A prior diagnosis of breast cancer is a risk factor for breast cancer in BRCA1 and BRCA2 carriers

Glucose-dependent effect of insulin receptor isoforms on tamoxifen antitumor activity in estrogen receptor-positive breast cancer cells

Introduction

Breast cancer is the most common malignancy in women, and it is linked to several risk factors including genetic alterations, obesity, estrogen signaling, insulin levels, and glucose metabolism deregulation. Insulin and Insulin-like growth factor signaling exert a mitogenic and pro-survival effect. Indeed, epidemiological and pre-clinical studies have shown its involvement in the development, progression, and therapy resistance of several cancer types including breast cancer. Insulin/Insulin-like growth factor signaling is triggered by two insulin receptor isoforms identified as IRA and IRB and by Insulin-like growth factor receptor I. Both classes of receptors show high homology and can initiate the intracellular signaling cascade alone or by hybrids formation. While the role of Insulin-like growth factor receptor I in breast cancer progression and therapy resistance is well established, the effects of insulin receptors in this context are complex and not completely elucidated.

Methods

We used estrogen-dependent insulin-like growth factor receptor I deleted gene (MCF7^IGFIRKO) breast cancer cell models, lentivirally transduced to over-express empty-vector (MCF7^IGFIRKO/EV), IRA (MCF7^IGFIRKO/IRA) or IRB (MCF7^IGFIRKO/IRB), to investigate the role of insulin receptors on the antiproliferative activity of tamoxifen in presence of low and high glucose concentrations. The tamoxifen-dependent cytotoxic effects on cell proliferation were determined by MTT assay and clonogenic potential measurement. Cell cycle and apoptosis were assessed by FACS, while immunoblot was used for protein analysis. Gene expression profiling was investigated by a PCR array concerning genes involved in apoptotic process by RT-qPCR.

Results

We found that glucose levels played a crucial role in tamoxifen response mediated by IRA and IRB. High glucose increased the IC50 value of tamoxifen for both insulin receptors and IRA-promoted cell cycle progression more than IRB, independently of glucose levels and insulin stimulation. IRB, in turn, showed anti-apoptotic properties, preserving cells' survival after prolonged tamoxifen exposure, and negatively modulated pro-apoptotic genes when compared to IRA.

Discussion

Our findings suggest that glucose levels modify insulin receptors signaling and that this event can interfere with the tamoxifen therapeutic activity. The investigation of glucose metabolism and insulin receptor expression could have clinical implications in Estrogen Receptor positive breast cancer patients receiving endocrine treatments.

The risk of contralateral breast cancer: a SEER-based analysis

BACKGROUND

We sought to estimate the annual risk and 25-year cumulative risk of contralateral breast cancer among women with stage 0-III unilateral breast cancer.

METHODS

We identified 812,851 women with unilateral breast cancer diagnosed between 1990 and 2015 in the SEER database and followed them for contralateral breast cancer for up to 25 years. Women with a known bilateral mastectomy were excluded. We calculated the annual risk of contralateral breast cancer by age at diagnosis, by time since diagnosis and by current age. We compared risks by ductal carcinoma in situ (DCIS) versus invasive disease, by race and by oestrogen receptor (ER) status of the first cancer.

RESULTS

There were 25,958 cases of contralateral invasive breast cancer diagnosed (3.2% of all patients). The annual risk of contralateral breast cancer over the 25-year follow-up period was 0.37% and the 25-year actuarial risk of contralateral invasive breast cancer was 9.9%. The annual risk varied to a small degree by age of diagnosis, by time elapsed since diagnosis and by current age. The 25-year actuarial risk was similar for DCIS and invasive breast cancer patients (10.1 versus 9.9%). The 25-year actuarial risk was higher for black women (12.7%) than for white women (9.7%) and was lower for women with ER-positive breast cancer (9.5%) than for women with ER-negative breast cancer (11.2%).

CONCLUSIONS

Women with unilateral breast cancer experience an annual risk of contralateral breast cancer ~0.4% per year, which persists over the 25-year follow-up period.

Age-specific risks of incident, contralateral and ipsilateral breast cancer among 1776 Polish BRCA1 mutation carriers

PURPOSE

Women with an inherited germline BRCA1 mutation have a high lifetime risk of developing breast cancer. We have previously shown that, among BRCA mutation carriers, incidence rates of breast cancer vary by country of residence.

METHODS

In the current study, we prospectively calculated the cumulative and annual incidence rates of incident breast cancer, contralateral breast cancer and ipsilateral breast cancer recurrence among BRCA1 mutation carriers in Poland. Study subjects comprised a cohort of 1776 Polish women with a BRCA1 mutation who had no prior diagnosis of breast or ovarian cancer at the time of enrollment, the women were followed with a biennial follow-up by questionnaire. Women were followed for an average of 6.1 years (range 0.0-18.2) and 191 new breast cancer cases were diagnosed.

RESULTS

The cumulative incidence of breast cancer to age 70 was 52%. The annual risk of breast cancer was estimated at 1.78%; the maximum annual risk was observed between the ages of 30 and 65. Among the 941 women with a prior diagnosis of breast cancer, 106 women developed a contralateral breast cancer. The 20-year cumulative incidence of contralateral breast cancer was 31% and the annual rate of contralateral breast cancer was 1.96%. There were 11 recurrences among the 215 women with breast cancer (ipsilateral breast cancers). The cumulative incidence at 20 years was 17% and the annual rate of an ipsilateral recurrence was 1.03%.

CONCLUSION

Our findings confirm the high annual rates of early-onset incident, contralateral and recurrent breast cancer among Polish BRCA1 mutation carriers. These risk estimates are important in the context of the clinical management of unaffected women as well as in the treatment of newly diagnosed primary breast cancers and can also be used as the basis for the planning of prevention trials.

Bilateral breast cancers

An increasingly large proportion of women with unilateral breast cancer are treated with bilateral mastectomy. The rationale behind bilateral surgery is to prevent a second primary breast cancer and thereby to avoid the resultant therapy and eliminate the risk of death from contralateral breast cancer. Bilateral mastectomy has been proposed to benefit women at high risk of contralateral cancer, such as carriers of BRCA1 and BRCA2 mutations, but for women without such mutations, the decision to remove the contralateral breast is controversial. It is important to evaluate the risk of contralateral breast cancer on an individual basis, and to tailor surgical treatment accordingly. On average, the annual risk of contralateral breast cancer is approximately 0.5%, but increases to 3% in carriers of a BRCA1 or BRCA2 mutation. Risk factors for contralateral breast cancer include a young age at first diagnosis of breast cancer and a family history of breast cancer. Contralateral mastectomy has not been proven to reduce mortality from breast cancer, but the benefit of such surgery is not expected to become apparent until the second decade after treatment. An alternative to contralateral mastectomy is adjuvant hormonal therapy (such as tamoxifen), but the extent of risk reduction is smaller (approximately 50%) compared to 95% or more for contralateral mastectomy. This Review focuses on the risk factors for contralateral breast cancer, and discusses the evidence that bilateral mastectomy might reduce mortality in patients with unilateral breast cancer.