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.

METHODS

To identify conserved features of residual tumor cells, we modeled minimal residual disease using inducible transgenic mouse models for HER2/neu and Wnt1-driven tumorigenesis that recapitulate cardinal features of human breast cancer progression, as well as human breast cancer cell xenografts subjected to targeted therapy. Fluorescence-activated cell sorting was used to isolate tumor cells from primary tumors, residual lesions following oncogene blockade, and recurrent tumors to analyze gene expression signatures and evaluate tumor-initiating cell properties.

RESULTS

We demonstrate that residual tumor cells surviving oncogenic pathway inhibition at both local and distant sites exist in a state of cellular dormancy, despite adequate vascularization and the absence of adaptive immunity, and retain the ability to re-enter the cell cycle and give rise to recurrent tumors after extended latency periods. Compared to primary or recurrent tumor cells, dormant residual tumor cells possess unique features that are conserved across mouse models for human breast cancer driven by different oncogenes, and express a gene signature that is strongly associated with recurrence-free survival in breast cancer patients and similar to that of tumor cells in which dormancy is induced by the microenvironment. Although residual tumor cells in both the HER2/neu and Wnt1 models are enriched for phenotypic features associated with tumor-initiating cells, limiting dilution experiments revealed that residual tumor cells are not enriched for cells capable of giving rise to primary tumors, but are enriched for cells capable of giving rise to recurrent tumors, suggesting that tumor-initiating populations underlying primary tumorigenesis may be distinct from those that give rise to recurrence following therapy.

CONCLUSIONS

Residual cancer cells surviving targeted therapy reside in a well-vascularized, desmoplastic microenvironment at both local and distant sites. These cells exist in a state of cellular dormancy that bears little resemblance to primary or recurrent tumor cells, but shares similarities with cells in which dormancy is induced by microenvironmental cues. Our observations suggest that dormancy may be a conserved response to targeted therapy independent of the oncogenic pathway inhibited or properties of the primary tumor, that the mechanisms underlying dormancy at local and distant sites may be related, and that the dormant state represents a potential therapeutic target for preventing cancer recurrence.

Potential use of contrast-enhanced ultrasound (CEUS) in the detection of metastatic superficial lymph nodes in melanoma patients

PURPOSE

Malignant melanoma represents a significant and growing public health burden worldwide. Ultrasonography is the most useful diagnostic modality for regional lymph nodal staging. Because any focal areas of cortical lobulation or thickening-swelling should also be considered as a sign of metastases, we are going to report the usefulness of contrast-enhanced ultrasonography (CEUS) in the differential diagnosis of benign or malignant lymph nodes in patients with malignant melanoma based on blood stream patterns and investigate the diagnostic capability.

PATIENTS AND METHODS

After the excision of cutaneous melanoma with positive excision margins but with negative sentinel lymph node, 540 patients underwent US of superficial lymph nodes. The inclusion criteria for CEUS consisted of both major signs (absence of the echogenic hilus, round shape, and peripheral capsular vascularity) and minor ones (the presence of focal cortical thickening). The diagnostic capability was evaluated by comparing the cytological findings with the enhancement pattern on CEUS. 

RESULTS

US in combination with CEUS correctly classified 534/540 patients. CEUS applied to lymph nodes with focal cortical thickening on grayscale US confirmed great sensitivity (0.98) and specificity (0.99) but above all, it showed a markedly improved accuracy of 0.99. The likelihood ratios confirmed the good performance of the methods used.

CONCLUSION

CEUS increases the diagnostic accuracy of US in the differential diagnosis of benign and malignant LNs but it also allows us, when possible, to avoid unnecessary invasive operations such as LN FNAC. Moreover, CEUS may guide FNAC in the case of focal cortical thickening on the basis of hypoperfusion, with a reduction in the number of false negatives and much earlier detection of nodal metastatic foci.

Vascularity and angiogenesis as predictors of growth in optic pathway/hypothalamic gliomas

OBJECT

The authors' aim in conducting this study was to investigate retrospectively the prognostic significance of angiogenic features in optic pathway/hypothalamic gliomas (OPHGs) in children.

METHODS

Patients were identified in whom a diagnosis of OPHG was made using pathological analysis at the Toronto Hospital for Sick Children between 1985 and 2002. Tumor specimens were reviewed for diagnostic accuracy and adequacy of the specimen. Sections were immunostained with factor VIII to assess microvessel density (MVD). A ratio of alpha-smooth muscle actin to factor VIII immunostaining was calculated to arrive at a vascular maturity index (VMI). Vascular endothelial growth factor (VEGF) and VEGF receptor (VEGFR) immunostaining were performed to evaluate angiogenic factors. In addition, the MIB-1 labeling index (LI) was used to assess proliferation. These factors were evaluated with respect to progression-free survival (PFS). Forty-one of 60 patients originally identified had adequate samples and follow up for inclusion in the study. Of these, eight patients had coexisting neurofibromatosis Type 1. Twenty-eight patients experienced tumor progression after the initial treatment (surgery with or without adjuvant treatment). Thirty-eight patients are still alive. A high MVD (> 21 vessels/1.2 mm2) was associated with a significantly higher rate of progression compared with a low MVD (< 21 vessels/1.2 mm2; p = 0.017). Microvessel density was also predictive of reduced PFS on multivariate analysis stratified for extent of resection (p = 0.04), and VMI as well as intensity and distribution of VEGF and VEGFR staining and the MIB-1 LI were not significantly associated with PFS.

CONCLUSIONS

These findings suggest that MVD is the best current predictor of PFS in incompletely resected OPHGs. This information highlights the importance of angiogenesis in regard to low-grade gliomas.

Sonographic evaluation of early-stage breast cancers that undergo neoadjuvant chemotherapy

OBJECTIVE

We prospectively evaluated low-stage breast cancers treated with neoadjuvant chemotherapy using whole-volume sonography and color Doppler imaging.

METHODS

Thirty-four women with breast cancer (mean maximum size, 2.4 cm) received neoadjuvant chemotherapy with doxorubicin and docetaxel. Targeted whole-volume sonography of tumor sites was performed before and after chemotherapy to assess mass size, color pixel speed-weighted density, and American College of Radiology Breast Imaging Reporting and Data System sonographic characteristics. After chemotherapy, tumor sites were excised by lumpectomy or mastectomy.

RESULTS

Three (11.3%) of 34 patients had a complete histologic response. After chemotherapy, correlation was r = 0.716 between final histologic and sonographic sizes. Compared with histologic residual tumors, sonography had 4 false-negative results, 3 false-positive results, and 27 true-positive results (sensitivity, 87%), with no false-negative results among a subgroup of tumors of 7 mm and larger (sensitivity, 100%). The 3 cases with false-positive results were histologic fibrosis or biopsy changes. Mean speed-weighted density was 0.015 before and 0.0082 after chemotherapy (P = .03). After chemotherapy, vascularity was less common within (P = .06) or adjacent to (P = .009) masses or in tumor sites (P = .05). Prechemotherapy variables of gray scale characteristics and vascularity were compared with final histologic size, and all had P > .20.

CONCLUSIONS

Postchemotherapy sensitivity of sonography was high for residual tumors of 7 mm or larger. Correlation was moderate between histologic and sonographic final tumor sizes. False-positive results were caused by fibrosis or biopsy-related changes. False-negative results occurred with residual tumor size of 6 mm or smaller. After chemotherapy, vascularity usually decreased, and this was not specific for complete response. Before chemotherapy, no vascular or gray scale feature at initial imaging predicted complete responders.

Pituitary surgery complicated by haemorrhagic necrosis of residual tumour

Haemorrhagic necrosis of residual pituitary tumour following partial excision has not previously been well described. This is differentiated from post-operative sellar haematoma due to inadequate haemostasis on the basis of absent free clot. The authors report two cases of large macroadenomas with significant supra-sellar extension which were complicated by haemorrhagic necrosis of residual tumour following initial surgery. The literature is reviewed and possible pathophysiogical mechanisms are discussed.

Synergy between angiostatin and endostatin: inhibition of ovarian cancer growth

Ovarian cancer is the leading cause of fatality among gynecological malignancies. Ovarian cancer growth is angiogenesis-dependent, and an increased production of angiogenic growth factors such as vascular endothelial growth factor is prognostically significant even during early stages of the disease. Therefore, we investigated whether antiangiogenic treatment can be used to inhibit the growth of ovarian cancer in an experimental model system. Mouse angiostatin (kringle 1-4) and endostatin were expressed in yeast. Purified angiostatin and endostatin were then used to treat established ovarian cancers in athymic mice. These studies showed that both angiostatin and endostatin inhibited tumor growth. However, angiostatin treatment was more effective in inhibiting ovarian cancer growth when compared with endostatin in parallel experiments. Residual tumors obtained from angiostatin- and endostatin-treated animals showed decreased number of blood vessels and, as a consequence, increased apoptosis of tumor cells. Subsequently, the efficacy of a combined treatment with angiostatin and endostatin was investigated. In the presence of both angiostatic proteins, endothelial cell proliferation was synergistically inhibited. Similarly, a combination regimen using equal amounts of angiostatin and endostatin showed more than additive effect in tumor growth inhibition when compared with treatment with individual angiostatic protein. These studies demonstrate synergism between two angiostatic molecules and that antiangiogenic therapy can be used to inhibit ovarian cancer growth.

An unusual case of multiple recurrence of a glomangioma

Glomus tumour is a benign lesion arising from the glomus apparatus of the skin and subcutaneous tissue. Glomangioma is the angiomatous variant, which is uncommon. We report a very rare presentation of a glomangioma with multiple recurrences. We advocate preoperative angiography to delineate the extent of the lesion to facilitate complete excision.

Neoadjuvant chemotherapy for hypervascular malignant brain tumors of childhood

Some large hypervascular brain tumors pose an exceptional challenge to surgical resection, particularly in young children with small blood volumes. To limit blood loss during resection of hypervascular tumors, the authors used upfront chemotherapy as the primary treatment modality in 2 young children. This produced a dramatic reduction in tumor size and vascularity and greatly facilitated definitive surgical removal.