Terapia endocrina dei tumori.

Presentazione sul tema: "Terapia endocrina dei tumori."— Transcript della presentazione:

1 Terapia endocrina dei tumori

2 STRUTTURA E BIOSINTESI DEGLI
ORMONI STEROIDEI

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4 PRODUZIONE E AZIONE DEGLI ANDROGENI
In the hypothalamus, androgens bind to the androgen receptor (AR) to stimulate production of luteinizing hormone (LH)-releasing hormone (LHRH). LHRH travels to the pituitary where it interacts with LHRH receptors (LHRH-Rs). This interaction stimulates the release of LH. LH that is released by the pituitary binds to LH receptors (LH-R) in the testes, inducing production of testosterone, which is synthesized from cholesterol. Testosterone enters prostate cells, where it is converted to dihydrotestosterone (DHT) by the enzyme 5 -reductase. DHT binds tightly to AR, enters the cytoplasm, and the complex translocates to the nucleus where it activates transcription of genes that regulate cell growth and survival. Increased testosterone levels can also decrease LHRH and LH production through negative-feedback loops, thereby maintaining serum testosterone at physiological levels. The adrenal gland can also produce androgens.

5 Androgen action.   Testosterone circulates in the blood bound to albumin (not shown) and sex-hormone-binding globulin (SHBG), and exchanges with free testosterone. Free testosterone enters prostate cells and is converted to dihydrotestosterone (DHT) by the enzyme 5 -reductase. Binding of DHT to the androgen receptor (AR) induces dissociation from heat-shock proteins (HSPs) and receptor phosphorylation. The AR dimerizes and can bind to androgen-response elements in the promoter regions of target genes6. Co-activators (such as ARA70) and corepressors (not shown) also bind the AR complex, facilitating or preventing, respectively, its interaction with the general transcription apparatus (GTA). Activation (or repression) of target genes leads to biological responses including growth, survival and the production of prostate-specific antigen (PSA). Potential transcription-independent actions of androgens are not shown.

6 GOSERELINA BUSERELINA
LEUPROLIDE GOSERELINA BUSERELINA NAFARELINA CETRORELIX ABARELIX ORGALUTRAN Hypothalamic production of luteinizing hormone (LH)-releasing hormone (LHRH) induces production of LH by the pituitary. LHRH production is inhibited when ligands bind to the progesterone receptor, the oestrogen receptor and the androgen receptor (AR), which binds dihydrotestosterone (DHT) and testosterone. Androgen-receptor inhibitors (anti-androgens) block the negative feedback of androgens to stimulate LHRH and LH release. Anti-androgens therefore eventually increase the levels of serum testosterone by disrupting normal negative-feedback loops. LHRH agonists, such as leuprolide, goserelin, buserelin and nafarelin, bind to LHRH receptors in the pituitary and initially stimulate LH release, which leads to increased testosterone production (the 'testosterone flare'). Prolonged exposure to LHRH agonists, however, downregulates the LHRH receptor, decreasing LH release and inhibiting testosterone production. LHRH antagonists, such as cetrorelix, abarelix and orgalutran, directly inhibit the LHRH receptor, leading to decreased production of LH and testosterone. Surgical castration also decreases testosterone levels by removing the source of production (testes). In the adrenal glands, cholesterol is converted to adrenal androgen. Adrenal androgen production can be inhibited by drugs such as aminoglutethimide and ketoconazole. 5 -Reductase inhibitors (finasteride) block the conversion of testosterone to DHT. As well as their main effects on LHRH and LH production, anti-androgens such as cyproterone, flutamide, bicalutamide and nilutamide are direct competitive inhibitors of DHT, binding to AR in the normal and cancerous prostate cancer cells. CIPROTERONE FLUTAMIDE BICALUTAMIDE FINASTERIDE

7 (anche noto come Gonadotropin-releasing Hormone o GnRH)
ANALOGHI DEL LHRH (anche noto come Gonadotropin-releasing Hormone o GnRH)

8 a) INIBITORI DELLA BIOSINTESI
ANTIANDROGENI a) INIBITORI DELLA BIOSINTESI

9 b) ANTAGONISTI RECETTORIALI
ANTIANDROGENI b) ANTAGONISTI RECETTORIALI

10 a | In the hypersensitive pathway, more androgen receptor (AR) is produced (usually by gene amplification), or AR has enhanced sensitivity (not shown) to compensate for low levels of androgen, or more testosterone is converted to the more potent androgen, dihydrotestosterone (DHT), by 5 -reductase. b | In the promiscuous pathway, the specificity of the AR is broadened so that it can be activated by non-androgenic molecules normally present in the circulation. c | In the outlaw pathway, receptor tyrosine kinases (RTKs) are activated, and the AR is phosphorylated by either the AKT (protein kinase B) or the mitogen-activated protein kinase (MAPK) pathway, producing a ligand-independent AR. d | In the bypass pathway, parallel survival pathways, such as that involving the anti-apoptotic protein BCL2 (B-cell lymphoma 2), obviate the need for AR or its ligand. Finally, e | in the lurker cell pathway, androgen-independent cancer cells that are present all the time in the prostate — possibly epithelial stem cells — might be selected for by therapy.

11 The promiscuous androgen receptor
The promiscuous androgen receptor.   a | Mutations that broaden the specificity of the androgen receptor (AR): in the wild-type receptor, testosterone (T) and dihydrotestosterone (DHT) are agonists, whereas flutamide is an antagonist. The T877A mutant is activated by various non-androgenic steroid hormones, and flutamide also behaves as an agonist. The L701H mutant has reduced affinity for DHT and binds corticosteroids, but when the T877A and L701H mutations are combined, the resulting receptor (ARccr) has high affinity for corticosteroids.

12 a | In the hypersensitive pathway, more androgen receptor (AR) is produced (usually by gene amplification), or AR has enhanced sensitivity (not shown) to compensate for low levels of androgen, or more testosterone is converted to the more potent androgen, dihydrotestosterone (DHT), by 5 -reductase. b | In the promiscuous pathway, the specificity of the AR is broadened so that it can be activated by non-androgenic molecules normally present in the circulation. c | In the outlaw pathway, receptor tyrosine kinases (RTKs) are activated, and the AR is phosphorylated by either the AKT (protein kinase B) or the mitogen-activated protein kinase (MAPK) pathway, producing a ligand-independent AR. d | In the bypass pathway, parallel survival pathways, such as that involving the anti-apoptotic protein BCL2 (B-cell lymphoma 2), obviate the need for AR or its ligand. Finally, e | in the lurker cell pathway, androgen-independent cancer cells that are present all the time in the prostate — possibly epithelial stem cells — might be selected for by therapy.

13 How growth factor signal transduction creates outlaw receptors
How growth factor signal transduction creates outlaw receptors.   In the tumour cells of a patient receiving androgen ablation therapy, HER-2/neu (and possibly other receptor tyrosine kinases) can become overexpressed. HER-2/neu indirectly activates mitogen-activated protein kinase (MAPK). MAPK might phosphorylate the androgen receptor (AR), creating an androgen-independent 'outlaw' receptor. An alternative means by which HER-2/neu (or other pathways) might activate the AR is by activating the AKT (protein kinase B) pathway. In this pathway, activation of receptor tyrosine kinases, such as HER-2/neu, increase the level of phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)P3) by activating phosphatidylinositol 3-kinase (PI3K). Another pathway might involve inactivation of the lipid phosphatase PTEN, so that PtdIns(3,4,5)P3 can no longer be converted back to its substrate, PtdIns(4,5)P2. AKT is activated by PtdIns(3,4,5)P3, and might be able to produce an outlaw AR by phosphorylating it. AKT can also activate parallel survival pathways by phosphorylating and inactivating pro-apoptotic molecules such as BAD and procaspase-9. ARE, androgen response element; PSA, prostate-specific antigen.

14 a | In the hypersensitive pathway, more androgen receptor (AR) is produced (usually by gene amplification), or AR has enhanced sensitivity (not shown) to compensate for low levels of androgen, or more testosterone is converted to the more potent androgen, dihydrotestosterone (DHT), by 5 -reductase. b | In the promiscuous pathway, the specificity of the AR is broadened so that it can be activated by non-androgenic molecules normally present in the circulation. c | In the outlaw pathway, receptor tyrosine kinases (RTKs) are activated, and the AR is phosphorylated by either the AKT (protein kinase B) or the mitogen-activated protein kinase (MAPK) pathway, producing a ligand-independent AR. d | In the bypass pathway, parallel survival pathways, such as that involving the anti-apoptotic protein BCL2 (B-cell lymphoma 2), obviate the need for AR or its ligand. Finally, e | in the lurker cell pathway, androgen-independent cancer cells that are present all the time in the prostate — possibly epithelial stem cells — might be selected for by therapy.

15 Structure of normal and malignant breast tissue
Structure of normal and malignant breast tissue.   a Anatomy of the human mammary gland. Each mammary gland contains 15–20 lobes, each lobe containing a series of branched ducts that drain into the nipple. b Each duct is lined with a layer of epithelial cells, responsible for milk production. These are surrounded by an outer layer of myoepithelial cells with contractile properties. The glandular ducts are embedded in fibroblast stroma. c This structure breaks down in breast cancer, resulting in an epithelial cell mass. b and c are immunostained using antibodies to the oestrogen receptor (ER; brown stained nuclei), showing that only a small proportion of epithelial cells are ER positive in the normal breast.

16 Most common metastasis sites of breast cancer at autopsy
Most common metastasis sites of breast cancer at autopsy.   Primary breast cancer cells metastasize through the blood vessels to various distant organs, preferentially, to the lung, liver and bones. Patients frequently develop metastases at multiple sites.

17 MECCANISMO D’AZIONE DEGLI AGENTI UTILIZZATI NELLA TERAPIA ENDOCRINA DEI TUMORI MAMMARI
Mechanisms of action of therapeutic agents used in endocrine therapy.   Ovarian oestrogen synthesis is regulated by the pituitary, which releases luteinizing hormone (LH)-releasing hormone (LHRH). This, in turn, regulates the release of LH and follicle-stimulating hormone (FSH) from the pituitary. In the ovary, both LH and FSH increase intracellular levels of cyclic AMP. This activates the transcription factor cAMP-response-element-binding protein (CREB) and increases the expression of aromatase, which catalyses the conversion of ovarian androgens to oestrogens. LHRH agonists first cause a release of stored LH and FSH and a subsequent LHRH-receptor downregulation that inhibits further LH and FSH release. In the normal breast, adipose tissue is a local source of oestrogen synthesis. Factors that regulate aromatase expression, resulting in local oestrogen synthesis, include interleukin-6 (IL-6), oncostatin M (OSM) and tumour necrosis factor- (TNF- )15. In breast cancer, the cancer cells themselves synthesize oestrogens, and aromatase inhibitors are used to suppress local production of oestrogens from adrenal steroids, as well as reducing ovarian oestrogen synthesis. Moreover, locally produced prostaglandin E2 (PGE2) seems to be an important regulator of aromatase activity. PGE2 can activate prostaglandin E receptors on breast cancer cells, which increase cAMP levels and activate aromatase expression. Cyclooxygenase-2 (COX-2) antagonists, by blocking prostaglandin production, might inhibit this pathway149. Finally, anti-oestrogens inhibit oestrogen action directly by binding to the oestrogen receptor (ER). AC, adenylyl cyclase; ER, oestrogen receptor.

18 PROFILO DI ESPRESSIONE DEI RECETTORI ESTROGENICI
ERα ERβ mammella utero vagina SNC sistema immunitario apparato CV apparato GI rene polmone ossa

19 Shang Nature Reviews Cancer 6, 360–368 (May 2006) | doi:10
Shang Nature Reviews Cancer 6, 360–368 (May 2006) | doi: /nrc1879 a | The functional domains of the oestrogen receptor (ER). Both ER and ER have six domains (A–F). The amino-terminal A and B domains together encode a hormone-independent transcriptional activation function (AF1) domain. Domain C corresponds to the highly conserved DNA-binding domain that is responsible for specific binding of the receptors to oestrogen response elements (EREs) in the promoter of target genes. Domain D, the hinge region that separates the DNA-binding domain and the ligand-binding domain, is thought to allow conformational changes in the receptor molecule during activation, and it is important in receptor dimerization. The E and F domains encode the ligand-binding domain that is located in the carboxy-terminal portion of the receptors. This region consists of 12 -helices, which form a hydrophobic pocket allowing for oestrogen or selective oestrogen-receptor modulator binding. Domain E/F also harbours a second transcriptional activation function domain (AF2), which activates transcription in response to oestrogen or synthetic agonists by interacting with co-activators. Figure 4 | Schematic structure of oestrogen receptor. Ligand binding to the oestrogen receptor causes it to bind to oestrogen-response elements (ERE) on DNA and recruit other proteins. a | Binding of corepressors (NCoRs) and histone deacetylases (HDACs) to the oestrogen receptor results in histone deacetylation and inhibition of transcription. b | Binding of co-activators (NCoAs) and histone acetyltransferases (HATs) results in histone acetylation and transcription activation. AF, activating function; LBD, ligand-binding domain.

20 Treatment regimes for oestrogen-receptor-positive breast cancer
Treatment regimes for oestrogen-receptor-positive breast cancer.   Sequential use of ovarian ablation (e.g. using luteinizing-hormone-releasing hormone antagonists), anti-oestrogens (typically tamoxifen, although the 'pure' oestrogen receptor (ER) antagonist faslodex is also used for women who have failed tamoxifen therapy), progestins and/or aromatase inhibitors are now commonly used in the management of hormone-sensitive breast cancer. The mechanism underlying the response to progestins is unclear. However, there is evidence that progestins push breast cancer cells through one cell division and subsequent cell-cycle arrest150. *If ovaries are still functioning, aromatase inhibitors should be used in conjunction with LHRH agonist.

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22 STRUTTURA CHIMICA DEGLI ESTROGENI E DEI SERM
(Selective Estrogen Receptor Modulators) Chemical structure of oestrogens and SERMs.   The three common circulating oestrogens are oestradiol (a), oestrone (b) and oestriol (c). Although the SERMs tamoxifen (d) and raloxifene (e) have distinct chemical structures, the similarity of their three-dimensional structures to the oestrogens allows them to bind to the ligand-binding domain of the oestrogen receptor.

23 The effects of oestrogen and tamoxifen on human tissues
The effects of oestrogen and tamoxifen on human tissues.   a | Oestrogen and b | tamoxifen have both good and bad effects on specific human tissues. Development of new SERMs should maximise the good effects and minimise the bad effects.

24 The effects of oestrogen and tamoxifen on human tissues
The effects of oestrogen and tamoxifen on human tissues.   a | Oestrogen and b | tamoxifen have both good and bad effects on specific human tissues. Development of new SERMs should maximise the good effects and minimise the bad effects.

25 STRUTTURA CHIMICA DEGLI ESTROGENI E DEI SERM
(Selective Estrogen Receptor Modulators) Chemical structure of oestrogens and SERMs.   The three common circulating oestrogens are oestradiol (a), oestrone (b) and oestriol (c). Although the SERMs tamoxifen (d) and raloxifene (e) have distinct chemical structures, the similarity of their three-dimensional structures to the oestrogens allows them to bind to the ligand-binding domain of the oestrogen receptor.

26 Characteristics of tamoxifen and raloxifene in postmenopausal women
Characteristics of tamoxifen and raloxifene in postmenopausal women. The question of whether raloxifene is a preventive for breast cancer is being addressed in clinical trials.

27 Mechanisms of oestrogen-receptor activation
Mechanisms of oestrogen-receptor activation.   The oestrogen receptor (ER) has three domains: AF1, which is regulated by phosphorylation; AF2, which is regulated by oestRogen binding; and a DNA-binding domain (DBD). In the inactivated state, the ER is bound to corepressor (CoR) complexes, which recruit histone deacetylases (HDACs). HDACs maintain histones in a deacetylated state, which favours chromatin condensation. Oestrogen binding results IN a conformational change in AF2 that facilitates interaction with co-activators (CoA), which bind histone acetyltransferases (HATs). Acetylation of histones by HATs leads to chromatin decondensation, facilitating transcriptional activation. Modulation of ER activity by selective ER modulators (SERMs) is likely to be achieved by a balance between co-activator and corepressor complex recruitment to AF2, depending on the conformation induced by the SERM, as well as tissue-specific differences in co-activator/corepressor availability. Other factors, such as cyclin D1 and growth-factor-induced phosphorylation of AF1, might facilitate ligand-independent recruitment of co-activators. ERE, oestrogen response element; H12, helix 12.

28 EFFETTI NON-GENOMICI

29 MECCANISMI DI RESISTENZA AI SERM IN TUMORI ER-POSITIVI
attivazione di ER in assenza di estrogeni; ipersensibilità di ER a bassi livelli di estrogeni circolanti; attivazione, anziché inibizione, di ER da parte dei SERM

30 ligando-indipendente
MECCANISMI MOLECOLARI DI RESISTENZA AI SERM IN TUMORI ER-POSITIVI  sensibilità al ligando Mutazioni a carico di ER 1)  reclutamento di co-attivatori attivazione ligando-indipendente 2) Modificazioni post-traduzionali di ER

31 Post-translational modification of the oestrogen receptor
Post-translational modification of the oestrogen receptor.   As well as being regulated by ligand binding (Fig. 4), oestrogen receptor (ER) activity is modulated by post-translational modifications. Activation of the ER by growth factors (epidermal growth factor (EGF), heregulin, insulin, insulin-like growth factor 1 (IGF-1), and transforming growth factor- (TGF- )), as well as dopamine, cyclic AMP and phorbol esters (not shown), has been described31, 151. ER activation by these signal-transduction pathways is mediated, at least in part, by direct phosphorylation, which can stimulate the transcriptional potential of ER, often in a ligand-independent manner. Growth-factor receptor tyrosine kinases (RTKs) can lead to ER phosphorylation through at least two pathways: the RAS–RAF–ERK pathway and the phosphatidylinositol-3-OH kinase (PI3K) pathway. In the first, the adaptor proteins GRB2 and SOS activate RAS, which, in turn, activates a serine kinase cascade through RAF, MEK and, finally, the extracellular-signal-regulated kinases ERK1 and ERK2. ERKs can phosphorylate the ER directly, and can activate another kinase, RSK, which also phosphorylates the ER. In the second growth-factor-activated pathway, the receptors activate PI3K, which catalyses the production of a lipid messenger that activates the serine kinase AKT. The ligands of G protein (G)-coupled receptors that activate adenylyl cyclase (AC) can lead to an ER phosphorylation event that causes its dimerization, through protein kinase A (PKA). Other kinases that can phosphorylate the ER include the cyclin-E–CDK2 complex, the general transcription factor TFIIH and casein kinase II (CKII). E2 sensitivity is regulated by acetylation of lysines 302 and 303, by CREB-binding protein (CBP). DBD, DNA-binding domain; GPCR, G-protein-coupled receptor; LBD, ligand-binding domain.

32 ligando-indipendente
MECCANISMI MOLECOLARI DI RESISTENZA AI SERM IN TUMORI ER-POSITIVI  sensibilità al ligando Mutazioni a carico di ER 1)  reclutamento di co-attivatori attivazione ligando-indipendente 2) Modificazioni post-traduzionali di ER 3)  espressione di co-attivatori o downregulation di co-repressori 4) Attivazione di vie di trasduzione di segnali che dipendono da effetti non-genomici di ER

33 ANTIESTROGENI STEROIDEI
Fulvestrant (Faslodex)

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35 INIBITORI DELLA AROMATASI
Fig. 1. Aromatase reaction. During the aromatization of androgen precursors androstenedione and testosterone to estradiol and estrone, the A ring is converted to an aromatic ring, with the loss of the carbon at C-19.

36 INIBITORI DELLA AROMATASI

37 Mechanism of action of aromatase inhibitors and tamoxifen
Mechanism of action of aromatase inhibitors and tamoxifen.   Oestradiol binds to the oestrogen receptor (ER), leading to dimerization, conformational change and binding to oestrogen response elements (EREs) upstream of oestrogen-responsive genes including those responsible for proliferation. Tamoxifen competes with oestradiol for ER binding whereas aromatase inhibitors reduce the synthesis of oestrogens from their androgenic precursors.

38 INIBITORI DELLA AROMATASI
TIPO 1: STEROIDEI (INATTIVATORI) Molecular structures of aromatase inhibitors in clinical use.   a | Androstenedione, the natural substrate. b | Steroidal drugs that act as substrate analogues. c | Non-steroidal drugs that bind to the haem group of the enzyme (see d). d | The two third-generation non-steroidal aromatase inhibitors compared with aminoglutethimide in computer models of the active site of aromatase. Aminoglutethimide can be seen to be a poorer fit and less space filling than anastrozole and particularly letrozole94. Red, substrate-binding pocket; blue, haem prosthetic group; yellow, inhibitor.

39 INIBITORI DELLA AROMATASI
Tipo 1: inibitori non competitivi Fig. 3. Substrate analogs, such as formestane, initially compete with androstenedione for the enzyme. Aromatase is thought to convert these analogs to a structure that binds very tightly or irreversibly to the enzyme, causing its inactivation and ability to synthesize estrogens. Abbreviations; E, enzyme; I, inhibitor; k, rate constant.

40 INIBITORI DELLA AROMATASI
TIPO 2: NON-STEROIDEI Molecular structures of aromatase inhibitors in clinical use.   a | Androstenedione, the natural substrate. b | Steroidal drugs that act as substrate analogues. c | Non-steroidal drugs that bind to the haem group of the enzyme (see d). d | The two third-generation non-steroidal aromatase inhibitors compared with aminoglutethimide in computer models of the active site of aromatase. Aminoglutethimide can be seen to be a poorer fit and less space filling than anastrozole and particularly letrozole94. Red, substrate-binding pocket; blue, haem prosthetic group; yellow, inhibitor.

41 EFFETTI MOLECOLARI DEL TAMOXIFEN E DELLA DEPRIVAZIONE DI ESTROGENI
Molecular effects of tamoxifen and oestrogen deprivation on oestrogen receptor.   Both oestradiol and tamoxifen bind to the oestrogen receptor (ER) and lead to dimerization, conformational change in the activating function-2 (AF2) domain of ER and binding to oestrogen-response elements (EREs). The conformational change with tamoxifen is different from that with oestradiol and leads to persistent but less efficient transcription of most oestrogen-dependent genes. Oestrogen depletion leads to an absence of oestrogen-dependent transcription

42 A comparison of the effects of tamoxifen and the aromatase inhibitor anastrozole.   Tamoxifen can have both oestrogenic and anti-oestrogenic effects on tissues (see Fig. 2); however, anastrozole inhibits oestrogen, so is purely anti-oestrogenic. *Indicates unknown but theoretically possible toxicity with anastrazole.

43 FATTORI DI RISCHIO PER LO SVILUPPO DI TUMORI DELLA MAMMELLA
Predisposizione familiare durata dell’esposizione agli estrogeni: età età al menarca età alla menopausa contraccezione orale terapia ormonale sostitutiva parti (età al momento del primo parto) fattori alimentari attività fisica

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