145, but not in PC-3. Furthermore, a reduction of uPAR mRNA was found in TKI-treated DU-145 cells, while PC-3 was not affected. Our results indicate a possible role of TKI as cancer suppressors by acting as a regulator of uPAR expression.

Tyrosine kinase inhibitors alter adhesivity of prostatic cancer cells to extracellular matrix components

Tyrosine kinase inhibitors (TKIs) are thought to have potential as a new generation of anti-cancer drugs. Since invasiveness, the main characteristic of malignant behaviour, is believed to depend on altered cell-matrix interactions, we investigated the effect of two potent TKIs, genistein and tyrphostin AG-1478, on the interaction of prostate cancer cells with extracellular matrix components. PC-3 and DU-145 cells were treated with various concentrations of genistein and tyrphostin AG-1478. Adhesion to extracellular matrix was assayed using fluorescence-labelled cells seeded on collagen type I, collagen type IV, fibronectin, laminin and vitronectin. The expression levels of integrin beta1, alpha2, alpha3 and alpha5 subunits were measured using flow cytometry of cells labelled with monoclonal murine antibodies. Genistein treatment reduced the ability of both cell lines to adhere to the matrix proteins tested. This effect was more pronounced for PC-3 cells than for DU-145 cells. Genistein treatment decreased the expression of beta1 integrins by 40% in PC-3 cells and 22% in DU-145. AG-1478 treatment slightly reduced the ability of DU-145 cells to adhere, but did not decrease PC-3 cell adhesion. Nevertheless, expression levels were reduced for most integrins tested, except the expression of alpha-5, for which no significant effect was measured. Our results point to a possible role of TKIs as suppressors of prostate carcinoma cell adhesion to extracellular matrix components, by acting as inhibitors of integrin expression.

The invasive behaviour of prostatic cancer cells is suppressed by inhibitors of tyrosine kinase

Proteolytic enzymes, and especially urokinase plasminogen activator (uPA), play an important role in tumour invasion and metastasis. Previously we demonstrated that the production of urokinase plasminogen activator (uPA) was decreased by several tyrosine kinase inhibitors (TKI) in two prostatic carcinoma cell lines. The effect of the two TKI genistein and tyrphostin AG-1478 was investigated in the prostate carcinoma cell lines PC-3 and DU-145. A reconstituted basal lamina (Matrigel) was used as a migration barrier. The production of matrix metalloproteinases (MMP) was also measured. Roles of plasminogen and uPA were examined. Cell invasion was increased by plasminogen, but this enhanced cell migration was counteracted by TKI treatment. The increased cell invasion induced by plasminogen was decreased by at least 60% in both cell lines when alpha-2 anti-plasmin was added to the assay. Cells in the absence of plasminogen were not affected by TKI. External uPA failed to regenerate the decreased cell invasion caused by TKI. The production of MMP was inhibited by both TKI. Our results indicate a possible role of TKI as inhibitors of cancer cell invasion by inhibiting uPA and MMP production.