Many theories mention hypersensitive, promiscuous, outlaw or bypass signalling pathways to explain the acquisition of hormone independence in prostate cancer. Hormonal escape of prostate tumours is marked by many biological changes, including mucinous and neuroendocrine differentiation. Since expression of several mucins has been linked to carcinoma tumour progression, we have characterised the expression of mucins at both RNA and protein levels in an in vivo model of prostate cancer in hormonal escape. Using PAC120, a xenograft of a human hormone-dependent prostate tumour, and its hormone-independent variants, we analysed the expression of mucins (MUC1, MUC2, MUC4, MUC5AC, MUC5B, MUC6) by immunohistochemistry or reverse transcriptase (RT) -PCR. While the parental PAC120 tumour was a compact poorly-differentiated tumour of Gleason score 9 (5 þ 4), hormoneindependent variants displayed mucinous, neuroendocrine-like or mixed histological changes; these changes were stable through serial transplantations or after testosterone supply. MUC1 mRNA was expressed in both PAC120 and the hormone-independent variants, although at variable levels. All tumours displayed a high and constant expression of MUC2 and no expression of MUC4 mRNA. While MUC1 was expressed in all xenografts whatever their hormone dependence status, MUC2, MUC5B and MUC6 were preferentially expressed in hormone-independent variants. The loss of hormone dependence in this prostate cancer xenograft model is therefore marked by irreversible histological alterations, mucinous or neuro-endocrine, associated with an expression of secretory MUC2, MUC5B and MUC6, independent of the histological differentiation subtype. These data point to mucinous differentiation as an important step in the acquisition of hormone independence in this cancer, and suggest that secretory mucins might participate in an unknown pathway of hormonal escape in prostate cancer.

Antitumour activity of docetaxel (Taxotere s ) in hormone-dependent (HD) and hormone-independent (HID) prostate cancer PAC120 xenograft model was previously reported, and its level was associated with HER2 protein expression. In the present study, we evaluate the antitumour effects of docetaxel combined with trastuzumab (Herceptin s ), an anti-HER2 antibody. Although trastuzumab alone had no effect on tumour growth, it potentiated the antitumour activity of docetaxel in HD tumours and more strongly in HID variants. Using the HID28 variant, we show that docetaxel treatment of tumour-bearing mice induces an increased HER2 mRNA expression of the tyrosine kinase receptor of 25-fold 24 h after docetaxel treatment, while HER2 protein and p-AKT decreased. This was followed by an increase of HER2 protein 3 days (two-fold) after docetaxel treatment and by a strong HER2 release in the serum of treated mice; expression of phospho-ERK, p27, BCL2 and HSP70 concomitantly increased. Similar molecular alterations were induced by docetaxel plus trastuzumab combination, except for that there was a transient and complete disappearance of AR and HSP90 proteins 24 h after treatment. We show that in addition to its known effects on tubulin and mitotic spindles, docetaxel induces complex signalisation pathway mechanisms in surviving cells, including HER2, which can be pharmacologically targeted. This study suggests that the docetaxel/trastuzumab combination may prove an effective therapeutic approach for HER2-expressing hormone-refractory prostate cancer. Escape from androgen ablation therapy is a constant feature of prostate cancer progression, leaving patients with few therapeutic options. Hormone-refractory prostate cancer (HRPC) was regarded as chemoresistant, until the recent demonstration of taxane activity (Petrylak et al, 1999). A preclinical in vivo study using our PAC120 model of hormone-dependent (HD) human prostate cancer xenograft confirmed these data (de Pinieux et al, 2001;Oudard et al, 2003). A randomised phase II study demonstrated the efficacy of docetaxel-based chemotherapy vs a mitoxantroneprednisone combination, significantly decrease PSA and prolongs time to progression of metastatic HRPC patients (Oudard et al, 2005). Despite these encouraging preclinical and clinical data, the therapeutic efficacy of taxane-based chemotherapy of HRPC remains modest. A better knowledge of the mechanisms of tumour hormonal escape and of key molecular targets is needed to design more effective combination therapies for HRPC.Several preclinical studies have implicated the ERBB family of tyrosine kinase receptors, especially HER2, in the progression of prostate cancer to a hormone-refractory state. The CWR22 hormone-independent prostate cancer xenograft expresses HER2 and its growth is inhibited in vivo by an anti-HER2 antibody (Agus et al, 1999;Mendoza et al, 2002). Increased hormone independence in prostate cancer cells was associated with androgen receptor (AR) phosphorylation mediated by transfected HER2 (Craft et al, 1999;Yeh e...

Triple negative breast cancer (TNBC) is a tumor subtype characterized by the absence of overexpressed estrogen receptor-alpha (ER), progesterone receptor (PR), and HER2 receptor, encoded by ERBB2, a known proto-oncogene. This type of tumors account for approximately 15–25% of breast cancers at diagnosis, and is one of the most aggressive subtypes, with 77% of patients that live free of disease 5 years post-diagnosis. One of the most reliable predictive markers of patient outcome is the pathological complete response (pCR), which indicates that the surgical specimen removed after neoadjuvant chemotherapy contains no viable tumor cells detectable at histopathological level. For patients with pCR, the probability of surviving the disease is very high, however, pCR is observed only in about 20–30% of TNBC. On the other hand, for patients with no pCR the probablity of developing recurrent disease at 5 years is 50%.\ud \ud As pCR is strongly correlated with treatment efficacy, it is mandatory to develop methods that allow to tell as quick as possible if the treatment chosen for a given patient is efficiently working or if it should be abandoned in favor of an alternative strategy that could prove more efficacious. XenTech collection of breast cancer patient-derived xenografts (PDXs) includes 25 models of TNBC that display heterogeneous response to different chemotherapy agents. We used our models to investigate if transcriptional changes could be detected in PDXs that responded well to genotoxic agents. To do this we analyzed the gene expression profile of laser-microdissected residual tumor nodules interspersed in the murine stroma upon very efficient response to Adriamycin/Cyclophosphamide (AC). When doing so, we identified several genes of the IFN/STAT1 pathway that were over-expressed when compared to untreated tumors. This activation seems to be a transient event, as it was lost in tumors relapsing after the residual tumor nodule stage.\ud \ud The finding that residual cells from tumors strongly responding to AC treatment over-expressed IFN/STAT1 pathway-related genes prompted us to investigate whether this effect could be detected as an early event upon tumor exposure to chemotherapy. All TNBC models tested that were good responders to AC treatment displayed over-expression of IFN/STAT1 pathway-related genes as early as 3 days post-treatment, most of them reaching a plateau of intensity at day 7 post-treatment. By contrast, TNBC insensitive or low responders to AC treatment failed to show over-expression of IFN/STAT1 pathway-related genes.\ud \ud To verify if the selective over-expression of these genes in TNBC models sensitive to AC was independent of the treatment administered, Irinotecan and Capecitabine were used to treat TNBC models with heterogeneous response to these drugs. Again, we found that overexpression of IFN/STAT1 pathway-related genes was specifically identified at early stages only in TNBC models that responded well to these drugs.\ud \ud These results suggest that genes of the IFN/STAT1 pathway ...

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