The effects of surgery on tumor growth: a century of investigations

Blockade of extracellular NM23 or its endothelial target slows breast cancer growth and metastasis

BACKGROUND

Nucleoside Diphosphate Kinase (NDPK), described as NM23 a metastasis suppressor, is found in the culture medium of cancer cells lines suggesting that the kinase may have an extracellular role. We propose that extracellular NM23 released from breast cancers in vivo stimulates tumor cell migration, proliferation and endothelial cell angiogenesis in support of metastasis development.

METHODS

NM23 in the bloodstream of immunocompromised mice carrying human triple-negative breast cancers or in breast cancer patients was measured by ELISA. Primary and metastatic tumor development, the impact of blockade of NM23 and/or its stimulation of nucleotide receptors were measured using in vivo imaging. NM23 expression data in the Curtis breast dataset was examined to test our hypothesis that NM23 may play a mechanistic role in breast cancer development.

RESULTS

SCID mice carrying metastatic MDA-MB-231Luc+ triple-negative human breast tumor cells elaborate NM23 into the circulation correlated with primary tumor growth. Treatment of mice with the NM23 inhibitor ellagic acid (EA) or the purinergic receptor antagonist MRS2179 slowed primary tumor growth. At 16 weeks following implantation, lung metastases were reduced in mice treated with EA, MRS2179 or the combination. Expression of NM23 in the Curtis breast dataset confirmed a likely role for NM23 in tumor metastasis.

CONCLUSIONS

Extracellular NM23 may constitute both a biomarker and a therapeutic target in the management of breast cancer.

Microenvironmental regulation of therapeutic response in cancer

The tumor microenvironment (TME) not only plays a pivotal role during cancer progression and metastasis but also has profound effects on therapeutic efficacy. In the case of microenvironment-mediated resistance this can involve an intrinsic response, including the co-option of pre-existing structural elements and signaling networks, or an acquired response of the tumor stroma following the therapeutic insult. Alternatively, in other contexts, the TME has a multifaceted ability to enhance therapeutic efficacy. This review examines recent advances in our understanding of the contribution of the TME during cancer therapy and discusses key concepts that may be amenable to therapeutic intervention.

Postsurgical adjuvant tumor therapy by combining anti-angiopoietin-2 and metronomic chemotherapy limits metastatic growth

Antiangiogenic tumor therapy has failed in the adjuvant setting. Here we show that inhibition of the Tie2 ligand angiopoietin-2 (Ang2) effectively blocks metastatic growth in preclinical mouse models of postsurgical adjuvant therapy. Ang2 antibody treatment combines well with low-dose metronomic chemotherapy (LDMC) in settings in which maximum-dose chemotherapy does not prove effective. Mechanistically, Ang2 blockade could be linked to quenching the inflammatory and angiogenic response of endothelial cells (ECs) in the metastatic niche. Reduced EC adhesion molecule and chemokine expression inhibits the recruitment of tumor-promoting CCR2(+)Tie2(-) metastasis-associated macrophages. Moreover, LDMC contributes to therapeutic efficacy by inhibiting the recruitment of protumorigenic bone marrow-derived myeloid cells. Collectively, these data provide a rationale for mechanism-guided adjuvant tumor therapies.

Core needle biopsy of breast cancer tumors increases distant metastases in a mouse model

INTRODUCTION: Incisional biopsies, including the diagnostic core needle biopsy (CNB), routinely performed before surgical excision of breast cancer tumors are hypothesized to increase the risk of metastatic disease. In this study, we experimentally determined whether CNB of breast cancer tumors results in increased distant metastases and examine important resultant changes in the primary tumor and tumor microenvironment associated with this outcome. METHOD: To evaluate the effect of CNB on metastasis development, we implanted murine mammary 4T1 tumor cells in BALB/c mice and performed CNB on palpable tumors in half the mice. Subsequently, emulating the human scenario, all mice underwent complete tumor excision and were allowed to recover, with attendant metastasis development. Tumor growth, lung metastasis, circulating tumor cell (CTC) levels, variation in gene expression, composition of the tumor microenvironment, and changes in immunologic markers were compared in biopsied and non-biopsied mice. RESULTS: Mice with biopsied tumors developed significantly more lung metastases compared to non-biopsied mice. Tumors from biopsied mice contained a higher frequency of myeloid-derived suppressor cells (MDSCs) accompanied by reduced CD4 + T cells, CD8 + T cells, and macrophages, suggesting biopsy-mediated development of an increasingly immunosuppressive tumor microenvironment. We also observed a CNB-dependent up-regulation in the expression of SOX4, Ezh2, and other key epithelial-mesenchymal transition (EMT) genes, as well as increased CTC levels among the biopsy group. CONCLUSION: CNB creates an immunosuppressive tumor microenvironment, increases EMT, and facilitates release of CTCs, all of which likely contribute to the observed increase in development of distant metastases.

Single cell gene expression analysis in injury-induced collective cell migration

Collective cell behavior in response to mechanical injury is central to various regenerative and pathological processes. Using a double-stranded locked nucleic acid probe for monitoring real-time intracellular gene expression, we examined the spatiotemporal response of epithelial cells during injury-induced collective migration and compared to the blocker assay with minimal injury as control. We showed that cells ∼150 μm from the wound edge exhibit a gradient in response to mechanical injury, expressing different genes depending on the wounding process. While release of contact inhibition is sufficient to trigger the migratory behavior, cell injury additionally induces reactive oxygen species, Nrf2 protein, and stress response genes, including heat shock protein 70 and heme oxygenase-1, in a spatiotemporal manner. Furthermore, we show that Nrf2 has an inhibitory role in injury-induced epithelial-mesenchymal transition, suggesting a potential autoregulatory mechanism in injury-induced response. Taken together, our single-cell gene expression analyses reveal modular cell responses to mechanical injury, manipulation of which may afford novel strategies for tissue repair and prevention of tumor invasion in the future.

Therapeutic adenoviral gene transfer of a glycosyltransferase for prevention of peritoneal dissemination and metastasis of gastric cancer

Increased expression of sialyl Lewis(x/a) carbohydrates, ligands for E-selectin, correlates with clinically advanced stages and metastasis of gastric and colon cancers. In contrast, Sd(a) carbohydrate is abundantly detected in the normal gastrointestinal mucosa but dramatically reduced or lost in cancer tissues. A glycosyltransferase, β1,4N-acetylgalactosaminyltransferase 2 (B4GALNT2) that catalyzes Sd(a) carbohydrate synthesis, is silenced in cancer. In the present study, we aimed at reducing the expression of sialyl Lewis(x/a) of cancer cells in vivo by forced expression of B4GALNT2 and Sd(a), thereby preventing dissemination/metastasis, especially metastasis triggered by surgical maneuvers. We used a fiber-modified adenovirus (Ad) vector that contained a chimeric construct with a serotype 5 shaft and a serotype 3 knob. Using this Ad5/3 vector, we successfully introduced the B4GALNT2 gene into a human gastric cancer cell line KATO III in vitro and confirmed replacement of sialyl Lewis(x) to Sd(a) with a decrease in E-selectin-dependent adhesion. Administration of Ad5/3-B4GALNT2 vectors into the peritoneal cavity of mice after inoculation of KATO III cells with laparotomy significantly reduced the incidence of metastasis. Our results indicate that the transfer of a single gene encoding B4GALNT2 modified carbohydrate chains of cancer cells in vivo and decreased tumor dissemination and metastasis.

Can we negotiate with a tumor?

Recent progress in deciphering the molecular portraits of tumors promises an era of more personalized drug choices. However, current protocols still follow standard fixed-time schedules, which is not entirely coherent with the common observation that most tumors do not grow continuously. This unpredictability of the increases in tumor mass is not necessarily an obstacle to therapeutic efficiency, particularly if tumor dynamics could be exploited. We propose a model of tumor mass evolution as the integrated result of the dynamics of two linked complex systems, tumor cell population and tumor microenvironment, and show the practical relevance of this nonlinear approach.

Bimodal mortality dynamics for uveal melanoma: a cue for metastasis development traits?

Background

The study estimates mortality dynamics (event-specific hazard rates over a follow-up time interval) for uveal melanoma.

Methods

Three thousands six hundred seventy two patients undergoing radical or conservative treatment for unilateral uveal melanoma, whose yearly follow-up data were reported in three published datasets, were analysed. Mortality dynamics was studied by estimating with the life-table method the discrete hazard rate for death. Smoothed curves were obtained by a Kernel-like smoothing procedure and a piecewise exponential regression model. The ratio deaths/patients at risk per year was the main outcome measure.

Results

The three explored hazard rate curves display a common bimodal pattern, with a sudden increase peaking at about three years, followed by reduction until the sixth-seventh year and a second surge peaking at about nine years after treatment.

Conclusions

The bimodal pattern of mortality indicates that uveal melanoma metastatic development cannot be explained by a continuous growth model. Similar metastasis dynamics have been reported for other tumours, including early breast cancer, for which it supported a paradigm shift to an interrupted growth model, the implications of which are episodes of ‘tumour dormancy’. We propose that the concepts of tumour homeostasis, tumour dormancy and enhancement of metastasis growth related to primary tumour removal, convincingly explaining the clinical behaviour of breast cancer, may be used for uveal melanoma as well. To confirm this proposition, a careful analysis of uveal melanoma metastasis dynamics is strongly warranted.

Interval between neoadjuvant treatment and definitive surgery in locally advanced rectal cancer: impact on response and oncologic outcomes

PURPOSE

The optimal waiting period between neoadjuvant treatment completion and surgery in locally advanced rectal cancer (LARC) is controversial. The specific purpose of this study was to evaluate the effect of prolonging this interval on the pathologic response, postoperative morbidity, and long-term oncologic outcomes.

METHODS

Retrospective data analysis is reported from LARC patients who had been treated with chemoradiation followed by surgery and intra-operative radiotherapy, between February 1995 and December 2012. In total, two groups were studied, according to the time elapsed between neoadjuvant treatment and surgery: conventional interval (CI; <6 weeks) and delayed interval (DI; ≥6 weeks). Clinicopathological data related to tumor response, postoperative morbidity, and oncologic outcomes were compared.

RESULTS

This study included 335 consecutive LARC patients. There was a higher proportion of patients with clinical staging nodal involvement (cN+) in the DI group (76.6 vs. 64.1 %; p = 0.01). The pathologic complete response (pCR) was not significantly different among groups (8.8 vs. 12.1 %; p = 0.34). Longer intervals did not affect complication incidence or severity or hospital admission length. Certain postneoadjuvant tumor effect parameters were significantly increased in the DI group, including N-downstaging and T-downsizing. After a median follow-up of 71 months, patients in the DI group presented with superior 5-year overall survival (OS) (55.9 vs. 70.4 %, p = 0.014); however, no statistically significant differences were observed in 5-year disease-free survival (DFS) or 5-year local control (LC) (69.9 vs. 74.9 %, p = 0.223; 90.4 vs. 94.5 %, p = 0.123, respectively).

CONCLUSIONS

A modest surgical interval delay (≥6 weeks) did not increase postoperative complications and was identified as a favorable prognostic factor for OS, although no differences were observed in pCR, LC, or DFS. Innovative multidisciplinary strategies incorporating further time extension of the surgical interval can be safely explored.

The role of gene regulatory networks in promoting cancer progression and metastasis

ABSTRACT: 

The majority of deaths owing to cancer are ultimately caused by metastatic disease. However, most research, to date, has focused on the molecular features of cancers at their primary sites rather than on understanding disseminated malignancy in its systemic form. The dynamic nature of metastatic malignancy and its behavior as a co-ordinated systemic disease require a cancer progression paradigm that is integrative and can incorporate both the proximate causes of cancer and the broader ultimate causes in an evolutionary and developmental context. The study of robust cellular attractor states that arise directly from the architectural patterns contained within gene regulatory networks is proposed as a conceptual framework through which many of the other disparate models of cancer metastasis can be more clearly viewed and, ultimately, unified, thus providing a new conceptual framework in which to understand cancer progression and metastasis.

The wound healing, chronic fibrosis, and cancer progression triad

For decades tumors have been recognized as "wounds that do not heal." Besides the commonalities that tumors and wounded tissues share, the process of wound healing also portrays similar characteristics with chronic fibrosis. In this review, we suggest a tight interrelationship, which is governed as a concurrence of cellular and microenvironmental reactivity among wound healing, chronic fibrosis, and cancer development/progression (i.e., the WHFC triad). It is clear that the same cell types, as well as soluble and matrix elements that drive wound healing (including regeneration) via distinct signaling pathways, also fuel chronic fibrosis and tumor progression. Hence, here we review the relationship between fibrosis and cancer through the lens of wound healing.

A microRNA signature associated with early recurrence in breast cancer

Recurrent breast cancer occurring after the initial treatment is associated with poor outcome. A bimodal relapse pattern after surgery for primary tumor has been described with peaks of early and late recurrence occurring at about 2 and 5 years, respectively. Although several clinical and pathological features have been used to discriminate between low- and high-risk patients, the identification of molecular biomarkers with prognostic value remains an unmet need in the current management of breast cancer. Using microarray-based technology, we have performed a microRNA expression analysis in 71 primary breast tumors from patients that either remained disease-free at 5 years post-surgery (group A) or developed early (group B) or late (group C) recurrence. Unsupervised hierarchical clustering of microRNA expression data segregated tumors in two groups, mainly corresponding to patients with early recurrence and those with no recurrence. Microarray data analysis and RT-qPCR validation led to the identification of a set of 5 microRNAs (the 5-miRNA signature) differentially expressed between these two groups: miR-149, miR-10a, miR-20b, miR-30a-3p and miR-342-5p. All five microRNAs were down-regulated in tumors from patients with early recurrence. We show here that the 5-miRNA signature defines a high-risk group of patients with shorter relapse-free survival and has predictive value to discriminate non-relapsing versus early-relapsing patients (AUC = 0.993, p-value<0.05). Network analysis based on miRNA-target interactions curated by public databases suggests that down-regulation of the 5-miRNA signature in the subset of early-relapsing tumors would result in an overall increased proliferative and angiogenic capacity. In summary, we have identified a set of recurrence-related microRNAs with potential prognostic value to identify patients who will likely develop metastasis early after primary breast surgery.

Prognostic relevance of ¹⁸F-FDG PET uptake in patients with locally advanced, extremity soft tissue sarcomas undergoing neoadjuvant isolated limb perfusion with TNF-α and melphalan

PURPOSE

The objective of this study was to determine whether (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) can adequately assess the risk of systemic disease progression in patients with primary, localized, high-grade soft tissue sarcomas of the extremities undergoing neoadjuvant isolated limb perfusion (ILP) with tumour necrosis factor and melphalan.

METHODS

This was a retrospective analysis of the files of 35 patients who underwent a PET or PET/CT scan prior to and after ILP followed by surgical resection with curative intent between 2006 and 2012. SUVmax₁ was defined as the maximum standardized uptake value (SUV) at diagnosis, SUVmax₂ as the maximum SUV after ILP and ΔSUVmax as the percentage difference between SUVmax1 and SUVmax₂.

RESULTS

The median follow-up was 40 months for all patients. The median SUVmax1 amounted to 7.6, while the median SUVmax₂ was 4.7. The median ΔSUVmax was -44%. Overall survival (OS) probability at 2 and 5 years amounted to 78 and 70%, respectively, while metastasis-free survival (MFS) probability at 2 and 5 years was 67 and 64%, respectively. Receiver-operating characteristic (ROC) curve analysis showed that both SUVmax2 and ΔSUVmax could predict systemic disease progression, while SUVmax1 could not adequately identify patients who went on to develop metastatic disease. The optimal cut-off value was 6.9 for SUVmax2 and -31 % for ΔSUVmax. Patients with an SUVmax2 <6.9 had a 2-year MFS of 80%, compared to 31 % for patients with an SUVmax2 ≥ 6.9 (p < 0.001). Patients with a ΔSUVmax < -31 %, i.e. patients with a higher metabolic response, had an MFS of 76% at 2 years, compared to 42% for patients with a ΔSUVmax ≥ -31% (p = 0.050).

CONCLUSION

SUVmax after ILP for primary, locally advanced, non-metastatic high-grade soft tissue sarcomas of the extremities appears to be significantly correlated with prognosis. Whether patients with a high SUVmax after ILP will benefit from standard or experimental adjuvant systemic treatment options should be evaluated in future studies.

The efficacy of surgical treatment of cancer - 20 years later

INTRODUCTION

Cancer treatment will be effective only if it is be based on a valid paradigm of what cancer is and therefore capable of affecting the course of the disease. A review in 1993 found no evidence that surgery affected the course of the disease and an alternative paradigm was proposed. A review of mammography screening trials in 1996 found no benefits from breast cancer screening. This was predicted by this alternative paradigm. This review updates the evidence twenty years later.

AIM

To identify evidence that the primary treatment of cancer, surgery, has been shown to affect the course of the disease. If there is no such evidence, then to identify the correct paradigm of what cancer is from other cancer treatments that have been shown to be effective.

METHOD

Because surgery has never been shown in a randomised controlled trial to affect the course of cancer seven other indirect methods were used to evaluate its efficacy.

RESULTS

None of the seven indirect methods used showed that surgery clearly affects the course of the disease for any type of cancer. The lack of benefits from cancer screening now includes not only from breast cancer but also from bowel, lung, prostate and ovarian cancer screening. This confirms that cancer surgery is based on an invalid paradigm of what cancer is. Survival figures following treatments based on an alternative paradigm that assumes cancer is a systemic disease were found to be superior to those following surgery, reinforcing the conclusion that cancer is a systemic disease and that cancer surgery is unlikely to be of benefit in most cases.

CONCLUSION

No benefits can be expected to be achieved from using cancer surgery except in a few immediately life-threatening situations. Surgery appears to be based on an invalid paradigm of what cancer is. Cancer appears to be a systemic disease and therefore standard treatments need to be reassessed in this light.

Stimuli-induced organ-specific injury enhancement of organotropic metastasis in a spatiotemporal regulation

The relationship between inflammation and tumorigenesis has been established. Recently, inflammation is also reported to be a drive force for cancer metastasis. Further evidences show that various stimuli directly induced-injury in a specific organ can also promote metastasis in this organ, which include epidemiological reports, clinical series and experimental studies. Each type of cancer has preferential sites for metastasis, which is also due to inflammatory factors that are released by primary cancer to act on these sites and indirectly induce injuries on them. Host factors such as stress,fever can also influence distant metastasis in a specific site through stimulation of immune and inflammatory effects. The five aspects support an idea that specific-organ injury directly induced by various stimuli or indirectly induced by primary tumor or host factors activation of proinflammatory modulators can promote metastasis in this organ through a spatiotemporal regulation, which has important implications for personalized prediction, prevention and management of cancer metastasis.

Reconstruction of the natural history of metastatic cancer and assessment of the effects of surgery: Gompertzian growth of the primary tumor

This work deals with retrospective reconstruction of the individual natural history of solid cancer and assessment of the effects of treatment on metastatic progression. This is achieved through a mathematical model of cancer progression accounting for the growth of the primary tumor, shedding of metastases, their dormancy and growth at secondary sites. To describe dynamics of the primary tumor, we used the Gompertz law, a parsimonious model of tumor growth accounting for its saturation. Parameters of the model were estimated from the age and volume of the primary tumor at surgery and volumes of detectable bone metastases collected from one breast cancer patient and one prostate cancer patient. This allowed us to estimate, for each patient, the ages at cancer onset and inception of all detected metastases, the expected metastasis latency time, parameters of the Gompertzian growth of the primary tumor, and the rates of growth of metastases before and after surgery. We found that for both patients: (1) onset of metastasis occurred when primary tumor was undetectable; (2) inception of all surveyed metastases except one occurred before surgery; and most importantly, (3) resection of the primary tumor led to a dramatic increase in the rate of growth of metastases. The model provides an excellent fit to the observed volumes of bone metastases in both patients. Our results agree well with those obtained previously based on exponential growth of the primary tumor, which serves as model validation. Our findings support the notion of metastatic dormancy and indirectly confirm the existence of stem-like cancer cells in breast and prostate tumors. We also explored the logistic law of primary tumor growth; however, it degenerated into the exponential law for both patients analyzed. The conclusions of this work are supported by a vast body of experimental, clinical and epidemiological knowledge accumulated over the last century.

Does regional anaesthesia and analgesia or opioid analgesia influence recurrence after primary cancer surgery? An update of available evidence

Cancer continues to be a key cause of morbidity and mortality worldwide and its overall incidence continues to increase. Anaesthetists are increasingly faced with the challenge of managing cancer patients, for surgical resection to debulk or excise the primary tumour, or for surgical emergencies in patients on chemotherapy or for the analgesic management of disease- or treatment-related chronic pain. Metastatic recurrence is a concern. Surgery and a number of perioperative factors are suspected to accelerate tumour growth and potentially increase the risk of metastatic recurrence. Retrospective analyses have suggested an association between anaesthetic technique and cancer outcomes, and anaesthetists have sought to ameliorate the consequences of surgical trauma and minimise the impact of anaesthetic interventions. Just how anaesthesia and analgesia impact cancer recurrence and consequent survival is very topical, as understanding the potential mechanisms and interactions has an impact on the anaesthetist's ability to contribute to the successful outcome of oncological interventions. The outcome of ongoing, prospective, randomized trials are awaited with interest.

Impact of breast cancer surgery on angiogenesis circulating biomarkers: a prospective longitudinal study

BACKGROUND

Debate about the potential effects that surgery might have on cancer cells dormancy and angiogenesis prompted us to investigate the impact of breast surgery on circulating angiogenesis modulating gene transcripts and proteins.

METHODS

Blood samples from 10 female patients diagnosed with breast cancer and 6 with fibroadenoma were collected before surgery and post-operatively on days 3 and 7 (breast cancer patients only). A set of 84 angiogenesis-associated transcripts were assessed using quantitative PCR arrays, and circulating protein levels (vascular endothelial growth factor A (VEGFA), IL8 and fibroblast growth factor 2 (FGF2) were measured using ELISA in the same samples. The results were investigated against clinicopathological data and patient outcome.

RESULTS

Plasma levels of VEGFA and IL8 after surgery were significantly elevated in the breast cancer group compared to the control group (P = 0.038 and P = 0.021, respectively). In the cohort of breast cancer patients, VEGFA increased on day 3 (P = 0.038) and declined on day 7 (P= 0.017), while IL8 did not change on day 3 but showed a significant decline on day 7 (P = 0.02). FGF2 levels did not change significantly over time. Regarding gene transcripts, we detected upregulation of a significant number of angiogenesis-specific genes in patients with breast cancer versus controls: sphingosine kinase 1(SPHK1), epidermal growth factor (EGF), vascular endothelial growth factor C (VEGFC), neuropilin 1 (NRP1), fibroblast growth factor (FGF1), laminin alpha 5 (LAMA5), collagen type IV alpha 3 (COL4A3), IL8, ephrin B2 (EFNB2), ephrin A3 (EFNA3), tyrosine endothelial kinase (TEK), integrin beta 3 (ITGB3), AKT1, thrombospondin 1 (THBS1), chemokine (C-C motif) ligand 11 (CCL11) and TIMP metallopeptidase inhibitor 3 (TIMP3). Surgery induced an altered expression in several keygenes in breast cancer patients. We identified an upregulation of COL4A3 and downregulation of chemokine (C-X-C motif) ligand 9 (CXCL9), EGF, FGF1, Kinase insert domain receptor (KDR), Placental growth factor (PGF), TIMP3 and VEGFC.

CONCLUSION

Breast cancer patients have a different expression profile of circulating angiogenesis biomarkers compared to patients with fibroadenoma. Moreover, mastectomy promotes a transient increase of VEGFA and a shift in the expression patterns of a broad panel of angiogenesis-related circulating gene transcripts.

Surgery, wound healing, and metastasis: recent insights and clinical implications

BACKGROUND

Surgery-induced acceleration of tumour growth has been observed since several centuries.

METHODS

We reviewed recent insights from in vitro data, animal experimentation, and clinical studies on how surgery-induced wound healing or resection of a primary cancer influences the tumour-host ecosystem in patients harbouring minimal residual or metastatic disease.

RESULTS

Most of the growth factors, chemokines, and cytokines orchestrating surgical wound healing promote tumour growth, invasion, or angiogenesis. In addition, resection of a primary tumour may accelerate synchronous metastatic growth. In the clinical setting, indirect evidence supports the relevance of the above findings. Randomized clinical trials are underway comparing resection versus observation in metastatic breast and colon cancer with asymptomatic primary tumours.

CONCLUSIONS

In depth knowledge of how surgical intervention alters the tumour-host-metastasis communicating ecosystems could have important implications for clinical decision making in patients with synchronous metastatic disease and for the design and timing of multimodality treatment strategies.

Short-course radiotherapy followed by neo-adjuvant chemotherapy in locally advanced rectal cancer--the RAPIDO trial

BACKGROUND

Current standard for most of the locally advanced rectal cancers is preoperative chemoradiotherapy, and, variably per institution, postoperative adjuvant chemotherapy. Short-course preoperative radiation with delayed surgery has been shown to induce tumour down-staging in both randomized and observational studies. The concept of neo-adjuvant chemotherapy has been proven successful in gastric cancer, hepatic metastases from colorectal cancer and is currently tested in primary colon cancer.

METHODS AND DESIGN

Patients with rectal cancer with high risk features for local or systemic failure on magnetic resonance imaging are randomized to either a standard arm or an experimental arm. The standard arm consists of chemoradiation (1.8 Gy x 25 or 2 Gy x 25 with capecitabine) preoperatively, followed by selective postoperative adjuvant chemotherapy. Postoperative chemotherapy is optional and may be omitted by participating institutions. The experimental arm includes short-course radiotherapy (5 Gy x 5) followed by full-dose chemotherapy (capecitabine and oxaliplatin) in 6 cycles before surgery. In the experimental arm, no postoperative chemotherapy is prescribed. Surgery is performed according to TME principles in both study arms. The hypothesis is that short-course radiotherapy with neo-adjuvant chemotherapy increases disease-free and overall survival without compromising local control. Primary end-point is disease-free survival at 3 years. Secondary endpoints include overall survival, local control, toxicity profile, and treatment completion rate, rate of pathological complete response and microscopically radical resection, and quality of life.

DISCUSSION

Following the advances in rectal cancer management, increased focus on survival rather than only on local control is now justified. In an experimental arm, short-course radiotherapy is combined with full-dose chemotherapy preoperatively, an alternative that offers advantages compared to concomitant chemoradiotherapy with or without postoperative chemotherapy. In a multi-centre setting this regimen is compared to current standard with the aim of improving survival for patients with locally advanced rectal cancer.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01558921.

Metastasis dynamics for non-small-cell lung cancer: effect of patient and tumor-related factors

BACKGROUND

We studied event dynamics (probability of an event occurring over a specific time interval) in patients undergoing surgery for early-stage non-small-cell lung cancer (NSCLC) according to patient and tumor characteristics.

METHODS

By using a database of 1506 patients who underwent initial surgery for NSCLC, event dynamics, based on a time-specific hazard rate, were evaluated. The event of interest was the development of distant metastases, with or without a local recurrence. The effect of sex, tumor size, nodal involvement, histology, lymphovascular space invasion, pleural invasion, age, and race were studied.

RESULTS

The hazard rate for developing distant metastases was not constant over time but was characterized by specific peaks, the first being approximately 9 months after surgery and the second at 18 to 20 months for men and 24 to 26 months for women. For women, the hazard rate peaked considerably in the first year. For men, the hazard rate peaks were smaller but lasted for a longer duration. Pathologic factors associated with a higher risk of recurrence (eg, size, lymph node involvement, pleural invasion) all increased the sex-specific hazard rates.

CONCLUSIONS

The probability of developing distant metastases after surgery for NSCLC peaks at specific and consistent time intervals after surgery, with specific differences between men and women. A factor-specific modulation of peak heights that ranged from no impact (eg, race) to relevant effects for primary tumor size, nodal involvement, and pleural invasion, possibly related to sex, was also observed. The bimodal distant metastases dynamics may be an intrinsic feature of metastatic progression in NSCLC.

Significance of ipsilateral breast tumor recurrence after breast conserving treatment: role of surgical removal

OBJECTIVE

To analyze the pattern over time (dynamics) of further recurrence and death after ipsilateral breast tumor recurrence (IBTR) in breast cancer patients undergoing breast conserving treatment (BCT).

METHODS

A total of 338 evaluable patients experiencing IBTR were extracted from a database of 3,293 patients undergoing BCT. The hazard rates for recurrence and mortality throughout 10 years of follow-up after IBTR were assessed and were compared to the analogous estimates associated to the primary treatment.

RESULTS

In a time frame with the time origin at the surgical treatment for IBTR, the hazard rate for further recurrence displays a bimodal pattern (peaks at the second and at the sixth year). Patients receiving mastectomy for IBTR reveal recurrence and mortality dynamics similar to that of node positive (N+) patients receiving mastectomy as primary surgery, apart from the first two-three years, when IBTR patients do worse. If the patients with time to IBTR longer than 2.5 years are considered, differences disappear.

CONCLUSIONS

The recurrence and mortality dynamics following IBTR surgical removal is similar to the corresponding dynamics following primary tumor removal. In particular, patients with time to IBTR in excess of 2.5 years behave like N+ patients following primary tumor removal. Findings may be suitably explained by assuming that the surgical manoeuvre required by IBTR treatment is able to activate a sudden growing phase for tumor foci most of which, as suggested by the systemic model of breast cancer, would have reached the clinical level according to their own dynamics.

Biological stoichiometry in tumor micro-environments

Tumors can be viewed as evolving ecological systems, in which heterogeneous populations of cancer cells compete with each other and somatic cells for space and nutrients within the ecosystem of the human body. According to the growth rate hypothesis (GRH), increased phosphorus availability in an ecosystem, such as the tumor micro-environment, may promote selection within the tumor for a more proliferative and thus potentially more malignant phenotype. The applicability of the GRH to tumor growth is evaluated using a mathematical model, which suggests that limiting phosphorus availability might promote intercellular competition within a tumor, and thereby delay disease progression. It is also shown that a tumor can respond differently to changes in its micro-environment depending on the initial distribution of clones within the tumor, regardless of its initial size. This suggests that composition of the tumor as a whole needs to be evaluated in order to maximize the efficacy of therapy.

Reduction of breast cancer relapses with perioperative non-steroidal anti-inflammatory drugs: new findings and a review

To explain a bimodal pattern of hazard of relapse among early stage breast cancer patients identified in multiple databases, we proposed that late relapses result from steady stochastic progressions from single dormant malignant cells to avascular micrometastases and then on to growing deposits. However in order to explain early relapses, we had to postulate that something happens at about the time of surgery to provoke sudden exits from dormant phases to active growth and then to detection. Most relapses in breast cancer are in the early category. Recent data from Forget et al. suggest an unexpected mechanism. They retrospectively studied results from 327 consecutive breast cancer patients comparing various perioperative analgesics and anesthetics in one Belgian hospital and one surgeon. Patients were treated with mastectomy and conventional adjuvant therapy. Relapse hazard updated Sept 2011 are presented. A common Non-Steroidal Anti-Inflammatory Drug (NSAID) analgesic used in surgery produced far superior disease-free survival in the first 5 years after surgery. The expected prominent early relapse events in months 9-18 are reduced 5-fold. If this observation holds up to further scrutiny, it could mean that the simple use of this safe, inexpensive and effective anti-inflammatory agent at surgery might eliminate early relapses. Transient systemic inflammation accompanying surgery could facilitate angiogenesis of dormant micrometastases, proliferation of dormant single cells, and seeding of circulating cancer stem cells (perhaps in part released from bone marrow) resulting in early relapse and could have been effectively blocked by the perioperative anti-inflammatory agent.

Seeing the invisible: how mathematical models uncover tumor dormancy, reconstruct the natural history of cancer, and assess the effects of treatment

The hypothesis of early metastasis was debated for several decades. Dormant cancer cells and surgery-induced acceleration of metastatic growth were first observed in clinical studies and animal experiments conducted more than a century ago; later, these findings were confirmed in numerous modern studies.In this primarily methodological work, we discuss critically important, yet largely unobservable, aspects of the natural history of cancer, such as (1) early metastatic dissemination; (2) dormancy of secondary tumors; (3) treatment-related interruption of metastatic dormancy, induction of angiogenesis, and acceleration of the growth of vascular metastases; and (4) the existence of cancer stem cells. The hypothesis of early metastasis was debated for several decades. Dormant cancer cells and surgery-induced acceleration of metastatic growth were first observed in clinical studies and animal experiments conducted more than a century ago; later, these findings were confirmed in numerous modern studies.We focus on the unique role played by very general mathematical models of the individual natural history of cancer that are entirely mechanistic yet, somewhat paradoxically, essentially free of assumptions about specific nature of the underlying biological processes. These models make it possible to reconstruct in considerable detail the individual natural history of cancer and retrospectively assess the effects of treatment. Thus, the models can be used as a tool for generation and validation of biomedical hypotheses related to carcinogenesis, primary tumor growth, its metastatic dissemination, growth of metastases, and the effects of various treatment modalities. We discuss in detail one such general model and review the conclusions relevant to the aforementioned aspects of cancer progression that were drawn from fitting a parametric version of the model to data on the volumes of bone metastases in one breast cancer patient and 12 prostate cancer patients.

Pattern of recurrence of early breast cancer is different according to intrinsic subtype and proliferation index

INTRODUCTION

Recurrence risk in breast cancer varies throughout the follow-up time. We examined if these changes are related to the level of expression of the proliferation pathway and intrinsic subtypes.

METHODS

Expression of estrogen and progesterone receptor, Ki-67, human epidermal growth factor receptor 2 (HER2), epidermal growth factor receptor (EGFR) and cytokeratin 5/6 (CK 5/6) was performed on tissue-microarrays constructed from a large and uniformly managed series of early breast cancer patients (N = 1,249). Subtype definitions by four biomarkers were as follows: luminal A (ER + and/or PR+, HER2−, Ki-67 <14), luminal B (ER + and/or PR+, HER2−, Ki-67 ≥14), HER2-enriched (any ER, any PR, HER2+, any Ki-67), triple-negative (ER−, PR−, HER2−, any Ki-67). Subtype definitions by six biomarkers were as follows: luminal A (ER + and/or PR+, HER2−, Ki-67 <14, any CK 5/6, any EGFR), luminal B (ER + and/or PR+, HER2−, Ki-67 ≥14, any CK 5/6, any EGFR), HER2-enriched (ER−, PR−, HER2+, any Ki-67, any CK 5/6, any EGFR), Luminal-HER2 (ER + and/or PR+, HER2+, any Ki-67, any CK 5/6, any EGFR), Basal-like (ER−, PR−, HER2−, any Ki-67, CK5/6+ and/or EGFR+), triple-negative nonbasal (ER−, PR−, HER2−, any Ki-67, CK 5/6−, EGFR−). Each four- or six-marker defined intrinsic subtype was divided in two groups, with Ki-67 <14% or with Ki-67 ≥14%. Recurrence hazard rate function was determined for each intrinsic subtype as a whole and according to Ki-67 value.

RESULTS

Luminal A displayed a slow risk increase, reaching its maximum after three years and then remained steady. Luminal B presented most of its relapses during the first five years. HER2-enriched tumors show a peak of recurrence nearly twenty months post-surgery, with a greater risk in Ki-67 ≥14%. However a second peak occurred at 72 months but the risk magnitude was greater in Ki-67 <14%. Triple negative tumors with low proliferation rate display a smooth risk curve, but with Ki-67 ≥14% show sharp peak at nearly 18 months.

CONCLUSIONS

Each intrinsic subtype has a particular pattern of relapses over time which change depending on the level of activation of the proliferation pathway assessed by Ki-67. These findings could have clinical implications both on adjuvant treatment trial design and on the recommendations concerning the surveillance of patients.

Tumor-derived microvesicles: the metastasomes

Metastasis is the leading cause of cancer death, yet it is mechanistically considered a very inefficient process suggesting the presence of some sort of (e.g. systemic) routes for fuelling the process. The pre-metastatic niche formation is described as one such metastasis promoting route. Now, the emerging potentials of tumor-derived microvesicles (TDMVs), not only in formulating the pre-metastatic niche, but also conferring neoplastic phenotypes onto normal cells, has integrated new concepts into the field. Here, we note as an ancillary proposition that, exerting functional disturbances in other sites, TDMVs (we have termed them metastasomes) may aid foundation of the secondary lesions via two seemingly interrelated models: (i) tumor-organ-training (TOTr), training a proper niche for the growth of the disseminated tumor cells; (ii) tumor-organ-targeting (TOTa), contribution to the propagation of the transformed phenotype via direct or indirect (TOTr-mediated disturbed stroma) transformation and/or heightened growth/survival states of the normal resident cells in the secondary organs. Respecting the high content of the RNA molecules (particularly microRNAs) identified in the secretory MVs, they may play crucial parts in such "malignant trait" spreading system. That is, the interactions between tumor tissue-specific RNA signatures, being transferred via metastasomes, and the cell-type/tissue-specific RNA stockrooms in other areas may settle a unique outcome in each organ. Thus, serving as tumor-organ matchmakers, the RNA molecules may also play substantial roles in the seeding and tropism of the process.

From Reductionism to Holism: Systems-oriented Approaches in Cancer Research

Somatic mutation theory of cancer has directed cancer research during the last century. A deluge of information on cellular, molecular, and genetic behavior was uncovered, but so was a mind-numbing complexity that still challenges research and concepts, and expectations in the war on cancer have by and large not been fulfilled. A change of paradigm beyond reductionism has been called for, especially as research ubiquitously points at the importance of tissue, microenvironment, extracellular matrix, embryonic and morphogenetic fields, and fields of tissue maintenance and organization in the processes of carcinogenesis, cancer control, and cancer progression, as well as in the control of cellular and genetic behavior. Holistic, organismic systems concepts open new perspectives for cancer research and treatment, as well as general biological understanding.

Loco-regional therapy and breast cancer survival: searching for a link

OBJECTIVE

The relationship between loco-regional (LR) control and breast cancer survival was investigated with the intention of generating a new biological hypothesis to explain some of the paradoxes unaccounted for by the prevailing conceptual model of the disease.

BACKGROUND

The progressive reduction of surgical aggressiveness has been accompanied by an increase of breast cancer survival mainly attributed to the adoption of adjuvant systemic therapies. More recently, it has been recognized that effective LR control may prolong the survival of breast cancer patients, although the reasons for this improvement have not yet been clearly defined.

METHODS

The literature (PubMed) was reviewed for publications related to breast cancer LR treatments using the following key words: breast cancer surgery, breast cancer radiotherapy, breast cancer loco-regional control, breast cancer survival.

RESULTS

Although breast cancer is frequently a multifocal disease, neither mastectomy nor whole breast irradiation are always mandatory to obtain adequate local control. Conversely, selected groups of patients carry a particularly elevated risk of LR relapse and require more effective treatments to be developed. True LR recurrences are associated with a decreased overall survival and this may be related to a complex relationship between circulating tumor cells, re-seeding of the primary tumor site and several metabolic effects linked to the act of surgery.

CONCLUSION

The prevention of LR recurrences is a major goal of breast cancer care, which requires a better understanding of the complex relationships between the primary tumor and its metastatic process.

Modeling the connection between primary and metastatic tumors

We put forward a model for cancer metastasis as a migration phenomenon between tumor cell populations coexisting and evolving in two different habitats. One of them is a primary tumor and the other one is a secondary or metastatic tumor. The evolution of the different cell phenotype populations in each habitat is described by means of a simple quasispecies model allowing for a cascade of mutations between the different phenotypes in each habitat. The cell migration event is supposed to be unidirectional and take place continuously in time. The possible clinical outcomes of the model depending on the parameter space are analyzed and the effect of the resection of the primary tumor is studied.

[Perioperative tumour dissemination. 1. Influence of perioperative factors]

There has been growing concern in the last few years on the effect of anaesthetic drugs used during oncological surgery could have on tumour progression in the long-term, as well as the influence of other perioperative factors. Although much of the available data has weak evidence, the role of the surgery itself, pain, transfusion of blood derivatives, etc., have been assessed in several studies. How some substances used during the anaesthetic process can influence tumour immune surveillance, cell proliferation or tumour angiogenesis processes have been observed in laboratory studies. The possible relevance of the anaesthetic technique used as regards the long-term tumour progression and survival is still to be determined. However, based on retrospective studies, it seems that those anaesthetic techniques combined with the use of regional anaesthesia and analgesia could be beneficial compared to those that are maintained on opioid use. Further research should help to elucidate the long-term clinical relevance of the perioperative procedures, including the anaesthetic, during oncological surgery.

Concomitant tumor resistance

Concomitant tumor resistance (CR) is a phenomenon in which a tumor-bearing host is resistant to the growth of secondary tumor implants. This phenomenon has been described in human and animal systems and it can be generated by both immunogenic and non-immunogenic tumors. The relevance of CR to the mechanisms of metastases control has been highlighted by numerous observations showing that the removal of human and murine tumors may be followed by an abrupt increase in metastatic growth, suggesting that a primary tumor may exert a controlling action on its metastases which could be considered as secondary tumor implants developed spontaneously during the primary tumor growth. A more profound understanding of the different mechanisms claimed to be associated with the phenomenon of CR could contribute to develop new and more harmless means to manage malignant diseases, especially by limiting the development of metastases that arise after resection of primary tumors or after other stressors that may promote the escape of metastases from dormancy.

Ginsenoside Rg3 inhibits growth of liver metastases in nude mice after surgical removal of primary tumor

AIM: To investigate the effect of 20(R)-Ginsenoside Rg3 on the growth of hepatic metastasis in nude mice after surgical removal of primary tumor.

METHODS: BALB/c mouse colon adenocarcinoma CT-26-GFP cell line was established by transfection of CT-26 cells with a lentiviral vector containing the enhanced green fluorescent protein (eGFP) gene. A nude mouse model of hepatic metastasis was then developed, and the mice were randomly divided into three groups: primary tumor resection group, primary tumor preservation group and Ginsenoside Rg3 group. After resection of the primary tumor and treatment with Ginsenoside Rg3 for 10 days, microvascular density (MVD) and cell multiplication of liver metastases were detected by immunohistochemistry, and tumor apoptosis was detected by TUNEL assay. The green fluorescence was observed using a fluorescence in vivo imaging system.

RESULTS: The average fluorescence intensity of liver metastases in the Ginsenoside Rg3 group was significantly lower than that in the primary tumor preservation group and primary tumor resection group (314.17 ± 54.23 vs 388.82 ± 25.97, 427.18 ± 44.31). The incidences of metastases in the Ginsenoside Rg3 group, primary tumor preservation group and primary tumor resection group were 40%, 50% and 100%, respectively. The average weight of the liver, MVD, and labeling index of Ki67 were lower and TUNEL apoptotic index was higher in the Ginsenoside Rg3 group than in the primary tumor preservation group and primary tumor resection group (liver weight: 2.92 ± 0.60 vs 3.80 ± 0.33, 3.98 ± 0.52; MVD: 27.10 ± 3.41 vs 42.60 ± 8.42, 62.40 ± 5.08; labeling index of Ki67: 34.70 ± 6.46 vs 54.30 ± 8.98, 65.20 ± 3.82; apoptotic index: 28.37 ± 3.86 vs 12.50 ± 2.99, 9.90 ± 2.88).

CONCLUSION: 20(R)-Ginsenoside-Rg3 could inhibit metastatic tumor growth, angiogenesis, proliferation and promote apoptosis in mice after surgical removal of primary tumor.

Totally laparoscopic strategies for the management of colorectal cancer with synchronous liver metastasis

INTRODUCTION

Laparoscopy is an accepted treatment for colorectal cancer and liver metastases, but there is no consensus for its use in the management of synchronous liver metastases (SCRLM). The purpose of this study was to evaluate totally laparoscopic strategies in the management of colorectal cancer with synchronous liver metastases.

METHODS

Patients presenting to Ninewells Hospital between July 2007 and August 2010, with adenocarcinoma of the colon and rectum with synchronous liver metastases were considered. Patients underwent simultaneous laparoscopic liver and colon cancer resection, a staged laparoscopic resection of SCRLM and colon cancer, or simultaneous colon resection and radiofrequency ablation (RFA) of SCRLM. Primary endpoints were in-hospital morbidity and mortality, total hospital stay, intraoperative blood loss, duration of surgery, and resection margin status.

RESULTS

Twenty-eight patients presented with synchronous colorectal liver metastases. Thirteen patients underwent a simultaneous laparoscopic liver and colon resection (median operating time, 370 (range, 190-540) min; median hospital stay, 7 (range, 3-54) days), seven patients had a staged laparoscopic resection of SCRLM and primary colon cancer (median operating time, 530 (range, 360-980) min; median hospital stay 14, (range, 6-51) days), and eight patients underwent laparoscopic colon resection and RFA of SCRLM (median operating time, 310 (range, 240-425) min; median hospital stay, 8 (range, 6-13) days). There were no conversions to an open procedure. Overall in-hospital morbidity and mortality was 28 and 0 % respectively. An R0 resection margin was achieved in 91 % of the resection group. At a median follow-up of 26 (range, 18-55) months, 19 (90 %) patients remain disease-free.

CONCLUSIONS

Totally laparoscopic strategies for the radical treatment of stage IV colorectal cancer are feasible with low morbidity and favorable outcomes. A laparoscopic approach for the simultaneous management of SCRLM and primary colon cancer is associated with reduced surgical access trauma, postoperative morbidity, and hospital stay with no compromise in short-term oncological outcome.

Totally laparoscopic strategies for the management of colorectal cancer with synchronous liver metastasis

INTRODUCTION

Laparoscopy is an accepted treatment for colorectal cancer and liver metastases, but there is no consensus for its use in the management of synchronous liver metastases (SCRLM). The purpose of this study was to evaluate totally laparoscopic strategies in the management of colorectal cancer with synchronous liver metastases.

METHODS

Patients presenting to Ninewells Hospital between July 2007 and August 2010, with adenocarcinoma of the colon and rectum with synchronous liver metastases were considered. Patients underwent simultaneous laparoscopic liver and colon cancer resection, a staged laparoscopic resection of SCRLM and colon cancer, or simultaneous colon resection and radiofrequency ablation (RFA) of SCRLM. Primary endpoints were in-hospital morbidity and mortality, total hospital stay, intraoperative blood loss, duration of surgery, and resection margin status.

RESULTS

Twenty-eight patients presented with synchronous colorectal liver metastases. Thirteen patients underwent a simultaneous laparoscopic liver and colon resection (median operating time, 370 (range, 190-540) min; median hospital stay, 7 (range, 3-54) days), seven patients had a staged laparoscopic resection of SCRLM and primary colon cancer (median operating time, 530 (range, 360-980) min; median hospital stay 14, (range, 6-51) days), and eight patients underwent laparoscopic colon resection and RFA of SCRLM (median operating time, 310 (range, 240-425) min; median hospital stay, 8 (range, 6-13) days). There were no conversions to an open procedure. Overall in-hospital morbidity and mortality was 28 and 0 % respectively. An R0 resection margin was achieved in 91 % of the resection group. At a median follow-up of 26 (range, 18-55) months, 19 (90 %) patients remain disease-free.

CONCLUSIONS

Totally laparoscopic strategies for the radical treatment of stage IV colorectal cancer are feasible with low morbidity and favorable outcomes. A laparoscopic approach for the simultaneous management of SCRLM and primary colon cancer is associated with reduced surgical access trauma, postoperative morbidity, and hospital stay with no compromise in short-term oncological outcome.

Does secondary inflammatory breast cancer represent post-surgical metastatic disease?

The phenomenon of accelerated tumor growth following surgery has been observed repeatedly and merits further study. Inflammatory breast carcinoma (IBC) is widely recognized as an extremely aggressive malignancy characterized by micrometastasis at the time of diagnosis, with one interesting subgroup defined as secondary IBC where pathologically identifiable IBC appears after surgical treatment of a primary non-inflammatory breast cancer. One possible mechanism can be related to the stimulation of dormant micrometastasis through local angiogenesis occurring as part of posttraumatic healing. In this report, we review cases of secondary IBC and others where localized trauma was followed by the appearance of IBC at the traumatized site that have been identified by our IBC Registry (IBCR) and hypothesize that angiogenesis appearing as part of the healing process could act as an accelerant to an otherwise latent breast malignancy. It is therefore possible that secondary IBC can be used as a model to support local angiogenesis as an important contributor to the development of an aggressive cancer.

Concomitant tumor resistance: the role of tyrosine isomers in the mechanisms of metastases control

Concomitant tumor resistance (CR) is a phenomenon in which a tumor-bearing host is resistant to the growth of secondary tumor implants and metastasis. Although previous studies indicated that T-cell-dependent processes mediate CR in hosts bearing immunogenic small tumors, manifestations of CR induced by immunogenic and nonimmunogenic large tumors have been associated with an elusive serum factor. In a recently published study, we identified this factor as meta-tyrosine and ortho-tyrosine, 2 isomers of tyrosine that would not be present in normal proteins. In 3 different murine models of cancer that generate CR, both meta- and ortho-tyrosine inhibited tumor growth. Additionally, we showed that both isoforms of tyrosine blocked metastasis in a fourth model that does not generate CR but is sensitive to CR induced by other tumors. Mechanistic studies showed that the antitumor effects of the tyrosine isomers were mediated in part by early inhibition of the MAP/ERK pathway and inactivation of STAT3, potentially driving tumor cells into a state of dormancy in G(0)-phase. Other mechanisms, putatively involving the activation of an intra-S-phase checkpoint, would also inhibit tumor proliferation by accumulating cells in S-phase. By revealing a molecular basis for the classical phenomenon of CR, our findings may stimulate new generalized approaches to limit the development of metastases that arise after resection of primary tumors or after other stressors that may promote the escape of metastases from dormancy, an issue that is of pivotal importance to oncologists and their patients.

SUFFICIENT TO RECOGNIZE SELF TO ATTACK NON-SELF: BLUEPRINT FOR A ONE-SIGNAL T CELL MODEL

Current consensus postulates that the class I-antigen processing system is evolved to present microbial antigens to specific T cells. Since such cells are rare and short-lived, they require three to five days to attain fighting strength. During this critical period he innate immune system holds back the briskly multiplying pathogens. Nevertheless, a T cell response is measurable in the lymph nodes draining the infection site within 12 to 18 h. In order to explain this paradox here we suggest a new T cell model. This is based on the observation that T cells require continuous contact of the T cell receptor (TCR) with selecting self-peptide–major histocompatibility complex (MHC) molecules in the periphery for their survival. We postulate that a dynamic steady state, a so-called coupled system is formed through low affinity complementary TCR–MHC interactions between T cells and host cells. Under such condition it is sufficient to recognize what is self in order to attack what is not self. A coupled system is regulated via soluble forms of peptide–MHC and TCR molecules by the law of mass action. In a coupled system one signal is sufficient for T cell activation. The new model implies that a significant fraction of the naive polyclonal T cells are recruited into the first line of defense from the very outset of an infection, so the number of activated T cells is increased by several orders of magnitude compared to conventional models. The one-signal model also predicts that therapeutic administration of soluble agonist or antagonist T cell receptor ligands may be able to fine tune the homeostatic physiological regulatory mechanism and thus improve the treatment of some chronic diseases such as metastatic cancer, HIV/AIDS, and transplantation.