Development of lymph node and pulmonary metastases after local irradiation and hyperthermia of footpad melanomas

Quo Vadis Oncological Hyperthermia (2020)?

Heating as a medical intervention in cancer treatment is an ancient approach, but effective deep heating techniques are lacking in modern practice. The use of electromagnetic interactions has enabled the development of more reliable local-regional hyperthermia (LRHT) techniques whole-body hyperthermia (WBH) techniques. Contrary to the relatively simple physical-physiological concepts behind hyperthermia, its development was not steady, and it has gone through periods of failures and renewals with mixed views on the benefits of heating seen in the medical community over the decades. In this review we study in detail the various techniques currently available and describe challenges and trends of oncological hyperthermia from a new perspective. Our aim is to describe what we believe to be a new and effective approach to oncologic hyperthermia, and a change in the paradigm of dosing. Physiological limits restrict the application of WBH which has moved toward the mild temperature range, targeting immune support. LRHT does not have a temperature limit in the tumor (which can be burned out in extreme conditions) but a trend has started toward milder temperatures with immune-oriented goals, developing toward immune modulation, and especially toward tumor-specific immune reactions by which LRHT seeks to target the malignancy systemically. The emerging research of bystander and abscopal effects, in both laboratory investigations and clinical applications, has been intensified. Our present review summarizes the methods and results, and discusses the trends of hyperthermia in oncology.

Review of the Clinical Evidences of Modulated Electro-Hyperthermia (mEHT) Method: An Update for the Practicing Oncologist

Background: Modulated electro-hyperthermia (mEHT) is a variation of the conventional hyperthermia which selectively targets the malignant cell membranes in order to heat the malignant tissue and sensitize the tissue to oncology treatments. Although widely applied, the formulation of guidelines for the use thereof is still in progress for many tumors. Aim: In this paper we review the literature on the effects of mEHT in cancer patients on local disease control and survival. Methodology: Our review on data presents the collected experience with capacitive hyperthermia treatments with the EHY-2000+ device (OncoTherm Ltd., Germany). A literature search was conducted in Pubmed and articles were grouped and discussed according to: trial type, animal studies, in vitro studies, and reviews. Search results from Conference Abstracts; Trial Registries; Thesis and Dissertations and the Oncothermia Journal were included in the discussions. Results: Modulated electro-hyperthermia is a safe form of hyperthermia which has shown to effectively sensitizes deep tumors, regardless of the thickness of the adipose layers. The technology has demonstrated equal benefits compared to other forms of hyperthermia for a variety of tumors. Given the effective heating ability to moderate temperatures, the improved tumor perfusion, and ability to increase drug absorption, mEHT is a safe and effective heating technology which can be easily applied to sensitize tumors which have demonstrated benefits with the addition of hyperthermia. Modulated electro-hyperthermia also appears to improve local control and survival rates and appears to induce an abscopal (systemic) response to ionizing radiation. Conclusion: Based on clinical studies, the method mEHT is a feasible hyperthermia technology for oncological applications. Concomitant utilization of mEHT is supported by the preclinical and clinical data.

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.

Establishment of Fischer 344 rat model of ovarian cancer with lymphatic metastasis

PURPOSE

To establish a model of ovarian cancer with highly lymphatic metastasis in immunocompetent rats.

METHODS

Thirty-two female Fischer 344 rats were divided randomly and equally into two groups: footpad group and intraperitoneal (i.p.) group. At 8 weeks after injection with NuTu-19 ovarian cancer cells, lymphatic metastasis were analyzed by pathohistology; body weight was monitored per week, Survival curves were determined by Kaplan-Meier analysis.

RESULTS

Footpad injection could efficiently generate the lymphatic metastasis; specifically, the incidences of metastasis in the ipsilateral popliteal, inguinal and para-iliac lymph nodes were 100% (8/8), 75% (6/8), and 37.5% (3/8), respectively. The mean volume and weight of the ipsilateral popliteal lymph nodes were 0.405 ± 0.096 cm(3) and 0.418 ± 0.118 g in footpad group. However, no lymphatic metastasis lesions were found in i.p. group. Moreover, Kaplan-Meier analysis showed that the average survival time of the footpad group was significantly longer than that of the i.p. group (18.429 ± 1.112 vs. 10.286 ± 0.505 weeks).

CONCLUSIONS

Our experiments suggest that footpad injection is a very efficient method to generate ovarian cancer with lymphatic metastasis in an immune-competent animal, and we believe that this model will be very helpful for shedding light on the mechanism of lymphogenous metastasis and developing novel therapeutic targets for ovarian cancer patients.

Preclinical models of regional lymph node tumor metastasis

Animal models have produced vital information regarding the mechanisms of RLN metastasis. Modern imaging and molecular techniques have made it clear that growing tumors secrete cytokines that induce invasion, angiogenesis, lymphangiogenesis, increased intratumoral IFV and IFP, increased fluid flow from the tumor to the surrounding tissues, increased lymphatic flow, an increase in the rate of entry of tumor cells into lymphatic capillaries, and an increased number of tumor cells reaching the RLN(s). This is important knowledge that will help direct translational research in human patients. We can look forward to continued improvement in the management of human tumors that metastasize to the RLNs.

Contrast-aided diagnostic ultrasound does not enhance lung metastasis in a mouse melanoma tumor model

OBJECTIVE

The purpose of this research was to test the hypothesis that contrast-aided diagnostic ultrasound (CADUS) could exacerbate the metastatic spread of mouse melanoma tumor cells to the lungs.

METHODS

The melanoma cell lines B16 and B16-D5 (metastatic specifically to lung) were implanted on a hind leg of female C57/bl6 mice. Growing tumors were scanned by 1.5-MHz diagnostic ultrasound in a 37 degrees C water bath. Four hundred image frames were triggered at a 1-Hz rate with 4 retro-orbital injections of an ultrasonographic contrast agent at dosage of 10 microL/kg at 100-second intervals. Sham-treated mice received 400 frames of ultrasonography followed by the contrast agent with the ultrasound off. The primary tumor was surgically removed 1 day after ultrasound administration. Lungs were removed and evaluated blind after 2 weeks of bleaching in Fekete solution.

RESULTS

Three experiments were performed. The first experiment involved scanning sham and CADUS groups of 20 mice each with B16 tumors; B16 metastasis was not enhanced. The second experiment repeated this test with the D5 cell line; the metastasis enhancement was marginally significant for average number (0.3 and 3.2; P = .06) and incidence (3 and 9 of 19; P = .08) in mice without tumor recurrence. Finally, a third experiment was performed to clarify ambiguous results in the second experiment and consisted of 2 groups of 40 mice each. In this larger experiment, the results were essentially equal for the sham and CADUS groups.

CONCLUSIONS

Overall, the results do not support the hypothesis of CADUS-enhanced metastasis.

Lithotripter shockwave-induced enhancement of mouse melanoma lung metastasis: dependence on cavitation nucleation

PURPOSE

To confirm a previous report of metastasis enhancement by lithotripter shockwaves (LSW) and to test the hypothesis that this effect is attributable to cavitation.

MATERIALS AND METHODS

The metastatic B16-D5 melanoma cell line was implanted on the hind legs of female C57/b16 mice 12 days before tumor treatment. The tumors were treated with 500 LSW in a waterbath arrangement. The effect of augmented cavitation nucleation was tested by intratumor injection of air bubbles or ultrasound contrast agent gas bodies (UCAGB). The primary tumor was surgically removed on day 1 after treatment. The six groups of mice were sham, LSW, sham + air bubbles, LSW + air bubbles, sham + UCAGB, and LSW + UCAGB. Data were collected for the 113 mice that survived at least 25 days. Lung evaluations were performed blind after 2 weeks of bleaching in Fekete's solution.

RESULTS

The outcomes of the three sham groups were very similar and indicated that the simple injection of material into the tumor did not increase metastasis. In comparison with the pooled shams, both the LSW + air bubbles and LSW + UCAGB groups had statistically significant increases in metastasis counts. Only the LSW + UCAGB group had a significant increase in incidence of metastasis relative to the pooled shams. The LSW + UCAGB also had significantly reduced survival.

CONCLUSION

Shockwaves can enhance metastasis from tumors, and this effect is attributable to cavitation.

Insights into the mechanisms of lymph node metastasis

The mechanisms by which malignant tumors leave the primary tumor site, invade lymphatics, and metastasize to regional lymph nodes (RLNs) are complex and interrelated. Although the phenomenon of lymph node metastasis has been recognized for over 200 years, the exact mechanisms have only recently been the subject of intense interest and sophisticated experimentation. Sentinel lymph node biopsy has rapidly entered the clinical mainstream for melanoma and breast carcinoma, and this technique has provided confirmation of the orderly anatomic progression of tumor cells from primary site to the RLNs through lymphatic capillaries and trunks. Exciting studies involving the pathophysiology of interstitial fluid pressure in tumors and the peritumoral extracellular matrix have focused on lymphatic flow and tumor microenvironment and microcirculation. Molecular techniques have led to the definition of unique markers found on lymphatic endothelial cells. These markers have enabled scientists to identify peritumoral and intratumoral lymphatics and to visualize the ingrowth of tumor cells into the lumena of lymphatic capillaries. Tumor-secreted cytokines, such as vascular endothelial growth factors (VEGF)-C and -D, bind to VEGF receptors on lymphatic endothelial cells and induce proliferation and growth of new lymphatic capillaries; this process is similar to the well-known mechanism of angiogenesis, which results from the proliferation of new blood vessel capillaries. Lymphangiogenesis is associated with an increased incidence of RLN metastasis, and it is possible that this step is essential to the metastatic process. Directional movement toward lymphatics and lymph nodes appears to follow a chemokine gradient, and it is likely that some tumor cells that express certain types of chemokine receptors are more likely to metastasize to the RLNs. In contrast, tumor cells that do not express specific receptors that are responsive to lymphatic chemokines may not metastasize. New knowledge regarding the molecules involved in these processes should enable improvements in prognostic and possibly therapeutic approaches to the management of malignant tumors.

A truncated isoform of the protein phosphatase 2A B56gamma regulatory subunit may promote genetic instability and cause tumor progression

F10, a subline of the B16 mouse melanoma cell line, is itself the parent of the more metastatic BL6 line. BL6 cells differ from F10 cells by an alteration of the gene encoding the B56gamma regulatory subunit of protein phosphatase 2A (PP2A), which results in the expression of a truncated variant of the subunit (Deltagamma1). PP2A is involved in regulating the cell-cycle checkpoint and we found that the checkpoint in BL6 cells is aberrant when the Deltagamma1 protein is expressed. That is, although Deltagamma1 protein levels in cultured BL6 cells are low and these cells do not show an altered checkpoint on gamma-irradiation, irradiated footpad BL6 tumor cells show both a marked increase in Deltagamma1 levels and more extensive polyploidy and less apoptosis than F10 cells. These observations were reproduced with Deltagamma1 gene-transfected F10 cells (F10(Deltagamma1)). Deltagamma1 expression and an aberrant checkpoint are also associated with a higher metastatic ability because irradiated F10(Deltagamma1) tumors metastasized much more frequently than F10 tumors, which rarely metastasized whether irradiated or not. Nonirradiated F10(Deltagamma1) tumors, which do not express Deltagamma1 protein, had similarly low rates of metastasis. The greater metastatic ability of irradiated F10(Deltagamma1) tumors also correlated with the acquisition of many more genomic alterations. Thus, it seems that Deltagamma1 expression may damage the checkpoint, which may then allow the acquisition of genetic alterations that promote metastasis. These observations support the notion that mechanisms promoting the genetic instability of tumors could also aid tumor progression from the nonmetastatic to the metastatic state.