Tumour dormancy and clinical implications in breast cancer

Applying artificial intelligence technology to assist with breast cancer diagnosis and prognosis prediction

Breast cancer remains the most diagnosed cancer in women. Advances in medical imaging modalities and technologies have greatly aided in the early detection of breast cancer and the decline of patient mortality rates. However, reading and interpreting breast images remains difficult due to the high heterogeneity of breast tumors and fibro-glandular tissue, which results in lower cancer detection sensitivity and specificity and large inter-reader variability. In order to help overcome these clinical challenges, researchers have made great efforts to develop computer-aided detection and/or diagnosis (CAD) schemes of breast images to provide radiologists with decision-making support tools. Recent rapid advances in high throughput data analysis methods and artificial intelligence (AI) technologies, particularly radiomics and deep learning techniques, have led to an exponential increase in the development of new AI-based models of breast images that cover a broad range of application topics. In this review paper, we focus on reviewing recent advances in better understanding the association between radiomics features and tumor microenvironment and the progress in developing new AI-based quantitative image feature analysis models in three realms of breast cancer: predicting breast cancer risk, the likelihood of tumor malignancy, and tumor response to treatment. The outlook and three major challenges of applying new AI-based models of breast images to clinical practice are also discussed. Through this review we conclude that although developing new AI-based models of breast images has achieved significant progress and promising results, several obstacles to applying these new AI-based models to clinical practice remain. Therefore, more research effort is needed in future studies.

Role of Neural (N)-Cadherin in Breast Cancer Cell Stemness and Dormancy in the Bone Microenvironment

Breast cancer cells that interact with spindle-shaped N-Cadherin+ Osteoblasts (SNOs) are recognised to become dormant through a Notch2-dependent mechanism. We found that Notch2High human BrCa MDA-MB231 (MDA) cells also expressed high level of N-Cadherin. This prompted us to hypothesize that N-Cadherin could have a role in MDA-SNO interaction. Of note, the expression of N-Cadherin in MDA cells reduced tumour incidence and bone osteolysis in BrCa mouse model. Moreover, similarly to Notch2High MDA cells, the N-CadherinHigh MDA cells revealed a high expression of the canonical Haematopoietic Stem cell (HSC) markers, suggesting an HSC mimicry, associated with higher ability to form mammospheres. Interestingly, N-CadherinHigh MDA cells showed greater capacity to adhere to SNOs, while the inhibition of SNO-mediating MDA cell proliferation was unremarkable. To investigate whether these features were shared by mouse BrCa, we used the 4T1 cell line in which N-Cadherin expression was abolished and then rescued. At variance with MDA cells, 4T1 cells expressing N-Cadherin revealed that the latter was associated with a lower expression of the HSC marker, Cxcr4, along with a lower capacity to form mammospheres. Furthermore, the rescue of N-Cadherin expression increased cell-cell adhesion and reduced proliferation of 4T1 cells when they were co-plated with SNOs. In conclusion, we demonstrated that: (i) N-CadherinHigh and Notch2High MDA cells showed similar HSC mimicry and dormancy features; (ii) N-Cadherin mediated BrCa-SNO adhesion; (iii) N-Cadherin had a positive Notch2-dependent role on SNO-induced dormancy and HSC mimicry in MDA cells, and a negative role in 4T1 cell stemness and HSC mimicry.

Specific N-cadherin-dependent pathways drive human breast cancer dormancy in bone marrow

The challenge for treating breast cancer (BC) is partly due to long-term dormancy driven by cancer stem cells (CSCs) capable of evading immune response and resist chemotherapy. BC cells show preference for the BM, resulting in poor prognosis. CSCs use connexin 43 (Cx43) to form gap junctional intercellular communication with BM niche cells, fibroblasts, and mesenchymal stem cells (MSCs). However, Cx43 is an unlikely target to reverse BC dormancy because of its role as a hematopoietic regulator. We found N-cadherin (CDH2) and its associated pathways as potential drug targets. CDH2, highly expressed in CSCs, interacts intracellularly with Cx43, colocalizes with Cx43 in BC cells within BM biopsies of patients, and is required for Cx43-mediated gap junctional intercellular communication with BM niche cells. Notably, CDH2 and anti-apoptotic pathways maintained BC dormancy. We thereby propose these pathways as potential pharmacological targets to prevent dormancy and chemosensitize resistant CSCs.

Rac inhibition as a novel therapeutic strategy for EGFR/HER2 targeted therapy resistant breast cancer

Background

Even though targeted therapies are available for cancers expressing oncogenic epidermal growth receptor (EGFR) and (or) human EGFR2 (HER2), acquired or intrinsic resistance often confounds therapy success. Common mechanisms of therapy resistance involve activating receptor point mutations and (or) upregulation of signaling downstream of EGFR/HER2 to Akt and (or) mitogen activated protein kinase (MAPK) pathways. However, additional pathways of resistance may exist thus, confounding successful therapy.

Methods

To determine novel mechanisms of EGFR/HER2 therapy resistance in breast cancer, gefitinib or lapatinib resistant variants were created from SKBR3 breast cancer cells. Syngenic therapy sensitive and resistant SKBR3 variants were characterized for mechanisms of resistance by mammosphere assays, viability assays, and western blotting for total and phospho proteins.

Results

Gefitinib and lapatinib treatments reduced mammosphere formation in the sensitive cells, but not in the therapy resistant variants, indicating enhanced mesenchymal and cancer stem cell-like characteristics in therapy resistant cells. The therapy resistant variants did not show significant changes in known therapy resistant pathways of AKT and MAPK activities downstream of EGFR/HER2. However, these cells exhibited elevated expression and activation of the small GTPase Rac, which is a pivotal intermediate of GFR signaling in EMT and metastasis. Therefore, the potential of the Rac inhibitors EHop-016 and MBQ-167 to overcome therapy resistance was tested, and found to inhibit viability and induce apoptosis of therapy resistant cells.

Conclusions

Rac inhibition may represent a viable strategy for treatment of EGFR/HER2 targeted therapy resistant breast cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08366-7.

Adipose MSCs Suppress MCF7 and MDA-MB-231 Breast Cancer Metastasis and EMT Pathways Leading to Dormancy via Exosomal-miRNAs Following Co-Culture Interaction

Globally, breast cancer is the most frequently diagnosed cancer in women, and it remains a substantial clinical challenge due to cancer relapse. The presence of a subpopulation of dormant breast cancer cells that survived chemotherapy and metastasized to distant organs may contribute to relapse. Tumor microenvironment (TME) plays a significant role as a niche in inducing cancer cells into dormancy as well as involves in the reversible epithelial-to-mesenchymal transition (EMT) into aggressive phenotype responsible for cancer-related mortality in patients. Mesenchymal stem cells (MSCs) are known to migrate to TME and interact with cancer cells via secretion of exosome- containing biomolecules, microRNA. Understanding of interaction between MSCs and cancer cells via exosomal miRNAs is important in determining the therapeutic role of MSC in treating breast cancer cells and relapse. In this study, exosomes were harvested from a medium of indirect co-culture of MCF7-luminal and MDA-MB-231-basal breast cancer cells (BCCs) subtypes with adipose MSCs. The interaction resulted in different exosomal miRNAs profiles that modulate essential signaling pathways and cell cycle arrest into dormancy via inhibition of metastasis and epithelial-to-mesenchymal transition (EMT). Overall, breast cancer cells displayed a change towards a more dormant-epithelial phenotype associated with lower rates of metastasis and higher chemoresistance. The study highlights the crucial roles of adipose MSCs in inducing dormancy and identifying miRNAs-dormancy related markers that could be used to identify the metastatic pattern, predict relapses in cancer patients and to be potential candidate targets for new targeted therapy.

A Case of Pulmonary Metastasis of Breast Cancer 23 Years after Surgery Accompanied with Non-Tuberculous Mycobacterium Infection

Recurrence of oestrogen receptor (ER)-positive breast cancer rarely occurs postoperatively after a long period. Breast cancer cells survive and settle in distant organs in a dormant state, a phenomenon known as "tumour dormancy." Here, we present a 66-year-old woman with recurrence of ER-positive breast cancer in the left lung 23 years after surgery accompanied with non-tuberculous mycobacterium infection (NTM). At the age of 43 years, the patient underwent a right mastectomy and adjuvant hormonotherapy to completely cure breast cancer. Twenty-three years after the operation, when the patient was 66 years old, computed tomography presented nodular shadows in the lower lobes bilaterally with bronchiectasis and ill-defined satellite tree-in-bud nodules. Mycobacterium intracellulare was detected in cultured bronchoalveolar lavage fluid obtained from the left lower lobe by bronchoscopy. Rifampicin, ethambutol, and clarithromycin were started, which resulted in shrinkage of the nodule in the right lower lobe and satellite nodules; however, the nodule in the left lower lobe increased in size gradually. Wedge resection of the left lower lobe containing the nodule by video-assisted thoracoscopic surgery was performed, which demonstrated that the nodule was adenocarcinoma in intraoperative pathological diagnosis; therefore, a left lower lobectomy and mediastinal lymph node dissection were performed. The tumour was revealed to be consistent with recurrence of previous breast cancer according to its morphology and immunohistochemical staining. Furthermore, caseous epithelioid cell granulomas existed in the periphery of the tumour. It is reported that inflammatory cytokines induce reawakening of dormant oestrogen-dependent breast cancer and, in our case, NTM infection might have stimulated the dormant tumour cells in the lower lobe.

Clinical Implications of Serum 25-Hydroxyvitamin D Status after 5-Year Adjuvant Endocrine Therapy for Late Recurrence of Hormone Receptor-positive Breast Cancer

Purpose

The prognostic implications of serum vitamin D status after a 5-year adjuvant endocrine therapy on the risk of late recurrence among hormone receptor (HR)-positive breast cancer patients remain unclear. Hence, we investigated this among Korean HR-positive breast cancer patients.

Methods

A total of 455 patients with HR-positive stage I–III invasive breast cancer who underwent curative surgery at St. Vincent's Hospital between February 2004 and April 2012 were included in this retrospective study. Patients were categorized based on their serum 25-hydroxyvitamin D (25(OH)D) levels after the 5-year adjuvant endocrine therapy. Initial recurrence sites were categorized. The primary clinical outcome was late recurrence-free survival (LRFS).

Results

Among the 455 patients, 242 and 213 were included in the 25(OH)D-deficient group and 25(OH)D-sufficient group, respectively. Forty-eight patients experienced late recurrence. Across all recurrence sites, the 25(OH)D-deficient group showed significantly worse LRFS rates than the 25(OH)D-sufficient group (hazard ratio [HR], 2.284; 95% confidence interval [CI], 1.155–4.515; p = 0.018). After patient subgrouping based on recurrence site, the 25(OH)D-deficient group also showed significantly worse LRFS rates in terms of regional lymph node (LN) (HR, 17.453; 95% CI, 2.46–128.83; p = 0.005), bone (HR, 2.394; 95% CI, 1.024–5.599; p = 0.044), and visceral (HR, 2.735; 95% CI, 1.182–6.328; p = 0.019) recurrence. However, there was no significant difference between the 2 groups in terms of local recurrence (p = 0.611).

Conclusions

We found that 25(OH)D deficiency after the 5-year adjuvant endocrine therapy was associated with worse LRFS among HR-positive breast cancer patients, particularly with respect to regional LN, bone, and visceral recurrence.

Thymic Function Associated With Cancer Development, Relapse, and Antitumor Immunity - A Mini-Review

The thymus is the central lymphoid organ for T cell development, a cradle of T cells, and for central tolerance establishment, an educator of T cells, maintaining homeostatic cellular immunity. T cell immunity is critical to control cancer occurrence, relapse, and antitumor immunity. Evidence on how aberrant thymic function influences cancer remains largely insufficient, however, there has been recent progress. For example, the involuted thymus results in reduced output of naïve T cells and a restricted T cell receptor (TCR) repertoire, inducing immunosenescence and potentially dampening immune surveillance of neoplasia. In addition, the involuted thymus relatively enhances regulatory T (Treg) cell generation. This coupled with age-related accumulation of Treg cells in the periphery, potentially provides a supportive microenvironment for tumors to escape T cell-mediated antitumor responses. Furthermore, acute thymic involution from chemotherapy can create a tumor reservoir, resulting from an inflammatory microenvironment in the thymus, which is suitable for disseminated tumor cells to hide, survive chemotherapy, and become dormant. This may eventually result in cancer metastatic relapse. On the other hand, if thymic involution is wisely taken advantage of, it may be potentially beneficial to antitumor immunity, since the involuted thymus increases output of self-reactive T cells, which may recognize certain tumor-associated self-antigens and enhance antitumor immunity, as demonstrated through depletion of autoimmune regulator (AIRE) gene in the thymus. Herein, we briefly review recent research progression regarding how altered thymic function modifies T cell immunity against tumors.

The bone metastasis niche in breast cancer-potential overlap with the haematopoietic stem cell niche in vivo

BACKGROUND

Bone metastasis is one of the most common complications of advanced breast cancer. During dissemination to bone, breast cancer cells locate in a putative 'metastatic niche', a microenvironment that regulates the colonisation, maintenance of tumour cell dormancy and subsequent tumour growth. The precise location and composition of the bone metastatic niche is not clearly defined. We have used in vivo models of early breast cancer dissemination to provide novel evidence that demonstrates overlap between endosteal, perivascular, HSC and the metastatic niche in bone.

METHODS

Estrogen Receptor (ER) +ve and -ve breast cancer cells were labelled with membrane dyes Vybrant-DiD and Vybrant-CM-DiI and injected via different routes in BALBc/nude mice of different ages. Two-photon microscopy was used to detect and quantitate tumour cells and map their location within the bone microenvironment as well as their distance to the nearest bone surface compared to the nearest other tumour cell. To investigate whether the metastatic niche overlapped with the HSC niche, animals were pre-treated with the CXCR4 antagonist AMD3100 to mobilise hematopoietic (HSCs) prior to injection of breast cancer cells.

RESULTS

Breast cancer cells displayed a characteristic pattern of homing in the long bones, with the majority of tumour cells seeded in the trabecular regions, regardless of the route of injection, cell-line characteristics (ER status) or animal age. Breast cancer cells located in close proximity to the nearest bone surface and the average distance between individual tumour cells was higher than their distance to bone. Mobilisation of HSCs from the niche to the circulation prior to injection of cell lines resulted in increased numbers of tumour cells disseminated in trabecular regions.

CONCLUSION

Our data provide evidence that homing of breast cancer cells is independent of their ER status and that the breast cancer bone metastasis niche is located within the trabecular region of bone, an area rich in osteoblasts and microvessels. The increased number of breast cancer cells homing to bone after mobilisation of HSCs suggests that the HSC and the bone metastasis niche overlap.

Parallels between hematopoietic stem cell and prostate cancer disseminated tumor cell regulation

The bone marrow is the primary site of hematopoiesis and the home for hematopoietic stem cells (HSCs) in adult mammals. Prostate cancer commonly metastasizes to the bone and forms bone metastases in almost all patients who die of the disease. Prostate cancer bone metastases are thought to develop after rare bone marrow disseminated tumor cells (DTCs) escape a dormant state and reactivate. Prostate cancer DTCs and normal HSCs have been shown to compete for residence in the bone marrow and share many of same regulatory mechanisms for survival, proliferation and homing. In this review, we highlight these parallels in order to help our readers use the literature in HSC and DTC biology to inform their research and generate hypotheses in both fields.

The influence of vascular endothelial growth factor-A and matrix metalloproteinase-2 and -9 in angiogenesis, metastasis, and prognosis of endometrial cancer

Angiogenesis (the growth of new blood vessels) is essential in most of the body’s physiological processes, such as in the normal functioning of the endometrium during and after the menstrual cycle. Vascular endothelial growth factor (VEGF) and matrix metalloproteinase (MMP) are the mostly expressed angiogenic factors, especially, during the process of endometrial degeneration and remodeling. In carcinogenesis, tumor hypoxia-induced factors, through the process of “angiogenic switch”, stimulate the production of angiogenic factors, particularly VEGF and MMP. Subsequently, these angiogenic factors are associated with degradation, differentiation, proliferation, and migration of vascular endothelial cells, enhancing the formation of new blood vessels to supply the tumor with oxygen and nutrients. This process is equally significant for tumor development and metastasis. Hence, like in other cancers, the overexpression of MMP and VEGF in endometrial cancer (EC) seems to play a significant role in its tumorigenesis and metastasis. This research will discuss the influence of MMP and VEGF on angiogenesis, metastasis, and the prognosis of EC as well as the clinical importance of the factors in the diagnosis of EC.

Trefoil Factor-3 (TFF3) Stimulates De Novo Angiogenesis in Mammary Carcinoma both Directly and Indirectly via IL-8/CXCR2

Mammary carcinoma cells produce pro-angiogenic factors to stimulate angiogenesis and tumor growth. Trefoil factor-3 (TFF3) is an oncogene secreted from mammary carcinoma cells and associated with poor prognosis. Herein, we demonstrate that TFF3 produced in mammary carcinoma cells functions as a promoter of tumor angiogenesis. Forced expression of TFF3 in mammary carcinoma cells promoted proliferation, survival, invasion and in vitro tubule formation of human umbilical vein endothelial cells (HUVEC). MCF7-TFF3 cells with forced expression of TFF3 generated tumors with enhanced microvessel density as compared to tumors formed by vector control cells. Depletion of TFF3 in mammary carcinoma cells by siRNA concordantly decreased the angiogenic behavior of HUVEC. Forced expression of TFF3 in mammary carcinoma cells stimulated IL-8 transcription and subsequently enhanced IL-8 expression in both mammary carcinoma cells and HUVEC. Depletion of IL-8 in mammary carcinoma cells with forced expression of TFF3, or antibody inhibition of IL-8, partially abrogated mammary carcinoma cell TFF3-stimulated HUVEC angiogenic behavior in vitro, as did inhibition of the IL-8 receptor, CXCR2. Depletion of STAT3 by siRNA in MCF-7 cells with forced expression of TFF3 partially diminished the angiogenic capability of TFF3 on stimulation of cellular processes of HUVEC. Exogenous recombinant hTFF3 also directly promoted the angiogenic behavior of HUVEC. Hence, TFF3 is a potent angiogenic factor and functions as a promoter of de novo angiogenesis in mammary carcinoma, which may co-coordinate with the growth promoting and metastatic actions of TFF3 in mammary carcinoma to enhance tumor progression.

Eukaryotic cell encystation and cancer cell dormancy: is a greater devil veiled in the details of a lesser evil?

Cancer cell dormancy is the main cause of cancer recurrence and failure of therapy as dormant cells evade not only the anticancer drugs but also the host immune system. These dormant cells veil themselves from detection by imaging and/or using biomarkers, which imposes an additional problem in targeting such cells. A similar form of hibernation process known as encystation is studied in detail for pathogenic unicellular eukaryotic microorganisms. By examination using microarray gene expression profiles, immunocytochemistry tools, and siRNAs during the process of encystation, understanding the covert features of cancer cell dormancy as proposed could be possible. This knowledge can be extended to dormant cancer cells to uncover the mechanisms that underlie this ghost, yet dangerous state of human cancers. We propose a strategy to induce dormancy and exit this state by application of knowledge gained from the encystation induction and retrieval processes in pathogenic eukaryotic microorganisms. Given that early detection and characterization of dormant malignant tumor cells is important as a general strategy to monitor and prevent the development of overt metastatic disease, this homology may enable the design of therapies that could either awake the dormant cell from dormancy to make it available for therapies or prolong such a phase to make cancer appear as a chronic disease.

IL-32 promotes breast cancer cell growth and invasiveness

Interleukin (IL)-32 is a newly identified cytokine in humans and primates. It has been established that IL-32 may antagonize cancer growth. However, to the best of our knowledge, the direct effect of IL-32 on breast cancer cell growth has not yet been investigated. In addition, rodents lack the expression of IL-32; hence, the effects of IL-32 on breast cancer xenografts in nude mice have not been studied. The present study aimed to examine the potential regulatory effects of IL-32 on breast cancer cells in nude mice. The effects of IL-32 on tumor cell growth in cell cuture and a tumor xenograft model were investigated, as well as the effects of IL-32 on apoptosis. The effects of IL-32 on cell proliferation and apoptosis were investigated by MTT assay and TUNEL staining, respectively. The results revealed that IL-32 increases the proliferation rate of cancer cells and decreases the rate of apoptosis, In addition, IL-32 was found to enhance the growth of tumor xenografts in vivo. In summary, IL-32 may represent a useful therapeutic target for human breast cancer.

Tumor dormancy: potential therapeutic target in tumor recurrence and metastasis prevention

In past decades, cancer patient survival has been improved with earlier detection and advancements in therapy. However, many patients who exhibit no clinical symptoms after frontline therapy subsequently suffer, often many years later, aggressive tumor recurrence. Cancer recurrence represents a critical clinical challenge in effectively treating malignancies and for patients’ quality of life. Tumor cell dormancy may help to explain treatment resistance and recurrence or metastatic reactivation. Understanding the dormant stage of tumor cells may help in discovering ways to maintain the dormant state or permanently eliminate dormant residual disseminated tumor cells. Over the past decade, numerous studies indicate that various mechanisms of tumor dormancy exist, including cellular dormancy (quiescence), angiogenic dormancy, and immunologic dormancy. In this short review, we summarize recent experimental and clinical evidence for these three mechanisms and other possible tumor microenvironment mechanisms that may influence tumor dormancy.