Genetic dissection of apoptosis and cell cycle control in response of colorectal cancer treated with preoperative radiochemotherapy

BACKGROUND: In previous analyses we identified therapy-induced upregulation of the CDK inhibitor p21(CIP/WAF-1 )and consequently decreased tumor cell proliferation or loss of Bax as adverse factors for survival in rectal cancer treated with radiochemotherapy. Here, we address the individual role of p53 and its transcriptional targets, p21(CIP/WAF-1 )and Bax, on apoptosis induced by individual components of multimodal anticancer therapy, i.e. 5-fluorouracil (5-FU), ionising γ-radiation (IR) and heat shock/hyperthermia. METHODS: We analysed tumor samples 66 patients with rectal carcinoma treated by a neoadjuvant approach with radiochemotherapy ± heat shock/hyperthermia for the expression and mutation of p53 and the expression of p21(CIP/WAF-1 )and Bax. These data were correlated with the tumor response. The functional relevance of p53, p21(CIP/WAF-1 )and Bax was investigated in isogeneic HCT116 cell mutants treated with 5-FU, IR and heat shock. RESULTS: Rectal carcinoma patients who received an optimal heat shock treatment showed a response that correlated well with Bax expression (p = 0.018). Local tumor response in the whole cohort was linked to expression of p21(CIP/WAF-1 )(p < 0.05), but not p53 expression or mutation. This dichotomy of p53 pathway components regulating response to therapy was confirmed in vitro. In isogeneic HCT116 cell mutants, loss of Bax but not p53 or p21(CIP/WAF-1 )resulted in resistance against heat shock. In contrast, loss of p21(CIP/WAF-1 )or, to a lesser extent, p53 sensitized predominantly for 5-FU and IR. CONCLUSION: These data establish a different impact of p53 pathway components on treatment responses. While chemotherapy and IR depend primarily on cell cycle control and p21, heat shock depends primarily on Bax. In contrast, p53 status poorly correlates with response. These analyses therefore provide a rational approach for dissecting the mode of action of single treatment modalities that may be employed to circumvent clinically relevant resistance mechanisms in rectal cancer

Successful long-term monotherapy with rituximab in a patient with chronic lymphocytic leukemia of the B-cell-lineage: a case report

<p>Abstract</p> <p>Introduction</p> <p>Treatment of chronic lymphocytic leukemia of the B-cell-lineage is strongly based upon clinical staging because of the heterogeneous clinical course of this disease.</p> <p>Case presentation</p> <p>We describe a 62-year-old patient with newly diagnosed chronic lymphocytic leukemia of the B-cell-lineage who did not respond to several chemotherapy regimens including chlorambucil, fludarabine and cyclophosphamide, developing a marked neutropenia and thrombocytopenia with life-threatening infections. Further chemotherapy appeared not feasible because of bone marrow toxicity. The patient was treated with 600 mg/m²rituximab weekly followed by eight courses of biweekly therapy and then by long-term maintenance therapy, achieving almost complete remission of the symptoms and disease control.</p> <p>Conclusion</p> <p>After resistance to standard chemotherapy with chlorambucil and fludarabine, a patient with chronic lymphocytic leukemia of the B-cell-lineage was successfully treated with rituximab.</p

The Clinical Relevance of Effectors in the p53 Tumor Suppressor Pathway.

Titel und Inhaltsverzeichnis 1 ZUSAMMENFASSUNG 5 2 EINLEITUNG 6 3 ZELLZYKLUSREGULATION 8 3.1 3.2 ZELLZYKLUSREGULATION DURCH DEN RB-SIGNALWEG CYCLINE UND DEREN INHIBITOREN 8 10 4 APOPTOSEREGULATION 11 4.1 4.2 4.3 ZELLULÄRE REAKTION AUF DNA-SCHÄDIGUNG VERNETZUNG DER SIGNALWEGE VON ZELLZYKLUS UND APOPTOSE MITOCHONDRIALER APOPTOSE-SIGNALWEG 11 12 16 5 SIGNALWEGDEFEKTE IN MALIGNEN ERKRANKUNGEN 18 5.1 5.2 5.3 5.4 5.5 P53/BAX P53/APAF-1 ATM/P53 P53-APOPTOSE UND -ZELLZYKLUSEFFEKTOREN NBK/BIK 19 22 23 25 26 6 UNTERSCHIEDLICHE ZYTOTOXISCHE THERAPIEN NUTZEN DIFFERENTE SIGNALWEGSKOMPONENTEN 28 7 FAZIT 37 8 LITERATUR 37 11 ANHANG 47Dysregulation von Zelltod und Zellproliferation ist an der Entstehung und der Progression maligner Erkrankungen beteiligt. Auch basieren fast alle nicht- chirurgischen Tumortherapien auf dem Prinzip, Zellzyklus-Arrest oder Zelltod in Tumorzellen auszulösen. Therapieresistenz maligner Tumoren resultiert somit in direkter Konsequenz aus Störungen zentraler Schlüsselgene der Zellzyklus- und Apoptose-Regulation. Die Analyse solcher genetischer Veränderungen ermöglicht die Identifikation von Risikopatienten mit ungenügendem Ansprechen auf Chemotherapeutika oder Bestrahlung, sowie schlechter Prognose der Tumorerkrankung. Eine zentrale Rolle für die Regulation von Zelltod und Zellproliferation spielt das p53-Gen. Das p53-Gen hat verschiedene downstream- Effektoren, die sowohl Zelltod (z.B. Bax, Noxa) als auch Zellzyklusarrest (z.B. p21WAF1/CIP1) und DNA-Reparatur regulieren. Das genaue Zusammenspiel dieser verschiedenen p53-Effektoren ist komplex. Es ist u.a. von Zelltyp, Stärke und Art des zytotoxischen Signals abhängig. Wir haben die klinische Relevanz einiger Komponenten des p53-Signalweges in verschiedenen Tumorentitäten untersucht: Bei kolorektalen Adenokarzinomen ist der p53/Bax Signalweg relevant für den natürlichen Verlauf der Erkrankung, wird aber im Fall einer Radiochemotherapie in seiner prognostischen Bedeutung abgelöst durch die p53/p21WAF1/CIP1 vermittelte Zellzyklusregulation. Lediglich die Wirkung von Hyperthermie ist vom p53/Bax-Signalweg abhängig. In Magenkarzinomen ist die Koinzidenz von Mutationen im p53-Gen und im Bax-Gen fatal für die Prognose. Hingegen ist für das Plattenepithelkarzinom des Ösophagus die Retinoblastom-Genprodukt (Rb) Regulation am G1-Restriktionspunkt des Zellzyklus neben dem p53/Bax-Signalweg prognostisch relevant. Bei Patienten mit chronisch lymphatischer Leukämie wurde die Bedeutung des p53-Bax-APAF-1 mitochondrialen Apoptosesignalwegs sowohl für die Prognose als auch für die Therapieresistenz gegen verschieden Zytostatika und ionisierender Bestrahlung untersucht. Dies ist einerseits die Basis für ein molekulares Verständnis der pharmakogenetischen Grundlagen des Ansprechens auf Tumortherapien und andererseits für den gezielteren klinischen Einsatz von Tumortherapeutika. Insbesondere zeigen diese Daten zur Pharmakogenomik maligner Tumoren, dass Defekte zentraler regulatorischer Gene, z.B. von Komponenten des p53 Signalwegs, nicht immer in globaler Therapieresistenz resultieren, sondern durch den Einsatz adäquater Therapiemodalitäten überwunden werden können.Dysregulation of cell death and cell proliferation is involved in the development and progression of malignant diseases. In addition, the major part of non-surgical anti-cancer therapies relies on the induction of cell death or cell cycle arrest. Therefore, disruptions of the cell-cycle- and apoptosis pathways result in therapy resistance of malignant diseases. The analysis of the key regulator components of these pathways therefore offers the possibility to identify patients at risk of a poor response to therapy with antineoplastic drugs or ionizing irradiation. Dysruption of central apoptotic pathways also confers a poor prognosis. The p53 tumor suppressor gene has a central regulatory role for apoptosis and cell proliferation. Downstream effectors of p53 control cell death (i.e. bax, noxa), cell cycle arrest (i.e. p21WAF1/CIP1) and DNA repair. The interaction of these p53 regulated pathways is complex. It is dependant on factors like cell type, nature and strength of the cytotoxic signal. We investigated the clinical relevance of such key effectors in the p53 pathway in various malignant diseases. For adenocarcinoma of the colon and rectum, the p53/bax pathway is relevant for the natural course of disease after surgical intervention. In the case of treatment with radiochemotherapy, its prognostic relevance is replaced by the p53/ p21WAF1/CIP1 -controlled cell cycle regulation. In contrast, the anti-tumor effect of heat shock/hyperthermia is dependent on the p53/bax status of the tumors. For gastric cancer, the combination of mutational inactivation of p53 and bax is fatal for the prognosis. For the squamous cell carcinoma of the esophagus, the regulation of the G1-cell cylce checkpoint by the retinoblastoma gene product (Rb) is - besides the p53/bax-pathway - of prognostic relevance for patient survival. For patients with chronic lymphocytic leukemia, the importance of the p53-bax-apaf-1 mitochondrial apoptosome with respect to resistance towards treatment with various cytotoxic drugs as well as patient survival was investigated. These data present a molecular basis for the pharmacogenetic approach of individualisation of tumor therapies. In future, these data might promote an individualized allocation of antitumor therapeutics. In particular, the presented pharmacogenomic data show that defects in central regulatory genes (like the p53 gene) do not lead to a global therapy resistance but might be overridden by the combination of adequate therapeutic modalities