Gaorav P. Gupta

Cancer Metastasis: Building a Framework

Metastasis occurs when genetically unstable cancer cells adapt to a tissue microenvironment that is distant from the primary tumor. This process involves both the selection of traits that are advantageous to cancer cells and the concomitant recruitment of traits in the tumor stroma that accommodate invasion by metastatic cells. Recent conceptual and technological advances promote our understanding of the origins and nature of cancer metastasis.

Genes that mediate breast cancer metastasis to lung

By means of in vivo selection, transcriptomic analysis, functional verification and clinical validation, here we identify a set of genes that marks and mediates breast cancer metastasis to the lungs. Some of these genes serve dual functions, providing growth advantages both in the primary tumour and in the lung microenvironment. Others contribute to aggressive growth selectively in the lung. Many encode extracellular proteins and are of previously unknown relevance to cancer metastasis.

Mediators of vascular remodelling co-opted for sequential steps in lung metastasis

Metastasis entails numerous biological functions that collectively enable cancerous cells from a primary site to disseminate and overtake distant organs. Using genetic and pharmacological approaches, we show that the epidermal growth factor receptor ligand epiregulin, the cyclooxygenase COX2, and the matrix metalloproteinases 1 and 2, when expressed in human breast cancer cells, collectively facilitate the assembly of new tumour blood vessels, the release of tumour cells into the circulation, and the breaching of lung capillaries by circulating tumour cells to seed pulmonary metastasis. These findings reveal how aggressive primary tumorigenic functions can be mechanistically coupled to greater lung metastatic potential, and how such biological activities may be therapeutically targeted with specific drug combinations.

Lung metastasis genes couple breast tumor size and metastatic spread

The association between large tumor size and metastatic risk in a majority of clinical cancers has led to questions as to whether these observations are causally related or whether one is simply a marker for the other. This is partly due to an uncertainty about how metastasis-promoting gene expression changes can arise in primary tumors. We investigated this question through the analysis of a previously defined “lung metastasis gene-expression signature” (LMS) that mediates experimental breast cancer metastasis selectively to the lung and is expressed by primary human breast cancer with a high risk for developing lung metastasis. Experimentally, we demonstrate that the LMS promotes primary tumor growth that enriches for LMS+ cells, and it allows for intravasation after reaching a critical tumor size. Clinically, this corresponds to LMS+ tumors being larger at diagnosis compared with LMS− tumors and to a marked rise in the incidence of metastasis after LMS+ tumors reach 2 cm. Patients with LMS-expressing primary tumors selectively fail in the lung compared with the bone or other visceral sites and have a worse overall survival. The mechanistic linkage between metastasis gene expression, accelerated tumor growth, and likelihood of metastatic recurrence provided by the LMS may help to explain observations of prognostic gene signatures in primary cancer and how tumor growth can both lead to metastasis and be a marker for cells destined to metastasize.

ID genes mediate tumor reinitiation during breast cancer lung metastasis

The establishment of distant metastases depends on the capacity of small numbers of cancer cells to regenerate a tumor after entering a target tissue. The mechanisms that confer this capacity remain to be defined. Here we identify a role for the transcriptional inhibitors of differentiation Id1 and Id3 as selective mediators of lung metastatic colonization in the triple negative [TN, i.e., lacking expression of estrogen receptor and progesterone receptor, and lacking Her2 (human epidermal growth factor receptor 2) amplification] subgroup of human breast cancer. Although broad expression of Id1 has recently been documented in tumors of the rare metaplastic subtype, here we report that rare Id1-expressing cells are also present in the more common TN subset of human breast tumors but not in other subtypes. We also provide evidence that Id1 expression is enriched in clinically obtained hormone receptor negative lung metastases. Functional studies demonstrate that Id1 and its closely related family member Id3 are required for tumor initiating functions, both in the context of primary tumor formation and during metastatic colonization of the lung microenvironment. In vivo characterization of lung metastatic progression reveals that Id1 and Id3 facilitate sustained proliferation during the early stages of metastatic colonization, subsequent to extravasation into the lung parenchyma. These results shed light on the proliferative mechanisms that initiate metastatic colonization, and they implicate Id1 and Id3 as mediators of this malignant function in the TN subgroup of breast cancers.

Platelets and metastasis revisited: a novel fatty link

Platelets have long been suspected of having a role in cancer progression and metastasis that has largely been attributed to platelet-mediated enhancement of tumor cell survival, extravasation, and angiogenesis. A study in this issue of the JCI suggests that platelet-derived lysophosphatidic acid is coopted by aggressive breast and ovarian cancer cells as a tumor cell mitogen and promoter of osteolysis during bone metastasis.

Favorable prognosis in patients with T1a/T1bN0 triple-negative breast cancers treated with multimodality therapy

The authors evaluated the clinical characteristics, natural history, and outcomes of patients who had ≤1 cm, lymph node‐negative, triple‐negative breast cancer (TNBC).

The Mre11 Complex Suppresses Oncogene-Driven Breast Tumorigenesis and Metastasis

The DNA damage response (DDR) is activated by oncogenic stress, but the mechanisms by which this occurs, and the particular DDR functions that constitute barriers to tumorigenesis, remain unclear. We established a mouse model of sporadic oncogene-driven breast tumorigenesis in a series of mutant mouse strains with specific DDR deficiencies to reveal a role for the Mre11 complex in the response to oncogene activation. We demonstrate that an Mre11-mediated DDR restrains mammary hyperplasia by effecting an oncogene-induced G2 arrest. Impairment of Mre11 complex functions promotes the progression of mammary hyperplasias into invasive and metastatic breast cancers, which are often associated with secondary inactivation of the Ink4a-Arf (CDKN2a) locus. These findings provide insight into the mechanism of DDR engagement by activated oncogenes and highlight genetic interactions between the DDR and Ink4a-Arf pathways in suppression of oncogene-driven tumorigenesis and metastasis.

Outcomes and Prognostic Factors in Women With 1 to 3 Breast Cancer Brain Metastases Treated With Definitive Stereotactic Radiosurgery

BACKGROUND With the continuing increase in the use of definitive stereotactic radiosurgery (SRS) for patients with limited brain metastases (BM), clinicians need more specific prognostic tools. We investigated clinical predictors of outcomes in patients with limited breast cancer BM treated with SRS alone. METHODS AND MATERIALS We identified 136 patients with breast cancer and 1-3 BM who underwent definitive SRS for 186 BM between 2000 and 2012. The Kaplan-Meier method was used to assess overall survival (OS), regional failure (RF), and local failure (LF). Associations between clinical factors and outcomes were tested using Cox regression. A point scoring system was used to stratify patients based on OS, and the predictive power was tested with concordance probability estimate (CPE). RESULTS The median OS was 17.6 months. The 12-month RF and LF rates were 45% and 10%, respectively. On multivariate analysis, >1 lesion (hazard ratio [HR] = 1.6, P=.02), triple-negative (TN) disease (HR=2.0, P=.006), and active extracranial disease (ED) (HR=2.7, P<.0001) were significantly associated with worse OS. The point score system was defined using proportional simplification of the multivariate Cox proportional hazards regression function. The median OS for patients with 3.0-4.0 points (n=37), 4.5-5.5 points (n=28), 6.0-6.5 points (n=37), and 8-8.5 points (n=34) were 9.2, 15.6, 25.1, and 45.1 months, respectively (P<.0001, CPE = 0.72). Active ED (HR=2.4, P=.0007) was significantly associated with RF. Higher risk for LF was significantly associated with larger BM size (HR=3.1, P=.0001). CONCLUSION Patients with >1 BM, active ED, and TN had the highest risk of death after SRS. Active ED is an important prognostic factor for OS and intracranial control.

Advances in managing breast cancer: a clinical update

Although substantial progress has been made in the screening and management of breast cancer, globally it remains the most common cause of cancer and cancer death in women. While breast cancer is potentially curable when detected at an early stage, it remains incurable in the metastatic setting. Thus, given its high prevalence, improved prevention and treatment of metastases remains a clinically meaningful unmet need. We review here the advances made in the last several years in the screening and treatment of breast cancer and explore how our increased insight into the underlying biology of breast cancer has influenced our efforts to individualize patient care.