Chemotherapy. 2013;59(1):14-23. doi: 10.1159/000351100.

Methyl sulfone manifests anticancer activity in a metastatic murine breast cancer cell line and in human breast cancer tissue–part I: murine 4T1 (66cl-4) cell line.

Caron JM, Bannon M, Rosshirt L, O’Donovan L.

Department of Cell Biology, School of Medicine, University of Connecticut Health Center, Farmington, CT 06030, USA.


BACKGROUND: The spread of cancer (metastasis) is usually associated with death. We have identified a new approach that may be useful for treating metastatic cancer.

METHODS: Here we studied the murine breast cancer cell line 66cl-4, because these cells are highly aggressive, potent inducers of metastasis and estrogen receptor negative.

RESULTS: We found that 200 mM methyl sulfone did not induce apoptosis in cancerous cells but instead decreased cell proliferation and DNA synthesis, inhibited migration of cells through an extracellular matrix and induced contact inhibition and anchorage-dependent growth. Methyl sulfone promoted proper wound healing, reversed the epithelial to mesenchymal transition associated with metastatic disease and increased expression of α-smooth muscle actin, a differentiation protein of breast myoepithelial cells.

CONCLUSION: Methyl sulfone did not kill the cancer cells but instead decreased metastatic phenotypes and increased normal differentiated phenotypes.

Copyright © 2013 S. Karger AG, Basel.

PMID: 23816666


Chemotherapy. 2013;59(1):24-34. doi: 10.1159/000351099.

Methyl sulfone manifests anticancer activity in a metastatic murine breast cancer cell line and in human breast cancer tissue–part 2: human breast cancer tissue.

Caron JM, Monteagudo L, Sanders M, Bannon M, Deckers PJ.

Department of Cell Biology, University of Connecticut Health Center, Farmington, CT 06030, USA.


BACKGROUND: Methyl sulfone is a small molecule that reverses cancerous phenotypes of a melanoma cell line. Here, we sought to determine whether methyl sulfone was effective against human breast cancer tissue.

METHODS: We studied normal and cancerous breast tissue obtained from 17 patients.

RESULTS: Methyl sulfone introduced structural order, with cancer tissue taking on the morphology of normal in vivo breast tissue; this structural order was sustainable over long-term culture. Methyl sulfone promoted proper wound healing, including migration of cells into wounded areas and establishment of stable contact inhibition once wounds were covered. Methyl sulfone decreased expression of two breast stem cell marker proteins, HCAM and OCT3/4, which are associated with aberrantly rapid migration of metastatic cells. Finally, normal and cancerous primary breast cells remained viable and healthy in methyl sulfone culture for at least 90 days.

CONCLUSION: Methyl sulfone reintroduced a normal structural phenotype to human breast cancer tissues.

Copyright © 2013 S. Karger AG, Basel.

PMID: 23816712



Methyl Sulfone and the Treatment of Metastatic Cancer  

Present Day Chemotherapy

The goal of present day chemotherapy is to kill cancer cells.  While these chemotherapeutic drugs are often effective against early stage tumors (primary tumors), these drugs are not effective against late stage or metastatic cancer cells.  Metastatic cancer means that cancer cells have migrated away from the primary tumor and have invaded other tissues.  Metastatic cancer accounts for approximately 90% of all cancer deaths.

Many of us know, as patients or caregivers, that the side effects of present day chemotherapy can be devastating.  What makes these side effects so physically and emotionally devastating is the fact that these drugs always kill some normal cells in your body, but often not the metastatic cancer cells.  Why metastatic cells are so hard to kill is not clear.  But neither broad-based chemotherapy nor more specific drug targeting has proved uniformly successful long-term against metastatic disease.

Researchers are always attempting to identify new and more effective chemotherapeutic drugs.  However, drug screening for anti-cancer activity is based on the ability of drugs to kill cancer cells.  These tests are most often performed with robotics.  This means that test results are looked at without ever looking at the cells.  We sought to determine a new approach to identify compounds that would stop cancer cells from growing (proliferating) without killing the normal cells, and in the process we discovered methyl sulfone.

Methyl Sulfone

Methyl sulfone is a small water-soluble molecule that displays no apparent toxicity to mammals including humans; i.e., no side effects.  Furthermore, methyl sulfone is a critical part of the oceanic-atmospheric-terra firma life cycle of sulfur.  Methyl sulfone and the metabolites that form methyl sulfone are natural molecules that are necessary for survival of many organisms including several species of plants, phytoplankton algae, diatoms and fishes.

Human beings do not synthesize methyl sulfone, and must acquire the molecule through diet.  However, certain plant species such as broccoli, cauliflower, Brussels sprouts, Swiss chard, onion and garlic, several of which have been consumed by humans for centuries, contain methyl sulfone.  Several ancient plants also contain significant quantities of methyl sulfone.  For example, the horsetail plant (Order Equisetales) has populated earth for over 100 million years.  This extraordinary long-term existence of ancient plants like the horsetail indicates the possibility that methyl sulfone has been in our environment for millions of years, which further suggests an important role for methyl sulfone in the maintenance of many forms of life on our planet.  Regrettably, over the last 50 years the level of methyl sulfone in the food we eat has significantly fallen due to mass industrialization of food processing (Steely JS. 1994. In: Mussinan K, ed. Sulfur Compounds in Foods. Washington, DC: American Chemical Society. 8p.).

Methyl Sulfone and Melanoma

We chose to study methyl sulfone because its chemical structure suggested anti-cancer activity.  We first tested the effect of methyl sulfone on an aggressive metastatic melanoma cell line (Caron et al., 2010, see below).  However, instead of looking for cell death by robotics, we observed the cells under a microscope.  Surprisingly, within 24-96 hours the melanoma cells lost properties associated with the metastatic state and reacquired properties of normal cells (melanocytes).  And by three weeks in methyl sulfone this transformation into non-growing, well-behaved normal cells was irreversible.

A most important function of a normal cell is to continue growing until it touches another growing cell, at which time both cells stop growing.  This is called “contact inhibition” and is critical for normal cell function; if the cells didn’t stop growing once they touch another cell, a tumor would form.  Cancer cells touch, but do not stop growing. The first observation we made by watching melanoma cells under the microscope was that methyl sulfone induced contact inhibition!  Current scientific methods for drug discovery do not involve observing the cells.  Therefore, methods presently being used are missing a fundamental cellular process that is able to prevent metastasis.  This also means that methyl sulfone would never have been discovered if only the ability to kill cancer cells and only robotics had been used to assay anti-cancer activity.  The fact that we looked through a microscope allowed the discovery of methyl sulfone.

Methyl Sulfone and Breast Cancer

We have now studied the effect of methyl sulfone on an aggressive metastatic breast cancer cell line (Caron et al., 2013a, see below), and extended the results with melanoma cells.  This means that methyl sulfone is active against more than one type of metastatic cancer.  We show that treatment of metastatic breast cancer cells with methyl sulfone causes a decrease in metastatic properties and the reemergence of normal cell properties.  For example, cells become contact inhibited, cell proliferation stops, DNA synthesis stops, and cells stop migrating.  Furthermore, a metastatic tumor promoter protein (N-cadherin) that is found in metastatic cells and is responsible for initiating migration of metastatic cells, is no longer found in methyl sulfone-treated cells and a metastatic tumor suppressor protein (E-cadherin) that is found in normal cells and prevents cancer cell migration, re-appears in the cells.  In addition, methyl sulfone causes the re-differentiation or re-appearance of normal types of breast cells such as ductal cells and myoepithelial cells.

We recently studied the effect of methyl sulfone on normal and cancerous human breast tissue obtained during surgery (Caron et al., 2013b, see below).  There were 17 patients, each with a unique pathology report.  For example, some patients had invasive carcinoma, some with necrosis, some with inflammatory elements, some with vascular involvement, some triple negative.  In most cases we were able to obtain both cancerous and normal breast tissue from the same patient.  We observed cells from these tissues living in culture dishes in a nutrient “soup” for up to 90 days, in either the presence or absence of methyl sulfone.  With all tissues, we obtained similar results.  Methyl sulfone normalizes the cancerous tissue and makes the normal tissue look even healthier.  For example, both cancerous and normal breast tissue form the 3D architecture of normal in situ breast tissue complete with lobular structures and “highways” of myoepithelial cells.  These results show that methyl sulfone is effective against different subtypes of human breast cancer tissue and methyl sulfone does not harm normal tissue.

We also show that cancerous human breast tissue, but not normal human breast tissue, contains two breast cancer stem cell proteins, HCAM (or CD44) and OCT 3/4, which allow metastatic breast cancer cells to rapidly move throughout the patient’s body.  However, when cancerous breast tissue is treated with methyl sulfone, HCAM and OCT 3/4 disappear, the cells stop moving so rapidly, and the cells take on the appearance and behavior of normal breast cells.

To summarize, our data show that chemotherapeutic agents need not kill cancer cells.  Instead, it is possible that metastatic cells can be reprogramed back into normal cells.  This in turn suggests that development of carcinogenesis or cancer is not a one way street (see Figure 1).

Joan M. Caron fig1

Make Peace, Not War

For many decades we have been trying to eradicate cancer by killing cancer cells.  We discuss the “war against cancer” and our “arsenal of weapons”.  For treatment of metastatic cancer, this approach has not worked.  And since 90% of cancer deaths are due to metastatic disease, this is a significant failure.

The role of a metastatic cancer cell is simple: stay alive and proliferate (multiply) and migrate through the patient’s body.  The metastatic cancer cell can use several different pathways in a cell to achieve these goals.  If one part of a pathway, for example for proliferation, is blocked by a targeted chemotherapeutic drug, the cancer cell can “evolve” so that it can circumvent that one specific part of the proliferating pathway thereby becoming resistant to the targeted therapy.  In fact, I believe that targeted chemotherapeutic drugs put pressure on metastatic cancer cells to evolve and become resistant to the drug.  This approach of present day chemotherapy may give patients some time, but ultimately I do not believe this method will be successful against metastatic disease.

An alternative approach is described by our studies with methyl sulfone.  Here we are not trying to kill cancer cells, but instead to redirect metastatic cancer cells away from proliferation and migration, and towards the functions of normal cells.  Using the approach with methyl sulfone, metastatic cancer cells are not under pressure to evolve and become resistant to this molecule, thus in turn avoiding unregulated proliferation.  In the presence of methyl sulfone, there should be no pressure on metastatic cancer cells to avoid re-acquisition of normal processes that lead to proper cell function.  After all, this is what cells do naturally in our bodies all the time.



  1. Caron, JM, et al., (2010) Methyl sulfone induces loss of metastatic properties and reemergence of normal phenotypes in a metastatic Cloudman S-91 (M3) murine melanoma cell line. PLoS One 5(8): e11788, DOI: 10.1371/journal.pone.0011788.
  2. Caron, JM, et al., (2013a) Methyl sulfone manifests anti-cancer activity in a metastatic murine breast cancer cell line and in human breast cancer tissue; Part 1: Murine 4T1 (66cl-4) cell line.  Chemotherapy 59:14-23, DOI: 10.1159/000351100.
  3. Caron, JM, et al., (2013b) Methyl sulfone manifests anti-cancer activity in a metastatic murine breast cancer cell line and in human breast cancer tissue; Part 2: Human breast cancer tissue.  Chemotherapy 59: 24-34, DOI: 10.1159/000351099.
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