Bcl-2high mantle cell lymphoma cells are sensitized to acadesine with ABT-199

Acadesine is a nucleoside analogue with known activity against B-cell malignancies. Herein, we showed that in mantle cell lymphoma (MCL) cells acadesine induced caspase-dependent apoptosis through turning on the mitochondrial apoptotic machinery. At the molecular level, the compound triggered the activation of the AMPK pathway, consequently modulating known downstream targets, such as mTOR and the cell motility-related vasodilator-stimulated phosphoprotein (VASP). VASP phosphorylation by acadesine was concomitant with a blockade of CXCL12-induced migration. The inhibition of the mTOR cascade by acadesine, committed MCL cells to enter in apoptosis by a translational downregulation of the antiapoptotic Mcl-1 protein. In contrast, Bcl-2 protein levels were unaffected by acadesine and MCL samples expressing high levels of Bcl-2 tended to have a reduced response to the drug. Targeting Bcl-2 with the selective BH3-mimetic agent ABT-199 sensitized Bcl-2 high MCL cells to acadesine. This effect was validated in vivo, where the combination of both agents displayed a more marked inhibition of tumor outgrowth than each drug alone. These findings support the notions that antiapoptotic proteins of the Bcl-2 family regulate MCL cell sensitivity to acadesine and that the combination of this agent with Bcl-2 inhibitors might be an interesting therapeutic option to treat MCL patients.     

CDKN1C-mediated growth inhibition by an EZH1/2 dual inhibitor overcomes resistance of mantle cell lymphoma to ibrutinib

Mantle cell lymphoma (MCL) is a rare subtype of non-Hodgkin's lymphoma, which is characterized by overexpression of cyclin D1. Although novel drugs, such as ibrutinib, show promising clinical outcomes, relapsed MCL often acquires drug resistance. Therefore, alternative approaches for refractory and relapsed MCL are needed. Here, we examined whether a novel inhibitor of enhancer of zeste homologs 1 and 2 (EZH1/2), OR-S1 (a close analog of the clinical-stage compound valemetostat), had an antitumor effect on MCL cells. In an ibrutinib-resistant MCL patient–derived xenograft (PDX) mouse model, OR-S1 treatment by oral administration significantly inhibited MCL tumor growth, whereas ibrutinib did not. In vitro growth assays showed that compared with an established EZH2-specific inhibitor GSK126, OR-S1 had a marked antitumor effect on MCL cell lines. Furthermore, comprehensive gene expression analysis was performed using OR-S1–sensitive or insensitive MCL cell lines and showed that OR-S1 treatment modulated B-cell activation, differentiation, and cell cycle. In addition, we identified Cyclin Dependent Kinase Inhibitor 1C (CDKN1C, also known as p57, KIP2), which contributes to cell cycle arrest, as a direct target of EZH1/2 and showed that its expression influenced MCL cell proliferation. These results suggest that EZH1/2 may be a potential novel target for the treatment of aggressive ibrutinib-resistant MCL via CDKN1C-mediated cell cycle arrest.     

BCL2 Amplicon Loss and Transcriptional Remodeling Drives ABT-199 Resistance in B Cell Lymphoma Models

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Targeting Bcl-2 family proteins in adult T-cell leukemia/lymphoma: in vitro and in vivo effects of the novel Bcl-2 family inhibitor ABT-737

Adult T-cell leukemia/lymphoma (ATLL) is a peripheral T-cell malignancy caused by human T-lymphotropic virus type I (HTLV-1). ABT-737, a small molecule inhibitor of Bcl-2, Bcl-X(L), and Bcl-w, significantly induced apoptosis in HTLV-1 infected T-cell lines as well as in fresh ATLL cells, and synergistically enhanced the cytotoxicity and apoptosis induced by conventional cytotoxic drugs. Moreover, ABT-737 significantly inhibited the in vivo tumor growth of an ATLL mouse model. These results suggest that the use of an agent targeting anti-apoptotic bcl-2 family proteins, either alone or in combination with other conventional drugs, represents a novel promising approach for ATLL.     

32例套细胞淋巴瘤中BTK蛋白的表达及临床意义

  目的  检测套细胞淋巴瘤(mantle cell lymphoma,MCL)患者病理组织中Bruton酪氨酸激酶(Bruton tyrosin kinase,BTK)表达水平并分析其与患者临床特征及预后的相关性。  方法  选取天津医科大学肿瘤医院2011年1月至2015年12月期间经病理检测诊断为MCL且随访资料完整的32例患者和10例良性淋巴结增生患者的病理组织。采用免疫组织化学法对32例MCL组织和10例良性淋巴结组织染色,并采用SPSS 17.0统计学软件对所收集的患者临床数据资料进行分析。  结果  BTK蛋白在MCL组织和正常的淋巴组织中均呈阳性表达,但在MCL病理组织中多为强阳性表达;BTK阳性表达与Ki-67和MIPI评分相关;应用Kaplan-Meier法对预后进行分析,显示BTK强阳性表达患者的无进展生存期(progression free survival,PFS)显著低于BTK弱表达患者(P=0.030),但总生存期(overall survival,OS)无统计学意义(P=0.073);PFS的单因素分析结果显示,年龄≥65岁,ECOG评分≥2分,骨髓受累,BTK强阳性表达,Ki-67＞30%,根据套细胞淋巴瘤国际预后指数(mantle cell lymphoma international prognostic index,MIPI)评分≥6分,皆是MCL患者的不良预后因素,但在Cox多因素分析结果中仅MIPI评分≥6分可作为MCL患者的独立不良预后因素。  结论  BTK在MCL患者中多为强阳性表达,且与Ki-67和MIPI评分呈正相关;BTK强阳性表达患者的PFS显著低于BTK弱表达患者,但由于随访时间短暂和样本量限制,BTK的强阳性表达尚不能作为PFS的一项独立不良预后因素。      

Harnessing Noxa demethylation to overcome Bortezomib resistance in mantle cell lymphoma

Bortezomib (BZM) is the first proteasome inhibitor approved for relapsed Mantle Cell Lymphoma (MCL) with durable responses seen in 30%–50% of patients. Given that a large proportion of patients will not respond, BZM resistance is a significant barrier to use this agent in MCL. We hypothesized that a subset of aberrantly methylated genes may be modulating BZM response in MCL patients. Genome-wide DNA methylation analysis using a NimbleGen array platform revealed a striking promoter hypomethylation in MCL patient samples following BZM treatment. Pathway analysis of differentially methylated genes identified molecular mechanisms of cancer as a top canonical pathway enriched among hypomethylated genes in BZM treated samples. Noxa, a pro-apoptotic Bcl-2 family member essential for the cytotoxicity of BZM, was significantly hypomethylated and induced following BZM treatment. Therapeutically, we could demethylate Noxa and induce anti-lymphoma activity using BZM and the DNA methytransferase inhibitor Decitabine (DAC) and their combination in vitro and in vivo in BZM resistant MCL cells. These findings suggest a role for dynamic Noxa methylation for the therapeutic benefit of BZM. Potent and synergistic cytotoxicity between BZM and DAC in vitro and in vivo supports a strategy for using epigenetic priming to overcome BZM resistance in relapsed MCL patients.     

Bruton tyrosine kinase is commonly overexpressed in mantle cell lymphoma and its attenuation by Ibrutinib induces apoptosis

Mantle cell lymphoma (MCL) is an aggressive B-cell malignancy that characteristically shows overexpression of cyclin-D1 due to an alteration in the t(11;14)(q13;q32) chromosomal region. Although there are some promising treatment modalities, great majority of patients with this disease remain incurable. The B-cell antigen receptor (BCR) signaling plays a crucial role in B-cell biology and lymphomagenesis. Bruton tyrosine kinase (BTK) has been identified as a key component of the BCR signaling pathway. Evidence suggests that the blockade of BTK activity by potent pharmacologic inhibitors attenuates BCR signaling and induces cell death. Notably, the expression levels and the role of BTK in MCL survival are still elusive. Here, we demonstrated a moderate to strong BTK expression in all MCL cases (n = 19) compared to benign lymphoid tissues. Treatment of MCL cell lines (Mino or Jeko-1) with a potent BTK pharmacologic inhibitor, Ibrutinib, decreased phospho-BTK-Tyr²²³ expression. Consistent with this observation, Ibrutinib inhibited the viability of both Mino and JeKo-1 cells in concentration- and time-dependent manners. Ibrutinib also induced a concentration-dependent apoptosis in both cell lines. Consistently, Ibrutinib treatment decreased the levels of anti-apoptotic Bcl-2, Bcl-xL, and Mcl-1 protein. These findings suggest that BTK signaling plays a critical role in MCL cell survival, and the targeting of BTK could represent a promising therapeutic modality for aggressive lymphoma     

Efficacy and safety of ibrutinib in Japanese patients with relapsed or refractory mantle cell lymphoma

In this multicenter, single‐arm, phase II study, the efficacy and safety of ibrutinib were examined in Japanese patients with relapsed or refractory mantle cell lymphoma (MCL). Patients (age ≥20 years) with relapsed or refractory MCL who had progressed after receiving at least one prior treatment regimen, were enrolled. Patients were treated with oral ibrutinib (560 mg once daily; 28‐day cycle) until disease progression (or relapse), unacceptable toxicity, or study end. The primary end‐point was overall response rate. Secondary end‐points included duration of response (DOR), time to response, progression‐free survival (PFS), overall survival, and safety. Of the 16 patients who received treatment, 5 patients discontinued the study (progressive disease, 4; sepsis, 1). Median duration of ibrutinib exposure was 6.5 months (range, 2.8–8.3 months). The overall response rate was 87.5% (90% confidence interval, 65.6–97.7; complete response = 2 [12.5%]; partial response = 12 [75.0%]). Median time to response for all responders (n = 14) was 1.8 months (range, 0.7–5.3 months). The median DOR and PFS were not estimable due to censoring (range: DOR, 1.1–6.4+ months; PFS, 2.8–8.0+ months). Overall survival data were immature due to the limited observation period. A total of 8/16 patients (50%) had at least one grade 3 adverse event (AE), and 5 (31.3%) patients reported serious AEs. The most commonly reported AEs were diarrhea and stomatitis (37.5% each), platelet count decrease (31.3%), and anemia (25%). Overall, orally administered single agent ibrutinib was efficacious with an acceptable safety profile in Japanese patients with relapsed or refractory MCL. Clinical trial registration NCT02169180 (ClinicalTrials.gov).     

A synthetic peptide targeting the BH4 domain of Bcl-2 induces apoptosis in multiple myeloma and follicular lymphoma cells alone or in combination with agents targeting the BH3-binding pocket of Bcl-2

Bcl-2 inhibits apoptosis by two distinct mechanisms but only one is targeted to treat Bcl-2-positive malignancies. In this mechanism, the BH1-3 domains of Bcl-2 form a hydrophobic pocket, binding and inhibiting pro-apoptotic proteins, including Bim. In the other mechanism, the BH4 domain mediates interaction of Bcl-2 with inositol 1,4, 5-trisphosphate receptors (IP₃Rs), inhibiting pro-apoptotic Ca²⁺ signals. The current anti-Bcl-2 agents, ABT-263 (Navitoclax) and ABT-199 (Venetoclax), induce apoptosis by displacing pro-apoptotic proteins from the hydrophobic pocket, but do not inhibit Bcl-2-IP₃R interaction. Therefore, to target this interaction we developed BIRD-2 (Bcl-2 IP₃ Receptor Disruptor-2), a decoy peptide that binds to the BH4 domain, blocking Bcl-2-IP₃R interaction and thus inducing Ca²⁺-mediated apoptosis in chronic lymphocytic leukemia, multiple myeloma, and follicular lymphoma cells, including cells resistant to ABT-263, ABT-199, or the Bruton’s tyrosine kinase inhibitor Ibrutinib. Moreover, combining BIRD-2 with ABT-263 or ABT-199 enhances apoptosis induction compared to single agent treatment. Overall, these findings provide strong rationale for developing novel therapeutic agents that mimic the action of BIRD-2 in targeting the BH4 domain of Bcl-2 and disrupting Bcl-2-IP₃R interaction.     

靶向CD19 抗原的CAR-NK-92MI和CAR-CD19-T 细胞对套细胞淋巴瘤的体外杀伤

[摘要] 目的：探讨靶向CD19 抗原的CAR-NK-92MI和CAR-CD19-T 细胞对套细胞淋巴瘤（mantle cell lymphoma,MCL）的体外杀伤作用。方法：利用近年来在B细胞急性淋巴细胞白血病（B-lineage acute lymphoblastic leukemia, B-ALL）临床试验中获得的成功嵌合抗原受体基因修饰的T（CAR-T 细胞）技术,针对MCL高表达CD19 抗原的情况,分别构建了靶向CD19 抗原的CAR-CD19-T和CAR-NK-92MI细胞,运用LDH释放法检测两者对MCL细胞的体外杀伤作用,另外通过流式细胞术对其杀伤作用进行了验证。结果：相对于对照,无论是CAR-NK-92MI细胞还是CAR-CD19-T 细胞,都对MCL细胞具有极高的杀伤能力（均P <0.01）,都对K562-CD19 细胞具有非常高的毒性（均P <0.01）,而对K562 细胞基本不起作用。CAR-NK-92MI细胞组MCL细胞的死亡率比对照组高30%~40%,CAR-CD19-T 细胞组MCL细胞的死亡率比对照组高40%~50%。结论：CAR-NK-92MI和CARCD19-T细胞在体外对MCL细胞具有强的特异性杀伤作用。     

套细胞淋巴瘤诊疗进展

套细胞淋巴瘤（mant lecell lymphoma ,MCL ）是一种少见的B 细胞非霍奇金淋巴瘤（non-Hodgkin's lymphoma,NHL ）类型,兼具有惰性淋巴瘤和侵袭性淋巴瘤的临床病理特点。目前MCL 的临床治疗仍然是以全身化疗为主,含有阿糖胞苷的强诱导化疗,随后行自体造血干细胞移植（autologous stem cell transplantation,Auto-HSCT ）巩固,可以显著延长生存期,但MCL 仍然属于不可治愈的淋巴瘤类型。近年来,随着对MCL 发病机制的深入研究,更多的新药如Btk抑制剂、PI 3K 抑制剂、免疫调节剂等在MCL 中得到应用。初治、复发难治MCL 都具有更多的治疗选择,如何将新药和现有的化疗更为有机的结合,更好的改善MCL 患者的生存期是未来研究的重点。     

套细胞淋巴瘤的诊治进展

套细胞淋巴瘤(MCL)是一组以t(11;14)和细胞周期蛋白D1阳性(cyclinD1 )过度表达为特征的侵袭性非霍奇金淋巴瘤(NHL),约占NHL发病的5%~8%,预后差,近期通过比较基因组杂交(CGH),基因芯片和蛋白质组分析等研究MCL取得令人关注的进展。化疗 利妥昔治疗使治疗有效率较前明显提高,异体或自体干细胞移植亦使MCL的预后大为改善,新的治疗方案如蛋白酶体抑制剂硼替佐米(borte-zomib),反应停 利妥昔,细胞周期依赖激酶抑制剂(flavopridol)及哺乳动物雷帕霉素靶蛋白(mTOR)抑制剂CCI-779等的疗效令人鼓舞。     

An overlapping case of in situ mantle cell neoplasia and leukemic non-nodal mantle cell lymphoma

In situ mantle cell neoplasia (isMCN) and leukemic non-nodal mantle cell lymphoma (nnMCL) are classified as an indolent subtype of mantle cell lymphoma (MCL). The tumor cells of isMCN are restricted to the inner layer of the lymphoid tissue mantle zone, exhibiting an in situ pattern histologically. On the other hand, nnMCL is distributed in the peripheral blood, bone marrow and sometimes the spleen, but lymphadenopathy or systemic organ involvement is rare. We report a case of isMCN in a submandibular lymph node resected from a 65-year-old Japanese male. The tumor cells were positive for cyclin D1 (CCND1) and SOX11 expression, and were restricted to the mantle zone area of the lymph node. However, tumor cells were also detected in the stomach mucosa, bone marrow tissue and peripheral blood, suggesting nnMCL. isMCN and nnMCL may have a partly overlapping disease spectrum, although the correlation between these two subtypes has not been well described. This present case demonstrated characteristics overlapping between isMCN and nnMCL.     

Serum beta‐2 microglobulin as a prognostic biomarker in patients with mantle cell lymphoma

Although serum beta‐2 microglobulin (B2M) has been suggested as a prognostic factor for mantle cell lymphoma (MCL), additional data are necessary to confirm its role. Between November 2005 and July 2014, a total of 52 patients with MCL were identified from the database of Asan Medical Center, Seoul, Korea. Pretreatment serum B2M information was available in 50 patients (96%). Overall survival (OS) was compared according to the serum B2M level with a cut‐off value of 2.5 mg/L. The median MCL international prognostic index (MIPI) score was 5.84 (range 4.72–7.80), and the median biologic MIPI (MIPI‐b) score was 6.27 (4.93–8.47). Pretreatment serum B2M was elevated in 30 patients (60%) and was significantly related to advanced stage (p = 0.02) and high MIPI (p = 0.03) and MIPI‐b (p = 0.03) scores. With median follow‐up duration of 29.8 months (range 0.8–87.0 months), the median OS was 56.2 months [95% confidence interval (CI) 36.6‐75.9 months] in all patients, and serum B2M was significantly associated with OS (p = 0.001). In multivariate analyses adjusted for MIPI or MIPI‐b scores and rituximab, elevated serum B2M was significantly associated with poor OS (when adjusting MIPI, hazard ratio = 26.4, 95% CI 2.9–241.3, p = 0.004; when adjusting MIPI‐b, hazard ratio = 20.1, 95% CI 2.4–170.1, p = 0.006). Thus, pretreatment serum B2M may be an independent and significant prognostic factor in patients with MCL. Copyright © 2015 John Wiley & Sons, Ltd.     

Bcl-2和Bcl-6与淋巴瘤相关性的研究进展

在大多数类型淋巴瘤中,凋亡指数显著减少、增生指数显著增高、细胞凋亡减少是淋巴瘤发生发展的主要原因。细胞凋亡受凋亡相关基因的调控。Bcl-2是一种原癌基因,它具有抑制细胞淍亡的作用。91%的滤泡性淋巴瘤(Fls)中可发现染色体t(14;18)(q32;q21)-IgH/Bcl-2。Bcl-2可作为诊断Fls和染色体表型为t(14;18)的淋巴瘤的重要依据。细胞凋亡受阻还是导致肿瘤细胞对细胞毒药物耐药的原因之一。Bcl-2基因编码的p26-Bcl-2过度表达引起肿瘤细胞抵抗凋亡,从而导致肿瘤细胞对化疗耐药。Bcl-6是生发中心结构来源的淋巴瘤尤其是弥漫大B细胞淋巴瘤(defuselargeBcelllymphoma,DLBCL)的特异性标志,它的功能是阻止细胞分化和淍亡,促进细胞的发育增殖,根据Bcl-6在FLs中特异性表达,有助于鉴别FLs与其他淋巴细胞异常增生性疾病。Bcl-2和Bcl-6与淋巴瘤的预后是否相关,目前仍存在有争议。Bcl-6和Bcl-2有密切关系,Bcl-2引起肿瘤对治疗耐药,可能是多基因作用的复杂过程,Bcl-2和Bcl-6基因成为淋巴瘤治疗的新靶点。已有研究设计针对Bcl-2的拮抗剂及针对Bcl-6的抑制性复合物特异肽段(BPI),通过调控Bcl-2和Bcl-6的表达以达到治疗淋巴瘤的目的。     

Inhibition of Lyn is a promising treatment for mantle cell lymphoma with bortezomib resistance

Although proteasome inhibition with bortezomib (BTZ) is a validated treatment for relapsed or refractory mantle cell lymphoma (MCL), many patients show resistance to BTZ. However, the molecular mechanism of BTZ resistance in MCL has not been elucidated. In the present study, we investigated BTZ-resistant MCL cells in vitro and in vivo. We demonstrate that BTZ-resistant MCL cells showed highly increased expression of the B-cell receptor (BCR) components CD79A and CD19. Activation of the BCR signaling pathway enhanced the activity of Src family kinases (SFKs), especially Lyn, and downstream kinases PI3K/AKT/mTOR in BTZ-resistant MCL cells. Depletion of CD79A and Lyn significantly reduced several kinase activities involved in PI3K signaling, leading to inhibition of proliferation. In addition, the SFKs inhibitor dasatinib inhibited the proliferation of BTZ-resistant cells, preventing the binding of CD19 with Lyn and PI3K p85. We also verified our findings with the mouse xenograft tumor model. Dasatinib treatment significantly decreased tumor size in the mouse bearing BTZ-resistant MCL cells, but not in the mouse bearing BTZ-sensitive MCL cells. Collectively, our data show that overexpression of the BCR and its activated signaling confers BTZ resistance in MCL cells. Thus, targeting BCR signaling with dasatinib could be a novel therapeutic approach for patients with MCL that has relapsed or is refractory to treatment with BTZ.     

Phase 2 trial of rituximab and bortezomib in patients with relapsed or refractory mantle cell and follicular lymphoma

BACKGROUND:

In vitro studies in mantle cell lymphoma (MCL) cell lines and patient‐derived cells have demonstrated synergistic apoptosis with combined rituximab and bortezomib (R‐bortezomib) compared with single‐agent bortezomib. Therefore, the authors of this report evaluated R‐bortezomib in a preclinical model and in a phase 2 clinical trial.

METHODS:

A Hu‐MCL‐severe combined immunodeficiency (SCID) model engrafted with the Jeko cell line was treated with R‐bortezomib, bortezomib, or rituximab. Twenty‐five patients with relapsed follicular lymphoma (n = 11) and MCL (n = 14) received 375 mg/m² rituximab on Days 1 and 8 and 1.3 to 1.5 mg/m² bortezomib on Days 1, 4, 8, and 11 every 21 days for a median of 3 cycles (range, 1‐5 cycles).

RESULTS:

R‐bortezomib resulted in a statistically significant improvement in overall survival in Hu‐MCL‐SCID mice. In the clinical trial, the overall response rate was 40% in all 25 patients, 55% in patients with follicular lymphoma, and 29% in patients with MCL. The estimated 2‐year progression‐free survival (PFS) rate was 24% (95% confidence interval [CI], 10%‐53%) in all patients and 60% (95% CI, 20%‐85%) in responding patients. Thirteen patients (52%) developed grade 3 neurotoxicity, which consisted of constipation/ileus, sensory or motor neuropathy, or orthostatic hypotension. Patients who were heterozygous for the CD32a (Fcγ receptor IIa) 131 histidine (H) to arginine (R) polymorphism had a significantly decreased PFS (P = .009) after R‐bortezomib compared with HH and RR homozygotes.

CONCLUSIONS:

R‐bortezomib had significant activity in patients with relapsed or refractory follicular lymphoma and MCL, although an unexpectedly high incidence of grade 3 neurologic toxicity was a potential limiting factor with this combination. Cancer 2011. © 2010 American Cancer Society.     

Src tyrosine kinase augments taxotere-induced apoptosis through enhanced expression and phosphorylation of Bcl-2

Activation of Src, which has an intrinsic protein tyrosine kinase activity, has been demonstrated in many human tumours, such as colorectal and breast cancers, and is closely associated with the pathogenesis and metastatic potential of these cancers. In this study, we have examined the effect of activated Src on the sensitivity to taxotere, an anticancer drug targeting microtubules, using v-src-transfected HAG-1 human gall bladder epithelial cells. As compared with parental HAG-1 cell line, v-src-transfected HAG/src3-1 cells became 5.9 and 7.0-fold sensitive to taxotere for 2 and 24-h exposure, respectively. By contrast, HAG-1 cells transfected with activated Ras, which acts downstream of Src, acquired approximately 2.5- approximately 4.8-fold taxotere resistance. The taxotere sensitivity in HAG/src3-1 cells was reversed, if not completely, by herbimycin A, a specific inhibitor of Src family protein tyrosine kinase, indicating that Src protein tyrosine kinase augments sensitivity to taxotere. Treatment of HAG/src3-1 cells with taxotere resulted in phosphorylation of Bcl-2 and subsequent induction of apoptotic cell death, whereas neither Bcl-2 phosphorylation nor apoptosis occurred in parental or c-H-ras-transfected HAG-1 cells. Interestingly, the Bcl-2 protein is overexpressed in v-src-transfected cell line, compared to those in parental or Ras-transfected cell line. Treatment of HAG/src3-1 cells with herbimycin A significantly reduced the expression and phosphorylation of Bcl-2, and abrogated taxotere-induced apoptosis, suggesting a potential role for Src protein tyrosine kinase in the taxotere-induced apoptotic events. H-7, a protein kinase C inhibitor and wortmannin, a phosphatidylinositol-3 kinase (PI-3 kinase) inhibitor, neither altered taxotere sensitivity nor inhibited taxotere-induced apoptosis in these cells. These data indicate that the ability of activated Src to increase taxotere sensitivity would be mediated by apoptotic events occurring through Src to downstream signal transduction pathways toward Bcl-2 phosphorylation, but not by activated Ras, PI-3 kinase or protein kinase C.