HER2 Support Group Forums - View Single Post - getting her2+ER- bc to reexpress ER & consequences more complicated than thought

Rich66 · 01-03-2010, 11:44 PM

Since Fulvestrant seems to work after other antiestrogens/AIs cease working, could be prudent to save it for last. I will mention the makers of Tamoxitest had a poster at SABC 09 suggesting that in definite Her2 positives, Tamoxifen might not be a good choice. Not sure yet if anyone else is backing this up.

From Fulvestrant + chemo thread:

Ann Oncol. 2009 Oct 29. [Epub ahead of print]
Activity of fulvestrant in HER2-overexpressing advanced breast cancer.
Robertson JF, Steger GG, Neven P, Barni S, Gieseking F, Nolè F, Pritchard KI, O'Malley FP, Simon SD, Kaufman B, Petruzelka L.
Professorial Unit of Surgery, Division of Breast Surgery, University of Nottingham, Nottingham City Hospital, Nottingham, UK.
BACKGROUND: Human epidermal growth factor receptor 2 (HER2) overexpression increases the aggressiveness of breast cancer cells resulting in poorer prognosis. Patients with HER2-positive disease are less responsive to endocrine therapies. Trastuzumab monotherapy results in objective responses in only approximately 15% of patients. Fulvestrant retains activity in cells overexpressing HER2 that are resistant to other endocrine treatments. This retrospective study evaluated response to fulvestrant treatment among HER2-positive patients with advanced breast cancer (ABC). PATIENTS AND METHODS: Clinical experience data from 10 treatment centres were pooled. Postmenopausal patients with predominantly hormone receptor-positive and HER2-positive disease were included. Clinical benefit (CB) was defined as the proportion of patients achieving a response to treatment (partial or complete) or stable disease lasting >/=6 months. RESULTS: Data for 102 patients were analysed. Fulvestrant resulted in an overall CB rate of 42% (43/101) in HER2-positive patients and 40% (25/63) in patients with visceral disease. Median duration of treatment was 14.5 months (range 6-44 months). Fulvestrant showed activity up to the fourth line of endocrine therapy and up to the seventh line of overall therapy. CONCLUSIONS: Results indicate that fulvestrant may be a suitable treatment option in extensively pre-treated patients with HER2-positive, hormone receptor-positive ABC. Further exploration of its use in this patient population is warranted.
PMID: 19875750

From ER/Her2 crosstalk thread:

SABC 2009
[708] Different Mechanisms for Acquired Resistance to Trastuzumab and Lapatinib in HER2 Positive Breast Cancers: Role of ER and HER2 Reactivation.

Wang Y-C, Hennessy B, McAninch Ward R, Rimawi M, Huang C, Mills GB, Osborne CK, Schiff R Baylor College of Medicine, Houston, TX; M.D. Anderson, Houston, TX

About 25% of human breast cancers are amplified for HER2 with half of these tumors also expressing estrogen receptor (ER). Therapies targeting HER2 are very effective in the metastatic and the adjuvant settings, especially, although de novo or acquired resistance are still major problems. Trastuzumab (T) and lapatinib (L) are approved drugs now used in the clinic for treatment of HER2+ tumors. Data suggest that T works primarily by blocking signals generated by HER2 homodimers, while L is a small molecule tyrosine kinase inhibitor that more completely blocks the pathway by inhibiting HER1 in addition to HER2. In the clinic, these drugs demonstrate incomplete cross-resistance since L is active in some patients with T-resistant tumors. However, the mechanisms for this resistance have not been clarified.
To investigate the mechanisms for acquired resistance, we developed a panel of HER2+ cell lines resistant to T, L, and L+T by long-term exposure to increasing drug concentration in vitro. Two of these lines, BT474 and UACC812, are amplified for HER2 and also express ER, and they, together with subclones resistant to L, T, and L+T, were used to better understand potential resistance mechanisms. Western blot analysis of the parental BT474 and its resistant subclones showed that subclones resistant to T had reactivated the HER2 signaling pathway, while subclones resistant to L or L+T in which the HER receptor layer was more completely inhibited showed continued complete blockade of the HER2 pathway at the receptor layer but high levels of ER activity and phosphorylated-AKT. L, but not L+T, subclones after more prolonged time in culture did reactivate the HER pathway. UACC812 resistant cells were similar to BT474: T-resistant clones showed evidence of reactivation of HER signaling while L and L+T resistant clones showed enhanced ER activity. These cells showed no reactivation of HER signaling even after prolonged exposure in vitro. Consistent with these data, both BT474 and UACC812 T-resistant clones were still sensitive to and cell proliferation was inhibited by L. L-resistant clones, however, were also resistant to T. The potent anti-estrogen fulvestrant (F) was used to evaluate the role of ER in these resistant clones. T-resistant clones from both parental lines were resistant to F, indicating that ER had no role in resistance. In contrast, L and L+T-resistant clones, but not parental cells, were extremely sensitive to F with significant inhibition of cell proliferation in vitro.
These data demonstrate that only partial inhibition of the HER2 pathway in breast cancer cells by T can be overcome by activating other components of the HER pathway. Resistance to more complete HER2 blockade with L or L+T requires reactivation of a redundant cell survival pathway, in this case ER, which is upregulated by HER2 blockade. Optimal therapy in those tumors may require both ER and HER2-targeted therapy.

Saturday, December 12, 2009 7:00 AM

Note that a higher dose (500) than previous (250) is considered more effective now.

01-03-2010, 11:44 PM	#18
Rich66 Senior Member Join Date: Feb 2008 Location: South East Wisconsin Posts: 3,431	Re: getting her2+ER- bc to reexpress ER & consequences more complicated than thought Since Fulvestrant seems to work after other antiestrogens/AIs cease working, could be prudent to save it for last. I will mention the makers of Tamoxitest had a poster at SABC 09 suggesting that in definite Her2 positives, Tamoxifen might not be a good choice. Not sure yet if anyone else is backing this up. From Fulvestrant + chemo thread: Ann Oncol. 2009 Oct 29. [Epub ahead of print] Activity of fulvestrant in HER2-overexpressing advanced breast cancer. Robertson JF, Steger GG, Neven P, Barni S, Gieseking F, Nolè F, Pritchard KI, O'Malley FP, Simon SD, Kaufman B, Petruzelka L. Professorial Unit of Surgery, Division of Breast Surgery, University of Nottingham, Nottingham City Hospital, Nottingham, UK. BACKGROUND: Human epidermal growth factor receptor 2 (HER2) overexpression increases the aggressiveness of breast cancer cells resulting in poorer prognosis. Patients with HER2-positive disease are less responsive to endocrine therapies. Trastuzumab monotherapy results in objective responses in only approximately 15% of patients. Fulvestrant retains activity in cells overexpressing HER2 that are resistant to other endocrine treatments. This retrospective study evaluated response to fulvestrant treatment among HER2-positive patients with advanced breast cancer (ABC). PATIENTS AND METHODS: Clinical experience data from 10 treatment centres were pooled. Postmenopausal patients with predominantly hormone receptor-positive and HER2-positive disease were included. Clinical benefit (CB) was defined as the proportion of patients achieving a response to treatment (partial or complete) or stable disease lasting >/=6 months. RESULTS: Data for 102 patients were analysed. Fulvestrant resulted in an overall CB rate of 42% (43/101) in HER2-positive patients and 40% (25/63) in patients with visceral disease. Median duration of treatment was 14.5 months (range 6-44 months). Fulvestrant showed activity up to the fourth line of endocrine therapy and up to the seventh line of overall therapy. CONCLUSIONS: Results indicate that fulvestrant may be a suitable treatment option in extensively pre-treated patients with HER2-positive, hormone receptor-positive ABC. Further exploration of its use in this patient population is warranted. PMID: 19875750 From ER/Her2 crosstalk thread: SABC 2009 [708] Different Mechanisms for Acquired Resistance to Trastuzumab and Lapatinib in HER2 Positive Breast Cancers: Role of ER and HER2 Reactivation. *Wang Y-C, Hennessy B, McAninch Ward R, Rimawi M, Huang C, Mills GB, Osborne CK, Schiff R Baylor College of Medicine, Houston, TX; M.D. Anderson, Houston, TX* About 25% of human breast cancers are amplified for HER2 with half of these tumors also expressing estrogen receptor (ER). Therapies targeting HER2 are very effective in the metastatic and the adjuvant settings, especially, although de novo or acquired resistance are still major problems. Trastuzumab (T) and lapatinib (L) are approved drugs now used in the clinic for treatment of HER2+ tumors. Data suggest that T works primarily by blocking signals generated by HER2 homodimers, while L is a small molecule tyrosine kinase inhibitor that more completely blocks the pathway by inhibiting HER1 in addition to HER2. In the clinic, these drugs demonstrate incomplete cross-resistance since L is active in some patients with T-resistant tumors. However, the mechanisms for this resistance have not been clarified. To investigate the mechanisms for acquired resistance, we developed a panel of HER2+ cell lines resistant to T, L, and L+T by long-term exposure to increasing drug concentration in vitro. Two of these lines, BT474 and UACC812, are amplified for HER2 and also express ER, and they, together with subclones resistant to L, T, and L+T, were used to better understand potential resistance mechanisms. Western blot analysis of the parental BT474 and its resistant subclones showed that subclones resistant to T had reactivated the HER2 signaling pathway, while subclones resistant to L or L+T in which the HER receptor layer was more completely inhibited showed continued complete blockade of the HER2 pathway at the receptor layer but high levels of ER activity and phosphorylated-AKT. L, but not L+T, subclones after more prolonged time in culture did reactivate the HER pathway. UACC812 resistant cells were similar to BT474: T-resistant clones showed evidence of reactivation of HER signaling while L and L+T resistant clones showed enhanced ER activity. These cells showed no reactivation of HER signaling even after prolonged exposure in vitro. Consistent with these data, both BT474 and UACC812 T-resistant clones were still sensitive to and cell proliferation was inhibited by L. L-resistant clones, however, were also resistant to T. The potent anti-estrogen fulvestrant (F) was used to evaluate the role of ER in these resistant clones. T-resistant clones from both parental lines were resistant to F, indicating that ER had no role in resistance. In contrast, L and L+T-resistant clones, but not parental cells, were extremely sensitive to F with significant inhibition of cell proliferation in vitro. These data demonstrate that only partial inhibition of the HER2 pathway in breast cancer cells by T can be overcome by activating other components of the HER pathway. Resistance to more complete HER2 blockade with L or L+T requires reactivation of a redundant cell survival pathway, in this case ER, which is upregulated by HER2 blockade. Optimal therapy in those tumors may require both ER and HER2-targeted therapy. Saturday, December 12, 2009 7:00 AM Note that a higher dose (500) than previous (250) is considered more effective now. __________________ Mom's treatment history (link)