Classification of Receptors

1. G coupled receptors epinephrine, serotonine, glucagon

2. Ion channel receptors acetylcholine receptor

3. Tyrosine kinase-linked receptors -receptor family

4. Receptors with intrinsic enzymatic activity the receptor has intrinsic catalytic activity receptor tyrosine kinases Receptors with intrinsic enzymatic activity

1. RTKs: EGFR, Insulin, VEGFR

2. serin-threonine kinases: TGF–ß superfamily

3. receptor tyrosine phosphatases: CD45, expressed on B and T lymphocytes

4. Guanylatcyclase: GTP  cGMP The ANP Receptor Atrial natriuretic peptide

. atrium of heart . acts as vasodilater and reduces water, sodium and adipose loads . upon rising blood pressure (high V) – decreases vascular resistance . via a cGMP dependent kinase

Receptors with intrinsic enzymatic activity

1. RTKs: EGFR, Insulin, VEGFR

2. serin-threonine kinases: TGF –ß superfamily

3. receptor tyrosine phosphatases: CD45, expressed on B and T lymphocytes

4. Guanylatcyclase: GTP -> cGMP CD45 (PTPRC – protein tyrosine phospahatse receptor type C) exists in various isoforms mainly on T and B cells

cell type specific glycosylation B220 specific

D1: active phosphatase D2: inactive highly conserved required for correct folding Lymphocyte- specific protein tyrosine kinase Constitutive activation of CD45 leads to lymphoproliferation and autoimmunity in mice

Cell 2000, 103: 1059 Inactivation of CD45 leads to Severe combined Immuno Deficiency (SCID)

The hematopoietic-specific transmembrane protein tyrosine phosphatase CD45 functions to regulate Src kinases required for T- and B-cell receptor signal transduction. So far, there have been no reports to our knowledge of a human deficiency in a tyrosine-specific phosphatase. Here, we identified a male patient with a deficiency in CD45 due to a large deletion at one and a point mutation at the other. The point mutation resulted in the alteration of intervening sequence 13 donor splice site. The patient presented at 2 months of age with severe combined immunodeficiency disease. The population of peripheral blood T lymphocytes was greatly diminished and unresponsive to mitogen stimulation. Despite normal B- lymphocyte numbers, serum immunoglobulin levels decreased with age. Thus, CD45 deficiency in humans results in T- and B-lymphocyte dysfunction.

Nature Med 2000, 6:343 Implications for Medicine

Inhibitors of CD45 have implications in transplant medicine – prevention of kidney rejection in mouse models has been proven microglial activation by ß-amyloid peptide can be prevented – Alzheimer’s disease the various specific activation forms may allow for a relatively specific inhibition dependent on the indication 3. Receptor tyrosine kinases (RTKs):

NGF, PDGF, FGF, EGF, Insulin regulate cell survival, proliferation, differentiation often deregulated/mutated in cancer constitutive active RTKs

RTKs-Ras as important signalling cascade leading to cancer

RTKs – 7 subfamilies

EGF – epidermal GF; NGF – nerve GF; PDGF – platelet-derived GF FGF – fibroblast GF; VEGF – vascular endothelias GF; Eph - ephrin ligand binds a dimer – dimerization of the receptor – activation of its kinase activity – tyrosine phosphorylation of its own cytosolic domaine

RTKs are frequent targets in human cancer Signalling Pathways in Cancer downstream of RTK The IGF-receptor – a key molecule in cancer Growth factor receptors as therapeutic targets: strategies to inhibit the insulin-like growth factor I receptor

Oncogene (2003) 22, 6589–6597 Sorafenib

• Inhibits Serine/Threonine and Receptor-Tyrosine kinases

• = multi kinase inhibitor • Inhibits Ras-signalling by inhibiting RAF-kinase (=serine/threonine kinase) – reduced tumor cell proliferation

• Inhibits VEGF receptor – blocks angiogenesis – no O2/nutrient supply – no proliferation

• Inhibits PDGFR (Platelet-derived growth factor)

• Inhibits c-KIT (stem-cell growth factor) ErbB Protein Tyrosine Kinase Subfamily

Heregulin, EGF, TNFα, NDF.. ΗΒ−ΕΓΦ

dual cysteine cluster

tyrosine kinase domain

EGFR HER4 HER2 HER3 ErbB1 ErbB4 ErbB2 ErbB3 neu EGFR/ErbB2 Heterodimer

NH2

EGFR/ErbB1 ErbB2/HER2 membrane

Src P Tyr877 Ras P Tyr1023 GTP Raf1 P Cbl Tyr1112 Sos GDP P Tyr1139 Grb2 MEK P Tyr1196 P COOH Tyr1221 P Shc Tyr1248 MAPK Chk

Sustained MAPK activation:

G0/ G1 progression, differentiation Herceptin efficently inhibits Her2 signalling in breast cancer The EGFR – a key element in receptor cross-talk: signal transactivation GPCR activates metalloproteinases The ADAMS

VEGF

•VEGF is a homodimeric glycoprotein, binding to VEGF-Receptors on vaskular endothelial cells •Molecular weight: 45,000Da

•VEGF plays a key role for the formation of blood vessels (Angiogenesis)

VEGF = vascular endothelial growth factor Ferrara N, et al. Endocr Rev 1997;18:4–25 Die VEGF Familie und ihre Rezeptoren

VEGF-A VEGF-A VEGF-B VEGF-C PlGF VEGF-D VEGFR-1 VEGFR-2 VEGFR-3

P– – P P– – P – P P– P– – P P– – P P– – P

Migration, proliferation, permeability, DNA synthesis, survival

Angiogenesis Lymphangiogenesis

Adapted from Ferrara N. Nat Med 2003;9:669–76 Angiogenesis contributes to Tumorigenesis, tumor growth and Metastasis

Prämalignes Maligner Tumor- Gefäß- ruhende Offene Stadium Tumor Wachstum invasion Mikrometastase Metastasierung

(Avaskulärer (Angiogenic (Vaskularisierter (Tumorzell- (Streuung in (Zweite Tumor) switch) Tumor) freisetzung) entfernte Organe) Angiogenese)

Schritte, bei denen Angiogenese eine Rolle bei der Tumorprogression spielt

Modifiziert nach Poon RT-P, et al. J Clin Oncol 2001;19:1207–25 The “angiogene switch” and Tumordevelopment

Kleiner Tumor (1–2mm) größerer Tumor • avaskulär • vaskularisiert • ruhend • Metastasierungspotential

Angiogenic switch führt zur Überexpression von pro-angiogenen Faktoren, wie zum Beispiel VEGF

Modifiziert nach Bergers G, et al. Nat Rev Cancer 2002;3:401–10 VEGF overexpression correlates with a bad prognosis

Study Cancer n Tumours (%) Prognostic value

Gasparini, 1997 Breast 260 95 Relapse-free survival, overall survival Toi, 1995 152 55 Increased vascular density and relapse- free survival Imoto, 1998 Lung NSCLC 91 53 Overall survival O’Byrne, 2000 NSCLC 223 47 Tumour size, vascular density Volm, 1997 SCLC 109 59 Overall survival Maeda, 2000 GI CRC 100 37 Overall prognosis Amaya, 1997 CRC 136 43 Vascular density Ishigami, 1998 CRC 60 100 Clinical stage, metastasis Ogata, 2003 Oesophagus 92 24 Overall survival Shih, 2000 Oesophagus 117 31 Overall survival Paley, 1997 Ovarian 68 43 Disease-free survival Yamamoto, 1997 70 97 Overall survival Jacobsen, 2004 Renal 229 100 Tumour size and stage, survival Aguayo, 2002 Haem. AML 58 100 Survival Verstovsek, 2002 Haem. CML 184 100 Survival

Findings support a mechanism where VEGF inhibits pericyte function and blood vessel maturation through the induction of a VEGF-R2/PDGF-Rb complex, and may in part, explain the molecular basis of anti-VEGF therapy in cancer patients Antiangiogenic therapy – a double edged sword