This short review on 2 scientific publications about cannabinoids anti-tumour effects in lung and colon cancer.
Research team from Germany published in 2014 interesting results about cannabinoids involvement in lung cancer treatment. For their paper they have used metastatic cells from lung cancer patient and standard lung cancer cell lines to study the effect of cannabidiol (CBD).
It is already known that CBD promote the expression of a specific receptor (ICAM-1) on lung cancer cells. This effect is part of CBD mechanism which leads to suppression of tumour metastasis because this receptor is used by the immune system to destroy cancer cells.
In contract THC is known to have anti-tumour activity involving cannabinoid system – interactions with CB2.
Mice models have already shown that CBD leads to expression of ICAM-1 on lung cancer cells. Interestingly such effect is not observed with healthy cells. It is already published that lung cancer cells that express ICAM-1 are target for lymphocytes which attach to the cancer cells and lead to their destruction.
The authors suggest that this is a new anti-cancer mechanism of cannabinoids which could be explaining their anti-tumour effect. 
In 2013 an Italian team published their results on effect of high CBD Cannabis Sativa extracts on colon cancer cells in mice. Previous research has shown that cannabis extracts of high CBD strains are more potent or efficacious than pure CBD.
The extract had the following percentage mass fractions (percentage by weight): CBD – 65.9 %w/w; THC – 2.4 %w/w, cannabigerol – 1%w/w, cannabidivarin – 0.9 %w/w, cannabidiolic acid – 0.3 %w/w and cannabinol – 0.1 %w/w.
It is already known that cannabinoids can inhibit colorectal cancer cells growth via different mechanisms, including direct activation of CB1 and CB2.
In this research the authors have demonstrated that Cannabis Sativa extract has better effect on cell proliferation (inhibit cancer cells growth) in colorectal cancer than pure CBD. Further investigation showed that CBD activate CB1 receptor in colorectal cancer cells but not CB2. However, it is known that CBD does not bind efficiently CB1 receptor which suggests there are other mechanisms involved which result in CB1 activation. The authors suggest that this inhibitory effect on colorectal cancer cells is caused by combination of CBD, THC and cannabinol. 
The research data suggests that CBD anti-tumour activity in lung cancer is a result if triggering immune reaction, while according to the data for colorectal cancer, Cannabis Sativa extract has shown activation of the endocannabinoid receptor CB1, which leads to inhibition of tumour growth.