Omics analyses of a somatic Trp53R245W/+ breast cancer model identify cooperating driver events activating PI3K/AKT/mTOR signaling.

Alterations of the tumor suppressor TP53, one of the most common events in cancer, alone are insufficient for tumor development but serve as drivers of transformation. We sought to identify cooperating events through genomic analyses of a somatic Trp53R245W mouse model (equivalent to the TP53R248W hot spot mutation in human cancers) that recapitulates metastatic breast-cancer development. We identified cooperating lesions similar to those found in human breast cancers. Moreover, we identified activation of the Pi3k/Akt/mTOR pathway in most tumors via mutations in Pten, Erbb2, Kras, and/or a recurrent Pip5k1c mutation that stabilizes the Pip5k1c protein and activates Pi3k/Akt/mTOR signaling. Another PIP5K1C family member, PIP5K1A, is coamplified with PI4KB in 18% of human breast cancer patients; both encode kinases that are responsible for production of the PI3K substrate, phosphatidylinositol 4,5-bisphosphate. Thus, the TP53R248W mutation and PI3K/AKT/mTOR signaling are major cooperative events driving breast-cancer development. Additionally, a combination of two US Food and Drug Administration (FDA)-approved drugs, tigecycline and metformin, which target oxidative phosphorylation downstream of PI3K signaling, inhibited tumor cell growth and may be repurposed for breast-cancer treatment. These findings advance our understanding of how mutant p53 drives breast-tumor development and pinpoint the importance of PI3K/AKT/mTOR signaling, expanding combination therapies for breast-cancer treatment.

Is loss of p53 a driver of ductal carcinoma in situ progression?

Ductal carcinoma in situ (DCIS) is a non-obligate precursor of invasive carcinoma. Multiple studies have shown that DCIS lesions typically possess a driver mutation associated with cancer development. Mutation in the TP53 tumour suppressor gene is present in 15-30% of pure DCIS lesions and in ~30% of invasive breast cancers. Mutations in TP53 are significantly associated with high-grade DCIS, the most likely form of DCIS to progress to invasive carcinoma. In this review, we summarise published evidence on the prevalence of mutant TP53 in DCIS (including all DCIS subtypes), discuss the availability of mouse models for the study of DCIS and highlight the need for functional studies of the role of TP53 in the development of DCIS and progression from DCIS to invasive disease.