B3GALT6 promotes dormant breast cancer cell survival and recurrence by enabling heparan sulfate-mediated FGF signaling.

Breast cancer mortality results from incurable recurrences thought to be seeded by dormant, therapy-refractory residual tumor cells (RTCs). Understanding the mechanisms enabling RTC survival is therefore essential for improving patient outcomes. Here, we derive a dormancy-associated RTC signature that mirrors the transcriptional response to neoadjuvant therapy in patients and is enriched for extracellular matrix-related pathways.

PAQR8 promotes breast cancer recurrence and confers resistance to multiple therapies.

Background: Breast cancer mortality is principally due to recurrent disease that becomes resistant to therapy. We recently identified copy number (CN) gain of the putative membrane progesterone receptor PAQR8 as one of four focal CN alterations that preferentially occurred in recurrent metastatic tumors compared to primary tumors in breast cancer patients. Whether PAQR8 plays a functional role in cancer is unknown.

Cellular dormancy in minimal residual disease following targeted therapy.

Background: Breast cancer mortality is principally due to tumor recurrence, which can occur following extended periods of clinical remission that may last decades. While clinical latency has been postulated to reflect the ability of residual tumor cells to persist in a dormant state, this hypothesis remains unproven since little is known about the biology of these cells. Consequently, defining the properties of residual tumor cells is an essential goal with important clinical implications for preventing recurrence and improving cancer outcomes.

Impact of obesity on breast cancer recurrence and minimal residual disease.

Background: Obesity is associated with an increased risk of breast cancer recurrence and cancer death. Recurrent cancers arise from the pool of residual tumor cells, or minimal residual disease (MRD), that survives primary treatment and persists in the host. Whether the association of obesity with recurrence risk is causal is unknown, and the impact of obesity on MRD and breast cancer recurrence has not been reported in humans or in animal models.

Notch promotes recurrence of dormant tumor cells following HER2/neu-targeted therapy.

Breast cancer mortality is principally due to recurrent tumors that arise from a reservoir of residual tumor cells that survive therapy. Remarkably, breast cancers can recur after extended periods of clinical remission, implying that at least some residual tumor cells pass through a dormant phase prior to relapse. Nevertheless, the mechanisms that contribute to breast cancer recurrence are poorly understood.

Deletion of cyclooxygenase 2 in mouse mammary epithelial cells delays breast cancer onset through augmentation of type 1 immune responses in tumors.

Inhibition of cyclooxygenase (COX) 2, which is associated with >40% of breast cancers, decreases the risk of tumorigenesis and breast cancer recurrence. To study the role of COX-2 in breast cancer, we engineered mice that lack selectively mammary epithelial cell (MEC) COX-2 (COX-2 KO(MEC)). Compared with wild type (WT), MEC from COX-2 KO(MEC) mice expressed >90% less COX-2 messenger RNA (mRNA) and protein and produced 90% less of the dominant pro-oncogenic COX-2 product, prostaglandin (PG) E(2).

The transcriptional repressor Snail promotes mammary tumor recurrence.

Breast cancer recurrence is a fundamental clinical manifestation of tumor progression and represents the principal cause of death from this disease. Using a conditional transgenic mouse model for the recurrence of HER2/neu-induced mammary tumors, we demonstrate that the transcriptional repressor Snail is spontaneously upregulated in recurrent tumors in vivo and that recurrence is accompanied by epithelial-to-mesenchymal transition (EMT). Consistent with a causal role for Snail in these processes, we show that Snail is sufficient to induce EMT in primary tumor cells, that Snail is sufficient to promote mammary tumor recurrence in vivo, and that high levels of Snail predict decreased relapse-free survival in women with breast cancer.