Trastuzumab e carcinoma mammario HER2+: attività e possibili meccanismi di resistenza

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1 Innovazioni terapeutiche in Oncologia Medica Cagliari, giugno 2005 Trastuzumab e carcinoma mammario +: attività e possibili meccanismi di resistenza U.O.A.D.U. Oncologia Medica ed Ematologia I.R.C.C. Candiolo Massimo Aglietta

2 Trastuzumab (Herceptin) Approved for the treatment of overexpressing metastatic breast cancer and about to be approved for adjuvant treatment (ASCO 2005)

3 Trastuzumab in vitro and in vivo mechanism of action (1) down-regulation Inhibition of shedding YY Y Y Inhibition of angiogenesis Activation of ADCC

4 Trastuzumab prolongs median survival but response is frequently followed by tumor progression 1.0 Herceptin + Taxotere (n=92) Taxotere alone/crossover (n=45) Taxotere alone (n=49) Estimated probability Months Intent-to-treat population, 12-month cut-off

5 Possible mechanisms of resistance to Trastuzumab 1) IGF1-R overexpression (Lu, JNCI 2001) 2) PTEN loss (Nagata, Cancer Cell 2004) 3) Masking of the Herceptin epitope by MUC4 expression (Nagy, Cancer Res 2005) 4) Acquisition of properties leading to the overcoming of receptor degradation (Valabrega, Oncogene 2005) 5) Non linear relationship between expression and response to Trastuzumab (Valabrega, submitted 2005)

6 Possible molecular mechanisms of resistance to trastuzumab Nagata et al. Cancer Cell 2004 Pandolfi PP NEJM 2005

7 Machinery responsible for antibody induced receptor down-regulation Cbl Y Y P Cbl Cbl K Ub Ub C UbcH7 Cbl

8 Acquisition of properties leading to the overcoming of receptor degradation (1) No point mutations in Cbl nor in the Y1112 of responsible for Cbl- interaction Y368 Y371 Y1112 Cbl

9 Acquisition of properties leading to the overcoming of receptor degradation TGFa and breast cancer 1) TGFa induces heterodimerization and internalization but not degradation of EGFR and 2) TGFa is frequently overexpressed in breast cancer cells

10 TGFa expression increases after progression during trastuzumab PATIENT 1 PATIENT 2 PATIENT 3 Pre-Trastuzumab Upon-Trastuzumab

11 TGFa expression reduces sensitivity to Trastuzumab in vitro Cell counts Trastuzumab Cell counts Fluorescence intensity Anti mab Absorbance (562 nm) WT TGFa WT T+ TGFa T+ Days of treatment

12 TGFα expression reduces Trastuzumab induced downregulation and /Cbl association T T T T Hours C C WB α WB α β-actin WT TGFα T T C C WB α WB α Cbl Cbl IP α Cbl / TGFα Cbl Cbl TGFα

13 Conclusions (1) 1) Trastuzumab induces activation and Cbl-mediated ubiquitination and degradation. 2) TGFa overexpression correlates with acquisition of resistance to Trastuzumab in human breast cancers 3) TGFa overexpression reduces Trastuzumab inhibitory effect in experimental models 4) TGFa overexpression uncouples from Cbl thus interfering with downregulation

14 Non linear relationship between expression and response to Trastuzumab The formation of oligomers of order higher 2 or the formation of heterodimers may impair antibody-induced downregulation (Nagy, 1999) Y Y Y Y Y EGFR HER3 Y

15 modulation does not influence HercepTest positivity C sirna sirna C sirna 30 nm sirna 10 nm 30 nm 10 nm 20 nm 30 nm WB α- WB α-βactin (100%) (40%) (55%) (70%) sirna 20 nm sirna 30 nm

16 down-modulation results in increased sensitivity to Trastuzumab 60 % of cell growth inhibition adjusted for sirna effect C-siRNA C-siRNA -sirna10 -sirna20 -sirna30 Trastuzumab 10 mg/ml

17 Response to Trastuzumab depends on /Trastuzumab ratio inhibition of cell growth induced by Trastuzumab (%) C- sirna -10

18 Conclusions (2) 1) A difference of up to 70% of levels does not change HercepTest positivity in SKBR3 cells. 2) down-modulation results in increased sensitivity to Trastuzumab in SKBR3 cells 3) Response to Trastuzumab depends on /Trastuzumab ratio

19 Future directions (prognosis and prediction) 1) In vivo evaluation of TGFa, EGFR, pegfr, and p on primary tumors to assess their predictive and prognostic value in breast cancers treated with Trastuzumab 2) In vivo evaluation TGFa, EGFR, pegfr, and p before and after progression to assess the significance of the system in the development of resistance to Trastuzumab 3) Quantification of the exact number of receptors on neoplastic breast cancer tissues to predict response to Trastuzumab